The GNU libmicrohttpd Library 1 Introduction 2 Constants 3 Structures type definition 4 Callback functions definition 5 Starting and stopping the server 6 Implementing external ‘select’ 7 Handling requests 8 Building responses to requests 9 Flow control. 10 Utilizing Authentication 11 Adding a ‘POST’ processor 12 Obtaining and modifying status information. 13 Utility functions. GNU-LGPL eCos License GNU General Public License GNU-FDL Concept Index Function and Data Index Type Index The GNU libmicrohttpd Library 1 Introduction 1.1 Scope 1.2 Thread modes and event loops 1.3 Compiling GNU libmicrohttpd 1.4 Validity of pointers 1.5 Including the microhttpd.h header 1.6 SIGPIPE 1.7 MHD_UNSIGNED_LONG_LONG 1.8 Portability to W32 1.9 Portability to z/OS 2 Constants 3 Structures type definition 4 Callback functions definition 5 Starting and stopping the server 6 Implementing external ‘select’ 7 Handling requests 8 Building responses to requests 8.1 Enqueuing a response 8.2 Creating a response object 8.3 Adding headers to a response 8.4 Setting response options 8.5 Inspecting a response object 8.6 Creating a response for protocol upgrades 9 Flow control. 10 Utilizing Authentication 10.1 Using Basic Authentication 10.2 Using Digest Authentication 11 Adding a ‘POST’ processor 11.1 Programming interface for the ‘POST’ processor 12 Obtaining and modifying status information. 12.1 Obtaining state information about an MHD daemon 12.2 Obtaining state information about a connection 12.3 Setting custom options for an individual connection 13 Utility functions. 13.1 Testing for supported MHD features 13.2 Unescape strings GNU-LGPL eCos License GNU General Public License GNU-FDL Concept Index Function and Data Index Type Index The GNU libmicrohttpd Library ***************************** This manual is for GNU libmicrohttpd (version 0.9.71, 26 July 2020), a library for embedding an HTTP(S) server into C applications. Copyright © 2007–2019 Christian Grothoff Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". 1 Introduction ************** All symbols defined in the public API start with ‘MHD_’. MHD is a small HTTP daemon library. As such, it does not have any API for logging errors (you can only enable or disable logging to stderr). Also, it may not support all of the HTTP features directly, where applicable, portions of HTTP may have to be handled by clients of the library. The library is supposed to handle everything that it must handle (because the API would not allow clients to do this), such as basic connection management. However, detailed interpretations of headers, such as range requests, are left to the main application. In particular, if an application developer wants to support range requests, he needs to explicitly indicate support in responses and also explicitly parse the range header and generate a response (for example, using the ‘MHD_create_response_from_fd_at_offset’ call to serve ranges from a file). MHD does understands headers that control connection management (specifically, ‘Connection: close’ and ‘Expect: 100 continue’ are understood and handled automatically). ‘Connection: upgrade’ is supported by passing control over the socket (or something that behaves like the real socket in the case of TLS) to the application (after sending the desired HTTP response header). MHD largely ignores the semantics of the different HTTP methods, so clients are left to handle those. One exception is that MHD does understand ‘HEAD’ and will only send the headers of the response and not the body, even if the client supplied a body. (In fact, clients do need to construct a response with the correct length, even for ‘HEAD’ request.) MHD understands ‘POST’ data and is able to decode certain formats (at the moment only ‘application/x-www-form-urlencoded’ and ‘multipart/form-data’) using the post processor API. The data stream of a POST is also provided directly to the main application, so unsupported encodings could still be processed, just not conveniently by MHD. The header file defines various constants used by the HTTP protocol. This does not mean that MHD actually interprets all of these values. The provided constants are exported as a convenience for users of the library. MHD does not verify that transmitted HTTP headers are part of the standard specification; users of the library are free to define their own extensions of the HTTP standard and use those with MHD. All functions are guaranteed to be completely reentrant and thread-safe. MHD checks for allocation failures and tries to recover gracefully (for example, by closing the connection). Additionally, clients can specify resource limits on the overall number of connections, number of connections per IP address and memory used per connection to avoid resource exhaustion. 1.1 Scope ========= MHD is currently used in a wide range of implementations. Examples based on reports we’ve received from developers include: • Embedded HTTP server on a cortex M3 (128 KB code space) • Large-scale multimedia server (reportedly serving at the simulator limit of 7.5 GB/s) • Administrative console (via HTTP/HTTPS) for network appliances 1.2 Thread modes and event loops ================================ MHD supports four basic thread modes and up to three event loop styles. The four basic thread modes are external sockets polling (MHD creates no threads, event loop is fully managed by the application), internal polling (MHD creates one thread for all connections), polling in thread pool (MHD creates a thread pool which is used to process all connections) and thread-per-connection (MHD creates one thread for listen sockets and then one thread per accepted connection). These thread modes are then combined with the evet loop styles (polling function type). MHD support select, poll and epoll. select is available on all platforms, epoll and poll may not be available on some platforms. Note that it is possible to combine MHD using epoll with an external select-based event loop. The default (if no other option is passed) is “external select”. The highest performance can typically be obtained with a thread pool using ‘epoll’. Apache Benchmark (ab) was used to compare the performance of ‘select’ and ‘epoll’ when using a thread pool and a large number of connections. *note Figure 1.1: fig:performance. shows the resulting plot from the ‘benchmark.c’ example, which measures the latency between an incoming request and the completion of the transmission of the response. In this setting, the ‘epoll’ thread pool with four threads was able to handle more than 45,000 connections per second on loopback (with Apache Benchmark running three processes on the same machine). [Data] Figure 1.1: Performance measurements for select vs. epoll (with thread-pool). Not all combinations of thread modes and event loop styles are supported. This is partially to keep the API simple, and partially because some combinations simply make no sense as others are strictly superior. Note that the choice of style depends first of all on the application logic, and then on the performance requirements. Applications that perform a blocking operation while handling a request within the callbacks from MHD must use a thread per connection. This is typically rather costly. Applications that do not support threads or that must run on embedded devices without thread-support must use the external mode. Using ‘epoll’ is only supported on some platform, thus portable applications must at least have a fallback option available. *note Table 1.1: tbl:supported. lists the sane combinations. select poll epoll external yes no yes internal yes yes yes thread pool yes yes yes thread-per-connection yes yes no Table 1.1: Supported combinations of event styles and thread modes. 1.3 Compiling GNU libmicrohttpd =============================== MHD uses the standard GNU system where the usual build process involves running $ ./configure $ make $ make install MHD supports various options to be given to configure to tailor the binary to a specific situation. Note that some of these options will remove portions of the MHD code that are required for binary-compatibility. They should only be used on embedded systems with tight resource constraints and no concerns about library versioning. Standard distributions including MHD are expected to always ship with all features enabled, otherwise unexpected incompatibilities can arise! Here is a list of MHD-specific options that can be given to configure (canonical configure options such as “–prefix” are also supported, for a full list of options run “./configure –help”): ‘``--disable-curl''’ disable running testcases using libcurl ‘``--disable-largefile''’ disable support for 64-bit files ‘``--disable-messages''’ disable logging of error messages (smaller binary size, not so much fun for debugging) ‘``--disable-https''’ disable HTTPS support, even if GNUtls is found; this option must be used if eCOS license is desired as an option (in all cases the resulting binary falls under a GNU LGPL-only license) ‘``--disable-postprocessor''’ do not include the post processor API (results in binary incompatibility) ‘``--disable-dauth''’ do not include the authentication APIs (results in binary incompatibility) ‘``--disable-httpupgrade''’ do not build code for HTTP “Upgrade” (smaller binary size, binary incompatible library) ‘``--disable-epoll''’ do not include epoll support, even if it supported (minimally smaller binary size, good for portability testing) ‘``--enable-coverage''’ set flags for analysis of code-coverage with gcc/gcov (results in slow, large binaries) ‘``--with-threads=posix,w32,none,auto''’ sets threading library to use. With use “none” to not support threads. In this case, MHD will only support the “external” threading modes and not perform any locking of data structures! Use ‘MHD_is_feature_supported(MHD_FEATURE_THREADS)’ to test if threads are available. Default is “auto”. ‘``--with-gcrypt=PATH''’ specifies path to libgcrypt installation ‘``--with-gnutls=PATH''’ specifies path to libgnutls installation 1.4 Validity of pointers ======================== MHD will give applications access to its internal data structures via pointers via arguments and return values from its API. This creates the question as to how long those pointers are assured to stay valid. Most MHD data structures are associated with the connection of an HTTP client. Thus, pointers associated with a connection are typically valid until the connection is finished, at which point MHD will call the ‘MHD_RequestCompletedCallback’ if one is registered. Applications that have such a callback registered may assume that keys and values from the ‘MHD_KeyValueIterator’, return values from ‘MHD_lookup_connection_value’ and the ‘url’, ‘method’ and ‘version’ arguments to the ‘MHD_AccessHandlerCallback’ will remain valid until the respective ‘MHD_RequestCompletedCallback’ is invoked. In contrast, the ‘upload_data’ argument of ‘MHD_RequestCompletedCallback’ as well as all pointers from the ‘MHD_PostDataIterator’ are only valid for the duration of the callback. Pointers returned from ‘MHD_get_response_header’ are valid as long as the response itself is valid. 1.5 Including the microhttpd.h header ===================================== Ideally, before including "microhttpd.h" you should add the necessary includes to define the ‘uint64_t’, ‘size_t’, ‘fd_set’, ‘socklen_t’ and ‘struct sockaddr’ data types. Which specific headers are needed may depend on your platform and your build system might include some tests to provide you with the necessary conditional operations. For possible suggestions consult ‘platform.h’ and ‘configure.ac’ in the MHD distribution. Once you have ensured that you manually (!) included the right headers for your platform before "microhttpd.h", you should also add a line with ‘#define MHD_PLATFORM_H’ which will prevent the "microhttpd.h" header from trying (and, depending on your platform, failing) to include the right headers. If you do not define MHD_PLATFORM_H, the "microhttpd.h" header will automatically include headers needed on GNU/Linux systems (possibly causing problems when porting to other platforms). 1.6 SIGPIPE =========== MHD does not install a signal handler for SIGPIPE. On platforms where this is possible (such as GNU/Linux), it disables SIGPIPE for its I/O operations (by passing MSG_NOSIGNAL or similar). On other platforms, SIGPIPE signals may be generated from network operations by MHD and will cause the process to die unless the developer explicitly installs a signal handler for SIGPIPE. Hence portable code using MHD must install a SIGPIPE handler or explicitly block the SIGPIPE signal. MHD does not do so in order to avoid messing with other parts of the application that may need to handle SIGPIPE in a particular way. You can make your application handle SIGPIPE by calling the following function in ‘main’: static void catcher (int sig) { } static void ignore_sigpipe () { struct sigaction oldsig; struct sigaction sig; sig.sa_handler = &catcher; sigemptyset (&sig.sa_mask); #ifdef SA_INTERRUPT sig.sa_flags = SA_INTERRUPT; /* SunOS */ #else sig.sa_flags = SA_RESTART; #endif if (0 != sigaction (SIGPIPE, &sig, &oldsig)) fprintf (stderr, "Failed to install SIGPIPE handler: %s\n", strerror (errno)); } 1.7 MHD_UNSIGNED_LONG_LONG ========================== Some platforms do not support ‘long long’. Hence MHD defines a macro ‘MHD_UNSIGNED LONG_LONG’ which will default to ‘unsigned long long’. For standard desktop operating systems, this is all you need to know. However, if your platform does not support ‘unsigned long long’, you should change "platform.h" to define ‘MHD_LONG_LONG’ and ‘MHD_UNSIGNED_LONG_LONG’ to an appropriate alternative type and also define ‘MHD_LONG_LONG_PRINTF’ and ‘MHD_UNSIGNED_LONG_LONG_PRINTF’ to the corresponding format string for printing such a data type. Note that the “signed” versions are deprecated. Also, for historical reasons, ‘MHD_LONG_LONG_PRINTF’ is without the percent sign, whereas ‘MHD_UNSIGNED_LONG_LONG_PRINTF’ is with the percent sign. Newly written code should only use the unsigned versions. However, you need to define both in "platform.h" if you need to change the definition for the specific platform. 1.8 Portability to W32 ====================== libmicrohttpd in general ported well to W32. Most libmicrohttpd features are supported. W32 do not support some functions, like epoll and corresponding MHD features are not available on W32. 1.9 Portability to z/OS ======================= To compile MHD on z/OS, extract the archive and run iconv -f UTF-8 -t IBM-1047 contrib/ascebc > /tmp/ascebc.sh chmod +x /tmp/ascebc.sh for n in `find * -type f` do /tmp/ascebc.sh $n done to convert all source files to EBCDIC. Note that you must run ‘configure’ from the directory where the configure script is located. Otherwise, configure will fail to find the ‘contrib/xcc’ script (which is a wrapper around the z/OS c89 compiler). 2 Constants *********** -- Enumeration: MHD_FLAG Options for the MHD daemon. Note that MHD will run automatically in background thread(s) only if ‘MHD_USE_INTERNAL_POLLING_THREAD’ is used. Otherwise caller (application) must use ‘MHD_run’ or ‘MHD_run_from_select’ to have MHD processed network connections and data. Starting the daemon may also fail if a particular option is not implemented or not supported on the target platform (i.e. no support for TLS, threads or IPv6). TLS support generally depends on options given during MHD compilation. ‘MHD_NO_FLAG’ No options selected. ‘MHD_USE_ERROR_LOG’ If this flag is used, the library should print error messages and warnings to stderr (or to custom error printer if it’s specified by options). Note that for this run-time option to have any effect, MHD needs to be compiled with messages enabled. This is done by default except you ran configure with the ‘--disable-messages’ flag set. ‘MHD_USE_DEBUG’ Currently the same as ‘MHD_USE_ERROR_LOG’. ‘MHD_USE_TLS’ Run in HTTPS-mode. If you specify ‘MHD_USE_TLS’ and MHD was compiled without SSL support, ‘MHD_start_daemon’ will return NULL. ‘MHD_USE_THREAD_PER_CONNECTION’ Run using one thread per connection. ‘MHD_USE_INTERNAL_POLLING_THREAD’ Run using an internal thread doing ‘SELECT’. ‘MHD_USE_IPv6’ Run using the IPv6 protocol (otherwise, MHD will just support IPv4). If you specify ‘MHD_USE_IPV6’ and the local platform does not support it, ‘MHD_start_daemon’ will return NULL. If you want MHD to support IPv4 and IPv6 using a single socket, pass MHD_USE_DUAL_STACK, otherwise, if you only pass this option, MHD will try to bind to IPv6-only (resulting in no IPv4 support). ‘MHD_USE_DUAL_STACK’ Use a single socket for IPv4 and IPv6. Note that this will mean that IPv4 addresses are returned by MHD in the IPv6-mapped format (the ’struct sockaddr_in6’ format will be used for IPv4 and IPv6). ‘MHD_USE_PEDANTIC_CHECKS’ Deprecated (use ‘MHD_OPTION_STRICT_FOR_CLIENT’). Be pedantic about the protocol. Specifically, at the moment, this flag causes MHD to reject HTTP 1.1 connections without a ‘Host’ header. This is required by the standard, but of course in violation of the “be as liberal as possible in what you accept” norm. It is recommended to turn this *ON* if you are testing clients against MHD, and *OFF* in production. ‘MHD_USE_POLL’ Use ‘poll()’ instead of ‘select()’. This allows sockets with descriptors ‘>= FD_SETSIZE’. This option currently only works in conjunction with ‘MHD_USE_INTERNAL_POLLING_THREAD’ (at this point). If you specify ‘MHD_USE_POLL’ and the local platform does not support it, ‘MHD_start_daemon’ will return NULL. ‘MHD_USE_EPOLL’ Use ‘epoll()’ instead of ‘poll()’ or ‘select()’. This allows sockets with descriptors ‘>= FD_SETSIZE’. This option is only available on some systems and does not work in conjunction with ‘MHD_USE_THREAD_PER_CONNECTION’ (at this point). If you specify ‘MHD_USE_EPOLL’ and the local platform does not support it, ‘MHD_start_daemon’ will return NULL. Using ‘epoll()’ instead of ‘select()’ or ‘poll()’ can in some situations result in significantly higher performance as the system call has fundamentally lower complexity (O(1) for ‘epoll()’ vs. O(n) for ‘select()’/‘poll()’ where n is the number of open connections). ‘MHD_USE_TURBO’ Enable optimizations to aggressively improve performance. Currently, the optimizations this option enables are based on opportunistic reads and writes. Basically, MHD will simply try to read or write or accept on a socket before checking that the socket is ready for IO using the event loop mechanism. As the sockets are non-blocking, this may fail (at a loss of performance), but generally MHD does this in situations where the operation is likely to succeed, in which case performance is improved. Setting the flag should generally be safe (even though the code is slightly more experimental). You may want to benchmark your application to see if this makes any difference for you. ‘MHD_USE_SUPPRESS_DATE_NO_CLOCK’ Suppress (automatically) adding the ’Date:’ header to HTTP responses. This option should ONLY be used on systems that do not have a clock and that DO provide other mechanisms for cache control. See also RFC 2616, section 14.18 (exception 3). ‘MHD_USE_NO_LISTEN_SOCKET’ Run the HTTP server without any listen socket. This option only makes sense if ‘MHD_add_connection’ is going to be used exclusively to connect HTTP clients to the HTTP server. This option is incompatible with using a thread pool; if it is used, ‘MHD_OPTION_THREAD_POOL_SIZE’ is ignored. ‘MHD_USE_ITC’ Force MHD to use a signal inter-thread communication channel to notify the event loop (of threads) of our shutdown and other events. This is required if an application uses ‘MHD_USE_INTERNAL_POLLING_THREAD’ and then performs ‘MHD_quiesce_daemon’ (which eliminates our ability to signal termination via the listen socket). In these modes, ‘MHD_quiesce_daemon’ will fail if this option was not set. Also, use of this option is automatic (as in, you do not even have to specify it), if ‘MHD_USE_NO_LISTEN_SOCKET’ is specified. In "external" select mode, this option is always simply ignored. Using this option also guarantees that MHD will not call ‘shutdown()’ on the listen socket, which means a parent process can continue to use the socket. ‘MHD_ALLOW_SUSPEND_RESUME’ Enables using ‘MHD_suspend_connection’ and ‘MHD_resume_connection’, as performing these calls requires some additional inter-thred communication channels to be created, and code not using these calls should not pay the cost. ‘MHD_USE_TCP_FASTOPEN’ Enable TCP_FASTOPEN on the listen socket. TCP_FASTOPEN is currently supported on Linux >= 3.6. On other systems using this option with cause ‘MHD_start_daemon’ to fail. ‘MHD_ALLOW_UPGRADE’ This option must be set if you want to upgrade connections (via “101 Switching Protocols” responses). This requires MHD to allocate additional resources, and hence we require this special flag so we only use the resources that are really needed. ‘MHD_USE_AUTO’ Automatically select best event loop style (polling function) depending on requested mode by other MHD flags and functions available on platform. If application doesn’t have requirements for any specific polling function, it’s recommended to use this flag. This flag is very convenient for multiplatform applications. ‘MHD_USE_POST_HANDSHAKE_AUTH_SUPPORT’ Tell the TLS library to support post handshake client authentication. Only useful in combination with ‘MHD_USE_TLS’. This option will only work if the underlying TLS library supports it (i.e. GnuTLS after 3.6.3). If the TLS library does not support it, MHD may ignore the option and proceed without supporting this features. ‘MHD_USE_INSECURE_TLS_EARLY_DATA’ Tell the TLS library to support TLS v1.3 early data (0-RTT) with the resulting security drawbacks. Only enable this if you really know what you are doing. MHD currently does NOT enforce that this only affects GET requests! You have been warned. This option will only work if the underlying TLS library supports it (i.e. GnuTLS after 3.6.3). If the TLS library does not support it, MHD may ignore the option and proceed without supporting this features. -- Enumeration: MHD_OPTION MHD options. Passed in the varargs portion of ‘MHD_start_daemon()’. ‘MHD_OPTION_END’ No more options / last option. This is used to terminate the VARARGs list. ‘MHD_OPTION_CONNECTION_MEMORY_LIMIT’ Maximum memory size per connection (followed by a ‘size_t’). The default is 32 kB (32*1024 bytes) as defined by the internal constant ‘MHD_POOL_SIZE_DEFAULT’. Values above 128k are unlikely to result in much benefit, as half of the memory will be typically used for IO, and TCP buffers are unlikely to support window sizes above 64k on most systems. ‘MHD_OPTION_CONNECTION_MEMORY_INCREMENT’ Increment to use for growing the read buffer (followed by a ‘size_t’). The default is 1024 (bytes). Increasing this value will make MHD use memory for reading more aggressively, which can reduce the number of ‘recvfrom’ calls but may increase the number of ‘sendto’ calls. The given value must fit within MHD_OPTION_CONNECTION_MEMORY_LIMIT. ‘MHD_OPTION_CONNECTION_LIMIT’ Maximum number of concurrent connections to accept (followed by an ‘unsigned int’). The default is ‘FD_SETSIZE - 4’ (the maximum number of file descriptors supported by ‘select’ minus four for ‘stdin’, ‘stdout’, ‘stderr’ and the server socket). In other words, the default is as large as possible. If the connection limit is reached, MHD’s behavior depends a bit on other options. If ‘MHD_USE_ITC’ was given, MHD will stop accepting connections on the listen socket. This will cause the operating system to queue connections (up to the ‘listen()’ limit) above the connection limit. Those connections will be held until MHD is done processing at least one of the active connections. If ‘MHD_USE_ITC’ is not set, then MHD will continue to ‘accept()’ and immediately ‘close()’ these connections. Note that if you set a low connection limit, you can easily get into trouble with browsers doing request pipelining. For example, if your connection limit is “1”, a browser may open a first connection to access your “index.html” file, keep it open but use a second connection to retrieve CSS files, images and the like. In fact, modern browsers are typically by default configured for up to 15 parallel connections to a single server. If this happens, MHD will refuse to even accept the second connection until the first connection is closed — which does not happen until timeout. As a result, the browser will fail to render the page and seem to hang. If you expect your server to operate close to the connection limit, you should first consider using a lower timeout value and also possibly add a “Connection: close” header to your response to ensure that request pipelining is not used and connections are closed immediately after the request has completed: MHD_add_response_header (response, MHD_HTTP_HEADER_CONNECTION, "close"); ‘MHD_OPTION_CONNECTION_TIMEOUT’ After how many seconds of inactivity should a connection automatically be timed out? (followed by an ‘unsigned int’; use zero for no timeout). The default is zero (no timeout). ‘MHD_OPTION_NOTIFY_COMPLETED’ Register a function that should be called whenever a request has been completed (this can be used for application-specific clean up). Requests that have never been presented to the application (via ‘MHD_AccessHandlerCallback()’) will not result in notifications. This option should be followed by *TWO* pointers. First a pointer to a function of type ‘MHD_RequestCompletedCallback()’ and second a pointer to a closure to pass to the request completed callback. The second pointer maybe ‘NULL’. ‘MHD_OPTION_NOTIFY_CONNECTION’ Register a function that should be called when the TCP connection to a client is opened or closed. Note that ‘MHD_OPTION_NOTIFY_COMPLETED’ and the ‘con_cls’ argument to the ‘MHD_AccessHandlerCallback’ are per HTTP request (and there can be multiple HTTP requests per TCP connection). The registered callback is called twice per TCP connection, with ‘MHD_CONNECTION_NOTIFY_STARTED’ and ‘MHD_CONNECTION_NOTIFY_CLOSED’ respectively. An additional argument can be used to store TCP connection specific information, which can be retrieved using ‘MHD_CONNECTION_INFO_SOCKET_CONTEXT’ during the lifetime of the TCP connection. The respective location is not the same as the HTTP-request-specific ‘con_cls’ from the ‘MHD_AccessHandlerCallback’. This option should be followed by *TWO* pointers. First a pointer to a function of type ‘MHD_NotifyConnectionCallback()’ and second a pointer to a closure to pass to the request completed callback. The second pointer maybe ‘NULL’. ‘MHD_OPTION_PER_IP_CONNECTION_LIMIT’ Limit on the number of (concurrent) connections made to the server from the same IP address. Can be used to prevent one IP from taking over all of the allowed connections. If the same IP tries to establish more than the specified number of connections, they will be immediately rejected. The option should be followed by an ‘unsigned int’. The default is zero, which means no limit on the number of connections from the same IP address. ‘MHD_OPTION_LISTEN_BACKLOG_SIZE’ Set the size of the ‘listen()’ back log queue of the TCP socket. Takes an ‘unsigned int’ as the argument. Default is the platform-specific value of ‘SOMAXCONN’. ‘MHD_OPTION_STRICT_FOR_CLIENT’ Specify how strict we should enforce the HTTP protocol. Takes an ‘int’ as the argument. Default is zero. If set to 1, MHD will be strict about the protocol. Specifically, at the moment, this flag uses MHD to reject HTTP 1.1 connections without a "Host" header. This is required by the standard, but of course in violation of the "be as liberal as possible in what you accept" norm. It is recommended to set this to 1 if you are testing clients against MHD, and 0 in production. If set to -1 MHD will be permissive about the protocol, allowing slight deviations that are technically not allowed by the RFC. Specifically, at the moment, this flag causes MHD to allow spaces in header field names. This is disallowed by the standard. It is not recommended to set it to -1 on publicly available servers as it may potentially lower level of protection. ‘MHD_OPTION_SERVER_INSANITY’ Allows the application to disable certain sanity precautions in MHD. With these, the client can break the HTTP protocol, so this should never be used in production. The options are, however, useful for testing HTTP clients against "broken" server implementations. This argument must be followed by an ‘unsigned int’, corresponding to an ‘enum MHD_DisableSanityCheck’. Right now, no sanity checks can be disabled. ‘MHD_OPTION_SOCK_ADDR’ Bind daemon to the supplied socket address. This option should be followed by a ‘struct sockaddr *’. If ‘MHD_USE_IPv6’ is specified, the ‘struct sockaddr*’ should point to a ‘struct sockaddr_in6’, otherwise to a ‘struct sockaddr_in’. If this option is not specified, the daemon will listen to incoming connections from anywhere. If you use this option, the ’port’ argument from ‘MHD_start_daemon’ is ignored and the port from the given ‘struct sockaddr *’ will be used instead. ‘MHD_OPTION_URI_LOG_CALLBACK’ Specify a function that should be called before parsing the URI from the client. The specified callback function can be used for processing the URI (including the options) before it is parsed. The URI after parsing will no longer contain the options, which maybe inconvenient for logging. This option should be followed by two arguments, the first one must be of the form void * my_logger(void * cls, const char * uri, struct MHD_Connection *con) where the return value will be passed as ‘*con_cls’ in calls to the ‘MHD_AccessHandlerCallback’ when this request is processed later; returning a value of ‘NULL’ has no special significance; (however, note that if you return non-‘NULL’, you can no longer rely on the first call to the access handler having ‘NULL == *con_cls’ on entry) ‘cls’ will be set to the second argument following MHD_OPTION_URI_LOG_CALLBACK. Finally, ‘uri’ will be the 0-terminated URI of the request. Note that during the time of this call, most of the connection’s state is not initialized (as we have not yet parsed he headers). However, information about the connecting client (IP, socket) is available. ‘MHD_OPTION_HTTPS_MEM_KEY’ Memory pointer to the private key to be used by the HTTPS daemon. This option should be followed by an "const char*" argument. This should be used in conjunction with ’MHD_OPTION_HTTPS_MEM_CERT’. ‘MHD_OPTION_HTTPS_KEY_PASSWORD’ Memory pointer to the password that decrypts the private key to be used by the HTTPS daemon. This option should be followed by an "const char*" argument. This should be used in conjunction with ’MHD_OPTION_HTTPS_MEM_KEY’. The password (or passphrase) is only used immediately during ‘MHD_start_daemon()’. Thus, the application may want to erase it from memory afterwards for additional security. ‘MHD_OPTION_HTTPS_MEM_CERT’ Memory pointer to the certificate to be used by the HTTPS daemon. This option should be followed by an "const char*" argument. This should be used in conjunction with ’MHD_OPTION_HTTPS_MEM_KEY’. ‘MHD_OPTION_HTTPS_MEM_TRUST’ Memory pointer to the CA certificate to be used by the HTTPS daemon to authenticate and trust clients certificates. This option should be followed by an "const char*" argument. The presence of this option activates the request of certificate to the client. The request to the client is marked optional, and it is the responsibility of the server to check the presence of the certificate if needed. Note that most browsers will only present a client certificate only if they have one matching the specified CA, not sending any certificate otherwise. ‘MHD_OPTION_HTTPS_CRED_TYPE’ Daemon credentials type. Either certificate or anonymous, this option should be followed by one of the values listed in "enum gnutls_credentials_type_t". ‘MHD_OPTION_HTTPS_PRIORITIES’ SSL/TLS protocol version and ciphers. This option must be followed by an "const char *" argument specifying the SSL/TLS protocol versions and ciphers that are acceptable for the application. The string is passed unchanged to gnutls_priority_init. If this option is not specified, “NORMAL” is used. ‘MHD_OPTION_HTTPS_CERT_CALLBACK’ Use a callback to determine which X.509 certificate should be used for a given HTTPS connection. This option should be followed by a argument of type "gnutls_certificate_retrieve_function2 *". This option provides an alternative to MHD_OPTION_HTTPS_MEM_KEY and MHD_OPTION_HTTPS_MEM_CERT. You must use this version if multiple domains are to be hosted at the same IP address using TLS’s Server Name Indication (SNI) extension. In this case, the callback is expected to select the correct certificate based on the SNI information provided. The callback is expected to access the SNI data using gnutls_server_name_get(). Using this option requires GnuTLS 3.0 or higher. ‘MHD_OPTION_HTTPS_CERT_CALLBACK2’ Use a callback to determine which X.509 certificate should be used for a given HTTPS connection. This option should be followed by a argument of type ‘gnutls_certificate_retrieve_function3 *‘. This option provides an alternative/extension to #MHD_OPTION_HTTPS_CERT_CALLBACK. You must use this version if you want to use OCSP stapling. Using this option requires GnuTLS 3.6.3 or higher. ‘MHD_OPTION_GNUTLS_PSK_CRED_HANDLER’ Use pre-shared key for TLS credentials. Pass a pointer to callback of type ‘MHD_PskServerCredentialsCallback’ and a closure. The function will be called to retrieve the shared key for a given username. ‘MHD_OPTION_DIGEST_AUTH_RANDOM’ Digest Authentication nonce’s seed. This option should be followed by two arguments. First an integer of type "size_t" which specifies the size of the buffer pointed to by the second argument in bytes. Note that the application must ensure that the buffer of the second argument remains allocated and unmodified while the daemon is running. For security, you SHOULD provide a fresh random nonce when using MHD with Digest Authentication. ‘MHD_OPTION_NONCE_NC_SIZE’ Size of an array of nonce and nonce counter map. This option must be followed by an "unsigned int" argument that have the size (number of elements) of a map of a nonce and a nonce-counter. If this option is not specified, a default value of 4 will be used (which might be too small for servers handling many requests). If you do not use digest authentication at all, you can specify a value of zero to save some memory. You should calculate the value of NC_SIZE based on the number of connections per second multiplied by your expected session duration plus a factor of about two for hash table collisions. For example, if you expect 100 digest-authenticated connections per second and the average user to stay on your site for 5 minutes, then you likely need a value of about 60000. On the other hand, if you can only expect only 10 digest-authenticated connections per second, tolerate browsers getting a fresh nonce for each request and expect a HTTP request latency of 250 ms, then a value of about 5 should be fine. ‘MHD_OPTION_LISTEN_SOCKET’ Listen socket to use. Pass a listen socket for MHD to use (systemd-style). If this option is used, MHD will not open its own listen socket(s). The argument passed must be of type "int" and refer to an existing socket that has been bound to a port and is listening. ‘MHD_OPTION_EXTERNAL_LOGGER’ Use the given function for logging error messages. This option must be followed by two arguments; the first must be a pointer to a function of type ’void fun(void * arg, const char * fmt, va_list ap)’ and the second a pointer of type ’void*’ which will be passed as the "arg" argument to "fun". Note that MHD will not generate any log messages without the MHD_USE_ERROR_LOG flag set and if MHD was compiled with the "–disable-messages" flag. ‘MHD_OPTION_THREAD_POOL_SIZE’ Number (unsigned int) of threads in thread pool. Enable thread pooling by setting this value to to something greater than 1. Currently, thread mode must be MHD_USE_INTERNAL_POLLING_THREAD if thread pooling is enabled (‘MHD_start_daemon’ returns ‘NULL’ for an unsupported thread mode). ‘MHD_OPTION_ARRAY’ This option can be used for initializing MHD using options from an array. A common use for this is writing an FFI for MHD. The actual options given are in an array of ’struct MHD_OptionItem’, so this option requires a single argument of type ’struct MHD_OptionItem’. The array must be terminated with an entry ‘MHD_OPTION_END’. An example for code using MHD_OPTION_ARRAY is: struct MHD_OptionItem ops[] = { { MHD_OPTION_CONNECTION_LIMIT, 100, NULL }, { MHD_OPTION_CONNECTION_TIMEOUT, 10, NULL }, { MHD_OPTION_END, 0, NULL } }; d = MHD_start_daemon(0, 8080, NULL, NULL, dh, NULL, MHD_OPTION_ARRAY, ops, MHD_OPTION_END); For options that expect a single pointer argument, the second member of the ‘struct MHD_OptionItem’ is ignored. For options that expect two pointer arguments, the first argument must be cast to ‘intptr_t’. ‘MHD_OPTION_UNESCAPE_CALLBACK’ Specify a function that should be called for unescaping escape sequences in URIs and URI arguments. Note that this function will NOT be used by the MHD_PostProcessor. If this option is not specified, the default method will be used which decodes escape sequences of the form "%HH". This option should be followed by two arguments, the first one must be of the form size_t my_unescaper(void * cls, struct MHD_Connection *c, char *s) where the return value must be ‘strlen(s)’ and ‘s’ should be updated. Note that the unescape function must not lengthen ‘s’ (the result must be shorter than the input and still be 0-terminated). ‘cls’ will be set to the second argument following MHD_OPTION_UNESCAPE_CALLBACK. ‘MHD_OPTION_THREAD_STACK_SIZE’ Maximum stack size for threads created by MHD. This option must be followed by a ‘size_t’). Not specifying this option or using a value of zero means using the system default (which is likely to differ based on your platform). ‘MHD_OPTION_TCP_FASTQUEUE_QUEUE_SIZE’ When the flag ‘MHD_USE_TCP_FASTOPEN’ is used, this option sets the connection handshake queue size for the TCP FASTOPEN connections. Note that a TCP FASTOPEN connection handshake occupies more resources than a TCP handshake as the SYN packets also contain DATA which is kept in the associate state until handshake is completed. If this option is not given the queue size is set to a default value of 10. This option must be followed by a ‘unsigned int’. ‘MHD_OPTION_HTTPS_MEM_DHPARAMS’ Memory pointer for the Diffie-Hellman parameters (dh.pem) to be used by the HTTPS daemon for key exchange. This option must be followed by a ‘const char *’ argument. The argument would be a zero-terminated string with a PEM encoded PKCS3 DH parameters structure suitable for passing to ‘gnutls_dh_parms_import_pkcs3’. ‘MHD_OPTION_LISTENING_ADDRESS_REUSE’ This option must be followed by a ‘unsigned int’ argument. If this option is present and true (nonzero) parameter is given, allow reusing the address:port of the listening socket (using ‘SO_REUSEPORT’ on most platforms, and ‘SO_REUSEADDR’ on Windows). If a false (zero) parameter is given, disallow reusing the the address:port of the listening socket (this usually requires no special action, but ‘SO_EXCLUSIVEADDRUSE’ is needed on Windows). If this option is not present ‘SO_REUSEADDR’ is used on all platforms except Windows so reusing of address:port is disallowed. -- C Struct: MHD_OptionItem Entry in an MHD_OPTION_ARRAY. See the ‘MHD_OPTION_ARRAY’ option argument for its use. The ‘option’ member is used to specify which option is specified in the array. The other members specify the respective argument. Note that for options taking only a single pointer, the ‘ptr_value’ member should be set. For options taking two pointer arguments, the first pointer must be cast to ‘intptr_t’ and both the ‘value’ and the ‘ptr_value’ members should be used to pass the two pointers. -- Enumeration: MHD_ValueKind The ‘MHD_ValueKind’ specifies the source of the key-value pairs in the HTTP protocol. ‘MHD_HEADER_KIND’ HTTP header. ‘MHD_COOKIE_KIND’ Cookies. Note that the original HTTP header containing the cookie(s) will still be available and intact. ‘MHD_POSTDATA_KIND’ ‘POST’ data. This is available only if a content encoding supported by MHD is used (currently only URL encoding), and only if the posted content fits within the available memory pool. Note that in that case, the upload data given to the ‘MHD_AccessHandlerCallback()’ will be empty (since it has already been processed). ‘MHD_GET_ARGUMENT_KIND’ ‘GET’ (URI) arguments. ‘MHD_FOOTER_KIND’ HTTP footer (only for http 1.1 chunked encodings). -- Enumeration: MHD_RequestTerminationCode The ‘MHD_RequestTerminationCode’ specifies reasons why a request has been terminated (or completed). ‘MHD_REQUEST_TERMINATED_COMPLETED_OK’ We finished sending the response. ‘MHD_REQUEST_TERMINATED_WITH_ERROR’ Error handling the connection (resources exhausted, other side closed connection, application error accepting request, etc.) ‘MHD_REQUEST_TERMINATED_TIMEOUT_REACHED’ No activity on the connection for the number of seconds specified using ‘MHD_OPTION_CONNECTION_TIMEOUT’. ‘MHD_REQUEST_TERMINATED_DAEMON_SHUTDOWN’ We had to close the session since MHD was being shut down. -- Enumeration: MHD_ResponseMemoryMode The ‘MHD_ResponeMemoryMode’ specifies how MHD should treat the memory buffer given for the response in ‘MHD_create_response_from_buffer’. ‘MHD_RESPMEM_PERSISTENT’ Buffer is a persistent (static/global) buffer that won’t change for at least the lifetime of the response, MHD should just use it, not free it, not copy it, just keep an alias to it. ‘MHD_RESPMEM_MUST_FREE’ Buffer is heap-allocated with ‘malloc’ (or equivalent) and should be freed by MHD after processing the response has concluded (response reference counter reaches zero). ‘MHD_RESPMEM_MUST_COPY’ Buffer is in transient memory, but not on the heap (for example, on the stack or non-malloc allocated) and only valid during the call to ‘MHD_create_response_from_buffer’. MHD must make its own private copy of the data for processing. -- Enumeration: MHD_ResponseFlags Response-specific flags. Passed as an argument to ‘MHD_set_response_options()’. ‘MHD_RF_NONE’ No special handling. ‘MHD_RF_HTTP_VERSION_1_0_ONLY’ Only respond in conservative HTTP 1.0-mode. In particular, do not (automatically) sent "Connection" headers and always close the connection after generating the response. By default, MHD will respond using the same HTTP version which was set in the request. You can also set the ‘MHD_RF_HTTP_VERSION_1_0_RESPONSE’ flag to force version 1.0 in the response. ‘MHD_RF_HTTP_VERSION_1_0_RESPONSE’ Only respond in HTTP 1.0-mode. Contrary to the ‘MHD_RF_HTTP_VERSION_1_0_ONLY’ flag, the response’s HTTP version will always be set to 1.0 and “Connection” headers are still supported. You can even combine this option with MHD_RF_HTTP_VERSION_1_0_ONLY to change the response’s HTTP version while maintaining strict compliance with HTTP 1.0 regarding connection management. This solution is not perfect as this flag is set on the response which is created after header processing. So MHD will behave as a HTTP 1.1 server until the response is queued. It means that an invalid HTTP 1.1 request will fail even if the response is sent with HTTP 1.0 and the request would be valid if interpreted with this version. For example, this request will fail in strict mode: GET / HTTP/1.1 as the “Host” header is missing and is mandatory in HTTP 1.1, but it should succeed when interpreted with HTTP 1.0. ‘MHD_RF_INSANITY_HEADER_CONTENT_LENGTH’ Disable sanity check preventing clients from manually setting the HTTP content length option. -- Enumeration: MHD_ResponseOptions Response-specific options. Passed in the varargs portion of ‘MHD_set_response_options()’. ‘MHD_RO_END’ No more options / last option. This is used to terminate the VARARGs list. 3 Structures type definition **************************** -- C Struct: MHD_Daemon Handle for the daemon (listening on a socket for HTTP traffic). -- C Struct: MHD_Connection Handle for a connection / HTTP request. With HTTP/1.1, multiple requests can be run over the same connection. However, MHD will only show one request per TCP connection to the client at any given time. -- C Struct: MHD_Response Handle for a response. -- C Struct: MHD_PostProcessor Handle for ‘POST’ processing. -- C Union: MHD_ConnectionInfo Information about a connection. -- C Union: MHD_DaemonInfo Information about an MHD daemon. 4 Callback functions definition ******************************* -- Function Pointer: enum MHD_Result *MHD_AcceptPolicyCallback (void *cls, const struct sockaddr * addr, socklen_t addrlen) Invoked in the context of a connection to allow or deny a client to connect. This callback return ‘MHD_YES’ if connection is allowed, ‘MHD_NO’ if not. CLS custom value selected at callback registration time; ADDR address information from the client; ADDRLEN length of the address information. -- Function Pointer: enum MHD_Result *MHD_AccessHandlerCallback (void *cls, struct MHD_Connection * connection, const char *url, const char *method, const char *version, const char *upload_data, size_t *upload_data_size, void **con_cls) Invoked in the context of a connection to answer a request from the client. This callback must call MHD functions (example: the ‘MHD_Response’ ones) to provide content to give back to the client and return an HTTP status code (i.e. ‘200’ for OK, ‘404’, etc.). *note microhttpd-post::, for details on how to code this callback. Must return ‘MHD_YES’ if the connection was handled successfully, ‘MHD_NO’ if the socket must be closed due to a serious error while handling the request CLS custom value selected at callback registration time; URL the URL requested by the client; METHOD the HTTP method used by the client (‘GET’, ‘PUT’, ‘DELETE’, ‘POST’, etc.); VERSION the HTTP version string (i.e. ‘HTTP/1.1’); UPLOAD_DATA the data being uploaded (excluding headers): ‘POST’ data *will* be made available incrementally in UPLOAD_DATA; even if ‘POST’ data is available, the first time the callback is invoked there won’t be upload data, as this is done just after MHD parses the headers. If supported by the client and the HTTP version, the application can at this point queue an error response to possibly avoid the upload entirely. If no response is generated, MHD will (if required) automatically send a 100 CONTINUE reply to the client. Afterwards, POST data will be passed to the callback to be processed incrementally by the application. The application may return ‘MHD_NO’ to forcefully terminate the TCP connection without generating a proper HTTP response. Once all of the upload data has been provided to the application, the application will be called again with 0 bytes of upload data. At this point, a response should be queued to complete the handling of the request. UPLOAD_DATA_SIZE set initially to the size of the UPLOAD_DATA provided; this callback must update this value to the number of bytes *NOT* processed; unless external select is used, the callback maybe required to process at least some data. If the callback fails to process data in multi-threaded or internal-select mode and if the read-buffer is already at the maximum size that MHD is willing to use for reading (about half of the maximum amount of memory allowed for the connection), then MHD will abort handling the connection and return an internal server error to the client. In order to avoid this, clients must be able to process upload data incrementally and reduce the value of ‘upload_data_size’. CON_CLS reference to a pointer, initially set to ‘NULL’, that this callback can set to some address and that will be preserved by MHD for future calls for this request; since the access handler may be called many times (i.e., for a ‘PUT’/‘POST’ operation with plenty of upload data) this allows the application to easily associate some request-specific state; if necessary, this state can be cleaned up in the global ‘MHD_RequestCompletedCallback’ (which can be set with the ‘MHD_OPTION_NOTIFY_COMPLETED’). -- Function Pointer: void *MHD_RequestCompletedCallback (void *cls, struct MHD_Connectionconnection, void **con_cls, enum MHD_RequestTerminationCode toe) Signature of the callback used by MHD to notify the application about completed requests. CLS custom value selected at callback registration time; CONNECTION connection handle; CON_CLS value as set by the last call to the ‘MHD_AccessHandlerCallback’; TOE reason for request termination see ‘MHD_OPTION_NOTIFY_COMPLETED’. -- Function Pointer: enum MHD_Result *MHD_KeyValueIterator (void *cls, enum MHD_ValueKind kind, const char *key, const char *value, size_t value_size) Iterator over key-value pairs. This iterator can be used to iterate over all of the cookies, headers, or ‘POST’-data fields of a request, and also to iterate over the headers that have been added to a response. CLS custom value specified when iteration was triggered; KIND kind of the header we are looking at KEY key for the value, can be an empty string VALUE value corresponding value, can be NULL VALUE_SIZE number of bytes in ‘value’. This argument was introduced in ‘MHD_VERSION’ 0x00096301 to allow applications to use binary zeros in values. Applications using this argument must ensure that they are using a sufficiently recent version of MHD, i.e. by testing ‘MHD_get_version()’ for values above or equal to 0.9.64. Applications that do not need zeros in values and that want to compile without warnings against newer versions of MHD should not declare this argument and cast the function pointer argument to ‘MHD_KeyValueIterator’. Return ‘MHD_YES’ to continue iterating, ‘MHD_NO’ to abort the iteration. -- Function Pointer: ssize_t *MHD_ContentReaderCallback (void *cls, uint64_t pos, char *buf, size_t max) Callback used by MHD in order to obtain content. The callback has to copy at most MAX bytes of content into BUF. The total number of bytes that has been placed into BUF should be returned. Note that returning zero will cause MHD to try again. Thus, returning zero should only be used in conjunction with ‘MHD_suspend_connection()’ to avoid busy waiting. While usually the callback simply returns the number of bytes written into BUF, there are two special return value: ‘MHD_CONTENT_READER_END_OF_STREAM’ (-1) should be returned for the regular end of transmission (with chunked encoding, MHD will then terminate the chunk and send any HTTP footers that might be present; without chunked encoding and given an unknown response size, MHD will simply close the connection; note that while returning ‘MHD_CONTENT_READER_END_OF_STREAM’ is not technically legal if a response size was specified, MHD accepts this and treats it just as ‘MHD_CONTENT_READER_END_WITH_ERROR’. ‘MHD_CONTENT_READER_END_WITH_ERROR’ (-2) is used to indicate a server error generating the response; this will cause MHD to simply close the connection immediately. If a response size was given or if chunked encoding is in use, this will indicate an error to the client. Note, however, that if the client does not know a response size and chunked encoding is not in use, then clients will not be able to tell the difference between ‘MHD_CONTENT_READER_END_WITH_ERROR’ and ‘MHD_CONTENT_READER_END_OF_STREAM’. This is not a limitation of MHD but rather of the HTTP protocol. CLS custom value selected at callback registration time; POS position in the datastream to access; note that if an ‘MHD_Response’ object is re-used, it is possible for the same content reader to be queried multiple times for the same data; however, if an ‘MHD_Response’ is not re-used, MHD guarantees that POS will be the sum of all non-negative return values obtained from the content reader so far. Return ‘-1’ on error (MHD will no longer try to read content and instead close the connection with the client). -- Function Pointer: void *MHD_ContentReaderFreeCallback (void *cls) This method is called by MHD if we are done with a content reader. It should be used to free resources associated with the content reader. -- Function Pointer: enum MHD_Result *MHD_PostDataIterator (void *cls, enum MHD_ValueKind kind, const char *key, const char *filename, const char *content_type, const char *transfer_encoding, const char *data, uint64_t off, size_t size) Iterator over key-value pairs where the value maybe made available in increments and/or may not be zero-terminated. Used for processing ‘POST’ data. CLS custom value selected at callback registration time; KIND type of the value; KEY zero-terminated key for the value; FILENAME name of the uploaded file, ‘NULL’ if not known; CONTENT_TYPE mime-type of the data, ‘NULL’ if not known; TRANSFER_ENCODING encoding of the data, ‘NULL’ if not known; DATA pointer to size bytes of data at the specified offset; OFF offset of data in the overall value; SIZE number of bytes in data available. Return ‘MHD_YES’ to continue iterating, ‘MHD_NO’ to abort the iteration. 5 Starting and stopping the server ********************************** -- Function: void MHD_set_panic_func (MHD_PanicCallback cb, void *cls) Set a handler for fatal errors. CB function to call if MHD encounters a fatal internal error. If no handler was set explicitly, MHD will call ‘abort’. CLS closure argument for cb; the other arguments are the name of the source file, line number and a string describing the nature of the fatal error (which can be ‘NULL’) -- Function: struct MHD_Daemon * MHD_start_daemon (unsigned int flags, unsigned short port, MHD_AcceptPolicyCallback apc, void *apc_cls, MHD_AccessHandlerCallback dh, void *dh_cls, ...) Start a webserver on the given port. FLAGS OR-ed combination of ‘MHD_FLAG’ values; PORT port to bind to; APC callback to call to check which clients will be allowed to connect; you can pass ‘NULL’ in which case connections from any IP will be accepted; APC_CLS extra argument to APC; DH default handler for all URIs; DH_CLS extra argument to DH. Additional arguments are a list of options (type-value pairs, terminated with ‘MHD_OPTION_END’). It is mandatory to use ‘MHD_OPTION_END’ as last argument, even when there are no additional arguments. Return ‘NULL’ on error, handle to daemon on success. -- Function: MHD_socket MHD_quiesce_daemon (struct MHD_Daemon *daemon) Stop accepting connections from the listening socket. Allows clients to continue processing, but stops accepting new connections. Note that the caller is responsible for closing the returned socket; however, if MHD is run using threads (anything but external select mode), it must not be closed until AFTER ‘MHD_stop_daemon’ has been called (as it is theoretically possible that an existing thread is still using it). This function is useful in the special case that a listen socket is to be migrated to another process (i.e. a newer version of the HTTP server) while existing connections should continue to be processed until they are finished. Return ‘-1’ on error (daemon not listening), the handle to the listen socket otherwise. -- Function: void MHD_stop_daemon (struct MHD_Daemon *daemon) Shutdown an HTTP daemon. -- Function: enum MHD_Result MHD_run (struct MHD_Daemon *daemon) Run webserver operations (without blocking unless in client callbacks). This method should be called by clients in combination with ‘MHD_get_fdset()’ if the client-controlled ‘select’-method is used. This function will work for external ‘poll’ and ‘select’ mode. However, if using external ‘select’ mode, you may want to instead use ‘MHD_run_from_select’, as it is more efficient. DAEMON daemon to process connections of Return ‘MHD_YES’ on success, ‘MHD_NO’ if this daemon was not started with the right options for this call. -- Function: enum MHD_Result MHD_run_from_select (struct MHD_Daemon *daemon, const fd_set *read_fd_set, const fd_set *write_fd_set, const fd_set *except_fd_set) Run webserver operations given sets of ready socket handles. This method should be called by clients in combination with ‘MHD_get_fdset’ if the client-controlled (external) select method is used. You can use this function instead of ‘MHD_run’ if you called ‘select’ on the result from ‘MHD_get_fdset’. File descriptors in the sets that are not controlled by MHD will be ignored. Calling this function instead of ‘MHD_run’ is more efficient as MHD will not have to call ‘select’ again to determine which operations are ready. DAEMON daemon to process connections of READ_FD_SET set of descriptors that must be ready for reading without blocking WRITE_FD_SET set of descriptors that must be ready for writing without blocking EXCEPT_FD_SET ignored, can be NULL Return ‘MHD_YES’ on success, ‘MHD_NO’ on serious internal errors. -- Function: void MHD_add_connection (struct MHD_Daemon *daemon, int client_socket, const struct sockaddr *addr, socklen_t addrlen) Add another client connection to the set of connections managed by MHD. This API is usually not needed (since MHD will accept inbound connections on the server socket). Use this API in special cases, for example if your HTTP server is behind NAT and needs to connect out to the HTTP client, or if you are building a proxy. If you use this API in conjunction with a internal select or a thread pool, you must set the option ‘MHD_USE_ITC’ to ensure that the freshly added connection is immediately processed by MHD. The given client socket will be managed (and closed!) by MHD after this call and must no longer be used directly by the application afterwards. DAEMON daemon that manages the connection CLIENT_SOCKET socket to manage (MHD will expect to receive an HTTP request from this socket next). ADDR IP address of the client ADDRLEN number of bytes in addr This function will return ‘MHD_YES’ on success, ‘MHD_NO’ if this daemon could not handle the connection (i.e. malloc failed, etc). The socket will be closed in any case; ’errno’ is set to indicate further details about the error. 6 Implementing external ‘select’ ******************************** -- Function: enum MHD_Result MHD_get_fdset (struct MHD_Daemon *daemon, fd_set * read_fd_set, fd_set * write_fd_set, fd_set * except_fd_set, int *max_fd) Obtain the ‘select()’ sets for this daemon. The daemon’s socket is added to READ_FD_SET. The list of currently existent connections is scanned and their file descriptors added to the correct set. When calling this function, FD_SETSIZE is assumed to be platform’s default. If you changed FD_SETSIZE for your application, you should use ‘MHD_get_fdset2()’ instead. This function should only be called in when MHD is configured to use external select with ‘select()’ or with ‘epoll()’. In the latter case, it will only add the single ‘epoll()’ file descriptor used by MHD to the sets. After the call completed successfully: the variable referenced by MAX_FD references the file descriptor with highest integer identifier. The variable must be set to zero before invoking this function. Return ‘MHD_YES’ on success, ‘MHD_NO’ if: the arguments are invalid (example: ‘NULL’ pointers); this daemon was not started with the right options for this call. -- Function: enum MHD_Result MHD_get_fdset2 (struct MHD_Daemon *daemon, fd_set * read_fd_set, fd_set * write_fd_set, fd_set * except_fd_set, int *max_fd, unsigned int fd_setsize) Like ‘MHD_get_fdset()’, except that you can manually specify the value of FD_SETSIZE used by your application. -- Function: enum MHD_Result MHD_get_timeout (struct MHD_Daemon *daemon, unsigned long long *timeout) Obtain timeout value for select for this daemon (only needed if connection timeout is used). The returned value is how many milliseconds ‘select’ should at most block, not the timeout value set for connections. This function must not be called if the ‘MHD_USE_THREAD_PER_CONNECTION’ mode is in use (since then it is not meaningful to ask for a timeout, after all, there is concurrenct activity). The function must also not be called by user-code if ‘MHD_USE_INTERNAL_POLLING_THREAD’ is in use. In the latter case, the behavior is undefined. DAEMON which daemon to obtain the timeout from. TIMEOUT will be set to the timeout (in milliseconds). Return ‘MHD_YES’ on success, ‘MHD_NO’ if timeouts are not used (or no connections exist that would necessitate the use of a timeout right now). 7 Handling requests ******************* -- Function: int MHD_get_connection_values (struct MHD_Connection *connection, enum MHD_ValueKind kind, MHD_KeyValueIterator iterator, void *iterator_cls) Get all the headers matching KIND from the request. The KIND argument can be a bitmask, ORing the various header kinds that are requested. The ITERATOR callback is invoked once for each header, with ITERATOR_CLS as first argument. After version 0.9.19, the headers are iterated in the same order as they were received from the network; previous versions iterated over the headers in reverse order. ‘MHD_get_connection_values’ returns the number of entries iterated over; this can be less than the number of headers if, while iterating, ITERATOR returns ‘MHD_NO’. ITERATOR can be ‘NULL’: in this case this function just counts and returns the number of headers. In the case of ‘MHD_GET_ARGUMENT_KIND’, the VALUE argument will be ‘NULL’ if the URL contained a key without an equals operator. For example, for a HTTP request to the URL “http://foo/bar?key”, the VALUE argument is ‘NULL’; in contrast, a HTTP request to the URL “http://foo/bar?key=”, the VALUE argument is the empty string. The normal case is that the URL contains “http://foo/bar?key=value” in which case VALUE would be the string “value” and KEY would contain the string “key”. -- Function: enum MHD_Result MHD_set_connection_value (struct MHD_Connection *connection, enum MHD_ValueKind kind, const char *key, const char *value) This function can be used to append an entry to the list of HTTP headers of a connection (so that the ‘MHD_get_connection_values function’ will return them – and the MHD PostProcessor will also see them). This maybe required in certain situations (see Mantis #1399) where (broken) HTTP implementations fail to supply values needed by the post processor (or other parts of the application). This function MUST only be called from within the MHD_AccessHandlerCallback (otherwise, access maybe improperly synchronized). Furthermore, the client must guarantee that the key and value arguments are 0-terminated strings that are NOT freed until the connection is closed. (The easiest way to do this is by passing only arguments to permanently allocated strings.). CONNECTION is the connection for which the entry for KEY of the given KIND should be set to the given VALUE. The function returns ‘MHD_NO’ if the operation could not be performed due to insufficient memory and ‘MHD_YES’ on success. -- Function: const char * MHD_lookup_connection_value (struct MHD_Connection *connection, enum MHD_ValueKind kind, const char *key) Get a particular header value. If multiple values match the KIND, return one of them (the “first”, whatever that means). KEY must reference a zero-terminated ASCII-coded string representing the header to look for: it is compared against the headers using (basically) ‘strcasecmp()’, so case is ignored. -- Function: const char * MHD_lookup_connection_value_n (struct MHD_Connection *connection, enum MHD_ValueKind kind, const char *key, size_t key_size, const char **value_ptr, size_t *value_size_ptr) Get a particular header value. If multiple values match the KIND, return one of them (the “first”, whatever that means). KEY must reference an ASCII-coded string representing the header to look for: it is compared against the headers using (basically) ‘strncasecmp()’, so case is ignored. The VALUE_PTR is set to the address of the value found, and VALUE_SIZE_PTR is set to the number of bytes in the value. 8 Building responses to requests ******************************** Response objects handling by MHD is asynchronous with respect to the application execution flow. Instances of the ‘MHD_Response’ structure are not associated to a daemon and neither to a client connection: they are managed with reference counting. In the simplest case: we allocate a new ‘MHD_Response’ structure for each response, we use it once and finally we destroy it. MHD allows more efficient resources usages. Example: we allocate a new ‘MHD_Response’ structure for each response *kind*, we use it every time we have to give that response and we finally destroy it only when the daemon shuts down. 8.1 Enqueuing a response ======================== -- Function: enum MHD_Result MHD_queue_response (struct MHD_Connection *connection, unsigned int status_code, struct MHD_Response *response) Queue a response to be transmitted to the client as soon as possible but only after MHD_AccessHandlerCallback returns. This function checks that it is legal to queue a response at this time for the given connection. It also increments the internal reference counter for the response object (the counter will be decremented automatically once the response has been transmitted). CONNECTION the connection identifying the client; STATUS_CODE HTTP status code (i.e. ‘200’ for OK); RESPONSE response to transmit. Return ‘MHD_YES’ on success or if message has been queued. Return ‘MHD_NO’: if arguments are invalid (example: ‘NULL’ pointer); on error (i.e. reply already sent). -- Function: void MHD_destroy_response (struct MHD_Response *response) Destroy a response object and associated resources (decrement the reference counter). Note that MHD may keep some of the resources around if the response is still in the queue for some clients, so the memory may not necessarily be freed immediately. An explanation of reference counting(1): 1. a ‘MHD_Response’ object is allocated: struct MHD_Response * response = MHD_create_response_from_buffer(...); /* here: reference counter = 1 */ 2. the ‘MHD_Response’ object is enqueued in a ‘MHD_Connection’: MHD_queue_response(connection, , response); /* here: reference counter = 2 */ 3. the creator of the response object discharges responsibility for it: MHD_destroy_response(response); /* here: reference counter = 1 */ 4. the daemon handles the connection sending the response’s data to the client then decrements the reference counter by calling ‘MHD_destroy_response()’: the counter’s value drops to zero and the ‘MHD_Response’ object is released. ---------- Footnotes ---------- (1) Note to readers acquainted to the Tcl API: reference counting on ‘MHD_Connection’ structures is handled in the same way as Tcl handles ‘Tcl_Obj’ structures through ‘Tcl_IncrRefCount()’ and ‘Tcl_DecrRefCount()’. 8.2 Creating a response object ============================== -- Function: struct MHD_Response * MHD_create_response_from_callback (uint64_t size, size_t block_size, MHD_ContentReaderCallback crc, void *crc_cls, MHD_ContentReaderFreeCallback crfc) Create a response object. The response object can be extended with header information and then it can be used any number of times. SIZE size of the data portion of the response, ‘-1’ for unknown; BLOCK_SIZE preferred block size for querying CRC (advisory only, MHD may still call CRC using smaller chunks); this is essentially the buffer size used for IO, clients should pick a value that is appropriate for IO and memory performance requirements; CRC callback to use to obtain response data; CRC_CLS extra argument to CRC; CRFC callback to call to free CRC_CLS resources. Return ‘NULL’ on error (i.e. invalid arguments, out of memory). -- Function: struct MHD_Response * MHD_create_response_from_fd (uint64_t size, int fd) Create a response object. The response object can be extended with header information and then it can be used any number of times. SIZE size of the data portion of the response (should be smaller or equal to the size of the file) FD file descriptor referring to a file on disk with the data; will be closed when response is destroyed; note that ’fd’ must be an actual file descriptor (not a pipe or socket) since MHD might use ’sendfile’ or ’seek’ on it. The descriptor should be in blocking-IO mode. Return ‘NULL’ on error (i.e. invalid arguments, out of memory). -- Function: struct MHD_Response * MHD_create_response_from_pipe (uint64_t size, int fd) Create a response object. The response object can be extended with header information and then it can be used ONLY ONCE. FD file descriptor of the read-end of the pipe; will be closed when response is destroyed. The descriptor should be in blocking-IO mode. Return ‘NULL’ on error (i.e. out of memory). -- Function: struct MHD_Response * MHD_create_response_from_fd_at_offset (size_t size, int fd, off_t offset) Create a response object. The response object can be extended with header information and then it can be used any number of times. Note that you need to be a bit careful about ‘off_t’ when writing this code. Depending on your platform, MHD is likely to have been compiled with support for 64-bit files. When you compile your own application, you must make sure that ‘off_t’ is also a 64-bit value. If not, your compiler may pass a 32-bit value as ‘off_t’, which will result in 32-bits of garbage. If you use the autotools, use the ‘AC_SYS_LARGEFILE’ autoconf macro and make sure to include the generated ‘config.h’ file before ‘microhttpd.h’ to avoid problems. If you do not have a build system and only want to run on a GNU/Linux system, you could also use #define _FILE_OFFSET_BITS 64 #include #include #include #include to ensure 64-bit ‘off_t’. Note that if your operating system does not support 64-bit files, MHD will be compiled with a 32-bit ‘off_t’ (in which case the above would be wrong). SIZE size of the data portion of the response (number of bytes to transmit from the file starting at offset). FD file descriptor referring to a file on disk with the data; will be closed when response is destroyed; note that ’fd’ must be an actual file descriptor (not a pipe or socket) since MHD might use ’sendfile’ or ’seek’ on it. The descriptor should be in blocking-IO mode. OFFSET offset to start reading from in the file Return ‘NULL’ on error (i.e. invalid arguments, out of memory). -- Function: struct MHD_Response * MHD_create_response_from_buffer (size_t size, void *data, enum MHD_ResponseMemoryMode mode) Create a response object. The response object can be extended with header information and then it can be used any number of times. SIZE size of the data portion of the response; BUFFER the data itself; MODE memory management options for buffer; use MHD_RESPMEM_PERSISTENT if the buffer is static/global memory, use MHD_RESPMEM_MUST_FREE if the buffer is heap-allocated and should be freed by MHD and MHD_RESPMEM_MUST_COPY if the buffer is in transient memory (i.e. on the stack) and must be copied by MHD; Return ‘NULL’ on error (i.e. invalid arguments, out of memory). -- Function: struct MHD_Response * MHD_create_response_from_buffer_with_free_callback (size_t size, void *data, MHD_ContentReaderFreeCallback crfc) Create a response object. The buffer at the end must be free’d by calling the CRFC function. SIZE size of the data portion of the response; BUFFER the data itself; CRFC function to call at the end to free memory allocated at BUFFER. Return ‘NULL’ on error (i.e. invalid arguments, out of memory). -- Function: struct MHD_Response * MHD_create_response_from_data (size_t size, void *data, int must_free, int must_copy) Create a response object. The response object can be extended with header information and then it can be used any number of times. This function is deprecated, use ‘MHD_create_response_from_buffer’ instead. SIZE size of the data portion of the response; DATA the data itself; MUST_FREE if true: MHD should free data when done; MUST_COPY if true: MHD allocates a block of memory and use it to make a copy of DATA embedded in the returned ‘MHD_Response’ structure; handling of the embedded memory is responsibility of MHD; DATA can be released anytime after this call returns. Return ‘NULL’ on error (i.e. invalid arguments, out of memory). Example: create a response from a statically allocated string: const char * data = "

Error!

"; struct MHD_Connection * connection = ...; struct MHD_Response * response; response = MHD_create_response_from_buffer (strlen(data), data, MHD_RESPMEM_PERSISTENT); MHD_queue_response(connection, 404, response); MHD_destroy_response(response); 8.3 Adding headers to a response ================================ -- Function: enum MHD_Result MHD_add_response_header (struct MHD_Response *response, const char *header, const char *content) Add a header line to the response. The strings referenced by HEADER and CONTENT must be zero-terminated and they are duplicated into memory blocks embedded in RESPONSE. Notice that the strings must not hold newlines, carriage returns or tab chars. MHD_add_response_header() prevents applications from setting a “Transfer-Encoding” header to values other than “identity” or “chunked” as other transfer encodings are not supported by MHD. Note that usually MHD will pick the transfer encoding correctly automatically, but applications can use the header to force a particular behavior. MHD_add_response_header() also prevents applications from setting a “Content-Length” header. MHD will automatically set a correct “Content-Length” header if it is possible and allowed. Return ‘MHD_NO’ on error (i.e. invalid header or content format or memory allocation error). -- Function: enum MHD_Result MHD_add_response_footer (struct MHD_Response *response, const char *footer, const char *content) Add a footer line to the response. The strings referenced by FOOTER and CONTENT must be zero-terminated and they are duplicated into memory blocks embedded in RESPONSE. Notice that the strings must not hold newlines, carriage returns or tab chars. You can add response footers at any time before signalling the end of the response to MHD (not just before calling ’MHD_queue_response’). Footers are useful for adding cryptographic checksums to the reply or to signal errors encountered during data generation. This call was introduced in MHD 0.9.3. Return ‘MHD_NO’ on error (i.e. invalid header or content format or memory allocation error). -- Function: enum MHD_Result MHD_del_response_header (struct MHD_Response *response, const char *header, const char *content) Delete a header (or footer) line from the response. Return ‘MHD_NO’ on error (arguments are invalid or no such header known). 8.4 Setting response options ============================ -- Function: enum MHD_Result MHD_set_response_options (struct MHD_Response *response, enum MHD_ResponseFlags flags, ...) Set special flags and options for a response. Calling this functions sets the given flags and options for the response. RESPONSE which response should be modified; FLAGS flags to set for the response; Additional arguments are a list of options (type-value pairs, terminated with ‘MHD_RO_END’). It is mandatory to use ‘MHD_RO_END’ as last argument, even when there are no additional arguments. Return ‘MHD_NO’ on error, ‘MHD_YES’ on success. 8.5 Inspecting a response object ================================ -- Function: int MHD_get_response_headers (struct MHD_Response *response, MHD_KeyValueIterator iterator, void *iterator_cls) Get all of the headers added to a response. Invoke the ITERATOR callback for each header in the response, using ITERATOR_CLS as first argument. Return number of entries iterated over. ITERATOR can be ‘NULL’: in this case the function just counts headers. ITERATOR should not modify the its key and value arguments, unless we know what we are doing. -- Function: const char * MHD_get_response_header (struct MHD_Response *response, const char *key) Find and return a pointer to the value of a particular header from the response. KEY must reference a zero-terminated string representing the header to look for. The search is case sensitive. Return ‘NULL’ if header does not exist or KEY is ‘NULL’. We should not modify the value, unless we know what we are doing. 8.6 Creating a response for protocol upgrades ============================================= With RFC 2817 a mechanism to switch protocols within HTTP was introduced. Here, a client sends a request with a “Connection: Upgrade” header. The server responds with a “101 Switching Protocols” response header, after which the two parties begin to speak a different (non-HTTP) protocol over the TCP connection. This mechanism is used for upgrading HTTP 1.1 connections to HTTP2 or HTTPS, as well as for implementing WebSockets. Which protocol upgrade is performed is negotiated between server and client in additional headers, in particular the “Upgrade” header. MHD supports switching protocols using this mechanism only if the ‘MHD_ALLOW_SUSPEND_RESUME’ flag has been set when starting the daemon. If this flag has been set, applications can upgrade a connection by queueing a response (using the ‘MHD_HTTP_SWITCHING_PROTOCOLS’ status code) which must have been created with the following function: -- Function: enum MHD_Result MHD_create_response_for_upgrade (MHD_UpgradeHandler upgrade_handler, void *upgrade_handler_cls) Create a response suitable for switching protocols. Returns ‘MHD_YES’ on success. ‘upgrade_handler’ must not be ‘NULL’. When creating this type of response, the “Connection: Upgrade” header will be set automatically for you. MHD requires that you additionally set an “Upgrade:” header. The “Upgrade” header must simply exist, the specific value is completely up to the application. The ‘upgrade_handler’ argument to the above has the following type: -- Function Pointer: void *MHD_UpgradeHandler (void *cls, struct MHD_Connection *connection, const char *extra_in, size_t extra_in_size, MHD_socket sock, struct MHD_UpgradeResponseHandle *urh) This function will be called once MHD has transmitted the header of the response to the connection that is being upgraded. At this point, the application is expected to take over the socket ‘sock’ and speak the non-HTTP protocol to which the connection was upgraded. MHD will no longer use the socket; this includes handling timeouts. The application must call ‘MHD_upgrade_action’ with an upgrade action of ‘MHD_UPGRADE_ACTION_CLOSE’ when it is done processing the connection to close the socket. The application must not call ‘MHD_stop_daemon’ on the respective daemon as long as it is still handling the connection. The arguments given to the ‘upgrade_handler’ have the following meaning: CLS matches the ‘upgrade_handler_cls’ that was given to ‘MHD_create_response_for_upgrade’ CONNECTION identifies the connection that is being upgraded; CON_CLS last value left in ‘*con_cls‘ in the ‘MHD_AccessHandlerCallback‘ EXTRA_IN buffer of bytes MHD read “by accident” from the socket already. This can happen if the client eagerly transmits more than just the HTTP request. The application should treat these as if it had read them from the socket. EXTRA_IN_SIZE number of bytes in ‘extra_in’ SOCK the socket which the application can now use directly for some bi-directional communication with the client. The application can henceforth use ‘recv()’ and ‘send()’ or ‘read()’ and ‘write()’ system calls on the socket. However, ‘ioctl()’ and ‘setsockopt()’ functions will not work as expected when using HTTPS. Such operations may be supported in the future via ‘MHD_upgrade_action’. Most importantly, the application must never call ‘close()’ on this socket. Closing the socket must be done using ‘MHD_upgrade_action’. However, while close is forbidden, the application may call ‘shutdown()’ on the socket. URH argument for calls to ‘MHD_upgrade_action’. Applications must eventually use this function to perform the ‘close()’ action on the socket. -- Function: enum MHD_Result MHD_upgrade_action (struct MHD_UpgradeResponseHandle *urh, enum MHD_UpgradeAction action, ...) Perform special operations related to upgraded connections. URH identifies the upgraded connection to perform an action on ACTION specifies the action to perform; further arguments to the function depend on the specifics of the action. -- Enumeration: MHD_UpgradeAction Set of actions to be performed on upgraded connections. Passed as an argument to ‘MHD_upgrade_action()’. ‘MHD_UPGRADE_ACTION_CLOSE’ Closes the connection. Must be called once the application is done with the client. Takes no additional arguments. ‘MHD_UPGRADE_ACTION_CORK_ON’ Enable corking on the underlying socket. ‘MHD_UPGRADE_ACTION_CORK_OFF’ Disable corking on the underlying socket. 9 Flow control. *************** Sometimes it may be possible that clients upload data faster than an application can process it, or that an application needs an extended period of time to generate a response. If ‘MHD_USE_THREAD_PER_CONNECTION’ is used, applications can simply deal with this by performing their logic within the thread and thus effectively blocking connection processing by MHD. In all other modes, blocking logic must not be placed within the callbacks invoked by MHD as this would also block processing of other requests, as a single thread may be responsible for tens of thousands of connections. Instead, applications using thread modes other than ‘MHD_USE_THREAD_PER_CONNECTION’ should use the following functions to perform flow control. -- Function: enum MHD_Result MHD_suspend_connection (struct MHD_Connection *connection) Suspend handling of network data for a given connection. This can be used to dequeue a connection from MHD’s event loop (external select, internal select or thread pool; not applicable to thread-per-connection!) for a while. If you use this API in conjunction with a internal select or a thread pool, you must set the option ‘MHD_ALLOW_SUSPEND_RESUME’ to ensure that a resumed connection is immediately processed by MHD. Suspended connections continue to count against the total number of connections allowed (per daemon, as well as per IP, if such limits are set). Suspended connections will NOT time out; timeouts will restart when the connection handling is resumed. While a connection is suspended, MHD will not detect disconnects by the client. The only safe time to suspend a connection is from the ‘MHD_AccessHandlerCallback’ or from the respective ‘MHD_ContentReaderCallback’ (but in this case the response object must not be shared among multiple connections). Finally, it is an API violation to call ‘MHD_stop_daemon’ while having suspended connections (this will at least create memory and socket leaks or lead to undefined behavior). You must explicitly resume all connections before stopping the daemon. CONNECTION the connection to suspend -- Function: enum MHD_Result MHD_resume_connection (struct MHD_Connection *connection) Resume handling of network data for suspended connection. It is safe to resume a suspended connection at any time. Calling this function on a connection that was not previously suspended will result in undefined behavior. If you are using this function in “external” select mode, you must make sure to run ‘MHD_run’ afterwards (before again calling ‘MHD_get_fdset’), as otherwise the change may not be reflected in the set returned by ‘MHD_get_fdset’ and you may end up with a connection that is stuck until the next network activity. You can check whether a connection is currently suspended using ‘MHD_get_connection_info’ by querying for ‘MHD_CONNECTION_INFO_CONNECTION_SUSPENDED’. CONNECTION the connection to resume 10 Utilizing Authentication *************************** MHD support three types of client authentication. Basic authentication uses a simple authentication method based on BASE64 algorithm. Username and password are exchanged in clear between the client and the server, so this method must only be used for non-sensitive content or when the session is protected with https. When using basic authentication MHD will have access to the clear password, possibly allowing to create a chained authentication toward an external authentication server. Digest authentication uses a one-way authentication method based on MD5 hash algorithm. Only the hash will transit over the network, hence protecting the user password. The nonce will prevent replay attacks. This method is appropriate for general use, especially when https is not used to encrypt the session. Client certificate authentication uses a X.509 certificate from the client. This is the strongest authentication mechanism but it requires the use of HTTPS. Client certificate authentication can be used simultaneously with Basic or Digest Authentication in order to provide a two levels authentication (like for instance separate machine and user authentication). A code example for using client certificates is presented in the MHD tutorial. 10.1 Using Basic Authentication =============================== -- Function: void MHD_free (void *ptr) Free the memory given at ‘ptr’. Used to free data structures allocated by MHD. Calls ‘free(ptr)’. -- Function: char * MHD_basic_auth_get_username_password (struct MHD_Connection *connection, char** password) Get the username and password from the basic authorization header sent by the client. Return ‘NULL’ if no username could be found, a pointer to the username if found. If returned value is not ‘NULL’, the value must be ‘MHD_free()’’ed. PASSWORD reference a buffer to store the password. It can be ‘NULL’. If returned value is not ‘NULL’, the value must be ‘MHD_free()’’ed. -- Function: enum MHD_Result MHD_queue_basic_auth_fail_response (struct MHD_Connection *connection, const char *realm, struct MHD_Response *response) Queues a response to request basic authentication from the client. Return ‘MHD_YES’ if successful, otherwise ‘MHD_NO’. REALM must reference to a zero-terminated string representing the realm. RESPONSE a response structure to specify what shall be presented to the client with a 401 HTTP status. 10.2 Using Digest Authentication ================================ MHD supports MD5 (deprecated by IETF) and SHA-256 hash algorithms for digest authentication. The ‘MHD_DigestAuthAlgorithm’ enumeration is used to specify which algorithm should be used. -- Enumeration: MHD_DigestAuthAlgorithm Which digest algorithm should be used. Must be used consistently. ‘MHD_DIGEST_ALG_AUTO’ Have MHD pick an algorithm currently considered secure. For now defaults to SHA-256. ‘MHD_DIGEST_ALG_MD5’ Force use of (deprecated, ancient, insecure) MD5. ‘MHD_DIGEST_ALG_SHA256’ Force use of SHA-256. -- Function: char * MHD_digest_auth_get_username (struct MHD_Connection *connection) Find and return a pointer to the username value from the request header. Return ‘NULL’ if the value is not found or header does not exist. If returned value is not ‘NULL’, the value must be ‘MHD_free()’’ed. -- Function: int MHD_digest_auth_check2 (struct MHD_Connection *connection, const char *realm, const char *username, const char *password, unsigned int nonce_timeout, enum MHD_DigestAuthAlgorithm algo) Checks if the provided values in the WWW-Authenticate header are valid and sound according to RFC2716. If valid return ‘MHD_YES’, otherwise return ‘MHD_NO’. REALM must reference to a zero-terminated string representing the realm. USERNAME must reference to a zero-terminated string representing the username, it is usually the returned value from MHD_digest_auth_get_username. PASSWORD must reference to a zero-terminated string representing the password, most probably it will be the result of a lookup of the username against a local database. NONCE_TIMEOUT is the amount of time in seconds for a nonce to be invalid. Most of the time it is sound to specify 300 seconds as its values. ALGO which digest algorithm should we use. -- Function: int MHD_digest_auth_check (struct MHD_Connection *connection, const char *realm, const char *username, const char *password, unsigned int nonce_timeout) Checks if the provided values in the WWW-Authenticate header are valid and sound according to RFC2716. If valid return ‘MHD_YES’, otherwise return ‘MHD_NO’. Deprecated, use ‘MHD_digest_auth_check2’ instead. REALM must reference to a zero-terminated string representing the realm. USERNAME must reference to a zero-terminated string representing the username, it is usually the returned value from MHD_digest_auth_get_username. PASSWORD must reference to a zero-terminated string representing the password, most probably it will be the result of a lookup of the username against a local database. NONCE_TIMEOUT is the amount of time in seconds for a nonce to be invalid. Most of the time it is sound to specify 300 seconds as its values. -- Function: int MHD_digest_auth_check_digest2 (struct MHD_Connection *connection, const char *realm, const char *username, const uint8_t *digest, unsigned int nonce_timeout, enum MHD_DigestAuthAlgorithm algo) Checks if the provided values in the WWW-Authenticate header are valid and sound according to RFC2716. If valid return ‘MHD_YES’, otherwise return ‘MHD_NO’. REALM must reference to a zero-terminated string representing the realm. USERNAME must reference to a zero-terminated string representing the username, it is usually the returned value from MHD_digest_auth_get_username. DIGEST pointer to the binary MD5 sum for the precalculated hash value “userame:realm:password”. The size must match the selected ALGO! NONCE_TIMEOUT is the amount of time in seconds for a nonce to be invalid. Most of the time it is sound to specify 300 seconds as its values. ALGO digest authentication algorithm to use. -- Function: int MHD_digest_auth_check_digest (struct MHD_Connection *connection, const char *realm, const char *username, const unsigned char digest[MHD_MD5_DIGEST_SIZE], unsigned int nonce_timeout) Checks if the provided values in the WWW-Authenticate header are valid and sound according to RFC2716. If valid return ‘MHD_YES’, otherwise return ‘MHD_NO’. Deprecated, use ‘MHD_digest_auth_check_digest2’ instead. REALM must reference to a zero-terminated string representing the realm. USERNAME must reference to a zero-terminated string representing the username, it is usually the returned value from MHD_digest_auth_get_username. DIGEST pointer to the binary MD5 sum for the precalculated hash value “userame:realm:password” of ‘MHD_MD5_DIGEST_SIZE’ bytes. NONCE_TIMEOUT is the amount of time in seconds for a nonce to be invalid. Most of the time it is sound to specify 300 seconds as its values. -- Function: enum MHD_Result MHD_queue_auth_fail_response2 (struct MHD_Connection *connection, const char *realm, const char *opaque, struct MHD_Response *response, int signal_stale, enum MHD_DigestAuthAlgorithm algo) Queues a response to request authentication from the client, return ‘MHD_YES’ if successful, otherwise ‘MHD_NO’. REALM must reference to a zero-terminated string representing the realm. OPAQUE must reference to a zero-terminated string representing a value that gets passed to the client and expected to be passed again to the server as-is. This value can be a hexadecimal or base64 string. RESPONSE a response structure to specify what shall be presented to the client with a 401 HTTP status. SIGNAL_STALE a value that signals "stale=true" in the response header to indicate the invalidity of the nonce and no need to ask for authentication parameters and only a new nonce gets generated. ‘MHD_YES’ to generate a new nonce, ‘MHD_NO’ to ask for authentication parameters. ALGO which digest algorithm should we use. The same algorithm must then be selected when checking digests received from clients! -- Function: enum MHD_Result MHD_queue_auth_fail_response (struct MHD_Connection *connection, const char *realm, const char *opaque, struct MHD_Response *response, int signal_stale) Queues a response to request authentication from the client, return ‘MHD_YES’ if successful, otherwise ‘MHD_NO’. REALM must reference to a zero-terminated string representing the realm. OPAQUE must reference to a zero-terminated string representing a value that gets passed to the client and expected to be passed again to the server as-is. This value can be a hexadecimal or base64 string. RESPONSE a response structure to specify what shall be presented to the client with a 401 HTTP status. SIGNAL_STALE a value that signals "stale=true" in the response header to indicate the invalidity of the nonce and no need to ask for authentication parameters and only a new nonce gets generated. ‘MHD_YES’ to generate a new nonce, ‘MHD_NO’ to ask for authentication parameters. Example: handling digest authentication requests and responses. #define PAGE "libmicrohttpd demoAccess granted" #define DENIED "libmicrohttpd demoAccess denied" #define OPAQUE "11733b200778ce33060f31c9af70a870ba96ddd4" static int ahc_echo (void *cls, struct MHD_Connection *connection, const char *url, const char *method, const char *version, const char *upload_data, size_t *upload_data_size, void **ptr) { struct MHD_Response *response; char *username; const char *password = "testpass"; const char *realm = "test@example.com"; int ret; username = MHD_digest_auth_get_username (connection); if (username == NULL) { response = MHD_create_response_from_buffer(strlen (DENIED), DENIED, MHD_RESPMEM_PERSISTENT); ret = MHD_queue_auth_fail_response2 (connection, realm, OPAQUE, response, MHD_NO, MHD_DIGEST_ALG_SHA256); MHD_destroy_response(response); return ret; } ret = MHD_digest_auth_check2 (connection, realm, username, password, 300, MHD_DIGEST_ALG_SHA256); free(username); if ( (ret == MHD_INVALID_NONCE) || (ret == MHD_NO) ) { response = MHD_create_response_from_buffer(strlen (DENIED), DENIED, MHD_RESPMEM_PERSISTENT); if (NULL == response) return MHD_NO; ret = MHD_queue_auth_fail_response2 (connection, realm, OPAQUE, response, (ret == MHD_INVALID_NONCE) ? MHD_YES : MHD_NO, MHD_DIGEST_ALG_SHA256); MHD_destroy_response(response); return ret; } response = MHD_create_response_from_buffer (strlen(PAGE), PAGE, MHD_RESPMEM_PERSISTENT); ret = MHD_queue_response (connection, MHD_HTTP_OK, response); MHD_destroy_response(response); return ret; } 11 Adding a ‘POST’ processor **************************** MHD provides the post processor API to make it easier for applications to parse the data of a client’s ‘POST’ request: the ‘MHD_AccessHandlerCallback’ will be invoked multiple times to process data as it arrives; at each invocation a new chunk of data must be processed. The arguments UPLOAD_DATA and UPLOAD_DATA_SIZE are used to reference the chunk of data. When ‘MHD_AccessHandlerCallback’ is invoked for a new connection: its ‘*CON_CLS’ argument is set to ‘NULL’. When ‘POST’ data comes in the upload buffer it is *mandatory* to use the CON_CLS to store a reference to per-connection data. The fact that the pointer was initially ‘NULL’ can be used to detect that this is a new request. One method to detect that a new connection was established is to set ‘*con_cls’ to an unused integer: int access_handler (void *cls, struct MHD_Connection * connection, const char *url, const char *method, const char *version, const char *upload_data, size_t *upload_data_size, void **con_cls) { static int old_connection_marker; int new_connection = (NULL == *con_cls); if (new_connection) { /* new connection with POST */ *con_cls = &old_connection_marker; } ... } In contrast to the previous example, for ‘POST’ requests in particular, it is more common to use the value of ‘*con_cls’ to keep track of actual state used during processing, such as the post processor (or a struct containing a post processor): int access_handler (void *cls, struct MHD_Connection * connection, const char *url, const char *method, const char *version, const char *upload_data, size_t *upload_data_size, void **con_cls) { struct MHD_PostProcessor * pp = *con_cls; if (pp == NULL) { pp = MHD_create_post_processor(connection, ...); *con_cls = pp; return MHD_YES; } if (*upload_data_size) { MHD_post_process(pp, upload_data, *upload_data_size); *upload_data_size = 0; return MHD_YES; } else { MHD_destroy_post_processor(pp); return MHD_queue_response(...); } } Note that the callback from ‘MHD_OPTION_NOTIFY_COMPLETED’ should be used to destroy the post processor. This cannot be done inside of the access handler since the connection may not always terminate normally. 11.1 Programming interface for the ‘POST’ processor =================================================== -- Function: struct MHD_PostProcessor * MHD_create_post_processor (struct MHD_Connection *connection, size_t buffer_size, MHD_PostDataIterator iterator, void *iterator_cls) Create a PostProcessor. A PostProcessor can be used to (incrementally) parse the data portion of a ‘POST’ request. CONNECTION the connection on which the ‘POST’ is happening (used to determine the ‘POST’ format); BUFFER_SIZE maximum number of bytes to use for internal buffering (used only for the parsing, specifically the parsing of the keys). A tiny value (256-1024) should be sufficient; do *NOT* use a value smaller than 256; for good performance, use 32k or 64k (i.e. 65536). ITERATOR iterator to be called with the parsed data; must *NOT* be ‘NULL’; ITERATOR_CLS custom value to be used as first argument to ITERATOR. Return ‘NULL’ on error (out of memory, unsupported encoding), otherwise a PP handle. -- Function: enum MHD_Result MHD_post_process (struct MHD_PostProcessor *pp, const char *post_data, size_t post_data_len) Parse and process ‘POST’ data. Call this function when ‘POST’ data is available (usually during an ‘MHD_AccessHandlerCallback’) with the UPLOAD_DATA and UPLOAD_DATA_SIZE. Whenever possible, this will then cause calls to the ‘MHD_IncrementalKeyValueIterator’. PP the post processor; POST_DATA POST_DATA_LEN bytes of ‘POST’ data; POST_DATA_LEN length of POST_DATA. Return ‘MHD_YES’ on success, ‘MHD_NO’ on error (out-of-memory, iterator aborted, parse error). -- Function: enum MHD_Result MHD_destroy_post_processor (struct MHD_PostProcessor *pp) Release PostProcessor resources. After this function is being called, the PostProcessor is guaranteed to no longer call its iterator. There is no special call to the iterator to indicate the end of the post processing stream. After destroying the PostProcessor, the programmer should perform any necessary work to complete the processing of the iterator. Return ‘MHD_YES’ if processing completed nicely, ‘MHD_NO’ if there were spurious characters or formatting problems with the post request. It is common to ignore the return value of this function. 12 Obtaining and modifying status information. ********************************************** 12.1 Obtaining state information about an MHD daemon ==================================================== -- Function: const union MHD_DaemonInfo * MHD_get_daemon_info (struct MHD_Daemon *daemon, enum MHD_DaemonInfoType infoType, ...) Obtain information about the given daemon. This function is currently not fully implemented. DAEMON the daemon about which information is desired; INFOTYPE type of information that is desired ... additional arguments about the desired information (depending on infoType) Returns a union with the respective member (depending on infoType) set to the desired information), or ‘NULL’ in case the desired information is not available or applicable. -- Enumeration: MHD_DaemonInfoType Values of this enum are used to specify what information about a daemon is desired. ‘MHD_DAEMON_INFO_KEY_SIZE’ Request information about the key size for a particular cipher algorithm. The cipher algorithm should be passed as an extra argument (of type ’enum MHD_GNUTLS_CipherAlgorithm’). No longer supported, using this value will cause ‘MHD_get_daemon_info’ to return NULL. ‘MHD_DAEMON_INFO_MAC_KEY_SIZE’ Request information about the key size for a particular cipher algorithm. The cipher algorithm should be passed as an extra argument (of type ’enum MHD_GNUTLS_HashAlgorithm’). No longer supported, using this value will cause ‘MHD_get_daemon_info’ to return NULL. ‘MHD_DAEMON_INFO_LISTEN_FD’ Request the file-descriptor number that MHD is using to listen to the server socket. This can be useful if no port was specified and a client needs to learn what port is actually being used by MHD. No extra arguments should be passed. ‘MHD_DAEMON_INFO_EPOLL_FD’ Request the file-descriptor number that MHD is using for epoll. If the build is not supporting epoll, NULL is returned; if we are using a thread pool or this daemon was not started with ‘MHD_USE_EPOLL’, (a pointer to) -1 is returned. If we are using ‘MHD_USE_INTERNAL_POLLING_THREAD’ or are in ’external’ select mode, the internal epoll FD is returned. This function must be used in external select mode with epoll to obtain the FD to call epoll on. No extra arguments should be passed. ‘MHD_DAEMON_INFO_CURRENT_CONNECTIONS’ Request the number of current connections handled by the daemon. No extra arguments should be passed and a pointer to a ‘union MHD_DaemonInfo’ value is returned, with the ‘num_connections’ member of type ‘unsigned int’ set to the number of active connections. Note that in multi-threaded or internal-select mode, the real number of current connections may already be different when ‘MHD_get_daemon_info’ returns. The number of current connections can be used (even in multi-threaded and internal-select mode) after ‘MHD_quiesce_daemon’ to detect whether all connections have been handled. 12.2 Obtaining state information about a connection =================================================== -- Function: const union MHD_ConnectionInfo * MHD_get_connection_info (struct MHD_Connection *connection, enum MHD_ConnectionInfoType infoType, ...) Obtain information about the given connection. CONNECTION the connection about which information is desired; INFOTYPE type of information that is desired ... additional arguments about the desired information (depending on infoType) Returns a union with the respective member (depending on infoType) set to the desired information), or ‘NULL’ in case the desired information is not available or applicable. -- Enumeration: MHD_ConnectionInfoType Values of this enum are used to specify what information about a connection is desired. ‘MHD_CONNECTION_INFO_CIPHER_ALGO’ What cipher algorithm is being used (HTTPS connections only). ‘NULL’ is returned for non-HTTPS connections. Takes no extra arguments. ‘MHD_CONNECTION_INFO_PROTOCOL,’ Allows finding out the TLS/SSL protocol used (HTTPS connections only). ‘NULL’ is returned for non-HTTPS connections. Takes no extra arguments. ‘MHD_CONNECTION_INFO_CLIENT_ADDRESS’ Returns information about the address of the client. Returns essentially a ‘struct sockaddr **’ (since the API returns a ‘union MHD_ConnectionInfo *’ and that union contains a ‘struct sockaddr *’). Takes no extra arguments. ‘MHD_CONNECTION_INFO_GNUTLS_SESSION,’ Takes no extra arguments. Allows access to the underlying GNUtls session, including access to the underlying GNUtls client certificate (HTTPS connections only). Takes no extra arguments. ‘NULL’ is returned for non-HTTPS connections. Takes no extra arguments. ‘MHD_CONNECTION_INFO_GNUTLS_CLIENT_CERT,’ Dysfunctional (never implemented, deprecated). Use MHD_CONNECTION_INFO_GNUTLS_SESSION to get the ‘gnutls_session_t’ and then call ‘gnutls_certificate_get_peers()’. ‘MHD_CONNECTION_INFO_DAEMON’ Returns information about ‘struct MHD_Daemon’ which manages this connection. Takes no extra arguments. ‘MHD_CONNECTION_INFO_CONNECTION_FD’ Returns the file descriptor (usually a TCP socket) associated with this connection (in the “connect-fd” member of the returned struct). Note that manipulating the descriptor directly can have problematic consequences (as in, break HTTP). Applications might use this access to manipulate TCP options, for example to set the “TCP-NODELAY” option for COMET-like applications. Note that MHD will set TCP-CORK after sending the HTTP header and clear it after finishing the footers automatically (if the platform supports it). As the connection callbacks are invoked in between, those might be used to set different values for TCP-CORK and TCP-NODELAY in the meantime. Takes no extra arguments. ‘MHD_CONNECTION_INFO_CONNECTION_SUSPENDED’ Returns pointer to an integer that is ‘MHD_YES’ if the connection is currently suspended (and thus can be safely resumed) and ‘MHD_NO’ otherwise. Takes no extra arguments. ‘MHD_CONNECTION_INFO_SOCKET_CONTEXT’ Returns the client-specific pointer to a ‘void *’ that was (possibly) set during a ‘MHD_NotifyConnectionCallback’ when the socket was first accepted. Note that this is NOT the same as the ‘con_cls’ argument of the ‘MHD_AccessHandlerCallback’. The ‘con_cls’ is fresh for each HTTP request, while the ‘socket_context’ is fresh for each socket. Takes no extra arguments. ‘MHD_CONNECTION_INFO_CONNECTION_TIMEOUT’ Returns pointer to an ‘unsigned int’ that is the current timeout used for the connection (in seconds, 0 for no timeout). Note that while suspended connections will not timeout, the timeout value returned for suspended connections will be the timeout that the connection will use after it is resumed, and thus might not be zero. Takes no extra arguments. ‘MHD_CONNECTION_INFO_REQUEST_HEADER_SIZE’ Returns pointer to an ‘size_t’ that represents the size of the HTTP header received from the client. Only valid after the first callback to the access handler. Takes no extra arguments. 12.3 Setting custom options for an individual connection ======================================================== -- Function: int MHD_set_connection_option (struct MHD_Connection *daemon, enum MHD_CONNECTION_OPTION option, ...) Set a custom option for the given connection. CONNECTION the connection for which an option should be set or modified; OPTION option to set ... additional arguments for the option (depending on option) Returns ‘MHD_YES’ on success, ‘MHD_NO’ for errors (i.e. option argument invalid or option unknown). -- Enumeration: MHD_CONNECTION_OPTION Values of this enum are used to specify which option for a connection should be changed. ‘MHD_CONNECTION_OPTION_TIMEOUT’ Set a custom timeout for the given connection. Specified as the number of seconds, given as an ‘unsigned int’. Use zero for no timeout. 13 Utility functions. ********************* 13.1 Testing for supported MHD features ======================================= -- Enumeration: MHD_FEATURE Values of this enum are used to specify what information about a daemon is desired. ‘MHD_FEATURE_MESSAGES’ Get whether messages are supported. If supported then in debug mode messages can be printed to stderr or to external logger. ‘MHD_FEATURE_SSL’ Get whether HTTPS is supported. If supported then flag MHD_USE_SSL and options MHD_OPTION_HTTPS_MEM_KEY, MHD_OPTION_HTTPS_MEM_CERT, MHD_OPTION_HTTPS_MEM_TRUST, MHD_OPTION_HTTPS_MEM_DHPARAMS, MHD_OPTION_HTTPS_CRED_TYPE, MHD_OPTION_HTTPS_PRIORITIES can be used. ‘MHD_FEATURE_HTTPS_CERT_CALLBACK’ Get whether option #MHD_OPTION_HTTPS_CERT_CALLBACK is supported. ‘MHD_FEATURE_IPv6’ Get whether IPv6 is supported. If supported then flag MHD_USE_IPv6 can be used. ‘MHD_FEATURE_IPv6_ONLY’ Get whether IPv6 without IPv4 is supported. If not supported then IPv4 is always enabled in IPv6 sockets and flag MHD_USE_DUAL_STACK if always used when MHD_USE_IPv6 is specified. ‘MHD_FEATURE_POLL’ Get whether ‘poll()’ is supported. If supported then flag MHD_USE_POLL can be used. ‘MHD_FEATURE_EPOLL’ Get whether ‘epoll()’ is supported. If supported then Flags MHD_USE_EPOLL and MHD_USE_EPOLL_INTERNAL_THREAD can be used. ‘MHD_FEATURE_SHUTDOWN_LISTEN_SOCKET’ Get whether shutdown on listen socket to signal other threads is supported. If not supported flag MHD_USE_ITC is automatically forced. ‘MHD_FEATURE_SOCKETPAIR’ Get whether a ‘socketpair()’ is used internally instead of a ‘pipe()’ to signal other threads. ‘MHD_FEATURE_TCP_FASTOPEN’ Get whether TCP Fast Open is supported. If supported then flag MHD_USE_TCP_FASTOPEN and option MHD_OPTION_TCP_FASTOPEN_QUEUE_SIZE can be used. ‘MHD_FEATURE_BASIC_AUTH’ Get whether HTTP Basic authorization is supported. If supported then functions ‘MHD_basic_auth_get_username_password()’ and ‘MHD_queue_basic_auth_fail_response()’ can be used. ‘MHD_FEATURE_DIGEST_AUTH’ Get whether HTTP Digest authorization is supported. If supported then options MHD_OPTION_DIGEST_AUTH_RANDOM, MHD_OPTION_NONCE_NC_SIZE and functions ‘MHD_digest_auth_check()’, can be used. ‘MHD_FEATURE_POSTPROCESSOR’ Get whether postprocessor is supported. If supported then functions ‘MHD_create_post_processor()’, ‘MHD_post_process()’, ‘MHD_destroy_post_processor()’ can be used. ‘MHD_FEATURE_SENDFILE’ Get whether ‘sendfile()’ is supported. -- Function: int MHD_is_feature_supported (enum MHD_FEATURE feature) Get information about supported MHD features. Indicate that MHD was compiled with or without support for particular feature. Some features require additional support by the kernel. However, kernel support is not checked by this function. FEATURE type of requested information Returns ‘MHD_YES’ if the feature is supported, and ‘MHD_NO’ if not. 13.2 Unescape strings ===================== -- Function: size_t MHD_http_unescape (char *val) Process escape sequences (’%HH’) Updates val in place; the result should be UTF-8 encoded and cannot be larger than the input. The result must also still be 0-terminated. VAL value to unescape (modified in the process), must be a 0-terminated UTF-8 string. Returns length of the resulting val (‘strlen(val)’ may be shorter afterwards due to elimination of escape sequences). GNU-LGPL ******** Version 2.1, February 1999 Copyright © 1991, 1999 Free Software Foundation, Inc. 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. [This is the first released version of the Lesser GPL. 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Any attempt otherwise to copy, modify, sublicense, link with, or distribute the Library is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance. 9. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Library or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Library (or any work based on the Library), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Library or works based on it. 10. Each time you redistribute the Library (or any work based on the Library), the recipient automatically receives a license from the original licensor to copy, distribute, link with or modify the Library subject to these terms and conditions. You may not impose any further restrictions on the recipients’ exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties with this License. 11. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Library at all. For example, if a patent license would not permit royalty-free redistribution of the Library by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Library. If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply, and the section as a whole is intended to apply in other circumstances. It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice. This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License. 12. If the distribution and/or use of the Library is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Library under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License. 13. The Free Software Foundation may publish revised and/or new versions of the Lesser General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Library specifies a version number of this License which applies to it and “any later version”, you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Library does not specify a license version number, you may choose any version ever published by the Free Software Foundation. 14. If you wish to incorporate parts of the Library into other free programs whose distribution conditions are incompatible with these, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. NO WARRANTY 15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE LIBRARY “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE LIBRARY IS WITH YOU. SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 16. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE LIBRARY (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. END OF TERMS AND CONDITIONS --------------------------- How to Apply These Terms to Your New Libraries ---------------------------------------------- If you develop a new library, and you want it to be of the greatest possible use to the public, we recommend making it free software that everyone can redistribute and change. You can do so by permitting redistribution under these terms (or, alternatively, under the terms of the ordinary General Public License). To apply these terms, attach the following notices to the library. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found. ONE LINE TO GIVE THE LIBRARY'S NAME AND AN IDEA OF WHAT IT DOES. Copyright (C) YEAR NAME OF AUTHOR This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. Also add information on how to contact you by electronic and paper mail. You should also get your employer (if you work as a programmer) or your school, if any, to sign a “copyright disclaimer” for the library, if necessary. Here is a sample; alter the names: Yoyodyne, Inc., hereby disclaims all copyright interest in the library `Frob' (a library for tweaking knobs) written by James Random Hacker. SIGNATURE OF TY COON, 1 April 1990 Ty Coon, President of Vice That’s all there is to it! eCos License ************ GNU libmicrohttpd is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 or (at your option) any later version. GNU libmicrohttpd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU libmicrohttpd; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. As a special exception, if other files instantiate templates or use macros or inline functions from this file, or you compile this file and link it with other works to produce a work based on this file, this file does not by itself cause the resulting work to be covered by the GNU General Public License. However the source code for this file must still be made available in accordance with section (3) of the GNU General Public License v2. This exception does not invalidate any other reasons why a work based on this file might be covered by the GNU General Public License. GNU General Public License ************************** Version 2, June 1991 Copyright © 1989, 1991 Free Software Foundation, Inc. 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble ======== The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software—to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation’s software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Lesser General Public License instead.) You can apply it to your programs, too. When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things. To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it. For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights. We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software. Also, for each author’s protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors’ reputations. Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone’s free use or not licensed at all. The precise terms and conditions for copying, distribution and modification follow. TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION =============================================================== 0. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The “Program”, below, refers to any such program or work, and a “work based on the Program” means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term “modification”.) Each licensee is addressed as “you”. Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does. 1. You may copy and distribute verbatim copies of the Program’s source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program. You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee. 2. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions: a. You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change. b. You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License. c. If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.) These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it. Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program. In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License. 3. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following: a. Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or, b. Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or, c. Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.) The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable. If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code. 4. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance. 5. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it. 6. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients’ exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License. 7. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program. If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances. It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice. This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License. 8. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License. 9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and “any later version”, you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation. 10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. NO WARRANTY 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. END OF TERMS AND CONDITIONS Appendix: How to Apply These Terms to Your New Programs ======================================================= If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms. To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found. ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES. Copyright (C) YYYY NAME OF AUTHOR This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. Also add information on how to contact you by electronic and paper mail. If the program is interactive, make it output a short notice like this when it starts in an interactive mode: Gnomovision version 69, Copyright (C) YEAR NAME OF AUTHOR Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details. The hypothetical commands ‘show w’ and ‘show c’ should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than ‘show w’ and ‘show c’; they could even be mouse-clicks or menu items—whatever suits your program. You should also get your employer (if you work as a programmer) or your school, if any, to sign a “copyright disclaimer” for the program, if necessary. Here is a sample; alter the names: Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. SIGNATURE OF TY COON, 1 April 1989 Ty Coon, President of Vice This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. GNU-FDL ******* Version 1.3, 3 November 2008 Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. 0. PREAMBLE The purpose of this License is to make a manual, textbook, or other functional and useful document “free” in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others. This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software. We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference. 1. APPLICABILITY AND DEFINITIONS This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law. A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language. A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them. The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none. The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words. A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”. Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only. The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text. The “publisher” means any person or entity that distributes copies of the Document to the public. A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition. The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License. 2. VERBATIM COPYING You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3. You may also lend copies, under the same conditions stated above, and you may publicly display copies. 3. COPYING IN QUANTITY If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects. If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages. If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public. 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The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing. ADDENDUM: How to use this License for your documents ==================================================== To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: Copyright (C) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''. If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this: with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software. Concept Index ************* * Menu: * ARM: microhttpd-intro. (line 351) * bind, restricting bind: microhttpd-const. (line 719) * bind, restricting bind <1>: microhttpd-const. (line 954) * cipher: microhttpd-const. (line 792) * clock: microhttpd-const. (line 492) * compilation: microhttpd-intro. (line 198) * connection, limiting number of connections: microhttpd-const. (line 596) * connection, limiting number of connections <1>: microhttpd-info daemon. (line 2661) * cookie: microhttpd-const. (line 986) * cortex m3: microhttpd-intro. (line 351) * date: microhttpd-const. (line 492) * debugging: microhttpd-const. (line 418) * debugging <1>: microhttpd-const. (line 730) * deprecated: microhttpd-const. (line 448) * DH: microhttpd-const. (line 946) * digest auth: microhttpd-const. (line 831) * digest auth <1>: microhttpd-const. (line 842) * eCos, GNU General Public License with eCos Extension: eCos License. (line 3447) * embedded systems: microhttpd-intro. (line 198) * embedded systems <1>: microhttpd-intro. (line 351) * embedded systems <2>: microhttpd-const. (line 492) * embedded systems <3>: microhttpd-const. (line 499) * embedded systems <4>: microhttpd-const. (line 930) * epoll: microhttpd-intro. (line 144) * epoll <1>: microhttpd-const. (line 464) * epoll <2>: microhttpd-info daemon. (line 2650) * escaping: microhttpd-const. (line 913) * FD_SETSIZE: microhttpd-const. (line 457) * FD_SETSIZE <1>: microhttpd-const. (line 464) * foreign-function interface: microhttpd-const. (line 891) * HTTP2: microhttpd-response upgrade. (line 1986) * IAR: microhttpd-intro. (line 351) * internationalization: microhttpd-const. (line 913) * IPv6: microhttpd-const. (line 432) * IPv6 <1>: microhttpd-const. (line 442) * license: GNU-LGPL. (line 2925) * license <1>: eCos License. (line 3447) * license <2>: GNU-GPL. (line 3476) * license <3>: GNU-FDL. (line 3834) * listen: microhttpd-const. (line 499) * listen <1>: microhttpd-const. (line 530) * listen <2>: microhttpd-const. (line 936) * listen <3>: microhttpd-info daemon. (line 2644) * logging: microhttpd-const. (line 730) * logging <1>: microhttpd-const. (line 872) * long long: microhttpd-intro. (line 351) * memory: microhttpd-const. (line 588) * memory, limiting memory utilization: microhttpd-const. (line 580) * MHD_LONG_LONG: microhttpd-intro. (line 351) * microhttpd.h: microhttpd-intro. (line 291) * OCSP: microhttpd-const. (line 815) * options: microhttpd-const. (line 891) * performance: microhttpd-intro. (line 168) * performance <1>: microhttpd-const. (line 477) * performance <2>: microhttpd-const. (line 883) * performance <3>: microhttpd-info conn. (line 2785) * poll: microhttpd-intro. (line 144) * poll <1>: microhttpd-const. (line 457) * poll <2>: microhttpd-init. (line 1429) * portability: microhttpd-intro. (line 198) * portability <1>: microhttpd-intro. (line 291) * POST method: microhttpd-const. (line 990) * POST method <1>: microhttpd-struct. (line 1112) * POST method <2>: microhttpd-cb. (line 1165) * POST method <3>: microhttpd-post. (line 2465) * POST method <4>: microhttpd-post api. (line 2542) * proxy: microhttpd-const. (line 499) * PSK: microhttpd-const. (line 825) * pthread: microhttpd-const. (line 930) * PUT method: microhttpd-cb. (line 1165) * query string: microhttpd-const. (line 730) * quiesce: microhttpd-const. (line 506) * quiesce <1>: microhttpd-init. (line 1406) * random: microhttpd-const. (line 831) * replay attack: microhttpd-const. (line 842) * reusing listening address: microhttpd-const. (line 954) * RFC2817: microhttpd-response upgrade. (line 1986) * select: microhttpd-intro. (line 144) * select <1>: microhttpd-const. (line 457) * select <2>: microhttpd-const. (line 464) * select <3>: microhttpd-init. (line 1429) * select <4>: microhttpd-init. (line 1444) * signals: microhttpd-intro. (line 312) * SNI: microhttpd-const. (line 800) * SNI <1>: microhttpd-const. (line 815) * SSL: microhttpd-const. (line 421) * SSL <1>: microhttpd-const. (line 753) * SSL <2>: microhttpd-const. (line 759) * SSL <3>: microhttpd-const. (line 769) * SSL <4>: microhttpd-const. (line 775) * SSL <5>: microhttpd-const. (line 787) * SSL <6>: microhttpd-const. (line 792) * SSL <7>: microhttpd-const. (line 800) * SSL <8>: microhttpd-const. (line 815) * SSL <9>: microhttpd-const. (line 825) * SSL <10>: microhttpd-const. (line 946) * stack: microhttpd-const. (line 930) * systemd: microhttpd-const. (line 865) * testing: microhttpd-const. (line 708) * thread: microhttpd-const. (line 930) * timeout: microhttpd-const. (line 634) * timeout <1>: microhttpd-inspect. (line 1537) * timeout <2>: microhttpd-option conn. (line 2794) * TLS: microhttpd-const. (line 421) * TLS <1>: microhttpd-const. (line 753) * TLS <2>: microhttpd-const. (line 759) * TLS <3>: microhttpd-const. (line 769) * TLS <4>: microhttpd-const. (line 775) * TLS <5>: microhttpd-const. (line 787) * TLS <6>: microhttpd-const. (line 792) * TLS <7>: microhttpd-const. (line 800) * TLS <8>: microhttpd-const. (line 815) * TLS <9>: microhttpd-const. (line 825) * TLS <10>: microhttpd-const. (line 946) * upgrade: microhttpd-const. (line 535) * Upgrade: microhttpd-response upgrade. (line 1986) * WebSockets: microhttpd-response upgrade. (line 1986) Function and Data Index *********************** * Menu: * *MHD_ContentReaderCallback: microhttpd-cb. (line 1267) * *MHD_ContentReaderFreeCallback: microhttpd-cb. (line 1314) * *MHD_RequestCompletedCallback: microhttpd-cb. (line 1213) * *MHD_UpgradeHandler: microhttpd-response upgrade. (line 2017) * MHD_add_connection: microhttpd-init. (line 1470) * MHD_basic_auth_get_username_password: microhttpd-dauth basic. (line 2197) * MHD_create_post_processor: microhttpd-post api. (line 2542) * MHD_create_response_from_buffer: microhttpd-response create. (line 1812) * MHD_create_response_from_buffer_with_free_callback: microhttpd-response create. (line 1833) * MHD_create_response_from_callback: microhttpd-response create. (line 1714) * MHD_create_response_from_data: microhttpd-response create. (line 1851) * MHD_create_response_from_fd: microhttpd-response create. (line 1740) * MHD_create_response_from_fd_at_offset: microhttpd-response create. (line 1770) * MHD_create_response_from_pipe: microhttpd-response create. (line 1758) * MHD_destroy_response: microhttpd-response enqueue. (line 1675) * MHD_digest_auth_check: microhttpd-dauth digest. (line 2272) * MHD_digest_auth_check2: microhttpd-dauth digest. (line 2247) * MHD_digest_auth_check_digest: microhttpd-dauth digest. (line 2320) * MHD_digest_auth_check_digest2: microhttpd-dauth digest. (line 2295) * MHD_digest_auth_get_username: microhttpd-dauth digest. (line 2240) * MHD_free: microhttpd-dauth basic. (line 2193) * MHD_get_connection_info: microhttpd-info conn. (line 2677) * MHD_get_connection_values: microhttpd-requests. (line 1559) * MHD_get_daemon_info: microhttpd-info daemon. (line 2607) * MHD_get_response_header: microhttpd-response inspect. (line 1974) * MHD_get_response_headers: microhttpd-response inspect. (line 1962) * MHD_http_unescape: microhttpd-util unescape. (line 2910) * MHD_is_feature_supported: microhttpd-util feature. (line 2896) * MHD_lookup_connection_value: microhttpd-requests. (line 1611) * MHD_lookup_connection_value_n: microhttpd-requests. (line 1620) * MHD_queue_basic_auth_fail_response: microhttpd-dauth basic. (line 2208) * MHD_quiesce_daemon: microhttpd-init. (line 1405) * MHD_Result: microhttpd-cb. (line 1123) * MHD_Result <1>: microhttpd-cb. (line 1136) * MHD_Result <2>: microhttpd-cb. (line 1233) * MHD_Result <3>: microhttpd-cb. (line 1319) * MHD_Result <4>: microhttpd-init. (line 1425) * MHD_Result <5>: microhttpd-init. (line 1441) * MHD_Result <6>: microhttpd-inspect. (line 1504) * MHD_Result <7>: microhttpd-inspect. (line 1529) * MHD_Result <8>: microhttpd-inspect. (line 1535) * MHD_Result <9>: microhttpd-requests. (line 1588) * MHD_Result <10>: microhttpd-response enqueue. (line 1652) * MHD_Result <11>: microhttpd-response headers. (line 1890) * MHD_Result <12>: microhttpd-response headers. (line 1914) * MHD_Result <13>: microhttpd-response headers. (line 1931) * MHD_Result <14>: microhttpd-response options. (line 1940) * MHD_Result <15>: microhttpd-response upgrade. (line 2003) * MHD_Result <16>: microhttpd-response upgrade. (line 2071) * MHD_Result <17>: microhttpd-flow. (line 2112) * MHD_Result <18>: microhttpd-flow. (line 2143) * MHD_Result <19>: microhttpd-dauth digest. (line 2343) * MHD_Result <20>: microhttpd-dauth digest. (line 2370) * MHD_Result <21>: microhttpd-post api. (line 2569) * MHD_Result <22>: microhttpd-post api. (line 2588) * MHD_set_connection_option: microhttpd-option conn. (line 2794) * MHD_set_panic_func: microhttpd-init. (line 1361) * MHD_start_daemon: microhttpd-init. (line 1373) * MHD_stop_daemon: microhttpd-init. (line 1422) Type Index ********** * Menu: * MHD_Connection: microhttpd-struct. (line 1102) * MHD_ConnectionInfo: microhttpd-struct. (line 1114) * MHD_ConnectionInfoType: microhttpd-info conn. (line 2696) * MHD_CONNECTION_OPTION: microhttpd-option conn. (line 2810) * MHD_Daemon: microhttpd-struct. (line 1099) * MHD_DaemonInfo: microhttpd-struct. (line 1117) * MHD_DaemonInfoType: microhttpd-info daemon. (line 2626) * MHD_DigestAuthAlgorithm: microhttpd-dauth digest. (line 2227) * MHD_FEATURE: microhttpd-util feature. (line 2825) * MHD_FLAG: microhttpd-const. (line 393) * MHD_OPTION: microhttpd-const. (line 571) * MHD_OptionItem: microhttpd-const. (line 965) * MHD_PostProcessor: microhttpd-struct. (line 1111) * MHD_RequestTerminationCode: microhttpd-const. (line 1003) * MHD_Response: microhttpd-struct. (line 1108) * MHD_ResponseFlags: microhttpd-const. (line 1043) * MHD_ResponseMemoryMode: microhttpd-const. (line 1021) * MHD_ResponseOptions: microhttpd-const. (line 1088) * MHD_UpgradeAction: microhttpd-response upgrade. (line 2083) * MHD_ValueKind: microhttpd-const. (line 978)