5.14 Macro Substitution

Some statements in the configuration files need to use the actual values of the attributes supplied with the request. These are:

• Exec-Program and Exec-Program-Wait assignments in `users' database
• SQL query templates in `sqlserver'

In these statements the following macros are replaced by the value of corresponding attributes:

%Cnum

(num is a decimal number). This variable is replaced by the value of attribute number `num'. The attribute is looked up in the incoming request pairlist.

%C{attr-name}

This is replaced by the value of attribute named `attr-name'. The attribute is looked up in the incoming request pairlist.

%Rnum

(num is a decimal number). This variable is replaced by the value of attribute number `num'. The attribute is looked up in the reply pairlist.

%R{attr-name}

This is replaced by the value of attribute named `attr-name'. The attribute is looked up in the reply pairlist.

%D

This is replaced by current date/time (localtime).

%G

This is replaced by current date/time in GMT.

The exact substitution procedure varies depending on the type of the attribute referenced by macro. If the attribute is of string or date type, radiusd first checks if the resulting substitution should be quoted. It does so by looking at the character immediately preceeding `%'. If it is a single or double quote, then radiusd assumes the macro must be quoted and replaces it by an appropriately modified attribute value. The purpose of the modification is to ensure that no characters within the expanded string would conflict with the quoting characters. In particular, radiusd searches the attribute value for any of the characters `\', `'', `"' and prepends a `\' to any occurrence of these. For example, suppose that attribute NAS-Identifier has the value `A "new" host'. Then:

nasid=%C{NAS-Identifier} ==> nasid=A "new" host nasid="%C{NAS-Identifier}" ==> nasid="A \"new\" host" nasid=%\C{NAS-Identifier} ==> nasid=A \"new\" host

The last example illustrates the use of backslash character to force string quoting in the absense of explicit quotation marks.

If an integer attribute reference is quoted, radiusd looks up the string translation of its value in the dictionary (see section 5.2.8 VALUE Statement) and uses this string as a replacement. If no translation is found, the numeric value is used. The following example assumes that the value of Acct-Terminate-Cause attribute is 10:

reason=%C{Acct-Terminate-Cause} ==> reason=10 reason='%C{Acct-Terminate-Cause}' ==> reason='NAS-Request' reason=%\C{Acct-Terminate-Cause} ==> reason=NAS-Request

Again, a backslash after percent sign can be used to force dictionary lookup.

<FIXME> The quoting rules are not flexible enough. For example, a string 'isn't it a string' may be produced, but backslash escape within a singly quoted string is useless in most implementations (e.g. in shell or SQL). Besides, quoting unconditionally replaces unprintable characters with their octal values, where the notion of "unprintable" is determined by the current locale. Is it always the right thing to do? </>

The "`{}' form" allows to specify default value for the substitution. The default value will be used when no such attribute is encountered in the pairlist. The syntax for specifying the default value resembles that of shell environment variables.

The substitution %C{attr-name:-defval} is expanded to the value of attr-name attribute, if it is present in the request pairlist, and to defval otherwise. For example:

%C{Acct-Session-Time:-0}

will return the value of Acct-Session-Time attribute or 0 if it doesn't exist in the request pairlist.

<FIXME> Should the quoting rules apply for defval as well? I'd say they should... </>

The substitution %C{attr-name:=defval} is expanded to the value of attr-name attribute. If this attribute is not present in the request pairlist, it will be created and assigned the value defval. E.g.:

%C{Acct-Session-Time:=0}

The substitution %C{attr-name:?message} is expanded to the value of attr-name attribute, if it is present. Otherwise the diagnostic message "attr-name: message" is issued to the log error channel, and string "message" is returned.

The substitution %C{attr-name:+retval} is expanded to empty string if the attribute attr-name is present in the referenced pairlist. Otherwise it is expanded to retval.

You can also use the following shortcuts:

%p

Port number

%n

NAS IP address

%f

Framed IP address

%u

User name

%c

Callback-Number

%i

Calling-Station-Id

%t

MTU

%a

Protocol (SLIP/PPP)

%s

Speed (Connect-Info attribute)