OpenSER Pseudo-variables for version 1.2.x

Authors of initial tutorial:
Elena-Ramona Modroiu
  <ramona (at) rosdev.ro>
Bogdan-Andrei Iancu
  <bogdan (at) voice-system.ro>
Daniel-Constantin Mierla
  <miconda (at) gmail.com>

The term “pseudo-variable” (short name PV) is used for special tokens that can be given as parameters to different script functions and they will be replaced with a value before the execution of the function.

The beginning of a “pseudo-variable” is marked by the character “$”. If you want to have the character “$” just double it “$$”.

There is a set of predefined pseudo-variables, which have the name composed from one to three letters, and special pseudo-variables that are references to dynamic fields (AVP and Headers).

Starting with OpenSER 1.2.0, you can apply transformations to pseudo-variables – see available transformations in 1.2.x.

Pseudo-variables can be used with many modules of OpenSER, among them:

* acc * avpops * textops * uac * xlog

Predefined pseudo-variables are listed in alphabetical order.

$$ - represents the character '$'

$ai - reference to URI in request's P-Asserted-Identity header (see RFC 3325)

$ar - realm from Authorization or Proxy-Authorization header

$au - username from Authorization or Proxy-Authorization header

$br - reference to request's first branch

$bR - reference to request's all branches

$bf - reference to branch flags of branch 0 (RURI) - decimal output

$bF - reference to branch flags of branch 0 (RURI) - hexa output

$ci - reference to body of call-id header

$cl - reference to body of content-length header

$cs - reference to body of cseq header

$ct - reference to body of contact header

$cT - reference to body of content-type header

$dd - reference to domain of destination uri

$di - reference to Diversion header URI

$dp - reference to port of destination uri

$dP - reference to transport protocol of destination uri

$ds - reference to destination set

$du - reference to destination uri

When is it used?

$du is used when the message must be sent to a destination other than pointed by $ru.

This occurs when using loose_route().
The next-hop destination is dictated by the “Route:” header field of the message >and not by $ru.

In such case $du may look like as follows:
sip:192.168.1.16;lr=on;ftag=012064706ddf1250

(070530) Emin Gabrielyan

$err.class - the class of error (now is '1' for parsing errors)

$err.level - severity level for the error

$err.info - text describing the error

$err.rcode - recommended reply code

$err.rreason - recommended reply reason phrase

$fd - reference to domain in URI of 'From' header

$fn - reference to display name of 'From' header

$ft - reference to tag parameter of 'From' header

$fu - reference to URI of 'From' header

$fU - reference to username in URI of 'From' header

$mb - reference to SIP message buffer

$mf - reference to flags set for current SIP request

$mF -reference to flags set for current SIP request in hexa

$mi - reference to SIP message id

$ml - reference to SIP message length

$od - reference to domain in request's original URI

$op - reference to port of original R-URI

$oP - reference to transport protocol of original R-URI

$ou - reference to request's original URI

$oU - reference to username in request's original URI

$pd - reference to domain in request's P-Preferred-Identity header URI (see RFC 3325)

$pn - reference to Display Name in request's P-Preferred-Identity header (see RFC 3325)

$pp - reference to process id (pid)

$pU - reference to user in request's P-Preferred-Identity header URI (see RFC 3325)

$pu - reference to URI in request's P-Preferred-Identity header (see RFC 3325)

$rd - reference to domain in request's URI

$rb - reference to message body

$rc - reference to returned code by last invoked function

$retcode - same as $rc

$rm - reference to request's method

$rp - reference to port of R-URI

$rP - reference to transport protocol of R-URI

$rr - reference to reply's reason (taken from the received replied) - works only for onreply route.

$rs - reference to reply's status (uses the received reply) - usable only on onreply route. For failure route, see the $T_reply_code variable in TM module docs.

$rt - reference to URI of refer-to header

$ru - reference to request's URI

$rU - reference to username in request's URI

$Ri - reference to IP address of the interface where the request has been received

$Rp - reference to the port where the message was received

$sf - reference to script flags - decimal output

$sF - reference to script flags - hexa output

$si - reference to IP source address of the message

$sp - reference to the source port of the message

$fs - reference to the forced socket for message sending (if any) in the form proto:ip:port

$td - reference to domain in URI of 'To' header

$tn - reference to display name of 'To' header

$tt - reference to tag parameter of 'To' header

$tu - reference to URI of 'To' header

$tU - reference to username in URI of 'To' header

$Tf - reference string formatted time

$Ts - reference to unix time stamp

$ua - reference to user agent header field

$re - reference to Remote-Party-ID header URI

$avp(id[N]) - represents the value of N-th AVP identified by 'id'.

The 'id' can be:

* “[si]:name” - name is the id of an AVP; 's' and 'i' specifies if the id is string or integer. If missing, it is considered to be string. * “$name” - the name is an AVP alias

$hdr(name[N]) - represents the body of the N-th header identified by 'name'. If [N] is omitted then the body of the first header is printed. The first header is got when N=0, for the second N=1, a.s.o. To print the last header of that type, use -1, no other negative values are supported now. No white spaces are allowed inside the specifier (before }, before or after {, [, ] symbols). When N='*', all headers of that type are printed.

The module should identify most of compact header names (the ones recognized by OpenSER which should be all at this moment), if not, the compact form has to be specified explicitly. It is recommended to use dedicated specifiers for headers (e.g., %ua for user agent header), if they are available – they are faster.

$var(name) - refers to variables that can be used in configuration script, having integer or string value. This kind of variables are faster than AVPs, being referenced directly to memory location. The value of script variables persists over the processing of SIP messages, being specific per each OpenSER process.

Example of usage:

$var(a) = 2; -- sets the value of variable 'a' to integer '2'
$var(a) = "2"; -- sets the value of variable 'a' to string '2'
$var(a) = 3 + (7&(~2));
$var(a) = "sip:" + $au + "@" + $fd; -- compose a value from authentication username and From URI domain

if( [ $var(a) & 4 ] ) {
  xlog("var a has third bit set\n");
}

Note: Script variables are per-process and exist within private memory. be aware that these values should not be relied on to hold information that needs to be persistent across multiple SIP messages.

Setting a variable to null is actually initializing the value to integer '0'. Script variables don't have NULL value.

These pseudo variables are used by xlog module to print messages in many colors using escape sequences. The other modules ingnore them or throw error if they met these pseudo-variables.

$Cxy - reference to an escape sequence. “x” represents the foreground color and “y” represents the background color.

Colors could be:

* x : default color of the terminal * s : Black * r : Red * g : Green * y : Yellow * b : Blue * p : Purple * c : Cyan * w : White

A few examples of usage.

Example 1. Pseudo-variables usage

...
avp_aliases="uuid=I:50"
...
route {
...
    $avp(uuid)="caller_id";
    $avp(i:20)= $avp(uuid) + ": " + $fu;
    xdbg("$(Cbg)i:20$(Cxx) [$avp(i:20)] $(Cbr)cseq$(Cxx)=[$hdr(cseq)]\n");
...
}
...

This document is valid for following OpenSER versions:

- OpenSER Devel v1.2.0-devX