– Kamailio SIP Server –

Table of Contents

OpenSER Pseudo-variables for version 1.3.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>

Introduction

The term “pseudo-variable” 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)

Pseudo-variables usage

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

  • acc
  • avpops
  • textops
  • uac
  • xlog

The list of pseudo-variables in OpenSER

Predefined pseudo-variables are listed in alphabetical order.

Pseudo-variable marker

$$ - represents the character '$'

URI in SIP Request's P-Asserted-Identity header

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

Auth Digest URI

$adu - URI from Authorization or Proxy-Authorization header. This URI is used when calculating the HTTP Digest Response.

Auth realm

$ar - realm from Authorization or Proxy-Authorization header

Auth username

$au - username from Authorization or Proxy-Authorization header

Auth whole username

$aU - whole username from Authorization or Proxy-Authorization header

Request's first branch

$br - reference to request's first branch

Request's all branches

$bR - reference to request's all branches

Branch flags

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

Branch flags

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

Call-Id

$ci - reference to body of call-id header

Content-Length

$cl - reference to body of content-length header

CSeq

$cs - reference to body of cseq header

Contact header

$ct - reference to body of contact header

Content-Type

$cT - reference to body of content-type header

Domain of destination URI

$dd - reference to domain of destination uri

Diversion header URI

$di - reference to Diversion header URI

Port of destination URI

$dp - reference to port of destination uri

Transport protocol of destination URI

$dP - reference to transport protocol of destination uri

Destination set

$ds - reference to destination set

Destination URI

$du - reference to destination uri
If loose_route() returns TRUE a destination uri is set according to the first Route header.
$du is also set if lookup() function of 'registrar' module finds contact(s) behind NAT.
To reset $du:

$du = null;

Error class

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

Error level

$err.level - severity level for the error

Error info

$err.info - text describing the error

Error reply code

$err.rcode - recommended reply code

Error reply reason

$err.rreason - recommended reply reason phrase

From URI domain

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

From display name

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

From tag

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

From URI

$fu - reference to URI of 'From' header

From URI username

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

SIP message buffer

$mb - reference to SIP message buffer

Flags

$mf - reference to message/transaction flags set for current SIP request

Flags in hexadecimal

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

SIP message id

$mi - reference to SIP message id

SIP message length

$ml - reference to SIP message length

Domain in SIP Request's original URI

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

Port of SIP request's original URI

$op - reference to port of original R-URI

Transport protocol of SIP request original URI

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

SIP Request's original URI

$ou - reference to request's original URI

Username in SIP Request's original URI

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

Domain in SIP Request's P-Preferred-Identity header URI

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

Display Name in SIP Request's P-Preferred-Identity header

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

Process id

$pp - reference to process id (pid)

Transport protocol of received message

$pr or $proto - transport protocol of received message (UDP, TCP, TLS, SCTP (not supported by OpenSER))

User in SIP Request's P-Preferred-Identity header URI

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

URI in SIP Request's P-Preferred-Identity header

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

Domain in SIP Request's URI

$rd - reference to domain in request's URI

It is R/W variable (you can assign values to it directly in configuration file)

Body of request/reply

$rb - reference to message body

Returned code

$rc - reference to returned code by last invoked function

$retcode - same as $rc

Remote-Party-ID header URI

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

SIP request's method

$rm - reference to request's method

SIP request's port

$rp - reference to port of R-URI

Transport protocol of SIP request URI

$rP - reference to transport protocol of R-URI

SIP reply's reason

$rr - reference to reply's reason

SIP reply's status

$rs - reference to reply's status

Refer-to URI

$rt - reference to URI of refer-to header

SIP Request's URI

$ru - reference to request's URI

It is R/W variable (you can assign values to it directly in configuration file)

Username in SIP Request's URI

$rU - reference to username in request's URI

It is R/W variable (you can assign values to it directly in configuration file)

Received IP address

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

Received port

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

Script flags

$sf - reference to script flags - decimal output

Script flags

$sF - reference to script flags - hexa output

IP source address

$si - reference to IP source address of the message

Source port

$sp - reference to the source port of the message

Forced socket

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

To URI Domain

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

To display name

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

To tag

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

To URI

$tu - reference to URI of 'To' header

To URI Username

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

String formatted time

$Tf - reference string formatted time

Unix time stamp

$Ts - reference to unix time stamp

User agent header

$ua - reference to user agent header field

AVPs

$(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

Note: By default AVP created during initial message is available in “failure_route[]” but not in “onreply_route[]”. To get the last is needed: modparam("tm", "onreply_avp_mode", 1)

Headers

$(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.

Script variables

$var(name) - refers to variables that can be used in configuration script, having integer or string value. This kind of variables are faster the 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");
}

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

Note: A script variable persists over the OpenSER process in which it was initialized, so be sure of giving it a new value before reading it or you'll get the value asigned in any other previous message processed by the same OpenSER process (pid).

Special pseudo-variables in OpenSER - Escape Sequences

These pseudo variables are exported, and mainly used, by xlog module to print messages in many colors (foreground and background) using escape sequences.

Foreground and background colors

$C(xy) - 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

Examples

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) + ": " + $fu;
    xdbg("$(C(bg))avp(i:20)$(C(xx)) [$avp(i:20)] $(C(br))cseq$(C(xx))=[$hdr(cseq)]\n");
...
}
...

OpenSER versions

This document is valid for following OpenSER versions:

- OpenSER Devel v1.2.0-devX

Pseudo-variables Stuff