Kamailio by example - Getting Started: Directive Operations

Directive Operations

Note: Read the official docs to get the most updated information.

defexp

defexp is similar to a define, but the ID is set to the value of an expression.

#!defexp ID exp
#!defenvs ID exp     // defenv for strings

Check snexpr for expression examples.

ifdef

It can also be user to define what parts of the config file are loaded, ensuring lower memory usage and faster execution.

#!ifdef ID   // check if an ID is defined
#!ifexp exp  // check if expression is true
#!ifndef     // check if an ID is not defined
#!else       // switch to false branch of if region
#!endif      // end if region

subst

subst perform substitutions inside the strings, even when concatenated. The define is replacing only IDs (alphanumeric tokens not enclosed in quotes). Be careful with the sub-string, to make sure it doesn’t match previous subst substitutions.

#!subst "/regexp/substring/flags"
#!substdef  "/regexp/substring/flags" // also do a #!define ID substring
#!substdefs "/regexp/substring/flags" // substdef for strings

Example

#!KAMAILIO

#!define MAINTENANCE 1
#!defenv KAMA_LISTEN
#!defexp ADDR "udp:" + KAMA_LISTEN
#!subst "/Hello/Hi/g"

listen=ADDR
auto_aliases=no

loadmodule "sl"
modparam("sl", "bind_tm", 0)

#!include_file "0.6.0-define-ops.inc.cfg"

request_route {
  #!ifexp MAINTENANCE
    sl_send_reply(500, "Hello");
  #!else
    sl_send_reply(200, "Hello");
  #!endif
}

How to test: Check the kamalab to prepare your lab.

# kamalab ❯
./kamalab
# select 0.6.0-define-ops.cfg
# Listening on
#              udp: 127.0.0.2 [127.0.0.2]:5060
# Aliases:

In another terminal let’s send OPTIONS to the server:

# >
sipexer 127.0.0.2
# ...
# OPTIONS sip:127.0.0.2:5060 SIP/2.0
# ...
# SIP/2.0 500 Hi
# ...

We see that:

• In ADDR an expression is used to concatenate strings.
• A subst was used to replace Hello in the response cause.
• The sl_send_reply(200, "Hello") was not loaded, since the define MAINTENANCE was set to 1.

Resources

• Wiki Core Cookbook