kamailio/modules/corex

COREX Module

Daniel-Constantin Mierla



Edited by

Daniel-Constantin Mierla



Muhammad Shahzad Shafi



Copyright � 2012 asipto.com
__________________________________________________________________

Table of Contents

1. Admin Guide

1. Overview
2. Dependencies

2.1. Kamailio Modules
2.2. External Libraries or Applications

3. Parameters

3.1. alias_subdomains (string)
3.2. network_io_intercept (int)
3.3. msg_min_len (int)
3.4. msg_avp (string)

4. Functions

4.1. append_branch([ uri, [ q ] ])
4.2. send([ host [ :port ] ])
4.3. send_tcp([ host [ :port ] ])
4.4. send_data(uri, data)
4.5. is_incoming()
4.6. msg_iflag_set(flagname)
4.7. msg_iflag_reset(flagname)
4.8. msg_iflag_is_set(flagname)

5. RPC Commands

5.1. corex.list_sockets
5.2. corex.list_aliases
5.3. corex.shm_status
5.4. corex.shm_summary

6. Event Routes

6.1. event_route[network:msg]

7. Examples of Usage

List of Examples

1.1. Set alias_subdomains parameter
1.2. Set network_io_intercept parameter
1.3. Set msg_min_len parameter
1.4. Set msg_avp parameter
1.5. append_branch usage
1.6. send usage
1.7. send_data usage
1.8. is_incoming usage
1.9. msg_iflag_set usage
1.10. msg_iflag_reset usage
1.11. msg_iflag_is_set usage
1.12. event_route[network:msg] use cases
1.13. Sample PERL code for do_compress and do_uncompress

Chapter 1. Admin Guide

Table of Contents

1. Overview
2. Dependencies

2.1. Kamailio Modules
2.2. External Libraries or Applications

3. Parameters

3.1. alias_subdomains (string)
3.2. network_io_intercept (int)
3.3. msg_min_len (int)
3.4. msg_avp (string)

4. Functions

4.1. append_branch([ uri, [ q ] ])
4.2. send([ host [ :port ] ])
4.3. send_tcp([ host [ :port ] ])
4.4. send_data(uri, data)
4.5. is_incoming()
4.6. msg_iflag_set(flagname)
4.7. msg_iflag_reset(flagname)
4.8. msg_iflag_is_set(flagname)

5. RPC Commands

5.1. corex.list_sockets
5.2. corex.list_aliases
5.3. corex.shm_status
5.4. corex.shm_summary

6. Event Routes

6.1. event_route[network:msg]

7. Examples of Usage

1. Overview

This module provides reimplementation of a few very old functions that
used to be in the core and supported only static string or integer
parameters. The new versions bring support for dynamic parameters
(allowing variables inside the parameters).

There are also brand new features, related to core internals, but
controlled from configuration file or via control interfaces.

Contributions to this module must be done under the BSD license, to
follow the requirements of the core contributions.

This module now also provides access to network input / output data
through event_route[network:msg]. The raw data received from a remote
host or about to be sent to a remote host is available in variable $mb.
The script writer may manipulate this data and save the final result in
an AVP defined by msg_avp module parameter. The content of this AVP
will then be processed by SIP worker as normal, i.e. a received message
will be parsed and sent to appropriate route block while a sent message
is forwarded to remote host.

2. Dependencies

2.1. Kamailio Modules
2.2. External Libraries or Applications

2.1. Kamailio Modules

The following modules must be loaded before this module:
* None.

2.2. External Libraries or Applications

The following libraries or applications must be installed before
running Kamailio with this module loaded:
* None

3. Parameters

3.1. alias_subdomains (string)
3.2. network_io_intercept (int)
3.3. msg_min_len (int)
3.4. msg_avp (string)

3.1. alias_subdomains (string)

Register a domain and all its sub-domains to match the "myself"
condition. It can be set many times. Its full format is:
'proto:domain:port', allowing to set restrictions on protocol and port
as well. Protocol and port are optional.

Default value is "NULL".

Example 1.1. Set alias_subdomains parameter
...
modparam("corex", "alias_subdomains", "kamailio.org")
modparam("corex", "alias_subdomains", "udp:sip-router.org:5060")
...

3.2. network_io_intercept (int)

If set to non-zero then raw data received from a remote host or about
to be sent to a remote host is made available in
event_route[network:msg]. The script writer may modify this and save to
msg_avp, which will then be processed by SIP worker as normal.

Default value is 0, i.e. do not allow access to network io data.

Example 1.2. Set network_io_intercept parameter
...
modparam("corex", "network_io_intercept", 1)
...

3.3. msg_min_len (int)

Minimum content length of the packet to execute the
event_route[network:msg]. This only works if network_io_intercept
parameter is set to non-zero.

Default value is 0.

Example 1.3. Set msg_min_len parameter
...
modparam("corex", "msg_min_len", 32)
...

3.4. msg_avp (string)

AVP name to store modified content to be set in the packet. If not set
in event_route[network:msg], then all changes are lost and original
contents are used. This only works if network_io_intercept parameter is
to set non-zero.

Default value is empty.

Example 1.4. Set msg_avp parameter
...
modparam("corex", "msg_avp", "$avp(msg)")
...

4. Functions

4.1. append_branch([ uri, [ q ] ])
4.2. send([ host [ :port ] ])
4.3. send_tcp([ host [ :port ] ])
4.4. send_data(uri, data)
4.5. is_incoming()
4.6. msg_iflag_set(flagname)
4.7. msg_iflag_reset(flagname)
4.8. msg_iflag_is_set(flagname)

4.1. append_branch([ uri, [ q ] ])

Append a new branch to the destination set, useful to build the set of
destination addresses for parallel forking or redirect replies.

Both parameters are optional, If no uri parameter is provided, then the
address from request URI (r-uri) is used to build the new branch.

Meaning of the parameters is as follows:
* uri - SIP address of the branch to be used as R-URI in the outgoing
request.
* q - the Q value to set the priority of the branch based on Contact
address specifications

This function can be used from REQUEST_ROUTE or FAILURE_ROUTE.

Example 1.5. append_branch usage
...
append_branch();
append_branch("$avp(uri)", "0.5");
...

4.2. send([ host [ :port ] ])

Send the original SIP message to a specific destination in stateless
mode. No changes are applied to received message, no Via header is
added. Host can be an IP address or hostname. Port is optional and
defaults to 5060. Used protocol: UDP.

The parameter is optional and defaults to the destination URI from the
SIP message if left out. Otherwise it's a string parameter (supporting
pseudo-variables) in format "hostname" or "hostname:port", where
hostname" can also be a numeric IP address.

This function can be used from REQUEST_ROUTE or FAILURE_ROUTE.

Example 1.6. send usage
...
send();
send("10.20.15.10");
send("sip.example.com:5070");
send("$var(res)");
...

4.3. send_tcp([ host [ :port ] ])

This function is identical to send() described above, except that it
sends the SIP message using the TCP protocol instead of UDP.

4.4. send_data(uri, data)

Send the data to address specified by uri. Both parameters can contain
pseudo-variables. The uri parameter has to be a valid SIP URI. The data
parameter can by any arbitrary content.

This function can be used from ANY_ROUTE.

Example 1.7. send_data usage
...
send_data("sip:example.com:5070;transport=sctp", "Message at $Ts");
...

4.5. is_incoming()

Returns true if contents of message buffer $mb are the data received
from remote host, otherwise false indicating that the contents of $mb
are data that is about to be sent out to remote host. This only works
if network_io_intercept parameter is set to non-zero.

This function can be used from event_route[network:msg].

Example 1.8. is_incoming usage
...
event_route[network:msg] {
if (is_incoming()) {
xlog("L_INFO", "Received message '$mb' \n");
$avp(msg) = $mb;
} else {
xlog("L_INFO", "Sending message '$mb' \n");
$avp(msg) = $mb;
};
}
...

4.6. msg_iflag_set(flagname)

Set internal SIP message flag. The parameter flagname can be:
USE_UAC_FROM, USE_UAC_TO or UAC_AUTH.

This functions should not be used in configuration file for (re)setting
the internal flags, those are done by various functions internally,
however, in very particular cases they might be useful (e.g., changing
From/To via textops functions).

This function can be used from ANY_ROUTE.

Example 1.9. msg_iflag_set usage
...
msg_iflag_set("UAC_AUTH");
...

4.7. msg_iflag_reset(flagname)

Reset the internal flag given as parameter.

This function can be used from ANY_ROUTE.

Example 1.10. msg_iflag_reset usage
...
msg_iflag_reset("UAC_AUTH");
...

4.8. msg_iflag_is_set(flagname)

Test if the internal flag given as parameter is set.

This function can be used from ANY_ROUTE.

Example 1.11. msg_iflag_is_set usage
...
if(msg_iflag_is_set("UAC_AUTH")) { ... }
...

- ("flagname") - ("flagname")

5. RPC Commands

5.1. corex.list_sockets
5.2. corex.list_aliases
5.3. corex.shm_status
5.4. corex.shm_summary

5.1. corex.list_sockets

Print the list of sockets the application is listening on.

Example:
kamcmd corex.list_sockets

5.2. corex.list_aliases

Print the list of hostname aliases used to match the myself condition.

Example:
kamcmd corex.list_aliases

5.3. corex.shm_status

Trigger shm status dump to syslog.

Example:
kamcmd corex.shm_status

5.4. corex.shm_summary

Trigger shm summary dump to syslog.

Example:
kamcmd corex.shm_summary

6. Event Routes

6.1. event_route[network:msg]

6.1. event_route[network:msg]

Event route block to be executed when new data is received from network
or the data that is about to be sent to a remote host by a SIP worker
process.

The kamailio script writer can check which type of data triggered this
event route using is_incoming method.

After executing of this event route, if msg_avp was defined and set
then its value is used for further processing, otherwise, original
value of $mb is used. If message was received from remote host, then it
is parsed and proceeds to appropriate route. Oterhwise if message set
to send out, then is sent to remote host per configured SIP timers in
config script.

Please note this event route is meant to prepare the message for
on-wire communication, e.g. to do custom encryption or decryption,
compression/decompression etc. of the message sent to or received from
remote host. Therefore, except text operations, no module fucntions or
pseudo variables are available in this event route.

7. Examples of Usage

To use network event_route[network:msg] the remote SIP UA must also
implement and understand the encoding / decoding done in this event
route. It is up to Kamailio config script writer to define and
implement how encoding and decoding is done. Any language module such
as app_perl or app_lua can be called in in event_route[network:msg] to
implement desired logic.

The most simple use case is to compress the SIP packet on-wire. As SIP
is a text based protocol, so it is highly compressable. Using this
module, one can compress entire SIP message, including headers and
message body before sending it to remote host using any compression
algorithm of choice, thus saving significant bandwidth on mobile data
networks.

A useful case is to use this function between SIP edge proxy and SIP
application server. The SIP messages received from end-user at SIP edge
proxy may be decrypted and sent to SIP application server at remote
location unencrypted, where they are processed as normal. One the way
back, the messages received from SIP application server at edge proxy
can be encrpyted before being sent to actual destination. The edge
proxy can check whether received message came from end-user or SIP
application server by using simple regular expressions.

Another use case is to implement a virtual HTTP tunnel for SIP
messages. The SIP client app can convert SIP message to binary e.g. by
doing XOR, Base64 etc., then prepend some fake HTTP headers to make it
look like an HTTP request before sending it to kamailio over SIP TCP
socket. At kamailio, the fake headers are removed and data is decoded
back to normal SIP and processed per config script logic. For the data
that is to be sent to SIP client app, one can prepend fake HTTP reply
headers to encoded data before sending it to client app.

More advance use cases may involve custom encryption algorithms such as
ITV encryption algorithm, https://github.com/mshary/itv

For example, the client app running on Android or iPhone, may send
device UUID along with ITV key, encrypted using RSA or AES256 with
pre-shared secret, as first packet, which is set as cookie by server in
e.g. memcache. This cookie is referred by client app in each next
packet, so server can retrive encyption key from cache and use that for
decryption. Same can be done for server at client app side, so messages
encrypted by server can be decrypted at client app.

Next is a basic usage example where encoding and decoding is done using
PERL,

Example 1.12. event_route[network:msg] use cases
...
loadmodule "app_perl.so"
loadmodule "corex.so"
...
# ----- app_perl params -----
modparam("app_perl", "filename", "/usr/local/etc/kamailio/custom_compress.pl")
modparam("app_perl", "modpath", "/usr/local/lib64/kamailio/perl")

# ----- corex params -----
modparam("corex", "network_io_intercept", 32)
modparam("corex", "min_msg_len", 32)
modparam("corex", "msg_avp", "$avp(msg)")
...
event_route[network:msg] {
if (is_incoming()) {
if (perl_exec_simple("do_uncompress", "" + $mb + "")) {
xlog("L_INFO", "Received message '$avp(msg)' \n");
} else {
xlog("L_INFO", "Received message '$mb' \n");
$avp(msg) = $mb;
};
} else {
xlog("L_INFO", "Sending message '$mb' \n");
if (!perl_exec_simple("do_compress", "" + $mb + "")) {
$avp(msg) = $mb;
};
};
}
...

Example 1.13. Sample PERL code for do_compress and do_uncompress
...
use strict;
use warnings;
use IO::Compress::Gzip qw(gzip $GzipError) ;
use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;

sub do_compress() {
my $input = shift;
my $output;

gzip \$input => \$output
or eval {
Kamailio::log(L_WARN, "GZIP failed: $GzipError\n");
$output = $input;
};

Kamailio::AVP::add("msg", $output);
}

sub do_uncompress() {
my $input = shift;
my $output;

gunzip \$input => \$output
or eval {
Kamailio::log(L_WARN, "GUNZIP failed: $GzipError\n");
$output = $input;
};

Kamailio::AVP::add("msg", $output);
}
...