kamailio/modules/msrp

MSRP Module

Daniel-Constantin Mierla

   <miconda@gmail.com>

Edited by

Daniel-Constantin Mierla

   <miconda@gmail.com>

Edited by

Alex Balashov

   <abalashov@evaristesys.com>

   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. sipmsg (int)

        4. Functions

              4.1. msrp_relay()
              4.2. msrp_reply(code, text [, hdrs])
              4.3. msrp_is_request()
              4.4. msrp_is_reply()
              4.5. msrp_set_dst(addr, sock)
              4.6. msrp_relay_flags(flags)
              4.7. msrp_reply_flags(flags)

        5. Pseudo Variables
        6. Event Routes
        7. Usage

   List of Examples

   1.1. Set sipmsg parameter
   1.2. msrp usage
   1.3. msrp_reply usage
   1.4. msrp_is_request usage
   1.5. msrp_is_reply usage
   1.6. msrp_set_dst usage
   1.7. msrp_relay_flags usage
   1.8. msrp_reply_flags usage
   1.9. Event Route

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. sipmsg (int)

   4. Functions

        4.1. msrp_relay()
        4.2. msrp_reply(code, text [, hdrs])
        4.3. msrp_is_request()
        4.4. msrp_is_reply()
        4.5. msrp_set_dst(addr, sock)
        4.6. msrp_relay_flags(flags)
        4.7. msrp_reply_flags(flags)

   5. Pseudo Variables
   6. Event Routes
   7. Usage

1. Overview

   This module provides a MSRP routing engine, a.k.a. MSRP relay. MSRP
   (Message Session Relay Protocol) is defined by RFC4975, and the
   extensions for an MSRP relay are covered in RFC4976.

   A typical use of MSRP is instant messaging sessions initiated via SIP.
   Unlike page-mode instant messaging, which is done via the SIP MESSAGE
   request, MSRP uses a different communication channel which is
   negotiated via INVITE-200 OK-ACK.

   However, MSRP is still a text-based protocol. It uses several routing
   mechanisms similar to what exists in SIP. Furthermore, MSRP requres
   TCP, and recommends TLS for confidentiality and security. In light of
   the scalability and performance of Kamailio in handling TCP/TLS, this
   module reuses Kamailio's core framework to offer MSRP routing
   capabilities. Along with embedded Presence and XCAP servers, Kamailio
   offers now a complete solution for SIP beyond VoIP.

   One of the main benefits of this module is the ability to reuse all the
   other extensions that exist in the SIP server, including accounting,
   authentication, authorization to database connectors, security and DoS
   attack protections.

   Kamailio can handle SIP and MSRP traffic received on the same port; the
   appropriate configuration file block being executed based on the type
   of message. Therefore, you can use Kamailio as a stand-alone MSRP relay
   or you can have an instance handling both SIP and MSRP. Another option
   is to configure Kamailio to listen on multiple ports, some of them for
   SIP and others for MSRP.

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. sipmsg (int)

3.1. sipmsg (int)

   If 1, the module will build a SIP message from MSRP frame headers,
   providing it to event_route[msrp:frame-in]. All the config file
   functions (apart from SIP request relay) that can be used in a request
   route block can be used in msrp event_route.

   Default value is '1'.

   Example 1.1. Set sipmsg parameter
...
modparam("msrp", "sipmsg", 1)
...

4. Functions

   4.1. msrp_relay()
   4.2. msrp_reply(code, text [, hdrs])
   4.3. msrp_is_request()
   4.4. msrp_is_reply()
   4.5. msrp_set_dst(addr, sock)
   4.6. msrp_relay_flags(flags)
   4.7. msrp_reply_flags(flags)

4.1.  msrp_relay()

   Relay MSRP frame according to the To-Path. This function has to be
   executed for each MSRP request or reply that has to be forwarded. Note
   that due to nature of MSRP transport layer, which is reliable
   (TCP/TLS), there is no retransmission of MSRP frames.

   This function can be used in ANY_ROUTE.

   Example 1.2. msrp usage
...
event_route[msrp:frame-in] {
    msrp_relay();
}
...

4.2.  msrp_reply(code, text [, hdrs])

   Send a reply for the current MSRP request, adding optional headers.

   The parameter can be a pseudo-variable.

   This function can be used in ANY_ROUTE.

   Example 1.3. msrp_reply usage
...
event_route[msrp:frame-in] {
    msrp_reply("403", "Not allowed");
}
...

4.3.  msrp_is_request()

   Return true if the MSRP frame is a request.

   This function can be used in ANY_ROUTE.

   Example 1.4. msrp_is_request usage
...
event_route[msrp:frame-in] {
    if(msrp_is_request())
    {
        msrp_relay();
        exit;
    }
}
...

4.4.  msrp_is_reply()

   Return true if the MSRP frame is a reply.

   This function can be used in ANY_ROUTE.

   Example 1.5. msrp_is_reply usage
...
event_route[msrp:frame-in] {
    if(msrp_is_reply())
    {
        msrp_relay();
        exit;
    }
}
...

4.5.  msrp_set_dst(addr, sock)

   Set destination attributes: addr - target address as MSRP URI; sock -
   local socket to be used (format 'proto:ip:port').

   The parameter can be a pseudo-variable.

   This function can be used in ANY_ROUTE.

   Example 1.6. msrp_set_dst usage
...
event_route[msrp:frame-in] {
    ...
    msrp_set_dst("msrp://127.0.0.1:8000", "tcp:127.0.0.1:5060");
    ...
}
...

4.6.  msrp_relay_flags(flags)

   Set transport layer sending flags for forwarding current MSRP frame;
   flags - a bitmask of flags - 1 (don't create a new connection), 2
   (close connection after send).

   The parameter can be a pseudo-variable.

   This function can be used in ANY_ROUTE.

   Example 1.7. msrp_relay_flags usage
...
event_route[msrp:frame-in] {
    ...
    msrp_relay_flags("1");
    ...
}
...

4.7.  msrp_reply_flags(flags)

   Set transport layer sending flags for replies to the current MSRP
   frame; flags - a bitmask of flags - 1 (don't create a new connection),
   2 (close connection after send).

   The parameter can be a pseudo-variable.

   This function can be used in ANY_ROUTE.

   Example 1.8. msrp_reply_flags usage
...
event_route[msrp:frame-in] {
    ...
    msrp_reply_flags("1");
    ...
}
...

5. Pseudo Variables

   The module exports a pseudo-variable class, $msrp(key), to access the
   MSRP frame (e.g. first line attributes, body, all frame content).

   The module exports a transformations class, 'msrpuri', to allow access
   attributes of a MSRP URI.

   These are documented in the appropriate Wiki pages hosted on the
   project web site.

6. Event Routes

   For each MSRP frame received from the network, the module executes
   event_route[msrp:frame-in] block in the config file.

7. Usage

   When 'sipmsg' parameter is set to 1 (which is default), the module
   internally builds a SIP request from the MSRP frame and exposes it to
   the config file interpreter. This way, all the functions that are valid
   for SIP requests can be used safely in event_route[msrp:frame-in].

   To build the SIP request, the module takes the first line and the
   headers from an MSRP message and appends them to a static buffer. The
   next two examples show an MSRP frame and the resulting SIP request.
...
MSRP 6aef SEND
To-Path: msrps://a.example.org:9000/kjfjan;tcp \
  msrps://b.example.net:9000/aeiug;tcp \
  msrps://bob.example.net:8145/foo;tcp
From-Path: msrps://alice.example.org:7965/bar;tcp
Success-Report: yes
Byte-Range: 1-*/*
Message-ID: 87652
Content-Type: text/plain

Hi Bob, I'm about to send you a photo.
-------6aef$
...
...
MSRP sip:a@127.0.0.1 SIP/2.0
Via: SIP/2.0/UDP 127.0.0.1:9;branch=z9hG4bKa
From: <b@127.0.0.1>;tag=a
To: <a@127.0.0.1>
Call-ID: a
CSeq: 1 MSRP
Content-Length: 0
MSRP-First-Line: MSRP 6aef SEND
To-Path: msrps://a.example.org:9000/kjfjan;tcp \
  msrps://b.example.net:9000/aeiug;tcp \
  msrps://bob.example.net:8145/foo;tcp
From-Path: msrps://alice.example.org:7965/bar;tcp
Success-Report: yes
Byte-Range: 1-*/*
Message-ID: 87652
Content-Type: text/plain

...

   Note that MSRP does not permit line folding. A "\" in the examples
   shows a line continuation due to the limitations of line length of this
   document. Neither the backslash nor the extra CRLF is included in the
   actual request or response.

   As can be observed, the MSRP frame content starts with the body of the
   'MSRP-First-Line:' header. Using static content to get to a valid SIP
   request is a perfect trade-off for performance.

   Besides the option to access parts of MSRP frame via an
   internally-built SIP message, the module exports a new pseudo-variable
   class $msrp(key) which returns attributes from the MSRP frame. There is
   also a new transformation, {msrpuri.key}, to get access to parts of an
   MSRP URI. See the appropriate Wiki pages on the project's web site for
   full details about new pseudo-variable and transformation classes.

   Next is an example of configuration file with the routing block for
   MSRP frames. In this config, the SIP traffic is rejected.

   Example 1.9. Event Route
...

#!KAMAILIO

debug=2
memdbg=5
memlog=5

children=4

log_stderror=yes
auto_aliases=no

tcp_accept_no_cl=yes
tcp_connection_lifetime=1810

listen=127.0.0.1:5060

mpath="modules_k/:modules/"

loadmodule "sl.so"
loadmodule "kex.so"
loadmodule "mi_fifo.so"
loadmodule "ctl.so"
loadmodule "msrp.so"
loadmodule "pv.so"
loadmodule "auth.so"
loadmodule "cfgutils.so"
loadmodule "htable.so"
loadmodule "xlog.so"

# ----- mi_fifo params -----
modparam("mi_fifo", "fifo_name", "/tmp/kamailio_fifo")

modparam("htable", "htable", "c=>size=8;autoexpire=1800;")

request_route {
        sl_send_reply("403", "No SIP Here");
        exit;
}

reply_route {
        drop;
}

event_route[msrp:frame-in] {
        xdbg("============#[[$msrp(method)]]===========\n");
        xdbg("============*[[$si:$sp]]\n");
        xdbg("============ crthop:   [$msrp(crthop)]\n");
        xdbg("============ prevhop:  [$msrp(prevhop)]\n");
        xdbg("============ nexthop:  [$msrp(nexthop)]\n");
        xdbg("============ firsthop: [$msrp(firsthop)]\n");
        xdbg("============ lasthop:  [$msrp(lasthop)]\n");
        xdbg("============ prevhops: [$msrp(prevhops)]\n");
        xdbg("============ nexthops: [$msrp(nexthops)]\n");
        xdbg("============ srcaddr:  [$msrp(srcaddr)]\n");
        xdbg("============ srcsock:  [$msrp(srcsock)]\n");
        xdbg("============ sessid:   [$msrp(sessid)]\n");

        msrp_reply_flags("1");

    if(msrp_is_reply())
    {
        msrp_relay();
        exit;
    }

        # handle AUTH MSRP requests
        if($msrp(method)=="AUTH")
        {
                if($msrp(nexthops)>0)
                {
                        msrp_relay();
                        exit;
                }
                # frame for local server - send Use-Path
                # -- passwd can be loaded from DB based on $au
                $var(passwd) = "xyz123";
                if(!pv_www_authenticate("myrealm", "$var(passwd)", "0"))
                {
                        if(auth_get_www_authenticate("myrealm", "0",
                                                "$var(wauth)"))
                        {
                                msrp_reply("401", "Authorization Required",
                                                "$var(wauth)");
                        } else {
                                msrp_reply("500", "Server Error");
                        }
                        exit;
                }
                $var(cnt) = $var(cnt) + 1;
                pv_printf("$var(sessid)", "s.$(pp).$(var(cnt)).$(RANDOM)");
                $sht(msrp=>$var(sessid)::srcaddr) = $msrp(srcaddr);
                $sht(msrp=>$var(sessid)::srcsock) = $msrp(srcsock);
                # - Use-Path: the MSRP address for server + session id
                $var(UsePath) = "Use-Path: msrp://127.0.0.1:5060/"
                                + $var(sessid) + ";tcp\r\n";
                msrp_reply("200", "OK", "$var(UsePath)");
                exit;
        }

        if($msrp(method)=="SEND")
        {
                if($msrp(nexthops)>1)
                {
                        msrp_reply("200", "Received");
                        msrp_relay();
                        exit;
                }
                $var(sessid) = $msrp(sessid);
                if($sht(msrp=>$var(sessid)::srcaddr) == $null)
                {
                        # one more hop, but we don't have address in htable
                        msrp_reply("481", "No Such Session");
                        exit;
                }
                msrp_relay_flags("1");
                msrp_set_dst("$sht(msrp=>$var(sessid)::srcaddr)",
                                "$sht(msrp=>$var(sessid)::srcsock)");
                msrp_relay();
                exit;
        }

        msrp_relay();
}

...