MSRP Module

Daniel-Constantin Mierla

   <miconda@gmail.com>

Edited by

Daniel-Constantin Mierla

   <miconda@gmail.com>

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)
              3.2. cmap_size (int)
              3.3. timer_interval (int)
              3.4. auth_min_expires (int)
              3.5. auth_max_expires (int)
              3.6. use_path_addr (str)
              3.7. event_callback (str)

        4. Functions

              4.1. msrp_forward([tpath [, fpath]])
              4.2. msrp_relay()
              4.3. msrp_reply(code, text [, hdrs])
              4.4. msrp_is_request()
              4.5. msrp_is_reply()
              4.6. msrp_set_dst(addr, sock)
              4.7. msrp_relay_flags(flags)
              4.8. msrp_reply_flags(flags)
              4.9. msrp_cmap_save()
              4.10. msrp_cmap_lookup()

        5. Pseudo Variables
        6. RPC Commands

              6.1. msrp.cmaplist

        7. Event Routes
        8. Usage

   List of Examples

   1.1. Set sipmsg parameter
   1.2. Set cmap_size parameter
   1.3. Set timer_interval parameter
   1.4. Set auth_min_expires parameter
   1.5. Set auth_max_expires parameter
   1.6. Set use_path_addr parameter
   1.7. Set event_callback parameter
   1.8. msrp_forward usage
   1.9. msrp_relay usage
   1.10. msrp_reply usage
   1.11. msrp_is_request usage
   1.12. msrp_is_reply usage
   1.13. msrp_set_dst usage
   1.14. msrp_relay_flags usage
   1.15. msrp_reply_flags usage
   1.16. msrp_cmap_save usage
   1.17. msrp_cmap_lookup usage
   1.18. Event Route (using htable for MSRP connection tracking)
   1.19. Event Route (using msrp_cmap_ functions for connection tracking)

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)
        3.2. cmap_size (int)
        3.3. timer_interval (int)
        3.4. auth_min_expires (int)
        3.5. auth_max_expires (int)
        3.6. use_path_addr (str)
        3.7. event_callback (str)

   4. Functions

        4.1. msrp_forward([tpath [, fpath]])
        4.2. msrp_relay()
        4.3. msrp_reply(code, text [, hdrs])
        4.4. msrp_is_request()
        4.5. msrp_is_reply()
        4.6. msrp_set_dst(addr, sock)
        4.7. msrp_relay_flags(flags)
        4.8. msrp_reply_flags(flags)
        4.9. msrp_cmap_save()
        4.10. msrp_cmap_lookup()

   5. Pseudo Variables
   6. RPC Commands

        6.1. msrp.cmaplist

   7. Event Routes
   8. 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 requires
   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
   now offers 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.

   The following modules are required to make proper use of this module:
     * tls.

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)
   3.2. cmap_size (int)
   3.3. timer_interval (int)
   3.4. auth_min_expires (int)
   3.5. auth_max_expires (int)
   3.6. use_path_addr (str)
   3.7. event_callback (str)

3.1. sipmsg (int)

   If set to 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 the MSRP event_route.

   Default value is '1'.

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

3.2. cmap_size (int)

   The size of connection map table, to be computed as power of 2 (e.g.,
   if the value is 4, then the number of slots in map table is 2^4 = 16).

   Default value is '0' (no internal map table to be used).

   Example 1.2. Set cmap_size parameter
...
modparam("msrp", "cmap_size", 8)
...

3.3. timer_interval (int)

   The timer interval in seconds to run the procedure for cleaning expired
   connections.

   Default value is '60'.

   Example 1.3. Set timer_interval parameter
...
modparam("msrp", "timer_interval", 90)
...

3.4. auth_min_expires (int)

   The minimum value accepted for the “Expires” header in AUTH requests.

   Default value is '60'.

   Example 1.4. Set auth_min_expires parameter
...
modparam("msrp", "auth_min_expiresl", 90)
...

3.5. auth_max_expires (int)

   The maximum value accepted for “Expires” header in AUTH requests.

   Default value is '3600'.

   Example 1.5. Set auth_max_expires parameter
...
modparam("msrp", "auth_max_expiresl", 1800)
...

3.6. use_path_addr (str)

   The hostname:port to be used when building the Path header.

   Default value is NULL (server IP and port are used).

   Example 1.6. Set use_path_addr parameter
...
modparam("msrp", "use_path_addr", "msrp.kamailio.org:5061")
...

3.7. event_callback (str)

   The name of the function in the kemi configuration file (embedded
   scripting language such as Lua, Python, ...) to be executed instead of
   event_route[...] blocks.

   The function receives a string parameter with the name of the event,
   the values can be: 'msrp:frame-in'.

   Default value is 'empty' (no function is executed for events).

   Example 1.7. Set event_callback parameter
...
modparam("msrp", "event_callback", "ksr_msrp_event")
...
-- event callback function implemented in Lua
function ksr_msrp_event(evname)
        KSR.info("===== msrp module triggered event: " .. evname .. "\n");
        return 1;
end
...

4. Functions

   4.1. msrp_forward([tpath [, fpath]])
   4.2. msrp_relay()
   4.3. msrp_reply(code, text [, hdrs])
   4.4. msrp_is_request()
   4.5. msrp_is_reply()
   4.6. msrp_set_dst(addr, sock)
   4.7. msrp_relay_flags(flags)
   4.8. msrp_reply_flags(flags)
   4.9. msrp_cmap_save()
   4.10. msrp_cmap_lookup()

4.1.  msrp_forward([tpath [, fpath]])

   Forward MSRP frame to target destination. If tpath is provided then the
   original To-Path is replaced by it and the From-Path is replaced by
   fpath or the original To-Path. If the target destination is not set
   then tpath will be used to set it.

   This function can be used in ANY_ROUTE.

   Example 1.8. msrp_forward usage
...
event_route[msrp:frame-in] {
        ...
        msrp_set_dst("msrp://127.0.0.1:8000", "tcp:127.0.0.1:5060");
        msrp_forward();
        ...

        ...
        msrp_forward("msrp://127.0.0.1:8000/jshA7weztas;tcp");
        ...

        ...
        msrp_forward("msrp://127.0.0.1:8000/jshA7weztas;tcp", "msrp://127.0.0.1:
8000/kjhd37s2s20w2a;tcp");
        ...
}
...

4.2.  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 the MSRP transport layer, which is reliable
   (TCP/TLS), there is no retransmission of MSRP frames.

   This function can be used in ANY_ROUTE.

   Example 1.9. msrp_relay usage
...
event_route[msrp:frame-in] {
    msrp_relay();
}
...

4.3.  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 1.10. msrp_reply usage
...
event_route[msrp:frame-in] {
    msrp_reply("403", "Not allowed");
}
...

4.4.  msrp_is_request()

   Return true if the MSRP frame is a request.

   This function can be used in ANY_ROUTE.

   Example 1.11. msrp_is_request usage
...
event_route[msrp:frame-in] {
    if(msrp_is_request())
    {
        msrp_relay();
        exit;
    }
}
...

4.5.  msrp_is_reply()

   Return true if the MSRP frame is a reply.

   This function can be used in ANY_ROUTE.

   Example 1.12. msrp_is_reply usage
...
event_route[msrp:frame-in] {
    if(msrp_is_reply())
    {
        msrp_relay();
        exit;
    }
}
...

4.6.  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 1.13. msrp_set_dst usage
...
event_route[msrp:frame-in] {
    ...
    msrp_set_dst("msrp://127.0.0.1:8000", "tcp:127.0.0.1:5060");
    ...
}
...

4.7.  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 1.14. msrp_relay_flags usage
...
event_route[msrp:frame-in] {
    ...
    msrp_relay_flags("1");
    ...
}
...

4.8.  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 1.15. msrp_reply_flags usage
...
event_route[msrp:frame-in] {
    ...
    msrp_reply_flags("1");
    ...
}
...

4.9.  msrp_cmap_save()

   Save details of a MSRP connection upon AUTH request inside the internal
   map table, indexed by session id.

   This function can be used in ANY_ROUTE.

   Example 1.16. msrp_cmap_save usage
...
event_route[msrp:frame-in] {
    ...
        if(method=="AUTH") { msrp_cmap_save(); exit; }
    ...
}
...

4.10.  msrp_cmap_lookup()

   Lookup MSRP connection details for current session id.

   This function can be used in ANY_ROUTE.

   Example 1.17. msrp_cmap_lookup usage
...
event_route[msrp:frame-in] {
    ...
        if(method=="SEND" and $msrp(nexthops)==1) {
                if(msrp_cmap_lookup()) {
                        msrp_relay();
                } else {
                        msrp_reply("481", "Session not found");
                }
        }
    ...
}
...

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. RPC Commands

   6.1. msrp.cmaplist

6.1.  msrp.cmaplist

   List active MSRP connections.

   Example:
...
kamcmd msrp.cmaplist
...

7. Event Routes

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

8. Usage

   When the sipmsg parameter is set to 1 (which is the 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 1.18. Event Route (using htable for MSRP connection tracking)
...

#!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"

modparam("mi_fifo", "fifo_name", "/tmp/kamailio_fifo")

modparam("auth", "nonce_count", 1)
modparam("auth", "qop", "auth")

#!substdef "!MSRP_MIN_EXPIRES!1800!g"
#!substdef "!MSRP_MAX_EXPIRES!3600!g"
modparam("htable", "htable", "msrp=>size=8;autoexpire=MSRP_MAX_EXPIRES;")

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();
        }
        else 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",
                                        "$msrp(method)"))
                {
                        if(auth_get_www_authenticate("myrealm", "1",
                                                        "$var(wauth)"))
                        {
                                msrp_reply("401", "Unauthorized",
                                                "$var(wauth)");
                        } else {
                                msrp_reply("500", "Server Error");
                        }
                        exit;
                }

                if ($hdr(Expires) != $null) {
                        $var(expires) = (int) $hdr(Expires);
                        if ($var(expires) < MSRP_MIN_EXPIRES) {
                                msrp_reply("423", "Interval Out-of-Bounds",
                                        "Min-Expires: MSRP_MIN_EXPIRES\r\n");
                                exit;
                        } else {
                                msrp_reply("423", "Interval Out-of-Bounds",
                                        "Max-Expires: MSRP_MAX_EXPIRES\r\n");
                                exit;
                        }

                } else
                        $var(expires) = MSRP_MAX_EXPIRES;

                $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);
                $shtex(msrp=>$var(sessid)) = $var(expires) + 5;
                # - Use-Path: the MSRP address for server + session id
                $var(headers) = "Use-Path: msrp://127.0.0.1:5060/"
                                + $var(sessid) + ";tcp\r\n"
                                + "Expires: " + $var(expires) + "\r\n";
                msrp_reply("200", "OK", "$var(headers)");
        }
        else if($msrp(method)=="SEND" || $msrp(method)=="REPORT")
        {
                if($msrp(nexthops)>1)
                {
                        if ($msrp(method)!="REPORT")
                        {
                                msrp_reply("200", "OK");
                        }
                        msrp_relay();
                        exit;
                }
                $var(sessid) = $msrp(sessid);
                if($sht(msrp=>$var(sessid)::srcaddr) == $null)
                {
                        # one more hop, but we don't have address in htable
                        if ($msrp(method)!="REPORT")
                        {
                                msrp_reply("481", "Session-does-not-exist");
                        }
                        exit;
                }
                else if($msrp(method)!="REPORT")
                {
                        msrp_reply("200", "OK");
                }
                msrp_relay_flags("1");
                msrp_set_dst("$sht(msrp=>$var(sessid)::srcaddr)",
                                "$sht(msrp=>$var(sessid)::srcsock)");
                msrp_relay();
        }
        else
        {
                msrp_reply("501", "Request-method-not-understood");
        }
}

...

   Example 1.19. Event Route (using msrp_cmap_ functions for connection
   tracking)
...

#!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 "xlog.so"

modparam("mi_fifo", "fifo_name", "/tmp/kamailio_fifo")

modparam("auth", "nonce_count", 1)
modparam("auth", "qop", "auth")

modparam("msrp", "cmap_size", 8)
modparam("msrp", "use_path_addr", "msrp://127.0.0.1:5060")

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();
        }
        else 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",
                                        "$msrp(method)"))
                {
                        if(auth_get_www_authenticate("myrealm", "1",
                                                        "$var(wauth)"))
                        {
                                msrp_reply("401", "Unauthorized",
                                                "$var(wauth)");
                        } else {
                                msrp_reply("500", "Server Error");
                        }
                        exit;
                }

                msrp_cmap_save();
        }
        else if ($msrp(method)=="SEND" || $msrp(method)=="REPORT")
        {
                if ($msrp(nexthops)>1)
                {
                        if ($msrp(method)!="REPORT")
                        {
                                msrp_reply("200", "OK");
                        }
                        msrp_relay();
                        exit;
                }

                if (msrp_cmap_lookup())
                {
                        if ($msrp(method)!="REPORT")
                        {
                                msrp_reply("200", "OK");
                        }
                        msrp_relay_flags("1");
                        msrp_relay();
                }
                else
                {
                        msrp_reply("481", "Session-does-not-exist");
                }
        }
        else
        {
                msrp_reply("501", "Request-method-not-understood");
        }
}

...
