# &adminguide;

## 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.

## Dependencies

### &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.

### External Libraries or Applications

The following libraries or applications must be installed before running &kamailio; with this module loaded:

- None

## Parameters

### `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'.

#### Set `sipmsg` parameter

    ...
    modparam("msrp", "sipmsg", 1)
    ...

### `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).

#### Set `cmap_size` parameter

    ...
    modparam("msrp", "cmap_size", 8)
    ...

### `timer_interval` (int)

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

Default value is '60'.

#### Set `timer_interval` parameter

    ...
    modparam("msrp", "timer_interval", 90)
    ...

### `auth_min_expires` (int)

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

Default value is '60'.

#### Set `auth_min_expires` parameter

    ...
    modparam("msrp", "auth_min_expiresl", 90)
    ...

### `auth_max_expires` (int)

The maximum value accepted for Expires header in AUTH requests.

Default value is '3600'.

#### Set `auth_max_expires` parameter

    ...
    modparam("msrp", "auth_max_expiresl", 1800)
    ...

### `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).

#### Set `use_path_addr` parameter

    ...
    modparam("msrp", "use_path_addr", "msrp.kamailio.org:5061")
    ...

### `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).

#### 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
    ...

## Functions

### `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.

#### `msrp_relay` usage

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

### `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.

#### `msrp_reply` usage

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

### `msrp_is_request()`

Return true if the MSRP frame is a request.

This function can be used in ANY_ROUTE.

#### `msrp_is_request` usage

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

### `msrp_is_reply()`

Return true if the MSRP frame is a reply.

This function can be used in ANY_ROUTE.

#### `msrp_is_reply` usage

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

### `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.

#### `msrp_set_dst` usage

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

### `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.

#### `msrp_relay_flags` usage

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

### `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.

#### `msrp_reply_flags` usage

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

### `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.

#### `msrp_cmap_save` usage

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

### `msrp_cmap_lookup()`

Lookup MSRP connection details for current session id.

This function can be used in ANY_ROUTE.

#### `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");
    		}
    	}
        ...
    }
    ...

## 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.

## RPC Commands

### `msrp.cmaplist`

List active MSRP connections.

Example:

    ...
    &sercmd; msrp.cmaplist
    ...

## Event Routes

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

## 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.

### 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");
    	}
    }

    ...

### 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");
    	}
    }

    ...