[mgcp] Add a simple mgcp gateway used for the BSC

The python script is a simple call-agent driving the
client. Currently it is sending a AuditEndpoint message
and is printing the result.

The bsc_mgcp.c is a standalone process that will implement
a MGCP Gateway for the MSC. On call handling the Call-Agent
will ask the Gateway to "CreateConnection" and then this
gateway needs to communicate with OpenBSC.

Currently CreateConnection,ModifiyConnection,DeleteConnection
and Endpoint auditing is implemented.

[mgcp] Send RSIP on start and on first receive of any message

Ignore the first request and send a RSIP. We do that because
we might tunnel UDP through some other things and have no direct
way to connect to the call-agent.
Also the transaction is not checked and we ignore the response
from the call-agent, actually we print the '200 ' or any other
value as unhandled...

[mgcp] Print the MGCP command next to the response code

This allows to see which commands were sent by the server

mgcp: Terminate it with a new line

[mgcp] Make number of endpoints static...

For now this is fixed to the number of endpoints as of the GSM
specification...

[mgcp] The endpoint names seem to be base 16... use strtoul to parse

Use strtoul to parse the base 16 number from the mgw string.

[mgcp] Log the endpoints as hex numbers...

[mgcp] Only send the RSIP on the first incoming message..

Remove call_agent option (also remove the number from the getopt
call).

[mgcp] Start couting at 1 for the mgcp

[mgcp] Slight attempt to improve the grammar of the strings

[mgcp] Share validation routines between DLCX and MDCX

[mgcp] Remove help for dead config options

[mgcp] Specify a different IN addr in the SDP records

In case of NAT traversal be able to listen on a given
interface (like 127.0.0.1) but claim to receive data
at the beginning of the tunnel.

[mgcp] Fix the static copy of the SDP file

WIP verify out factoring broken..

[mgcp] Introduce VTY to the mgcp for config file parsing...

Parse the MGCP config file via the VTY framework.

[mgcp] Handle SDP parameters through VTY..

Currently the payload type, name and rate can be specified
in the config file.

[mgcp] Add an option to bind all rtp ports early

This can be useful for testing and in deployment to make sure
no runtime resource limit can be hit.

[mgcp] Add some API doc comment

[mgcp] Convert the packets of the example server to ascii

This will allow to easily patch the call id... to run the
server in a loop and make it work with the mediagateway

[mgcp] Assign CI_UNUSED... to be more obvious...

[mgcp] Use DEBUG and not DEBUGPC and specially not printf

Improve the logging a bit in the mgcp

[mgcp] Change the fake server to change the call id

This assume the call-agent will just increment the id
as well.... this is true for our implementation

[mgcp] Generate the transaction id dynamically..

This way wireshark will be more happy about it...

[mgcp] Recognize responses from the network..

This is just recognizing the response code and
then is doing nothing with it. Also change the
script to generate response messages...

[mgcp] Improve debug messages for CRCX/MDCX..

Log on which ports the media gateway is listening
and where the other (server) gateway is located

openbsc/contrib/mgcp_server.py

@@ -0,0 +1,54 @@
+#!/usr/bin/env python
+# Simple server for mgcp... send audit, receive response..
+
+import socket, time
+
+MGCP_GATEWAY_PORT = 2427
+MGCP_CALLAGENT_PORT = 2727
+
+rsip_resp = """200 321321332\r\n"""
+audit_packet = """AUEP %d 13@mgw MGCP 1.0\r\n"""
+crcx_packet = """CRCX %d 14@mgw MGCP 1.0\r\nC: 4a84ad5d25f\r\nL: p:20, a:GSM-EFR, nt:IN\r\nM: recvonly\r\n"""
+dlcx_packet = """DLCX %d 14@mgw MGCP 1.0\r\nC: 4a84ad5d25f\r\nI: %d\r\n"""
+mdcx_packet = """MDCX %d 14@mgw MGCP 1.0\r\nC: 4a84ad5d25f\r\nI: %d\r\nL: p:20, a:GSM-EFR, nt:IN\r\nM: recvonly\r\n\r\nv=0\r\no=- 258696477 0 IN IP4 172.16.1.107\r\ns=-\r\nc=IN IP4 172.16.1.107\r\nt=0 0\r\nm=audio 4400 RTP/AVP 127\r\na=rtpmap:127 GSM-EFR/8000/1\r\na=ptime:20\r\na=recvonly\r\nm=image 4402 udptl t38\r\na=T38FaxVersion:0\r\na=T38MaxBitRate:14400\r\n"""
+
+def hexdump(src, length=8):
+    """Recipe is from http://code.activestate.com/recipes/142812/"""
+    result = []
+    digits = 4 if isinstance(src, unicode) else 2
+    for i in xrange(0, len(src), length):
+       s = src[i:i+length]
+       hexa = b' '.join(["%0*X" % (digits, ord(x))  for x in s])
+       text = b''.join([x if 0x20 <= ord(x) < 0x7F else b'.'  for x in s])
+       result.append( b"%04X   %-*s   %s" % (i, length*(digits + 1), hexa, text) )
+    return b'\n'.join(result)
+
+server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+server_socket.bind(("127.0.0.1", MGCP_CALLAGENT_PORT))
+server_socket.setblocking(0)
+
+
+def send_receive(packet):
+    server_socket.sendto(packet, ("127.0.0.1", MGCP_GATEWAY_PORT))
+    try:
+        data, addr = server_socket.recvfrom(4096)
+        print hexdump(data), addr
+    except socket.error:
+        pass
+
+def generate_tid():
+    import random
+    return random.randint(0, 65123)
+
+
+
+i = 1
+while True:
+    send_receive(rsip_resp)
+    send_receive(audit_packet)
+    send_receive(crcx_packet % generate_tid() )
+    send_receive(mdcx_packet % (generate_tid(), i))
+    send_receive(dlcx_packet % (generate_tid(), i))
+    i = i + 1
+
+    time.sleep(3)

openbsc/include/openbsc/mgcp.h

@@ -0,0 +1,48 @@
+/* A Media Gateway Control Protocol Media Gateway: RFC 3435 */
+
+/*
+ * (C) 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2009 by on-waves.com
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+unsigned int rtp_base_port = 4000;
+
+/**
+ * Calculate the RTP audio port for the given multiplex
+ * and the direction. This allows a semi static endpoint
+ * to port calculation removing the need for the BSC
+ * and the MediaGateway to communicate.
+ *
+ * Port usage explained:
+ *       base + (multiplex * 2) + 0 == local port to wait for network packets
+ *       base + (multiplex * 2) + 1 == local port for rtcp
+ *
+ * The above port will receive packets from the BTS that need
+ * to be patched and forwarded to the network.
+ * The above port will receive packets from the network that
+ * need to be patched and forwarded to the BTS.
+ *
+ * We assume to have a static BTS IP address so we can differentiate
+ * network and BTS.
+ *
+ */
+int rtp_calculate_port(int multiplex, int base)
+{
+	return base + (multiplex * 2);
+}

openbsc/include/vty/command.h

@@ -106,6 +106,7 @@ enum node_type {
 	TRX_NODE,
 	TS_NODE,
 	SUBSCR_NODE,
+	MGCP_NODE,
 };
 
 /* Node which has some commands and prompt string and configuration

openbsc/src/Makefile.am

@@ -1,7 +1,8 @@
 INCLUDES = $(all_includes) -I$(top_srcdir)/include
 AM_CFLAGS=-Wall
 
-sbin_PROGRAMS = bsc_hack bs11_config ipaccess-find ipaccess-config isdnsync
+sbin_PROGRAMS = bsc_hack bs11_config ipaccess-find ipaccess-config isdnsync \
+                isdnsync bsc_mgcp
 noinst_LIBRARIES = libbsc.a libmsc.a libvty.a libsccp.a
 noinst_HEADERS = vty/cardshell.h
 
@@ -32,3 +33,6 @@ ipaccess_config_SOURCES = ipaccess-config.c
 ipaccess_config_LDADD = libbsc.a libmsc.a libbsc.a libvty.a -ldl -ldbi $(LIBCRYPT)
 
 isdnsync_SOURCES = isdnsync.c
+
+bsc_mgcp_SOURCES = bsc_mgcp.c msgb.c talloc.c debug.c select.c timer.c
+bsc_mgcp_LDADD = libvty.a

openbsc/src/mgcp.cfg

@@ -0,0 +1,17 @@
+!
+! MGCP configuration hand edited
+!   !
+password foo
+!
+line vty
+ no login
+!
+mgcp
+  local ip 172.23.23.23
+  bts ip 192.168.100.100
+  bind ip 0.0.0.0
+  bind port 2427
+  bind early 1
+  rtp base 4000
+  sdp audio payload number 97
+  sdp audio payload name GSM-EFR/8000