Hi Nils,
Once again I'm writing to ask about more things and to give you an update on
what is happening with the FCP tests...
We have set up a simple scenario with 2 proxies separated by a firewall/NAT, and
2 UA, one within (UA1) and another outside the firewall (UA2). One UA registers
with the natted proxy (UA1), the other with the "public" proxy (UA2).
At the moment, SIP messages go forwards and backwards without problems, but
media is not flowing across the firewall.
It think the problem is in the replacement of the SDP information. The first
occurrence of the IP address in "v= " and the port in "m= " in the SDP
get
replaced, but the second IP in "c=" is not. I have been trying all sorts of
things, but no joy :( . Here are the INVITE messages in more detail. I also
include the latest fcp module for you to play with it.
---------- UA1 to proxy message ------------------
U 172.21.68.78:1129 -> 192.168.6.153:5060
INVITE sip:jaime@asereje.orange.co.uk SIP/2.0
Call-ID: 5812832001907970791(a)172.21.68.78
Content-Length: 121
Content-Type: application/sdp
To: sip:jaime@asereje.orange.co.uk
From: sip:pepe@asereje.orange.co.uk;tag=-779729009
Contact: sip:pepe@172.21.68.78:5061
CSeq: 1 INVITE
Via: SIP/2.0/UDP 172.21.68.78:5061;branch=AC15444E13C5000000F38F819DE5-2*0
v=0..o=- 1046084768435 1046084768465 IN IP4 172.21.68.78
s=-
c=IN IP4 172.21.68.78
t=0 0
m=audio 5006 RTP/AVP 8 3 0
---------- End of UA1 to proxy message -----------------
-------- Proxy to UA2 message ---------------------
U 192.168.6.153:5060 -> 172.21.68.78:15592
INVITE sip:172.21.68.78:15592 SIP/2.0
Call-ID: 5812832001907970791(a)172.21.68.78
Content-Length: 121
Content-Type: application/sdp
To: sip:jaime@asereje.orange.co.uk
From: sip:pepe@asereje.orange.co.uk;tag=-779729009
Contact:<sip:192.168.0.1:33240>
CSeq: 1 INVITE..Via: SIP/2.0/UDP 192.168.6.153;branch=z9hG4bK1019.21c52996.0
Via: SIP/2.0/UDP 172.21.68.78:5061;branch=AC15444E13C5000000F38F819DE5-2*0
v=0..o=- 1046084768435 1046084768465 IN IP4 192.168.0.1
s=-
c=IN IP4 172.21.68.78 <--- Need to change this as well!!!
t=0 0
m=audio 33240 RTP/AVP 8 3 0
------------ End of Proxy to UA2 message -------------------
(See attached file: fcp-module210203.tar.gz)
I have been trying to understand how the proxy builds the forwarded message from
the old one, and realised that for the Via replacement (or adding of more
params), I need to be using a string called add_to_branch_s and
add_to_branch_len (so ignore the replace_via implementation in the current
tar.gz). But for the SDP, whenever I work with get_body, it does not modify it
appropriately. So currently, I'm using msg->orig to get to the initial message,
search for certain IP4 and audio strings and replace them with the information
provided by the fcp server. That means, in the case of the SDP, 2 IP address
replacements (in v=.. and c=..) and 1 port replacement (in m=..). As I mentioned
before, I only manged to change the v=.. and m=... Whenever I try to replace
more than one appearance, strange things happen, like strings in non expected
places, like Via, and cannot work out why. So my question is an open one:): what
is the best way to change the SDP part?
The other of my questions is whether all this mess with NAT's will get solved
when the proxy supports TCP, and whether this is the best approach to solve the
SIP through NAT/FW problem. For example, how about a nathelper module for
netfilter/iptables that gets this working, in the same manner as IRC or ftp
currently? Does anybody know about any work progressing this for linux/FreeBSD?
Greetings,
Jaime
Nils Ohlmeier <nils(a)ohlmeier.de> on 18/02/2003 02:58:47
To: Jaime GILL/EN/HTLUK@HTLUK
cc: Jan Janak <J.Janak(a)sh.cvut.cz>
Jiri Kuthan <jiri(a)iptel.org>
Subject: Re: [Serusers] FCP support in SER: Modifying SDP
Hi Jaime,
debugging without the code is really hard :-)
But maybe your problme with SDP is correlated to a bug in the Via header which
i marked below.
Greetings
Nils
On Monday 17 February 2003 11:58, jaime.gill(a)orange.co.uk wrote:
U 192.168.6.153:5060 -> 172.21.68.78:5061
INVITE sip:pepe@172.21.68.78:5061 SIP/2.0..Via: SIP/2.0/UDP
192.168.6.153;b ranch=z9hG4bKb848.8a014f84.0..Via: SIP/2.0/UDP
192.168.0.1192.168.0.1:9439. .From: "jaime"
^^^^^^^^^^^^^^^^^^^^^^
Here you inserted the external IP twice.
Maybe your SDP replacer did this?
<sip:jaime@asereje.orange.co.uk>;tag=8c20540f-4259-11d7-9cc5
-00065b4c11cb..To: <sip:pepe@asereje.orange.co.uk>..Call-ID: 8c205410-4259-
11d7-9cc5-00065b4c11cb@172.21.68.78..CSeq: 1 INVITE..Contact:<sip:192.168.0
.1:33186>.User-Agent: Windows RTC/1.0..Content-Type: application/sdp..Conte
nt-Length: 211....v=0..o=gill_j 0 0 IN IP4 172.21.68.78..s=session..c=IN IP
4 172.21.68.78..b=CT:1000..t=0 0..m=audio 33186 RTP/AVP 97 0 8 4..a=rtpmap:
97 red/8000..a=rtpmap:0 PCMU/8000..a=rtpmap:8 PCMA/8000..a=rtpmap:4 G723/80
00..
--
gpg-key:
http://www.ohlmeier.org/public_key.asc
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