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Summary:ASTERISK-15826: [regression][patch] SDP c and o lines contain the wrong IP address when using an externally mapped IP(extern{ip,host})
Reporter:Elazar Broad (ebroad)Labels:
Date Opened:2010-03-16 15:45:18Date Closed:2010-08-10 11:55:50
Priority:MinorRegression?No
Status:Closed/CompleteComponents:Channels/chan_sip/General
Versions:Frequency of
Occurrence
Related
Issues:
Environment:Attachments:
Description:The problem stems from a call to ast_rtp_instance_get_local_address() in chan_sip.c in get_our_media_address(). ast_rtp_instance_get_local_address() will always return the internal IP address of the Asterisk machine, which could pose a problem when using NAT.

A simple solution would be to override {v,t}sin->sin_addr in get_our_media_address() with p->ourip.sin_addr.s_addr if it is different, though I don't know what that might break.  

****** ADDITIONAL INFORMATION ******

SIP/2.0 200 OK
Via: SIP/2.0/UDP 64.154.41.100:5060;branch=z9hG4bK02f92e83f22e56e634998f3e31edc07f;received=64.154.41.100;rport=5060
From: <sip:6463126269@64.154.41.100>;tag=3477761011-584029
To: <sip:401xxxxxxx@64.154.41.100>;tag=as26d7ea77
Call-ID: 5808065-3477761011-583993@msx71.mydomain.com
CSeq: 1 INVITE
Server: Asterisk PBX
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO
Supported: replaces, timer
Contact: <sip:401xxxxxxx@72.xx.157.xx>
Content-Type: application/sdp
Content-Length: 254

v=0
o=asterisk 2050955676 2050955676 IN IP4 10.xx.50.xx
s=Asterisk PBX
c=IN IP4 10.xx.50.xx
t=0 0
m=audio 16482 RTP/AVP 0 8 101
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
a=sendrecv
Comments:By: Leif Madsen (lmadsen) 2010-03-16 18:43:12

Marking this as Confirmed as I think this should be put on reviewboard as any non-trivial changes to chan_sip should go through that process.
By: Elazar Broad (ebroad) 2010-03-16 21:01:41

Duly noted and done, thanks Leif!
By: Elazar Broad (ebroad) 2010-08-10 11:46:11

chan_sip r250617(http://svnview.digium.com/svn/asterisk?view=revision&revision=250917) changed the behavior of get_our_media_address(). Before the commit, if media_address was set, we would us it, otherwise, we would use p->ourip which would contain the external mapped IP address of the machine when running Asterisk behind NAT, which is correct. Now, we go through the following order:
1. media_address
2. Local address returned by the RTP engine
3. p->ourip

The problem is that the RTP engine will always return the local address of the machine(AFAIK, it is not NAT aware), which means the IP address sent in the SDP payload will be incorrect in a NAT scenario.
By: Digium Subversion (svnbot) 2010-08-10 11:54:18

Repository: asterisk
Revision: 281532

U   branches/1.8/channels/chan_sip.c

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r281532 | russell | 2010-08-10 11:54:18 -0500 (Tue, 10 Aug 2010) | 8 lines

Ensure that the proper external address is used for the RTP destination.

(closes issue ASTERISK-15826)
Reported by: ebroad
Tested by: ebroad

Review: https://reviewboard.asterisk.org/r/566/

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http://svn.digium.com/view/asterisk?view=rev&revision=281532
By: Digium Subversion (svnbot) 2010-08-10 11:55:50

Repository: asterisk
Revision: 281533

_U  trunk/
U   trunk/channels/chan_sip.c

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r281533 | russell | 2010-08-10 11:55:49 -0500 (Tue, 10 Aug 2010) | 15 lines

Merged revisions 281532 via svnmerge from
https://origsvn.digium.com/svn/asterisk/branches/1.8

........
 r281532 | russell | 2010-08-10 11:54:20 -0500 (Tue, 10 Aug 2010) | 8 lines
 
 Ensure that the proper external address is used for the RTP destination.
 
 (closes issue ASTERISK-15826)
 Reported by: ebroad
 Tested by: ebroad
 
 Review: https://reviewboard.asterisk.org/r/566/
........

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http://svn.digium.com/view/asterisk?view=rev&revision=281533