[Blink] IP Address problems with multiple interfaces

Mark Murawski markm-lists at intellasoft.net
Thu Oct 31 16:09:02 CET 2013


I use openvpn to make links to other voip servers, and then use a soft 
phone to place calls.

Say you have the following setup:

eth0: 192.168.0.201
tun0: 10.3.2.7

remote sip proxy: 10.3.2.20


I set up an account in blink to make all calls through the proxy. 
Registration is successful.

I make a call:

The sip invite packet looks like this:

INVITE sip:918882472425 at acs-pa.client.local SIP/2.0
Via: SIP/2.0/UDP 
192.168.0.120:48668;rport;branch=z9hG4bKPjm2Gg2fuVCKao1yq3PY4D-QHp2I.nTwBJ
Max-Forwards: 70
From: "ACS Pa 6322" 
<sip:6322 at acs-pa.client>;tag=teK6SpsD-ayASv1UlD1e3rLS-y7-rqhf
To: <sip:918882472425 at acs-pa.client>
Contact: <sip:34298057 at 10.3.2.7:48668>
Call-ID: RHwr5rXnHSa5ndd-pNtsLRZhahNEXCIx
CSeq: 18309 INVITE
Allow: SUBSCRIBE, NOTIFY, PRACK, INVITE, ACK, BYE, CANCEL, UPDATE, 
MESSAGE, REFER
Supported: 100rel, replaces, norefersub, gruu
User-Agent: Blink 0.5.0 (Linux)
Content-Type: application/sdp
Content-Length:   548

v=0
o=- 3592220363 3592220363 IN IP4 10.3.2.7
s=Blink 0.5.0 (Linux)
c=IN IP4 10.3.2.20
t=0 0
m=audio 50004 RTP/AVP 108 99 98 9 0 8 96
c=IN IP4 192.168.0.120
a=rtcp:50005
a=rtpmap:108 opus/48000
a=rtpmap:99 speex/32000
a=rtpmap:98 speex/16000
a=rtpmap:9 G722/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=crypto:1 AES_CM_128_HMAC_SHA1_80 
inline:OLcvitcpR/nYXwo/d1nI0LyNiX4aUIJ8zunGKkzl
a=crypto:2 AES_CM_128_HMAC_SHA1_32 
inline:Kf3AntnCUpDg0qesncqVgGrsvfcj7s9v+oe3TwuD
a=sendrecv

The packet is going out tun0, but blink's sip elements are wrong in two 
locations:

Via: SIP/2.0/UDP 
192.168.0.120:48668;rport;branch=z9hG4bKPjm2Gg2fuVCKao1yq3PY4D-QHp2I.nTwBJ
c=IN IP4 192.168.0.120

These should be using the tun0 interface of 10.3.2.7

You'll notice these two elements are correct:
Contact: <sip:34298057 at 10.3.2.7:48668>
o=- 3592220363 3592220363 IN IP4 10.3.2.7

And obviously a public stun server isn't going to work to address this 
because this is all private/internal networks.

Blink never receives any response to the invite (success or failure), 
the return packets from the proxy are going to the wrong address.




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