[OpenSIPS-Users] Am I seeing SIP message fragmentation?

[Răzvan Crainea]

Hi, Mark!

Most likely the problem appear prior to that Contact header you're 
seeing - somehow OpenSIPS thinks the packet starts with the Contact 
token, whereas, most likely, the Contact is part of a previous message, 
not shown in this report.
There's no such thing as SIP message fragmentation - it's either UDP or 
TCP fragmentation. However, fragmentation only appears when the package 
is higher than MTU. I don't think this is the case here - What I think 
there is, is a broken UA which is not setting a correct Content-Length, 
or is sending garbage after sending the packet. But the only way to 
figure out is to make a pcap for the entire connection and see where it 
starts breaking.

Best regards,

Răzvan Crainea
OpenSIPS Core Developer
http://www.opensips-solutions.com

On 5/26/21 2:15 PM, Mark Allen wrote:
> I'm seeing a weird, intermittent error. The most common occurrence is 
> with a 200OK returned by Mid-Registrar on a re-REGISTER using 
> registration throttling, but we see it elsewhere. It appears that the 
> 200OK message is getting garbled.
> 
> We have a bit of a weird setup to overcome issues we were having with 
> Mid-Registrar and WebSocket addressing. Mid-Registrar is looping back 
> 200OK to OpenSIPS before it then gets sent down the WebSocket. 90+% of 
> the time it's absolutely fine, but occasionally the 200OK seems to be 
> corrupted.
> 
> Here's an example. What we are seeing in this message is...
> 
>      Contact: <sip:1234 at abc.def.com:5060 <http://sip:1234@abc.def.com:5060>>
>      User-Agent: MWWRTC 3.4.21042#015#012Accept: 
> application/sdp,application/dtmf-relay,text/plain
> 
> ...preceding...
> 
>      SIP/2.0 200 OK
>      Via: SIP/2.0/TCP 
> 192.168.1.23:5060;received=192.168.1.23;rport=42385;branch=z9hG4bK22a8.4fa6d127.0;i=b4986fe4
>      ...etc...
> 
> ...so OpenSIPS is failing to parse the message.
> 
> What I'd like to know is, is this a sign of SIP message fragmentation?
> 
> 
> 
> Log entries (IP addresses, domains, and extensions changed to protect 
> the innocent!):
> 
> ERROR:core:parse_method: invalid character :
> DBG:core:tcp_read_req: tcp_read_req end
> INFO:core:parse_first_line: failed to parse the method
> INFO:core:parse_first_line: bad message
> DBG:core:parse_msg: invalid message
> ERROR:core:parse_msg: message=<Contact: <sip:1234 at abc.def.com:5060 
> <http://sip:1234@abc.def.com:5060>>#015#012User-Agent: MWWRTC 
> 3.4.21042#015#012Accept: 
> application/sdp,application/dtmf-relay,text/plain#015#012SIP/2.0 200 
> OK#015#012Via: SIP/2.0/TCP 
> 192.168.1.23:5060;received=192.168.1.23;rport=42385;branch=z9hG4bK22a8.4fa6d127.0;i=b4986fe4#015#012Via: 
> SIP/2.0/WSS 
> 98kaag0xmybq.invalid;received=4.56.78.110;branch=z9hG4bKU6O3fJQGeLvuACMTXTArJgJW73rOD5dU;rport=52570#015#012From: 
> <sip:1234 at abc.def.com 
> <mailto:sip%3A1234 at abc.def.com>>;tag=Lyk010G476K7xcKrE84M#015#012To: 
> <sip:1234 at abc.def.com 
> <mailto:sip%3A1234 at abc.def.com>>;tag=af78-6213d386c3edcd02707b0c0aa8423d3a#015#012Call-ID: 
> 666b5e7c-cef3-f306-4b79-60d3160dc5d0#015#012CSeq: 28825 
> REGISTER#015#012Contact: 
> <sips:1234 at 98kaag0xmybq.invalid;transport=wss>;expires=60;received="sip:4.56.78.110:52570 
> <http://4.56.78.110:52570>"#015#012Server: OpenSIPS (3.1.1 
> (x86_64/linux))#015#012Content-Length: 0#015#012#015#012>
> ERROR:core:receive_msg: Unable to parse msg received from 
> [192.168.1.23:5060 <http://192.168.1.23:5060>]
> ERROR:core:tcp_handle_req: receive_msg failed
> DBG:core:tcp_read_req: tcp_read_req end
> 
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