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

[Mark Allen]

Hi Răzvan - thanks for the reply

Looking into it, our working theory is that the problem is as follows...

UAC (WebRTC dialer) is sending a corrupted SIP 200OK to an OPTIONS message
over WebSocket. Message has a blank line in it and the content length is 0.
OpenSIPS sees the blank line as the end of the SIP message but UAC is
sending more (garbage text) after the blank line. I assume that what comes
after the blank line is buffered and seen as the start of a new SIP
message? When the next SIP message comes in it gets appended to the corrupt
message segment and when OpenSIPS tries to parse it, it sees it as nonsense
(which it is).

Just waiting on testing a new version of UAC which will hopefully confirm
that this is the problem.

cheers,

M

On Wed, 2 Jun 2021 at 08:57, Răzvan Crainea <razvan at opensips.org> wrote:

> 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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> >
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