[SR-Users] rtpproxy_manage() doesn't recognize SDP when Content-Length is not present

Alex Balashov abalashov at evaristesys.com
Sun Dec 22 23:41:55 CET 2019


To be completely fair to these implementation decisions, 3261 says that
Content-Length "SHOULD" be included over UDP; it just does not say that
it "MUST" be. 

However:

1. You can remove flag 128 from the sanity_check() headers and likely
remove the complaint about the missing CL field (I would guess):

https://kamailio.org/docs/modules/5.3.x/modules/sanity.html#sanity.overview

2. Strictly speaking, it is the rtpproxy control module which complains
about the lack of a CL header, not the SIP stack. No message parsing
error or complaint about lack of message validity is being emitted from
Kamailio.

This is likewise true of RTPEngine, in a quick test:

Dec 22 17:37:05 allegro-1.evaristesys.com /usr/local/sbin/kamailio[3785]: ERROR: rtpengine [rtpengine_funcs.c:181]: extract_body(): failed to get the content length in message

Dec 22 17:37:05 allegro-1.evaristesys.com /usr/local/sbin/kamailio[3785]: ERROR: rtpengine [rtpengine.c:2334]: rtpp_function_call(): can't extract body from the message

These modules and the rtpproxy control protocols they front-end are free
to impose their own requirements above and beyond 3261, particularly if
they are following RFC guidance that, while falling short of "MUST", is
nevertheless a matter of "SHOULD".

One could argue that this is a problem for the rtpproxy/rtpengine module
maintainers rather than Kamailio, and that the real problem is that the
requirement of a CL header is not clearly documented, rather than that
Kamailio does not recognise such a SIP message to be valid.

-- Alex

On Sun, Dec 22, 2019 at 01:29:02PM +0200, Leonid Fainshtein wrote:

> Hi,
> According to RFC-3261 p.20.14, the Content-Length header field must be
> present only if a stream-base transport protocol (such as TCP) is used.
> Therefore, in the case of the UDP transport protocol, this field is
> optional.
> Unfortunately, the rtpproxy_manage() function in Kamailio v.5.2.5 doesn't
> recognize the SDP body when the Content-Length header field is not present:
> Dec 22 08:58:34 pbx kamailio[13456]:  4(13488) WARNING: {1 1 INVITE
> wrjxwyuke5ukvvwwxd00zwtu0ktfuzuf at 10.18.5.64} sanity [sanity.c:585]:
> check_cl(): content length header missing in request
> Dec 22 08:58:34 pbx kamailio[13456]:  4(13488) INFO: {1 1 INVITE
> wrjxwyuke5ukvvwwxd00zwtu0ktfuzuf at 10.18.5.64} <script>: rtproxy ei.
> \(source:81.xxx.xxx.xxx, INVITE sip:098232787 at xxx.xxx.xxx.xxx:5060;user=phone
> \)
> Dec 22 08:58:34 pbx kamailio[13456]:  4(13488) ERROR: {1 1 INVITE
> wrjxwyuke5ukvvwwxd00zwtu0ktfuzuf at 10.18.5.64} rtpproxy
> [rtpproxy_funcs.c:182]: extract_body(): failed to get the content length in
> message
> Dec 22 08:58:34 pbx kamailio[13456]:  4(13488) ERROR: {1 1 INVITE
> wrjxwyuke5ukvvwwxd00zwtu0ktfuzuf at 10.18.5.64} rtpproxy [rtpproxy.c:2271]:
> force_rtp_proxy(): can't extract body from the message
> Dec 22 08:58:34 pbx rtpproxy[1386]: DBUG:GLOBAL:get_command: received
> command "13498_4 LSEIc0,101 wrjxwyuke5ukvvwwxd00zwtu0ktfuzuf at 10.18.5.64
> 10.70.227.183 13592 d5k0w3ft-CC-1116-OFC-253;1 as0bf73ed7;1"
> Dec 22 08:58:34 pbx rtpproxy[1386]: INFO:GLOBAL:handle_command: lookup
> request failed: session wrjxwyuke5ukvvwwxd00zwtu0ktfuzuf at 10.18.5.64, tags
> d5k0w3ft-CC-1116-OFC-253;1/as0bf73ed7;1 not found
> Dec 22 08:58:34 pbx rtpproxy[1386]: DBUG:GLOBAL:rtpc_doreply: sending reply
> "0\n"
> 
> Also, the textops' has_body() function always checks the “Content-Length”
> presence that is not 100% correct behavior.
> 
> Just for your information, the problem was discovered in a system where
> Huawei SoftX3000 is used. It looks like the softswitch removes
> the “Content-Length”  field in an attempt to decrease size of SIP message
> when it is too long. If the user disables some codecs in their SIP phone
> then SoftX3000 keeps the “Content-Length” untouched.
> 
> Should I open a bug regarding this matter?
> 
> Best regards,
> Leonid Fainshtein
> Xorcom Ltd

> _______________________________________________
> Kamailio (SER) - Users Mailing List
> sr-users at lists.kamailio.org
> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users


-- 
Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free) 
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/



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