23 Mar
2020
23 Mar
'20
8:24 p.m.
Hi Alex,
to refresh this old discussion, are you sure that the requirement that the Content-Length
header needs to be at the end of the SIP message is enforced or even defined? If you use
old Kamailio standard modules like "path" it places its header directly at the
end of the message, after the Content-Length.
I also failed to find a MUST in the section 7.5 of the RFC and also in 20.14. about the
header position.
Cheers,
Henning
--
Henning Westerholt – https://skalatan.de/blog/
Kamailio services – https://gilawa.com
-----Original Message-----
From: sr-users <sr-users-bounces(a)lists.kamailio.org> On Behalf Of Alex Balashov
Sent: Thursday, March 19, 2020 2:49 AM
To: Kamailio (SER) - Users Mailing List <sr-users(a)lists.kamailio.org>
Subject: Re: [SR-Users] Manipulating contacts header results in a malformed SIP packet
Hi Andrew,
The Content-Length header, if present, is the header that must appear last in a SIP
message, per RFC 3261 § 7.5
So, any method of manipulation of the Contact must manipulate it in place. A common
favourite - if you absolutely must manipulate the Contact - is to substitute it. You can
also insert the header at an arbitrary position:
https://kamailio.org/docs/modules/5.3.x/modules/textopsx.html#textopsx.f.in…
But a better question might perhaps be: why do you want to manipulate the Contact header?
While it may perhaps be legitimately necessary occasionally, my finding has been that in
99% of cases, it's the wrong way to solve a problem.
-- Alex
On Thu, Mar 19, 2020 at 12:42:51PM +1100, Andrew White wrote:
Hi all,
Hope everyone is well, and looking forward to seeing you all whenever Kamailio World ends
up being!
I’m currently dealing with an issue which I’m unsure if it’s due to my own
implementation, or a bug.
When attempting to manipulate the Contact header via app_ruby, the SIP message I send
ends up being malformed. Here’s the code I’m using:
def replace_contact_header(uri)
#KSR::HDR.remove("Contact") if KSR::HDR.is_present('Contact') >
0
#KSR::HDR.append("Contact: #{uri}\r\n")
KSR::HDR.rmappend("Contact", "Contact: #{uri}\r\n") end
Note that I have tried both rmappend and the commented out functions too. I call this
with a custom built URI, such as <61400123123(a)kamailio.test.uconnected.com.au
<mailto:61400123123@kamailio.test.uconnected.com.au>>. This function is called
just before a KSR::TM.t_relay(). Here’s the result I get watching from tshark (some info
scrubbed for privacy):
Record-Route:
<sip:1.2.3.4;lr;ftag=e3p42efd3635HH;vst=AAAAAAAAAAAAAAAAAAAAAAoUXVFHDQ
AAs83AEGwAAFgwCQA8QY3RlZC5jb20uYXU-;did=927.f0f2>
…
Call-ID: 3de29646-e423-1238-e712-023563fb337c
CSeq: 17736747 INVITE
sip:4.5.6.7:5060;alias=10.100.1.1~5060~1Content-Type: application/sdp
Content-Length: 483
Contact: <sip:61400123123@kamailio.test.uconnected.com.au>
In this case, 4.5.6.7 is the PBX I made the call from (and the value of the original
Contact header), and 1.2.3.4 is what kamailio.test.uconnected.com.au
<http://kamailio.test.uconnected.com.au/> resolves to, and is this Kamailio
instance.
Here’s a copy of the same thing when I don’t call my replace_contact_header function and
t_relay:
Record-Route:
<sip:1.2.3.4;lr;ftag=j6jebCSa5Qap6c;vst=AAAAAAAAAAAAAAAAAAAAAAoUXVND38
dTgwEGEAEGwAAFgwCQA8Fdn83lZC5jb20uYXU-;did=827.40b>
...
Call-ID: 249571c5-e91a-ae91-6d8e-023563fb337c
CSeq: 17735867 INVITE
Contact: <sip:4.5.6.7:5060;alias=10.100.1.1~5060~1>
Content-Type: application/sdp
Content-Length: 483
Given the relative simplicity of the function, I have to assume this is an error with how
the function is manipulating the existing Contact header? It seems that the “Contact:
<“ part of the header is being removed as well as the “>\r\n", but the rest
being left.
I’m currently using commit 283e468401d809ca9b71368c32badf3a70d48b8b
<https://github.com/kamailio/kamailio/commit/283e46> on Amazon Linux 2, which is
CentOS/RHEL based.
Thanks!
Andrew
_______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)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/
_______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)lists.kamailio.org
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users