[SR-Users] bug ? remap_503_500 breaks dialogs
Henning Westerholt
hw at skalatan.de
Thu Jul 23 14:53:42 CEST 2020
Hello,
just to add to the RFC quoted below: this is referring to 1xx or 2xx responses. But later on, in the section, the RFC seems to be quite clear:
If the only
response that was received is a 503, the proxy SHOULD generate
a 500 response and forward that upstream.
A proxy MUST NOT modify the To tag in any forwarded response to
a request that contains a To tag.
Cheers,
Henning
From: sr-users <sr-users-bounces at lists.kamailio.org> On Behalf Of Gerry | Rigatta
Sent: Thursday, July 23, 2020 2:41 PM
To: miconda at gmail.com
Cc: Kamailio (SER) - Users Mailing List <sr-users at lists.kamailio.org>
Subject: Re: [SR-Users] bug ? remap_503_500 breaks dialogs
Hi Daniel,
thanks for looking into this.
The initial INVITE does not have a to-tag but there is an intermediate session progress with a to-tag. See grep below.
The RFC does not distinguish between established or provisional dialogs when it comes to the handling of the to-tags. If there is a to-tag it must not be changed by the Proxy. Clearly that must be so because the to-tag is used by the UAC to identify the call.
Best Gerry
IP addresses are changed in below dialog for security reasons
U 7.7.23.109:5060 -> 11.22.17.24:5060 #5
INVITE sip:111100791456321475 at 13.23.9.94:5060 SIP/2.0..Max-Forwards: 19.
.P-Asserted-Identity: tel:+4867777777..Via: SIP/2.0/UDP 7.7.23.109:5060
;rport;branch=z9hG4bK1682611991..From: "004867777777" <sip:004867777777 at 7
8.47.203.109>;tag=540342132..To: <sip:111100791456321475 at 13.23.9.94:5060
>..Call-ID: 1279305029 at 7.7.23.109<mailto:1279305029 at 7.7.23.109>..CSeq: 1 INVITE..User-Agent: nulltech.
.Contact: <sip:004867777777 at 7.7.23.109:5060>..Allow: ACK, INVITE, BYE,
CANCEL, REGISTER, REFER, OPTIONS, PRACK, INFO..Supported: 100rel..Content-T
ype: application/sdp..Content-Length: 209....v=0..o=yate 1595505273 1595505
273 IN IP4 7.7.23.109..s=SIP Call..c=IN IP4 7.7.23.109..t=0 0..m=audi
o 28610 RTP/AVP 8 0 101..a=rtpmap:8 PCMA/8000..a=rtpmap:0 PCMU/8000..a=rtpm
ap:101 telephone-event/8000..
#
U 11.22.17.24:5060 -> 7.7.23.109:5060 #6
SIP/2.0 100 trying -- your call is important to us..Via: SIP/2.0/UDP 78.47.
203.109:5060;rport=5061;branch=z9hG4bK1682611991;received=7.7.23.109..Fr
om: "004867777777" <sip:004867777777 at 7.7.23.109>;tag=540342132..To: <s
ip:111100791456321475 at 13.23.9.94<mailto:111100791456321475 at 13.23.9.94>:5060>..Call-ID: 1279305029 at 7.7.23.10<mailto:1279305029 at 7.7.23.10>
9..CSeq: 1 INVITE..Server: kamailio (5.2.3 (x86_64/linux))..Content-Length:
0....
#
U 11.22.17.24:5060 -> 13.23.9.94:5060 #7
INVITE sip:111100791456321475 at 13.23.9.94:5060 SIP/2.0..Record-Route: <si
p:11.22.17.24:5060;lr=on>..Max-Forwards: 18..P-Asserted-Identity: tel:+
4867777777..Via: SIP/2.0/UDP 11.22.17.24:5060;branch=z9hG4bK58d4.f1e37
b7feb047b6707c5fb8a298d36fc.0..Via: SIP/2.0/UDP 7.7.23.109:5060;received
=7.7.23.109;rport=5061;branch=z9hG4bK1682611991..From: "004867777777" <
sip:004867777777 at 7.7.23.109>;tag=540342132..To: <sip:111100791456321475
@13.23.9.94:5060>..Call-ID: 1279305029 at 7.7.23.109<mailto:1279305029 at 7.7.23.109>..CSeq: 1 INVITE..Us
er-Agent: nulltech..Contact: <sip:004867777777 at 7.7.23.109:5060>..Allow:
ACK, INVITE, BYE, CANCEL, REGISTER, REFER, OPTIONS, PRACK, INFO..Supported
: 100rel..Content-Type: application/sdp..Content-Length: 209....v=0..o=yate
1595505273 1595505273 IN IP4 7.7.23.109..s=SIP Call..c=IN IP4 7.7.23
.109..t=0 0..m=audio 28610 RTP/AVP 8 0 101..a=rtpmap:8 PCMA/8000..a=rtpmap:
0 PCMU/8000..a=rtpmap:101 telephone-event/8000..
#
U 13.23.9.94:5060 -> 11.22.17.24:5060 #8
SIP/2.0 100 Trying..Via: SIP/2.0/UDP 11.22.17.24:5060;branch=z9hG4bK58d
4.f1e37b7feb047b6707c5fb8a298d36fc.0;received=11.22.17.24..Via: SIP/2.0
/UDP 7.7.23.109:5060;received=7.7.23.109;rport=5061;branch=z9hG4bK168
2611991..Record-Route: <sip:11.22.17.24:5060;lr=on>..From: "00371673360
58" <sip:004867777777 at 7.7.23.109>;tag=540342132..To: <sip:1111007914563
21475 at 13.23.9.94<mailto:21475 at 13.23.9.94>:5060>..Call-ID: 1279305029 at 7.7.23.109<mailto:1279305029 at 7.7.23.109>..CSeq: 1 INVIT
E..User-Agent: Ravetel SIP proxy..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE,
REFER, SUBSCRIBE, NOTIFY, INFO..Supported: replaces..Contact: <sip:1111007
91456321475 at 13.23.9.94<mailto:91456321475 at 13.23.9.94>:5060>..Content-Length: 0....
#
U 13.23.9.94:5060 -> 11.22.17.24:5060 #9
SIP/2.0 183 Session Progress..Via: SIP/2.0/UDP 11.22.17.24:5060;branch=
z9hG4bK58d4.f1e37b7feb047b6707c5fb8a298d36fc.0;received=11.22.17.24..Vi
a: SIP/2.0/UDP 7.7.23.109:5060;received=7.7.23.109;rport=5061;branch=
z9hG4bK1682611991..Record-Route: <sip:11.22.17.24:5060;lr=on>..From: "0
04867777777" <sip:004867777777 at 7.7.23.109>;tag=540342132..To: <sip:103
000791456321475 at 13.23.9.94<mailto:000791456321475 at 13.23.9.94>:5060>;tag=as6d86b4e8..Call-ID: 1279305029 at 78.
47.203.109..CSeq: 1 INVITE..User-Agent: Ravetel SIP proxy..Allow: INVITE, A
CK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO..Supported: replac
es..Contact: <sip:111100791456321475 at 13.23.9.94:5060>..Content-Type: app
lication/sdp..Content-Length: 235....v=0..o=root 714 714 IN IP4 136.243.29.
94..s=session..c=IN IP4 13.23.9.94..t=0 0..m=audio 10454 RTP/AVP 8 0 101
..a=rtpmap:8 PCMA/8000..a=rtpmap:0 PCMU/8000..a=rtpmap:101 telephone-event/
8000..a=fmtp:101 0-16..a=ptime:20..a=sendrecv..
#
U 11.22.17.24:5060 -> 7.7.23.109:5060 #10
SIP/2.0 183 Session Progress..Via: SIP/2.0/UDP 7.7.23.109:5060;received=
7.7.23.109;rport=5061;branch=z9hG4bK1682611991..Record-Route: <sip:116.2
02.187.204:5060;lr=on>..From: "004867777777" <sip:004867777777 at 7.7.23.
109>;tag=540342132..To: <sip:111100791456321475 at 13.23.9.94:5060>;tag=as6
d86b4e8..Call-ID: 1279305029 at 7.7.23.109<mailto:1279305029 at 7.7.23.109>..CSeq: 1 INVITE..User-Agent: Ravet
el SIP proxy..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE,
NOTIFY, INFO..Supported: replaces..Contact: <sip:111100791456321475 at 136.24
3.29.94:5060>..Content-Type: application/sdp..Content-Length: 235....v=0..o
=root 714 714 IN IP4 13.23.9.94..s=session..c=IN IP4 13.23.9.94..t=0
0..m=audio 10454 RTP/AVP 8 0 101..a=rtpmap:8 PCMA/8000..a=rtpmap:0 PCMU/800
0..a=rtpmap:101 telephone-event/8000..a=fmtp:101 0-16..a=ptime:20..a=sendre
cv..
#
U 13.23.9.94:5060 -> 11.22.17.24:5060 #39
SIP/2.0 503 Service Unavailable..Via: SIP/2.0/UDP 11.22.17.24:5060;bran
ch=z9hG4bK58d4.f1e37b7feb047b6707c5fb8a298d36fc.0;received=11.22.17.24.
.Via: SIP/2.0/UDP 7.7.23.109:5060;received=7.7.23.109;rport=5061;bran
ch=z9hG4bK1682611991..From: "004867777777" <sip:004867777777 at 7.7.23.10
9>;tag=540342132..To: <sip:111100791456321475 at 13.23.9.94:5060>;tag=as6d8
6b4e8..Call-ID: 1279305029 at 7.7.23.109<mailto:1279305029 at 7.7.23.109>..CSeq: 1 INVITE..User-Agent: Ravet
el SIP proxy..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, N
OTIFY, INFO..Supported: replaces..X-Asterisk-HangupCause: Call Rejected..X-
Asterisk-HangupCauseCode: 21..Content-Length: 0....
#
U 11.22.17.24:5060 -> 13.23.9.94:5060 #40
ACK sip:111100791456321475 at 13.23.9.94:5060 SIP/2.0..Max-Forwards: 18..Vi
a: SIP/2.0/UDP 11.22.17.24:5060;branch=z9hG4bK58d4.f1e37b7feb047b6707c5
fb8a298d36fc.0..From: "004867777777" <sip:004867777777 at 7.7.23.109>;tag
=540342132..To: <sip:111100791456321475 at 13.23.9.94:5060>;tag=as6d86b4e8.
.Call-ID: 1279305029 at 7.7.23.109<mailto:1279305029 at 7.7.23.109>..CSeq: 1 ACK..Content-Length: 0....
#
U 11.22.17.24:5060 -> 7.7.23.109:5060 #41
SIP/2.0 500 Service Unavailable..Via: SIP/2.0/UDP 7.7.23.109:5060;rport=
5061;branch=z9hG4bK1682611991;received=7.7.23.109..From: "004867777777"
<sip:004867777777 at 7.7.23.109>;tag=540342132..To: <sip:1111007914563214
75 at 13.23.9.94<mailto:75 at 13.23.9.94>:5060>;tag=95329101123423eab1637e9ad490b3a6-9d3c..Call-ID:
1279305029 at 7.7.23.109<mailto:1279305029 at 7.7.23.109>..CSeq: 1 INVITE..Server: kamailio (5.2.3 (x86_64/l
inux))..Content-Length: 0....
#
U 11.22.17.24:5060 -> 7.7.23.109:5060 #42
SIP/2.0 500 Service Unavailable..Via: SIP/2.0/UDP 7.7.23.109:5060;rport=
5061;branch=z9hG4bK1682611991;received=7.7.23.109..From: "004867777777"
<sip:004867777777 at 7.7.23.109>;tag=540342132..To: <sip:1111007914563214
75 at 13.23.9.94<mailto:75 at 13.23.9.94>:5060>;tag=95329101123423eab1637e9ad490b3a6-9d3c..Call-ID:
1279305029 at 7.7.23.109<mailto:1279305029 at 7.7.23.109>..CSeq: 1 INVITE..Server: kamailio (5.2.3 (x86_64/l
inux))..Content-Length: 0....
#
On 23 Jul 2020, at 10:51, Daniel-Constantin Mierla <miconda at gmail.com<mailto:miconda at gmail.com>> wrote:
Did the initial INVITE received the 200ok, the call is connected and this is the case of a re-INVITE? In such case the dialog has to be terminated by a BYE.
If the call is not established, so it is between initial INVITE and no 200ok was received, then the INVITE request did not contain the To-tag. And what is done by Kamailio is valid as per email responses so far.
Maybe you can just send the ngrep output with all sip requests/replies for this case and we can see exactly which scenario you talk about.
Cheers,
Daniel
On 23.07.20 09:41, Gerry | Rigatta wrote:
Indeed, at this stage there is no dialog established and there can be many To-tags in 1xx provisional responses (eg, a parallel forking scenario) -- the to-tag of the dialog has to be taken from 200ok.
As far as I read this is not correct. Also a provisional dialog is a dialog according to RFC3261. Only in the case that the request did not contain a to-tag the provisional messages may insert their own to-tags:
"1xx and 2xx responses may be involved in the establishment of
dialogs. When a request does not contain a To tag, the To tag
in the response is used by the UAC to distinguish multiple
responses to a dialog creating request. A proxy MUST NOT
insert a tag into the To header field of a 1xx or 2xx response
if the request did not contain one. A proxy MUST NOT modify
the tag in the To header field of a 1xx or 2xx response.”
https://tools.ietf.org/html/rfc3261#page-111
In any case, this bug is not a about provisional messages. The 500 message terminates the dialog for the UAC (yate) and the UAC needs to be able to identify it. An UAC identifies the dialog by the call-id, local tag and remote tag.
12<https://tools.ietf.org/html/rfc3261#section-12> Dialogs
A dialog is identified at each UA with a dialog ID, which consists of a Call-ID value, a local tag and a remote tag…"
On 23 Jul 2020, at 10:07, Daniel-Constantin Mierla <miconda at gmail.com<mailto:miconda at gmail.com>> wrote:
Indeed, at this stage there is no dialog established and there can be many To-tags in 1xx provisional responses (eg, a parallel forking scenario) -- the to-tag of the dialog has to be taken from 200ok.
This parameter is probably to have a shortcut of doing:
failure_route[REMAP503] {
if(t_check_status("503")) {
t_reply("500", "Server error");
exit;
}
Being like the server application is generating the 500 (so using own tag), instead of forwarding the 503. Not a bug, but if anyone is willing to add an option to allow re-using the to-tag from received reply, I am fine with it.
Anyhow, even if this would be fixed, I am wondering how yate is going to work in parallel/serial forking scenarios where different to-tags flow for a while and the final failure response can have any to-tag, including a new one (e.g., from a device not sending any 1xx or again from kamailio (e.g., when last target doesn't reply at all)).
Cheers,
Daniel
On 23.07.20 06:08, M S wrote:
The SIP code 503 is tricky in the sense that i can indicate either server maintenance or server overload. In both cases it can send Retry-After header and any subsequent requests from same source are ignored for the duration of Retry-After interval. [1].
Additionally RFC3261 and RFC3263 define that transport failures (generally due to fatal ICMP errors in UDP and connection failures in TCP) should be treated as 503 response. [2].
So in all above cases, it is most likely that dialog does not establishes at all and 503 response is treated similar to stateless response. Therefore, a to-tag can be added/replaced before sending it to UAC.
Theoretically, kamailio should check and use to-tag from 503 response when converting it to 500 response and only create new to-tag if it is absent.
References:
[1] https://tools.ietf.org/html/rfc3261#section-21.5.4
[2] https://tools.ietf.org/html/draft-hilt-sip-correction-503-01#section-4
Hope this helps.
On Wed, 22 Jul 2020 at 21:08, Henning Westerholt <hw at skalatan.de<mailto:hw at skalatan.de>> wrote:
Hello,
Apparently, this is the way the code works:
t_reply.c:
if (relayed_code==503 && tm_remap_503_500){
/* replace a final 503 with a 500:
* generate a "FAKE" reply and a new to_tag (for easier
* debugging)*/
Lets see if maybe others can comment as well. Otherwise you could just open an issue on our tracker, it is probably not that hard to change this.
Cheers,
Henning
--
Henning Westerholt – https://skalatan.de/blog/
Kamailio services – https://gilawa.com<https://gilawa.com/>
From: sr-users <sr-users-bounces at lists.kamailio.org<mailto:sr-users-bounces at lists.kamailio.org>> On Behalf Of Gerry | Rigatta
Sent: Wednesday, July 22, 2020 8:58 PM
To: Kamailio (SER) - Users Mailing List <sr-users at lists.kamailio.org<mailto:sr-users at lists.kamailio.org>>
Subject: [SR-Users] bug ? remap_503_500 breaks dialogs
Hi,
I am using Kamailio 5.2.
Apparently the remapping of 503 to 500 codes in the tm module does also change the to-tag. This behaviour breaks dialogs with yate and therefore calls hang and the 503 remains unacknowledged. After disabling the 503 to 500 remapping with modparam("tm", "remap_503_500", 0) all works fine again.
Changing the to-tag in a dialog seems to contradict RFC3261, or do I see this wrongly?
12<https://tools.ietf.org/html/rfc3261#section-12> Dialogs
A dialog is identified at each UA with a dialog ID, which consists of a Call-ID value, a local tag and a remote tag…"
Thanks for looking into this.
Gerry
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--
Daniel-Constantin Mierla -- www.asipto.com<http://www.asipto.com/>
www.twitter.com/miconda<http://www.twitter.com/miconda> -- www.linkedin.com/in/miconda<http://www.linkedin.com/in/miconda>
Funding: https://www.paypal.me/dcmierla
_______________________________________________
Kamailio (SER) - Users Mailing List
sr-users at lists.kamailio.org<mailto:sr-users at lists.kamailio.org>
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
--
Daniel-Constantin Mierla -- www.asipto.com<http://www.asipto.com/>
www.twitter.com/miconda<http://www.twitter.com/miconda> -- www.linkedin.com/in/miconda<http://www.linkedin.com/in/miconda>
Funding: https://www.paypal.me/dcmierla
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