23 Nov
2012
23 Nov
'12
4:24 a.m.
Hi guys
I have a multihomed Kamailio proxy sitting between two B2BUAs on
separate networks and record-routing all dialogs.
The problem I have is that when one of these devices receives a 200
OK, it does not populate the RURI of the ACK correctly. Instead of
taking it from the Contact header on the 200 OK, it uses the user part
from the Contact header and sets the domain to the proxy IP. It then
also populates the Route headers.
The ACKs are below and the IPs are:
10.152.1.92:5060: UAC on outside
10.200.70.100:5060: proxy outside interface
192.168.242.100: proxy inside interface
192.168.242.102: UAS on inside
This the ACK message going into and coming out of the proxy.
# U 10.152.1.92:5060 -> 10.200.70.100:5060
ACK sip:natted_ua*9197**192.168.242.102*5080*udp@10.200.70.100 SIP/2.0.
Via: SIP/2.0/UDP 127.0.1.1:5060;branch=z9hG4bK-2280-1-5.
Route:
<sip:10.200.70.100;r2=on;lr=on;nat=yes>,<sip:192.168.242.100;r2=on;lr=on;nat=yes>.
From: sipp <sip:sipp@127.0.1.1:5060>;tag=2280SIPpTag001.
To: sut <sip:9197@10.200.70.100:5060>;tag=p0FaeQ1QUS9ae.
Call-ID: 1-2280(a)127.0.1.1.
CSeq: 1 ACK.
Contact: sip:sipp@127.0.1.1:5060.
Max-Forwards: 70.
Subject: Performance Test.
Content-Length: 0.
.
# U 10.200.70.100:5060 -> 192.168.242.100:5060
ACK sip:192.168.242.100;r2=on;lr=on;nat=yes SIP/2.0.
Via: SIP/2.0/UDP 10.200.70.100;branch=z9hG4bKcydzigwkX.
Via: SIP/2.0/UDP
127.0.1.1:5060;rport=5060;received=10.152.1.92;branch=z9hG4bK-2280-1-5.
Route: .
From: sipp <sip:sipp@127.0.1.1:5060>;tag=2280SIPpTag001.
To: sut <sip:9197@10.200.70.100:5060>;tag=p0FaeQ1QUS9ae.
Call-ID: 1-2280(a)127.0.1.1.
CSeq: 1 ACK.
Contact: <sip:sipp@127.0.1.1:5060;alias=10.152.1.92~5060~1>.
Max-Forwards: 69.
Subject: Performance Test.
Content-Length: 0.
So I am trying to understand why it is trying to relay to itself (I
have mhomed=1) and why it is rewriting the RURI as if it is a strict
router.
Currently decode_contact() is disabled but enabling doesn't seem to
help. Unless there is a very specific place where it belongs.
Any advice would be hugely appreciated. I can always paste logs /
configs / traces.
Richard
--
Richard Brady
M: +44 (0)7771 623 348
T: +44 (0)20 8144 8160
E: rnbrady(a)gmail.com
23 Nov
23 Nov
11:48 a.m.
Richard,
well, the RURI of remote ACK has proxy IP address 10.200.70.100 so proxy
thinks that previous hop was a strict router. I can't think of any
workaround that would not be an ugly hack at the moment, though.
On 11/23/2012 03:24 AM, Richard Brady wrote:
Hi guys
I have a multihomed Kamailio proxy sitting between two B2BUAs on
separate networks and record-routing all dialogs.
The problem I have is that when one of these devices receives a 200
OK, it does not populate the RURI of the ACK correctly. Instead of
taking it from the Contact header on the 200 OK, it uses the user part
from the Contact header and sets the domain to the proxy IP. It then
also populates the Route headers.
The ACKs are below and the IPs are:
10.152.1.92:5060: UAC on outside
10.200.70.100:5060: proxy outside interface
192.168.242.100: proxy inside interface
192.168.242.102: UAS on inside
This the ACK message going into and coming out of the proxy.
# U 10.152.1.92:5060 -> 10.200.70.100:5060
ACK sip:natted_ua*9197**192.168.242.102*5080*udp@10.200.70.100 SIP/2.0.
Via: SIP/2.0/UDP 127.0.1.1:5060;branch=z9hG4bK-2280-1-5.
Route:
<sip:10.200.70.100;r2=on;lr=on;nat=yes>,<sip:192.168.242.100;r2=on;lr=on;nat=yes>.
From: sipp <sip:sipp@127.0.1.1:5060>;tag=2280SIPpTag001.
To: sut <sip:9197@10.200.70.100:5060>;tag=p0FaeQ1QUS9ae.
Call-ID: 1-2280(a)127.0.1.1.
CSeq: 1 ACK.
Contact: sip:sipp@127.0.1.1:5060.
Max-Forwards: 70.
Subject: Performance Test.
Content-Length: 0.
.
# U 10.200.70.100:5060 -> 192.168.242.100:5060
ACK sip:192.168.242.100;r2=on;lr=on;nat=yes SIP/2.0.
Via: SIP/2.0/UDP 10.200.70.100;branch=z9hG4bKcydzigwkX.
Via: SIP/2.0/UDP
127.0.1.1:5060;rport=5060;received=10.152.1.92;branch=z9hG4bK-2280-1-5.
Route: .
From: sipp <sip:sipp@127.0.1.1:5060>;tag=2280SIPpTag001.
To: sut <sip:9197@10.200.70.100:5060>;tag=p0FaeQ1QUS9ae.
Call-ID: 1-2280(a)127.0.1.1.
CSeq: 1 ACK.
Contact: <sip:sipp@127.0.1.1:5060;alias=10.152.1.92~5060~1>.
Max-Forwards: 69.
Subject: Performance Test.
Content-Length: 0.
So I am trying to understand why it is trying to relay to itself (I
have mhomed=1) and why it is rewriting the RURI as if it is a strict
router.
Currently decode_contact() is disabled but enabling doesn't seem to
help. Unless there is a very specific place where it belongs.
Any advice would be hugely appreciated. I can always paste logs /
configs / traces.
Richard
--
Richard Brady
M: +44 (0)7771 623 348
T: +44 (0)20 8144 8160
E: rnbrady(a)gmail.com
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1:06 p.m.
Thanks Andrew
well, the RURI of remote ACK has proxy IP address
10.200.70.100 so proxy
thinks that previous hop was a strict router.
Aha, that makes sense. But why would that make Kamailio apply strict routing?
I can't think of any
workaround that would not be an ugly hack at the moment, though.
I thought encode_contact() and decode() contact were designed exactly
for this? Except I can't get them to work so I believe you!
Richard
24 Nov
24 Nov
6:02 p.m.
Hi Andrew
Now I understand this! Kamailio is not copying the *next* Route URI
into the R-URI because it is strict routing itself, but copying the
*last* Route URI into the R-URI because it thinks the previous hop is
a strict router. The fact that the next Route URI is the last one is
what confused me. Thanks for helping me get to the bottom of it!
Interestingly the previous hop is not really a strict router, it's
just badly behaved in that it takes the user part of the R-URI from
the Contact header and the domain part from the next hop. I won't name
the vendor but I am very surprised by this. I can only assume it's
some type of NAT traversal that is tuned on.
W.r.t. the Kamailio's strict routing behaviour, I wanted to point
something out. Here's the relevant bit from the RFC:
The proxy MUST inspect the Request-URI of the request. If the
Request-URI of the request contains a value this proxy previously
placed into a Record-Route header field (see Section 16.6 item 4),
the proxy MUST replace the Request-URI in the request with the last
value from the Route header field, and remove that value from the
Route header field.
So what is meant here by "a value"? In my case this R-URI has the same
IP as the proxy but contains a user part and parameters which were not
inserted by the proxy into a Record-Route header so I don't think this
test should pass, but because is_myself() is being used in
loose_route() it does.
The main issue with these is that loose_route() and decode_contact()
do not play nicely together. Ideally you would want to call
decode_contact() and then loose_route() which could look $ru /
new_uri, but it will only ever inspect $ou /parsed_uri. So you can't
put decode_contact() before loose_route().
Then on the other hand decode_contact() will only read from $ou if $ru
is not set, and because loos_route() sets $ru in after_strict(), you
also can't put decode_contact() after loose_route().
Unless you reset some of what loose_route() set, which is what I did
get this working:
if (loose_route()) {
if($ou =~ "^sip:natted_contact") {
$ru = $ou;
decode_contact();
$du = $ru;
$fs = $null;
}
...
}
What would be really useful would be if loose_route() used new_uri
where available or, to preserve backward compatibility, you could call
loose_route($ru).
Richard
well, the RURI
of remote ACK has proxy IP address 10.200.70.100 so proxy
thinks that previous hop was a strict router.
Aha, that makes sense. But why would that make Kamailio apply strict routing? I can't
think of any
workaround that would not be an ugly hack at the moment, though.
I thought encode_contact() and decode() contact were designed exactly
for this? Except I can't get them to work so I believe you!
4387
days inactive
4388
days old
3 comments
2 participants
participants (2)
-
Andrew Pogrebennyk -
Richard Brady