[SR-Users] Via in locally generated PUBLISH (using different presence server address)

[Asgaroth]

Hi All,

I have a configuration where we run a multi-homed proxy/loadbalancer and 
a seperate internal presence server. We then use pua/pua-dialoginfo on 
the proxies to publish dialog state to the internal presence server.

The proxies listen on udp:external_ip:5062 and udp:internal_ip1:5060. 
The presence server listens on udp:internal_ip2:5060 on a seperate server.

The problem I am coming accross is that when kamailio generates a 
PUBLISH message for some dialogs it creates the via header with address 
external:ip:5062, however the pua module is configured to send to the 
presence server address on internal_ip2:5060. I have a route which 
forces the sending socket ($fs) to be udp:internal_ip1:5060.

What happens then is that the presence server tries to send the 200 
reply to the PUBLISH message back to internal_ip1:5062 (when it should 
be internal_ip1:5060), I'm thinking this is because the Via header has 
host as external_ip:5062.

Is it possible, from event-route[tm:local-request] to rewrite the via 
header so that it reflects internal_ip1:5060 instead of external_ip:5062?

I did try the following snippet from event-route[tm:local-request], but 
I got module parse errors on the Via header:

if (is_method("PUBLISH")) {
       subst_hf("Via", "/ 1\.2\.3\.[0-9]+:5062;/ 
$sel(cfg_get.socket.internal_ip);/", "f");
}

[7370]: ERROR: <core> [parser/parse_via.c:2607]: parse_via(): 
ERROR:parse_via on <1> state 5 (default)
[7370]: ERROR: <core> [parser/parse_via.c:2708]: parse_via(): ERROR: 
parse_via on: <SIP/2.0/UDP 
external_ip:5062;branch=z9hG4bK96eb.0f014ae4000000000000000000000000.0#015#012 
internal_ip1;
[7370]: ERROR: <core> [parser/parse_via.c:2712]: parse_via(): ERROR: 
parse_via parse error, parsed so far:<SIP/2.0/UDP 
external_ip:5062;branch=z9hG4bK96eb.0f014ae4000000000000000000000000.0#015#012 
 >
[7370]: ERROR: <core> [parser/msg_parser.c:125]: get_hdr_field(): ERROR: 
get_hdr_field: bad via
[7370]: INFO: <core> [parser/msg_parser.c:338]: parse_headers(): ERROR: 
bad header field [Via: SIP/2.0/UDP 1]
[7370]: ERROR: <core> [parser/msg_parser.c:690]: parse_msg(): ERROR: 
parse_msg: message=<PUBLISH sip:user at domain;transport=UDP 
SIP/2.0#015#012Via: SIP/2.0/UDP 
external_ip:5062;branch=z9hG4bK96eb.0f014ae4000000000000000000000000.0#015#012 
internal_ip1;To: <sip:user at domain;transport=UDP>#015#012From: 
<sip:user at domain;transport=UDP>;tag=3e8fdaca277026bf3e6d75c5e5313096-f162#015#012CSeq: 
10 PUBLISH#015#012Call-ID: 
5634294b786134b3-7370 at external_ip#015#012Content-Length: 
692#015#012User-Agent: kamailio (bfievklb04)#015#012Max-Forwards: 
70#015#012Event: dialog#015#012Expires: 10901#015#012Content-Type: 
application/dialog-info+xml#015#012#015#012<?xml 
version="1.0"?>#012<dialog-info 
xmlns="urn:ietf:params:xml:ns:dialog-info" version="0" state="full" 
entity="sip:user at domain;transport=UDP">#012  <dialog 
id="mvqXXaAr24DHdfsffYKZeA.." call-id="mvqXXaAr24DHdfsffYKZeA.." 
direction="initiator">#012 <state>Trying</state>#012    <remote>#012 
<identity>sip:1234567 at domain;transport=UDP</identity>#012 <target 
uri="sip:1234567 at domain;transport=UDP"/>#012 </remote>#012    
<local>#012 <identity>sip:user at domain;transport=UDP</identity>#012 
<target uri="sip:user at domain;transport=UDP"/>#012 </local>#012  
</dialog>#012</dialog-info>#012>
[7370]: ERROR: <core> [msg_translator.c:3057]: build_sip_msg_from_buf(): 
parsing failed
[7370]: ERROR: tm [uac.c:163]: uac_refresh_hdr_shortcuts(): failed to 
parse msg buffer
[7370]: ERROR: tm [uac.c:487]: t_uac_prepare(): failed to refresh header 
shortcuts
[7370]: ERROR: pua [send_publish.c:700]: send_publish(): in t_request tm 
module function
[7370]: ERROR: pua_dialoginfo [dialog_publish.c:358]: dialog_publish(): 
while sending publish

To me, it looks like the replace section of the subst_hf sub expression 
is being appended to the end of the via header instead of replacing the 
address section found.

I have sanitized the above output to not show internal details, but if 
you need it, I can send it on to you privately.

Am I going about this issue in the correct way, and, if so, where am I 
going wrong with the subst_hf snippet above?

Kamailio version is 4.3.6.

Any pointers/tips/trciks are greatly appreciated.

Thanks