27 Oct
2021
27 Oct
'21
4:56 p.m.
### Description
I noticed an issue regarding loose_route() when using Topos module.
My architecture is the following:
```
Client (behind NAT or not) ------> Kamailio (Access SBC) -----------> Kamailio
(Interconnect SBC) -----------> Carrier
```
Kamailio Access SBC is listening on 2 interfaces:
```
Public interface : udp:A.A.A.A:5060
Core interface : udp:B.B.B.B:5060
```
Kamailio Interconnect SBC is listening on 2 interfaces:
```
Core interface : udp:C.C.C.C:5060
Carrier-side interface : udp:D.D.D.D:5060
```
TOPOS is configured only on second kamailio box (Interconnect SBC).
Record routing is used on both kamailios.
TOPOS module is configured as follows:
```
modparam("ndb_redis", "server",
"name=srv1;addr=127.0.0.1;port=6379")
modparam("topos_redis", "serverid", "srv1")
modparam("topos", "storage", "redis")
modparam("topos", "contact_mode", 1)
modparam("topos", "cparam_name", "id")
modparam("topos", "rr_update", 1)
```
RR module is configured as follows:
```
modparam("rr", "enable_full_lr", 1)
modparam("rr", "append_fromtag", 1)
modparam("rr", "enable_double_rr", 1)
```
For an incomoing INVITE (direction: client to carrier) all is fine and topos can strip
headers on bleg and insert the cookie on bleg contact as a param.
When Callee sends a BYE or re-INVITE, topos inserts route headers in aleg as shown in the
next trace: (BYE as received from the carrier on the carrier-side interface D.D.D.D)
```
BYE sip:D.D.D.D:5060 SIP/2.0
Via: SIP/2.0/UDP x.x.x.x:5060;branch=z9hG4bKrdhsvc001omkvssqvfk0sd0185mt1.1
From:
<sip:+33123456789@my-carrier-domain;transport=UDP;user=phone>;tag=SD69ao497-1472568650-1635329820043
To: <sip:+33987654321@my-own-domain;transport=UDP;user=phone>;tag=3ab10616
Call-ID: NjZjMDgyMGMxNzdkN2FhYmJlYzQyYjA5YWIzZThmZmI.
CSeq: 547381883 BYE
Max-Forwards: 64
Content-Length: 0
Route:
<sip:D.D.D.D;r2=on;lr=on;ftag=3ab10616>,<sip:C.C.C.C;r2=on;lr=on;ftag=3ab10616>
Route:
<sip:B.B.B.B;r2=on;lr=on;ftag=3ab10616;dlg_id=426.26c2>,<sip:A.A.A.A;r2=on;lr=on;ftag=3ab10616;dlg_id=426.26c2>
P-SR-XUID: atpsh-617925e5-82a5-1
```
Topos on the kamailio interconnect handles the BYE/re-INVITE and forward it to the second
interface C.C.C.C as shown in the following trace:
```
BYE sip:A.A.A.A;r2=on;lr=on;ftag=3ab10616;dlg_id=426.26c2 SIP/2.0
Via: SIP/2.0/UDP 185.164.213.110;branch=z9hG4bKbd7.ab692eeb60369aa3a5e07f6b63cc9dd7.0
From:
<sip:+33123456789@my-carrier-domain;transport=UDP;user=phone>;tag=SD69ao497-1472568650-1635329820043
To: <sip:+33987654321@my-own-domain;transport=UDP;user=phone>;tag=3ab10616
Call-ID: NjZjMDgyMGMxNzdkN2FhYmJlYzQyYjA5YWIzZThmZmI.
CSeq: 547381883 BYE
Max-Forwards: 63
Content-Length: 0
Route: <sip:C.C.C.C;r2=on;lr=on;ftag=3ab10616>
Route: <sip:B.B.B.B;r2=on;lr=on;ftag=3ab10616;dlg_id=426.26c2>
Contact: <sip:+33123456789@10.3.60.45;id=atpsh-617925e5-82a5-1>
```
When the BYE/re-INVITE request reaches the C.C.C.C interface, it is then forwarded
directly to the ruri sip:A.A.A.A.
Or what I expect to receive in C.C.C.C interface is the following :
```
BYE <HERE SHOULD BE THE CALLER CONTACT URI> SIP/2.0
Via: SIP/2.0/UDP 80.10.231.173:5060;branch=z9hG4bKrdhsvc001omkvssqvfk0sd0185mt1.1
From:
<sip:+33123456789@my-carrier-domain;transport=UDP;user=phone>;tag=SD69ao497-1472568650-1635329820043
To: <sip:+33987654321@my-own-domain;transport=UDP;user=phone>;tag=3ab10616
Call-ID: NjZjMDgyMGMxNzdkN2FhYmJlYzQyYjA5YWIzZThmZmI.
CSeq: 547381883 BYE
Max-Forwards: 64
Content-Length: 0
Route: <sip:D.D.D.D;r2=on;lr=on;ftag=3ab10616>
Route: <sip:C.C.C.C;r2=on;lr=on;ftag=3ab10616>
Route: <sip:B.B.B.B;r2=on;lr=on;ftag=3ab10616;dlg_id=426.26c2>
Route: <sip:A.A.A.A;r2=on;lr=on;ftag=3ab10616;dlg_id=426.26c2>
Contact: <sip:+33123456789@10.3.60.45;id=atpsh-617925e5-82a5-1>
```
I could work around this issue by doing the following :
1. When receiving the BYE/re-INVITE on interface D.D.D.D, I explode the Route headers,
delete old route headers and create new ones in order from the result of explode
2. I update the ru with the contact uri which I stored in a htable when the initial INVITE
was received
```
# Manage outgoing branches
branch_route[MANAGE_BRANCH] {
xdbg("new branch [$T_branch_idx] to $ru\n");
# TOPOS FIX
if (is_method("INVITE")) {
$sht(tpsindlg=>$ci) = $ci;
$sht(tpsindlg=>$ci:ft) = $ft;
$sht(tpsindlg=>$ci:ct) = $ct;
}
}
route[WITHINDLG] {
if (!has_totag()) return;
# Fix bad Route Headers caused by TOPOS module
if ($Ri == "D.D.D.D") {
$var(rh0) = $(hdr(Route)[0]{s.select,0,,});
$var(rh1) = $(hdr(Route)[0]{s.select,1,,});
$var(rh2) = $(hdr(Route)[1]{s.select,0,,});
$var(rh3) = $(hdr(Route)[1]{s.select,1,,});
remove_hf_re("^Route$");
append_hf("Route: $var(rh0)\r\n");
append_hf("Route: $var(rh1)\r\n");
append_hf("Route: $var(rh2)\r\n");
append_hf("Route: $var(rh3)\r\n");
}
# sequential request within a dialog should
# take the path determined by record-routing
if (loose_route()) {
# Fix R-URI caused by TOPOS module
if ($Ri == "D.D.D.D") {
if ($ci == $sht(tpsindlg=>$ci) && $tt == $sht(tpsindlg=>$ci:ft)) {
$ru = $(sht(tpsindlg=>$ci:ct){s.strip,1}{s.striptail,1});
if (is_method("BYE")) {
$sht(tpsindlg=>$ci) = $null;
$sht(tpsindlg=>$ci:ft) = $null;
$sht(tpsindlg=>$ci:ct) = $null;
}
}
}
route(RELAY);
exit;
}
if (is_method("ACK")) {
if ( t_check_trans() ) {
# no loose-route, but stateful ACK;
# must be an ACK after a 487
# or e.g. 404 from upstream server
route(RELAY);
exit;
} else {
# ACK without matching transaction ... ignore and discard
exit;
}
}
sl_send_reply("404","Not here");
exit;
}
```
Could you please tell if this is a normal behavior by TOPOS module or is it a bug?
Thank you.
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