[SR-Users] strange behavior when trying to reach PSTN gateway via TCP

[Dmitry Petrakoff]

Hi List!

I'm running Kamailio for about 1 year without any serious problems.
When it works with UDP only, it runs perfectly well for us. Without any
major issues.

But now we have a customer who wants to connect Lync to our network.
Unfortunately, Lync does not support UDP for SIP signalling, so we tried
to teach kamailio to send SIP messages via TCP.
And getting  strange error:

10(36629) DEBUG: tm [t_reply.c:659]: DEBUG: reply sent out.
buf=0x832c7ac: SIP/2.0 100 trying -..., shmem=0x28d97c7c: SIP/2.0 100
trying -
10(36629) DEBUG: tm [t_reply.c:669]: DEBUG: _reply_light: finished
10(36629) DEBUG: <core> [forward.c:213]: DEBUG: get_out_socket: socket
determined: 0x833ddc0
10(36629) DEBUG: <core> [msg_translator.c:457]: clen_builder:
content-length: 553 (553)
10(36629) DEBUG: <core> [msg_translator.c:204]:
check_via_address(10.200.245.200, 10.200.245.200, 0)
10(36629) DEBUG: <core> [tcp_main.c:1824]: tcp_send: no open tcp
connection found, opening new one
10(36629) DEBUG: <core> [ip_addr.c:247]: tcpconn_new: new tcp
connection: 10.198.3.100
10(36629) DEBUG: <core> [tcp_main.c:1081]: tcpconn_new: on port 5060, type 2
10(36629) DEBUG: <core> [tcp_main.c:1382]: tcpconn_add: hashes: 0:0:0, 1
10(36629) ERROR: <core> [tcp_main.c:2748]: connect 10.198.3.100:5060
failed Socket is not connected
10(36629) ERROR: <core> [tcp_main.c:2754]: 10.198.3.100:5060: connect &
send  for 0x28d988ac failed: Socket is not connected (57)
10(36629) DEBUG: <core> [tcp_main.c:2955]: tcpconn_chld_put: destroying
connection 0x28d988ac (1, -1) flags 0060
10(36629) ERROR: tm [../../forward.h:170]: msg_send: ERROR: tcp_send failed

We tested two different variants: one when defined Lync in dr_gateways
table as 10.198.3.100:5068;transport=tcp

And then, tried global options
udp_mtu=1300
udp_mtu_try_proto=TCP

As soon as these options were enabled, all other gateways became
unreachable with the same error as above.

Could you please to point me out, where I'm wrong?

fbsd-kam# /usr/local/sbin/kamailio -V
version: kamailio 3.1.5 (i386/freebsd) ec672a
flags: STATS: Off, USE_IPV6, USE_TCP, USE_TLS, TLS_HOOKS, USE_RAW_SOCKS,
DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MEM, SHM_MMAP, PKG_MALLOC,
DBG_QM_MALLOC, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER,
USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES
ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE 262144, MAX_LISTEN 16,
MAX_URI_SIZE 1024, BUF_SIZE 65535, PKG_SIZE 4MB
poll method support: poll, select, kqueue.
id: ec672a
compiled on 11:02:58 Nov 15 2011 with gcc 4.2.1

FreeBSD fbsd-kam.dprs-consulting.com 8.2-RELEASE-p2 FreeBSD
8.2-RELEASE-p2 #0: Sun Jul  3 17:49:13 GMT 2011    
root at fbsd-kam.dprs-consulting.com:/usr/obj/usr/src/sys/GENERIC  i386

Routing script could be sent on request.

Thank you very much!

WBR
Dimon