Unable to establish TCP connection with Kamailio - sr-users

17 Jun 2021

Hello,

I'm running Kamailio Version 5.3.2 on Ubuntu 20.04. Here my build information:

version: kamailio 5.3.2 (x86_64/linux)
flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST,
DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY,
USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR,
USE_DST_BLACKLIST, HAVE_RESOLV_RES, TLS_PTHREAD_MUTEX_SHARED
ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535,
DEFAULT PKG_SIZE 8MB
poll method support: poll, epoll_lt, epoll_et, sigio_rt, select.
id: unknown
compiled with gcc 9.2.1

I have the following configuration set in my kamalio.cfg file:

##!define WITH_MYSQL
##!define WITH_AUTH
##!define WITH_USRLOCDB
##!define WITH_TLS
##!define WITH_HOMER
##!define WITH_WEBSOCKETS
##!define WITH_ANTIFLOOD
##!define WITH_IPV6
##!define WITH_BRIDGE_ON_FAIL
##!define WITH_LOCALHOST_WS
##!define WITH_LOCALHOST_SIP

#!substdef "!MY_SIP_PORT!5060!g"
#!substdef "!MY_SIPS_PORT!5061!g"
#!substdef "!MY_WS_PORT!8088!g"
#!substdef "!MY_WSS_PORT!8089!g"

#!substdef "!MY_LOG_FACILITY!LOG_DAEMON!g"

#!substdef "!MY_IP4_ADDR!172.16.0.57!g"
#!substdef "!IP4_LOCALHOST!127.0.0.1!g"
#!substdef "!MY_WS4_ADDR!tcp:MY_IP4_ADDR:MY_WS_PORT!g"
#!substdef "!MY_WSS4_ADDR!tls:MY_IP4_ADDR:MY_WSS_PORT!g"
#!substdef "!LOCALHOST_WS4_ADDR!tcp:IP4_LOCALHOST:MY_WS_PORT!g"
#!substdef "!LOCALHOST_WSS4_ADDR!tls:IP4_LOCALHOST:MY_WSS_PORT!g"

#!ifdef WITH_IPV6
#!substdef "!MY_IP6_ADDR![fe80::d6e4:2f5f:e5b7:7dff]!g"
#!substdef "!IP6_LOCALHOST![::1]!g"
#!substdef "!MY_WS6_ADDR!tcp:MY_IP6_ADDR:MY_WS_PORT!g"
#!substdef "!MY_WSS6_ADDR!tls:MY_IP6_ADDR:MY_WSS_PORT!g"
#!substdef "!LOCALHOST_WS6_ADDR!tcp:IP6_LOCALHOST:MY_WS_PORT!g"
#!substdef "!LOCALHOST_WSS6_ADDR!tls:IP6_LOCALHOST:MY_WSS_PORT!g"
#!endif

#!substdef "!MY_DOMAIN!rtpengine.kombea.io!g"
debug=10         // debug level (cmd line: -dddddddddd)
children=4
#fork=yes
force_rport=yes // Add recieved port to VIA
#log_stderror=no        // (cmd line: -E)

// Uncomment these lines to enter debugging mode
fork=no
log_stderror=yes

check_via=no    // (cmd. line: -v)
dns=no          // (cmd. line: -r)
rev_dns=no      // (cmd. line: -R)

log_facility=MY_LOG_FACILITY

// Define the listening ports and addresses
port=MY_SIP_PORT
tls_port_no=MY_SIPS_PORT

// Define TCP parameters
tcp_children=4
tcp_no_connect=no
tcp_rd_buf_size=16384
tcp_max_connections=2048
tcp_connection_lifetime=3605
disable_tcp=no
#!ifdef WITH_TLS
enable_tls=yes
#!endif

listen=MY_IP4_ADDR
#!ifdef WITH_LOCALHOST_SIP
listen=IP4_LOCALHOST
#!endif
#!ifdef WITH_IPV6
listen=MY_IP6_ADDR
#!ifdef WITH_LOCALHOST_SIP
listen=IP6_LOCALHOST
#!endif
#!endif

#!ifdef WITH_WEBSOCKETS
listen=MY_WS4_ADDR
#!ifdef WITH_LOCALHOST_WS
listen=LOCALHOST_WS4_ADDR
#!endif
#!ifdef WITH_IPV6
listen=MY_WS6_ADDR
#!ifdef WITH_LOCALHOST_WS
listen=LOCALHOST_WS6_ADDR
#!endif
#!endif
#!ifdef WITH_TLS
listen=MY_WSS4_ADDR
#!ifdef WITH_LOCALHOST_WS
listen=LOCALHOST_WSS4_ADDR
#!endif
#!ifdef WITH_IPV6
listen=MY_WSS6_ADDR
#!ifdef WITH_LOCALHOST_WS
listen=LOCALHOST_WSS6_ADDR
#!endif
#!endif
#!endif
#!endif

force_rport=yes // Add received port to VIA

loadmodule "pv.so"          // Pseudo-Variable support
loadmodule "xlog.so"        // Formatted logging support
loadmodule "sl.so"          // Stateless request handling
loadmodule "siputils.so"    // SIP utility helpers
loadmodule "sanity.so"      // Sanity check
loadmodule "maxfwd.so"      // Support for Max-Forward header
loadmodule "textops.so"     // Text operations on SIP messages
loadmodule "textopsx.so"    // Extended Text operations on SIP messages
loadmodule "sdpops.so"      // SDP operations
loadmodule "nathelper.so"   // NAT traversal helpers
loadmodule "rr.so"          // Record Route handling
loadmodule "outbound.so"    // Outbound support
loadmodule "path.so"        // Path handling

#!ifdef WITH_TLS
loadmodule "tls.so"         // TLS Support
#!endif

#!ifdef WITH_WEBSOCKETS
loadmodule "xhttp.so"       // XHTTP support
loadmodule "websocket.so"   // WebSocket support
#!endif
loadmodule "rtpengine.so"   // RTPEngine control

#!ifdef WITH_DEBUG
loadmodule "debugger.so"
#!endif

When I start Kamailio, I see the following in the output to stderr:

Listening on
             udp: 172.16.0.57:5060
             tcp: 172.16.0.57:5060
Aliases:
             tcp: VRTPENGINE:5060
             udp: VRTPENGINE:5060

WARNING: no fork mode
 0(6299) INFO: <core> [core/tcp_main.c:5042]: init_tcp(): using epoll_lt as the io
watch method (auto detected)

Here's the problem:

When I connect via UDP, everything works fine. I can connect and see all SIP traffic.

However, if I try to connect via TCP, I see the initial SYN packet in attempting to
establish a connection.

Kamailio responds with an [RST,ACK] message and the TCP connection is never established.
No further TCP traffic is sent.

Any ideas on what I'm doing wrong?

Peter H. Manley, Ph.D.
Chief Software Architect
KomBea Corporation
3400 North Ashton Blvd, Suite
470<https://urldefense.proofpoint.com/v2/url?u=https-3A__maps.google.com…
Lehi, Utah
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www.kombea.com<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.k…

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