Problem with NAT and RTPProxy - sr-users

14 Nov 2011

Hi, I am using Kamailio 3.2.0 (x86_64/linux) and since some days ago I am
trying to call from a network with NAT to outside. This is the
configuration:

Softphone (192.168.0.5) <--> Kamailio (192.168.0.3) <-->
Router (192.168.0.1) <--> Softphone over smartphone

All the router ports are opened and redirected to 192.168.0.3. I have
installed rtpproxy 1.2.1-1 with the following configuration:

--------------------------/etc/defaults/rtpproxy--------------------------------
# The control socket.
#CONTROL_SOCK="unix:/var/run/rtpproxy/rtpproxy.sock"
# To listen on an UDP socket, uncomment this line:
CONTROL_SOCK=udp:127.0.0.1:22222

# Additional options that are passed to the daemon.
EXTRA_OPTS="-l candamil.dyndns.org"
----------------------------------------------------------------------------------------

and works properly. This is the log message:

----------------------------------------------------------------------------------------------
Nov 12 20:09:13 condor kamailio[7001]: INFO: rtpproxy [rtpproxy.c:1415]:
rtp proxy <udp:127.0.0.1:22222> found, support for it enabled
-----------------------------------------------------------------------------------------------

Both softphones are "linphone". The configuration of the network softphone
is the following:

SIP identity: sip:1001@192.168.0.3
SIP proxy: sip:192.168.0.3
Direct connection to the Internet.

In the softphone of the smartphone I set as proxy and domain "
candamil.dyndns.org", the DNS address of my router IP.

In this case, these are the symptoms:
Both softphones can autentify correctly. When calling, both softphones
ring, but when I answer, the voice signal is not received. This is the log
error:

----------------------------------------------------------------------------------------------
Nov 12 20:23:14 condor kamailio[6991]: ERROR: rtpproxy [rtpproxy.c:2260]:
incorrect port 0 in reply from rtp proxy
----------------------------------------------------------------------------------------------

The same happens if I set in the network softphone that it's behind NAT,
and I set the router IP.
The same happens if I set in the network softphone that it's behind NAT and
with a STUN server (stunserver.org). In the three cases, in the softphone
over smartphone, the caller is 1001(a)192.168.0.3, and in the network
softphone, the caller is 1002(a)candamil.dyndns.org.

If I set in the network softphone the proxy as sip:candamil.dyndns.org, the
same happens.
If what I do is setting the SIP identity as  sip:1001@candamil.dyndns.org,
when calling form inside to ouside the network, the softphone doesn't know
that the call was answered, and there is the following error in the log:

----------------------------------------------------------------------------------------------------------
Nov 12 20:53:00 condor kamailio[7306]: ERROR: <core>
[parser/parse_via.c:2600]: ERROR: parse_via: invalid port number
<5060ranch=z9hG4bKc
50f.b4825246.0>
Nov 12 20:53:00 condor kamailio[7306]: ERROR: <core>
[parser/parse_via.c:2629]: ERROR: parse_via on: <SIP/2.0/UDP
192.168.0.3:5060ranch=z
9hG4bKc50f.b4825246.0;received=87.223.138.84#015#012Via: SIP/2.0/UDP
87.223.138.84:5060;rport=5060;branch=z9hG4bK1021772993#015#012From:
<sip:1001@candamil.dyndns.org>;tag=783852345#015#012To: <
sip:1002@candamil.dyndns.org>#015#012Call-ID: 1644787160#015#012CSeq: 21
INVITE#
015#012User-Agent: Linphone/3.4.0 (eXosip2/unknown)#015#012Content-Length:
0#015#012#015#012>
------------------------------------------------------------------------------------------------------------

If the call is from outside to inside the network, it happens the same than
in the previous cases.

This is the relevant kamailio configuration:

-----------------------------------------kamailio.cfg----------------------------------------------------
#!define WITH_MYSQL
#!define WITH_AUTH
#!define WITH_NAT

####### Defined Values #########

# *** Value defines - IDs used later in config
#!ifdef WITH_MYSQL
# - database URL - used to connect to database server by modules such
#       as: auth_db, acc, usrloc, a.s.o.
#!define DBURL "mysql://openser:openserrw@localhost/openser"
#!endif
#!ifdef WITH_MULTIDOMAIN
# - the value for 'use_domain' parameters
#!define MULTIDOMAIN 1
#!else
#!define MULTIDOMAIN 0
#!endif

# - flags
#   FLT_ - per transaction (message) flags
# FLB_ - per branch flags
#!define FLT_ACC 1
#!define FLT_ACCMISSED 2
#!define FLT_ACCFAILED 3
#!define FLT_NATS 5

#!define FLB_NATB 6
#!define FLB_NATSIPPING 7

####### Global Parameters #########
/* uncomment the next line to disable the auto discovery of local aliases
  based on reverse DNS on IPs (default on) */
#auto_aliases=no

/* add local domain aliases */
alias="candamil.dyndns.org"

/* port to listen to
 * - can be specified more than once if needed to listen on many ports */
port=5060

#!ifdef WITH_TLS
enable_tls=yes
#!endif

# life time of TCP connection when there is no traffic
# - a bit higher than registration expires to cope with UA behind NAT
tcp_connection_lifetime=3605

####### Custom Parameters #########

#!ifdef WITH_PSTN
# PSTN GW Routing
#
# - pstn.gw_ip: valid IP or hostname as string value, example:
# pstn.gw_ip = "10.0.0.101" desc "My PSTN GW Address"
#
# - by default is empty to avoid misrouting
pstn.gw_ip = "" desc "PSTN GW Address"
#!endif

####### Modules Section ########

#!ifdef WITH_MYSQL
loadmodule "db_mysql.so"
#!endif

#!ifdef WITH_AUTH
loadmodule "auth.so"
loadmodule "auth_db.so"

#!ifdef WITH_NAT
loadmodule "nathelper.so"
loadmodule "rtpproxy.so"
#!endif

# ----------------- setting module-specific parameters ---------------

# ----- auth_db params -----
#!ifdef WITH_AUTH
modparam("auth_db", "db_url", DBURL)
modparam("auth_db", "calculate_ha1", yes)
modparam("auth_db", "password_column", "password")
modparam("auth_db", "load_credentials", "")
modparam("auth_db", "use_domain", MULTIDOMAIN)

#!ifdef WITH_NAT
# ----- rtpproxy params -----
modparam("rtpproxy", "rtpproxy_sock",
"udp:127.0.0.1:22222")

# ----- nathelper params -----
modparam("nathelper", "natping_interval", 30)
modparam("nathelper", "ping_nated_only", 1)
modparam("nathelper", "sipping_bflag", FLB_NATSIPPING)
modparam("nathelper", "sipping_from",
"sip:pinger@kamailio.org")

# params needed for NAT traversal in other modules
modparam("nathelper|registrar", "received_avp",
"$avp(RECEIVED)")
modparam("usrloc", "nat_bflag", FLB_NATB)
#!endif

####### Routing Logic ########

# Main SIP request routing logic
# - processing of any incoming SIP request starts with this route
# - note: this is the same as route { ... }
request_route {

# per request initial checks
route(REQINIT);

 # NAT detection
route(NATDETECT);

# handle requests within SIP dialogs
 route(WITHINDLG);

### only initial requests (no To tag)

 # CANCEL processing
if (is_method("CANCEL"))
{
 if (t_check_trans())
t_relay();
exit;
 }

t_check_trans();

# authentication
 route(AUTH);

# record routing for dialog forming requests (in case they are routed)
 # - remove preloaded route headers
remove_hf("Route");
if (is_method("INVITE|SUBSCRIBE"))
 record_route();

# account only INVITEs
if (is_method("INVITE"))
 {
setflag(FLT_ACC); # do accounting
}

# dispatch requests to foreign domains
route(SIPOUT);

 ### requests for my local domains

# handle presence related requests
 route(PRESENCE);

# handle registrations
route(REGISTRAR);

if ($rU==$null)
{
# request with no Username in RURI
 sl_send_reply("484","Address Incomplete");
exit;
}

# dispatch destinations to PSTN
route(PSTN);

 # user location service
route(LOCATION);

route(RELAY);
}

route[RELAY] {

# enable additional event routes for forwarded requests
# - serial forking, RTP relaying handling, a.s.o.
 if (is_method("INVITE|SUBSCRIBE")) {
t_on_branch("MANAGE_BRANCH");
 t_on_reply("MANAGE_REPLY");
}
if (is_method("INVITE")) {
 t_on_failure("MANAGE_FAILURE");
}

if (!t_relay()) {
 sl_reply_error();
}
exit;
}

# Per SIP request initial checks
route[REQINIT] {
#!ifdef WITH_ANTIFLOOD
# flood dection from same IP and traffic ban for a while
 # be sure you exclude checking trusted peers, such as pstn gateways
# - local host excluded (e.g., loop to self)
 if(src_ip!=myself)
{
if($sht(ipban=>$si)!=$null)
 {
# ip is already blocked
xdbg("request from blocked IP - $rm from $fu (IP:$si:$sp)\n");
 exit;
}
if (!pike_check_req())
 {
xlog("L_ALERT","ALERT: pike blocking $rm from $fu (IP:$si:$sp)\n");
 $sht(ipban=>$si) = 1;
exit;
}
 }
#!endif

if (!mf_process_maxfwd_header("10")) {
 sl_send_reply("483","Too Many Hops");
exit;
}

if(!sanity_check("1511", "7"))
{
xlog("Malformed SIP message from $si:$sp\n");
 exit;
}
}

# Handle requests within SIP dialogs
route[WITHINDLG] {
if (has_totag()) {
# sequential request withing a dialog should
 # take the path determined by record-routing
if (loose_route()) {
if (is_method("BYE")) {
 setflag(FLT_ACC); # do accounting ...
setflag(FLT_ACCFAILED); # ... even if the transaction fails
 }
if ( is_method("ACK") ) {
# ACK is forwarded statelessy
 route(NATMANAGE);
}
route(RELAY);
 } else {
if (is_method("SUBSCRIBE") && uri == myself) {
 # in-dialog subscribe requests
route(PRESENCE);
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
 t_relay();
exit;
} else {
 # ACK without matching transaction ... ignore and discard
exit;
}
 }
sl_send_reply("404","Not here");
}
 exit;
}
}

# Handle SIP registrations
route[REGISTRAR] {
 if (is_method("REGISTER"))
{
if(isflagset(FLT_NATS))
 {
setbflag(FLB_NATB);
# uncomment next line to do SIP NAT pinging
 setbflag(FLB_NATSIPPING);
}
if (!save("location"))
 sl_reply_error();

exit;
}
}

# USER location service
route[LOCATION] {

#!ifdef WITH_SPEEDIAL
# search for short dialing - 2-digit extension
 if($rU=~"^[0-9][0-9]$")
if(sd_lookup("speed_dial"))
route(SIPOUT);
#!endif

#!ifdef WITH_ALIASDB
# search in DB-based aliases
if(alias_db_lookup("dbaliases"))
 route(SIPOUT);
#!endif

$avp(oexten) = $rU;
if (!lookup("location")) {
 $var(rc) = $rc;
route(TOVOICEMAIL);
t_newtran();
 switch ($var(rc)) {
case -1:
case -3:
 send_reply("404", "Not Found");
exit;
case -2:
 send_reply("405", "Method Not Allowed");
exit;
}
 }

# when routing via usrloc, log the missed calls also
if (is_method("INVITE"))
 {
setflag(FLT_ACCMISSED);
}
}

# Presence server route
route[PRESENCE] {
if(!is_method("PUBLISH|SUBSCRIBE"))
return;

#!ifdef WITH_PRESENCE
if (!t_newtran())
{
sl_reply_error();
 exit;
};

if(is_method("PUBLISH"))
 {
handle_publish();
t_release();
 }
else
if( is_method("SUBSCRIBE"))
 {
handle_subscribe();
t_release();
 }
exit;
#!endif
 # if presence enabled, this part will not be executed
if (is_method("PUBLISH") || $rU==$null)
 {
sl_send_reply("404", "Not here");
exit;
 }
return;
}

# Authentication route
route[AUTH] {
#!ifdef WITH_AUTH
if (is_method("REGISTER"))
{
# authenticate the REGISTER requests (uncomment to enable auth)
 if (!www_authorize("$td", "subscriber"))
{
www_challenge("$td", "0");
 exit;
}

if ($au!=$tU)
 {
sl_send_reply("403","Forbidden auth ID");
exit;
 }
} else {

#!ifdef WITH_IPAUTH
if(allow_source_address())
 {
# source IP allowed
return;
 }
#!endif

# authenticate if from local subscriber
 if (from_uri==myself)
{
if (!proxy_authorize("$fd", "subscriber")) {
 proxy_challenge("$fd", "0");
exit;
}
 if (is_method("PUBLISH"))
{
if ($au!=$fU || $au!=$tU) {
 sl_send_reply("403","Forbidden auth ID");
exit;
 }
if ($au!=$rU) {
sl_send_reply("403","Forbidden R-URI");
 exit;
}
#!ifdef WITH_MULTIDOMAIN
if ($fd!=$rd) {
 sl_send_reply("403","Forbidden R-URI domain");
exit;
 }
#!endif
} else {
if ($au!=$fU) {
 sl_send_reply("403","Forbidden auth ID");
exit;
 }
}

consume_credentials();
 # caller authenticated
} else {
# caller is not local subscriber, then check if it calls
 # a local destination, otherwise deny, not an open relay here
if (!uri==myself)
 {
sl_send_reply("403","Not relaying");
exit;
 }
}
}
#!endif
return;
}

# Caller NAT detection route
route[NATDETECT] {
#!ifdef WITH_NAT
 force_rport();
if (nat_uac_test("19")) {
if (is_method("REGISTER")) {
 fix_nated_register();
} else {
fix_nated_contact();
 }
setflag(FLT_NATS);
}
#!endif
return;
}

# RTPProxy control
route[NATMANAGE] {
#!ifdef WITH_NAT
if (is_request()) {
 if(has_totag()) {
if(check_route_param("nat=yes")) {
setbflag(FLB_NATB);
 }
}
}
 if (!(isflagset(FLT_NATS) || isbflagset(FLB_NATB)))
return;

 rtpproxy_manage();

if (is_request()) {
if (!has_totag()) {
 add_rr_param(";nat=yes");
}
}
 if (is_reply()) {
if(isbflagset(FLB_NATB)) {
fix_nated_contact();
 }
}
#!endif
return;
}

# Routing to foreign domains
route[SIPOUT] {
if (!uri==myself)
{
 append_hf("P-hint: outbound\r\n");
route(RELAY);
}
}

# PSTN GW routing
route[PSTN] {
#!ifdef WITH_PSTN
# check if PSTN GW IP is defined
if (strempty($sel(cfg_get.pstn.gw_ip))) {
 xlog("SCRIPT: PSTN rotuing enabled but pstn.gw_ip not defined\n");
return;
 }

# route to PSTN dialed numbers starting with '+' or '00'
 #     (international format)
# - update the condition to match your dialing rules for PSTN routing
 if(!($rU=~"^(\+|00)[1-9][0-9]{3,20}$"))
return;

 # only local users allowed to call
if(from_uri!=myself) {
sl_send_reply("403", "Not Allowed");
 exit;
}

$ru = "sip:" + $rU + "@" + $sel(cfg_get.pstn.gw_ip);

route(RELAY);
exit;
#!endif

return;
}

# XMLRPC routing
#!ifdef WITH_XMLRPC
route[XMLRPC] {
# allow XMLRPC from localhost
if ((method=="POST" || method=="GET")
 && (src_ip==127.0.0.1)) {
# close connection only for xmlrpclib user agents (there is a bug in
 # xmlrpclib: it waits for EOF before interpreting the response).
if ($hdr(User-Agent) =~ "xmlrpclib")
 set_reply_close();
set_reply_no_connect();
dispatch_rpc();
 exit;
}
send_reply("403", "Forbidden");
 exit;
}
#!endif

# route to voicemail server
route[TOVOICEMAIL] {
#!ifdef WITH_VOICEMAIL
 if(!is_method("INVITE"))
return;

# check if VoiceMail server IP is defined
 if (strempty($sel(cfg_get.voicemail.srv_ip))) {
xlog("SCRIPT: VoiceMail rotuing enabled but IP not defined\n");
 return;
}
if($avp(oexten)==$null)
 return;

$ru = "sip:" + $avp(oexten) + "@" + $sel(cfg_get.voicemail.srv_ip)
 + $sel(cfg_get.voicemail.srv_port);
route(RELAY);
exit;
#!endif

return;
}

# manage outgoing branches
branch_route[MANAGE_BRANCH] {
 xdbg("new branch [$T_branch_idx] to $ru\n");
route(NATMANAGE);
}

# manage incoming replies
onreply_route[MANAGE_REPLY] {
xdbg("incoming reply\n");
if(status=~"[12][0-9][0-9]")
 route(NATMANAGE);
}

# manage failure routing cases
failure_route[MANAGE_FAILURE] {
route(NATMANAGE);

if (t_is_canceled()) {
exit;
}

#!ifdef WITH_BLOCK3XX
# block call redirect based on 3xx replies.
if (t_check_status("3[0-9][0-9]")) {
 t_reply("404","Not found");
exit;
}
#!endif

#!ifdef WITH_VOICEMAIL
# serial forking
# - route to voicemail on busy or no answer (timeout)
 if (t_check_status("486|408")) {
route(TOVOICEMAIL);
exit;
 }
#!endif
}
--------------------------------------------------------------------------------------------------------------

I hope you can help me. Thanks for your time.