[Serusers] Media cannot be passed through NAT

[gg]

Hi everyone!
   I come acrossed a problem
   I have installed SER-0.8.14 on Red Hat Liunx 9.0 in source form.
I also have installed rtpproxy. It can run normally. 
   Two IP phones both with public IP address are able to get through and
both can hear. Another two IP phones both with private IP address are able
to get throuh and both can hear too. 
   The problem is as follows: when one with public IP address and another
with private IP address, they can get through but only the one with public
IP address can hear. The other cannot. When two phones separated to two LAN,
they both can not hear.
           __________
           |        |
           | LAN 2  |---phone 5
           |________|
               |
         ______|________
         |             |   ___________
   SER---|   Internet  |---|         |--- phone 1
         |             |   |  LAN 1  |
         |_____________|   |_________|--- phone 2
           |         |
           |         |
       phone 3      phone 4

   The figure above shows phone 1 and phone 2 are both with private IP address.
Phone 3 and phone 4 are both with public IP address. Any two phones can get
through(can ring). When phone 1 calls phone 2, they both can hear. When phone 3
call phone 4, they both can hear too. When phone 1 call phone 3 or phone 3 call
phone 1, it can ring, and phone 3 can hear but phone 1 cannot hear. When phone 5
call phone 1 or phone 1 call phone 5, they both can not hear anything.  
   I have try many efforts but failed, Anyone help me will be appreciated!
   Thank you !


                                                      
# $Id: nathelper.cfg,v 1.1.2.1 2003/11/24 14:47:18 janakj Exp $
#
# simple quick-start config script including nathelper support

# This default script includes nathelper support. To make it work
# you will also have to install Maxim's RTP proxy. The proxy is enforced
# if one of the parties is behind a NAT.
#
# If you have an endpoing in the public internet which is known to
# support symmetric RTP (Cisco PSTN gateway or voicemail, for example),
# then you don't have to force RTP proxy. If you don't want to enforce
# RTP proxy for some destinations than simply use t_relay() instead of
# route(1)
#
# Sections marked with !! Nathelper contain modifications for nathelper
#
# NOTE !! This config is EXPERIMENTAL !
#
# ----------- global configuration parameters ------------------------

debug=3         # debug level (cmd line: -dddddddddd)
fork=yes
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)
port=5060
children=4
fifo="/tmp/ser_fifo"

# ------------------ module loading ----------------------------------

# Uncomment this if you want to use SQL database
#loadmodule "/usr/local/lib/ser/modules/mysql.so"

loadmodule "/usr/local/lib/ser/modules/sl.so"
loadmodule "/usr/local/lib/ser/modules/tm.so"
loadmodule "/usr/local/lib/ser/modules/rr.so"
loadmodule "/usr/local/lib/ser/modules/maxfwd.so"
loadmodule "/usr/local/lib/ser/modules/usrloc.so"
loadmodule "/usr/local/lib/ser/modules/registrar.so"
loadmodule "/usr/local/lib/ser/modules/textops.so"

# Uncomment this if you want digest authentication
# mysql.so must be loaded !
#loadmodule "/usr/local/lib/ser/modules/auth.so"
#loadmodule "/usr/local/lib/ser/modules/auth_db.so"

# !! Nathelper
loadmodule "/usr/local/lib/ser/modules/nathelper.so"

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

# -- usrloc params --

modparam("usrloc", "db_mode",   0)

# Uncomment this if you want to use SQL database 
# for persistent storage and comment the previous line
#modparam("usrloc", "db_mode", 2)

# -- auth params --
# Uncomment if you are using auth module
#
#modparam("auth_db", "calculate_ha1", yes)
#
# If you set "calculate_ha1" parameter to yes (which true in this config), 
# uncomment also the following parameter)
#
#modparam("auth_db", "password_column", "password")

# -- rr params --
# add value to ;lr param to make some broken UAs happy
modparam("rr", "enable_full_lr", 1)

# !! Nathelper
modparam("registrar", "nat_flag", 6)
modparam("nathelper", "natping_interval", 30) # Ping interval 30 s
modparam("nathelper", "ping_nated_only", 1)   # Ping only clients behind NAT

# -------------------------  request routing logic -------------------

# main routing logic

route{

	# initial sanity checks -- messages with
	# max_forwards==0, or excessively long requests
	if (!mf_process_maxfwd_header("10")) {
		sl_send_reply("483","Too Many Hops");
		break;
	};
	if (msg:len >=  max_len ) {
		sl_send_reply("513", "Message too big");
		break;
	};

        # !! Nathelper
	# Special handling for NATed clients; first, NAT test is
	# executed: it looks for via!=received and RFC1918 addresses
	# in Contact (may fail if line-folding is used); also,
	# the received test should, if completed, should check all
	# vias for rpesence of received
	if (nat_uac_test("3")) {
		# Allow RR-ed requests, as these may indicate that
		# a NAT-enabled proxy takes care of it; unless it is
		# a REGISTER
       fix_nated_contact();
		if (method == "REGISTER" || ! search("^Record-Route:")) {
		    log("LOG: Someone trying to register from private IP, rewriting\n");

		    # This will work only for user agents that support symmetric
		    # communication. We tested quite many of them and majority is
		    # smart enough to be symmetric. In some phones it takes a configuration
		    # option. With Cisco 7960, it is called NAT_Enable=Yes, with kphone it is
		    # called "symmetric media" and "symmetric signalling".

		   # fix_nated_contact(); # Rewrite contact with source IP of signalling
		    if (method == "INVITE") {
		        fix_nated_sdp("1"); # Add direction=active to SDP
		    };
		    force_rport(); # Add rport parameter to topmost Via
		    setflag(6);    # Mark as NATed
		};
	};

	# we record-route all messages -- to make sure that
	# subsequent messages will go through our proxy; that's
	# particularly good if upstream and downstream entities
	# use different transport protocol
	if (!method=="REGISTER") record_route();	

	# subsequent messages withing a dialog should take the
	# path determined by record-routing
	if (loose_route()) {
		# mark routing logic in request
		append_hf("P-hint: rr-enforced\r\n"); 
		route(1);
		break;
	};

	if (!uri==myself) {
		# mark routing logic in request
		append_hf("P-hint: outbound\r\n"); 
		route(1);
		break;
	};

	# if the request is for other domain use UsrLoc
	# (in case, it does not work, use the following command
	# with proper names and addresses in it)
	if (uri==myself) {

		if (method=="REGISTER") {

# Uncomment this if you want to use digest authentication
#			if (!www_authorize("iptel.org", "subscriber")) {
#				www_challenge("iptel.org", "0");
#				break;
#			};

			save("location");
			break;
		};

		lookup("aliases");
		if (!uri==myself) {
			append_hf("P-hint: outbound alias\r\n"); 
			route(1);
			break;
		};

		# native SIP destinations are handled using our USRLOC DB
		if (!lookup("location")) {
			sl_send_reply("404", "Not Found");
			break;
		};
	};
	append_hf("P-hint: usrloc applied\r\n"); 
	route(1);
}

route[1] 
{
	# !! Nathelper
	if ((uri=~"[@:](192\.168\.|10\.|172\.(1[6-9]|2[0-9]|3[0-1])\.)" || !search("^Route:")){
	    sl_send_reply("479", "We don't forward to private IP addresses");
	    break;
        };
	
	# if client or server know to be behind a NAT, enable relay
	if (isflagset(6)) {
	    force_rtp_proxy();
	};

	# NAT processing of replies; apply to all transactions (for example,
	# re-INVITEs from public to private UA are hard to identify as
	# NATed at the moment of request processing); look at replies
	t_on_reply("1");

	# send it out now; use stateful forwarding as it works reliably
	# even for UDP2TCP
	if (!t_relay()) {
		sl_reply_error();
	};
}

# !! Nathelper
onreply_route[1] {
    # NATed transaction ?
    if (isflagset(6) && status =~ "(183)|2[0-9][0-9]") {
        fix_nated_contact();
        fix_nated_sdp("1");
	force_rtp_proxy();
    # otherwise, is it a transaction behind a NAT and we did not
    # know at time of request processing ? (RFC1918 contacts)
    } else if (nat_uac_test("1")) 
       {
        fix_nated_contact();
        fix_nated_sdp("1");
        force_rtp_proxy();
    };
}