[Serusers] rtpproxy / nathelper - problem
Jiri Kuthan
jiri at iptel.org
Mon Feb 2 10:29:34 CET 2004
Even if there is just one UA behind a symmetric NAT and the other guy is
on the public Internet, you need to use RTP proxy. A way around would be
smart UAs that are able to detect this condition and use symmetric media
(comedia SDP extentsion) but I would be surprised if this technique would
be deployable with today's SIP phone.
-jiri
At 08:17 AM 2/2/2004, Dinesh wrote:
>I would like to know if force_rtp_proxy() is necessary when (UA behind
>NAT) is calling a (UA not behind NAT).
>
>I have no problem calling (ATA186 - Real IP) to (Grandstream behind NAT)
>However
>(Grandstream behind NAT) to (ATA186 - Real IP) ATA can hear but
>GrandStream cannot hear.
>NAT router is Vigor 2600 - known to be symetric.
>
>Also I am using Flag 6 to indicate behind NAT however when I look in the
>mysql db flags field shows a 1 and not a 6 is this as it should be?
>
>
>My ser.cfg is below.
>
>Thanks,
>Dinesh
>
>
>fork=yes
>log_stderror=no # (cmd line: -E)
>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/nathelper.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"
>
># ----------------- 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
># No Cache
>#modparam("usrloc", "db_mode", 1)
># With Cache
>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("2")) {
> # Allow RR-ed requests, as these may indicate that
> # a NAT-enabled proxy takes care of it; unless it is
> # a REGISTER
>
> if (method == "REGISTER" || ! search("^Record-Route:"))
>{
> log("LOG: Someone trying to register from private
>IP, rewriting\n");
> 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 (uri==myself) {
> if (method=="INVITE") {
> record_route();
> if (isflagset(6)) {
> force_rtp_proxy();
> };
> };
>
>
> if (method=="REGISTER") {
> 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]
>{
> # send it out now; use stateful forwarding as it works reliably
> # even for UDP2TCP
> if (!t_relay()) {
> sl_reply_error();
> };
>}
>
>onreply_route[1] {
> # NATed transaction ?
> if (isflagset(6) && status =~ "(183)|2[0-9][0-9]") {
> fix_nated_contact();
> 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();
> };
>}
>
>
>
>
>
>
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--
Jiri Kuthan http://iptel.org/~jiri/
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