[sr-dev] alias_contact()/handle_alias() ready for testing

[Klaus Darilion]

Juha Heinanen schrieb:
> "final" versions of alias functions are now ready for testing in in this
> sr_3.0 based nathelper.c:
> 
> http://box.tutpro.com/tmp/nathelper.c

Great, thanks.

> i changed the names to more descriptive ones: add_contact_alias() and
> handle_ruri_alias().  also helper function rr_count(pvar) is included
> that assigns into the pvar the number of rr headers in incoming message
> (request or reply).

I just wonder why "alias" is used, and not "received". Current similar 
features (fix_nated_register, Path) use the term "received" to refer to 
the socket from which the request was received, not alias. I know your 
mean purpose was TCP, but IMO this is proper method to handle both, 
NATed and TCP clients. Thus, I think by using add_contact_received and 
handle_uri_received it would be easier for people to understand what the 
function does.

But anyway, a name is just name :-)

thanks
klaus

> 
> usage example is below.  i believe (until otherwise shown) that it
> works correctly.
> 
> if you are interested, please try with different UAs and different
> transports with or without nat.
> 
> -- juha
> 
> add_contact_alias()/handle_ruri_alias() usage example
> -----------------------------------------------------
> 
> supports re-use of tcp sessions between proxy and UAs.  supports routing
> of requests to UAs behind NATs so that r-uri is always what UAs expect.
> proxying of media is not shown, but can be easily added.
> 
> NON_REGISTER_INITIAL_REQUESTS
> -----------------------------
> 
> - call alias_contact() for all non-register initial requests, which
>   don't come from another proxy (which takes care of its own UAs).
> 
> - if you know that non-register initial request is going to another
>   proxy, set TO_PROXY flag before relaying the request.
> 
> - in cases, where initial request may go to another proxy, but you are
>   not sure about it, store the number of record-route headers in
>   incoming request in an AVP that you can then later test in onreply
>   route and find out, if next hop was a proxy.
> 
> route [NON_REGISTER_INITIAL_REQUESTS] {
> 
>     if (!is_present_hf("Record-Route")) {
>         route(ADD_CONTACT_ALIAS);
>     };
>     ...
>     if (I_KNOW_FOR_SURE_THAT_NEXT_HOP_IS_ANOTHER_PROXY) {
>         setbflag("TO_PROXY");
>     };
> 
>     if (NEXT_HOP_MAY_BE_ANOTHER_PROXY_BUT_I_DONT_KNOW_FOR_SURE) {
>         if (!rr_count($avp("rr_count"))) {
>             send_reply("400", "Bad request");
>             exit;
> 	};
>     };
>     t_on_reply("REPLY");
>     if (!t_relay()) ...
> 
> route [ADD_CONTACT_ALIAS] {
>     if (!add_contact_alias()) {
>         xlog("L_ERR", "Error in aliasing contact <$ct>\n");
>         send_reply("400", "Bad request");
>         exit;
>     };
> }
> 
> REGISTER_REQUESTS
> -----------------
> 
> - call fix_nated_register() on register requests, if registering ua is
>   behind nat OR is using tcp.
> 
> route [REGISTER_REQUESTS] {
>     ...
>     if (isflagset(FROM_NATED) || (proto == TCP)) {
>         fix_nated_register();
> 	if (isflagset(FROM_NATED)) {
> 	    setbflag("TO_NATED");
> 	};
>     };
>     save("location");
>     ...
> 
> IN_DIALOG_REQUESTS
> ------------------
> 
> - call handle_ruri_alias() for all in-dialog requests before
>   t_relaying them, provided that loose_route() didn't set $du, which it
>   does if next hop is another proxy.  in the latter case set TO_PROXY
>   fag.
> 
> route [IN_DIALOG_REQUESTS] {
> 
>     loose_route();
>     ...
>     if ($du == "") {
>         handle_ruri_alias();
>         switch ($rc) {
>         case -1:
>             xlog("L_ERR", "Failed to handle alias of R-URI <$ru>\n");
>             send_reply("400", "Bad request");
>             exit;
>         case 1:
>             xlog("L_INFO", "Routing in-dialog $rm from <$fu> to <$du>\n");
>             break;
>         case 2:
>             xlog("L_INFO", "Routing in-dialog $rm from <$fu> to <$ru>\n");
>             break;
>          };
>     } else {
>         setbflag("TO_PROXY");
>     }
>     t_on_reply("REPLY");
>     if (!t_relay()) {
>         ...
> 
> REPLIES
> -------
> 
> - call add_contact_alias() on all replies except the ones that come from
>   another proxy.
> 
> onreply_route [REPLY] {
> 
>     if (!isbflagset("TO_PROXY") {
>         if (is_avp_set("rr_count")) {
> 	    if (!rr_count("$(var(rr_count)"))) {
>  	        xlog("L_NOTICE", "Bad R-R header in reply\n");
> 	        send_reply("400", "Bad reply");
>                 exit;
> 	    };
> 	    if ($var(rr_count) == $avp(rr_count) + 1) {
> 	        route(ADD_CONTACT_ALIAS);
>             };
>         } else {
> 	    route(ADD_CONTACT_ALIAS);
> 	}
>     }
>     ...
> 
> NOTE
> ----
> 
> - do NOT call fix_nated_contact() on anything, because
>   add_contact_alias() replaces it.
> 
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