[Asterisk-Dev] NAT patch for chan_sip.c

[William Waites]

This is not thoroughly tested, but seems to work for me. It consists in
three changes:

 1. introduction of inside_net, inside_mask and outside_addr global
    parameters for sip.conf
 2. change transmit_register to call ast_sip_ouraddrfor() before
    building the contact header
 3. change ast_sip_ouraddrfor() to check if the destination is
    internal or external. if internal, continue as usual, if external
    return outside_addr in *us

Consider this patch suitably disclaimed, and without any warranty
whatsoever. This code was produced on behalf of NTG Clarity Networks,
Montréal.

Index: chan_sip.c
===================================================================
RCS file: /usr/cvsroot/asterisk/channels/chan_sip.c,v
retrieving revision 1.203
diff -u -r1.203 chan_sip.c
--- chan_sip.c  25 Oct 2003 17:41:02 -0000      1.203
+++ chan_sip.c  30 Oct 2003 17:23:54 -0000
@@ -390,6 +390,9 @@
 
 
 static struct sockaddr_in bindaddr;
+static struct sockaddr_in inside_net;
+static struct sockaddr_in inside_mask;
+static struct sockaddr_in outside_addr;
 
 static struct ast_frame  *sip_read(struct ast_channel *ast);
 static int transmit_response(struct sip_pvt *p, char *msg, struct sip_request
*req);
@@ -425,7 +428,15 @@
 
 static int ast_sip_ouraddrfor(struct in_addr *them, struct in_addr *us)
 {
-       if (bindaddr.sin_addr.s_addr)
+       /*
+         check to see if them is contained in our inside_net/mask,
+         if not, use our outside_addr for us, otherwise use the 
+         real internal address in bindaddr
+         */
+       if (inside_net.sin_addr.s_addr && outside_addr.sin_addr.s_addr &&
+           ((htonl(them->s_addr) & htonl(inside_net.sin_addr.s_addr)) !=
htonl(inside_net.sin_addr.s_addr)))
+               memcpy(us, &outside_addr.sin_addr, sizeof(struct in_addr));
+       else if (bindaddr.sin_addr.s_addr)
                memcpy(us, &bindaddr.sin_addr, sizeof(struct in_addr));
        else
                return ast_ouraddrfor(them, us);
@@ -2951,6 +2962,8 @@
        char via[80];
        char addr[80];
        struct sip_pvt *p;
+       struct hostent *hp;
+
        /* exit if we are already in process with this registrar ?*/
        if ( r == NULL || ((auth==NULL) && (r->regstate==REG_STATE_REGSENT ||
r->regstate==REG_STATE_AUTHSENT))) {
                ast_log(LOG_NOTICE, "Strange, trying to register when
registration already pending\n");
@@ -2984,9 +2997,16 @@
                        strncpy(p->peername, r->username, sizeof(p->peername)-1);
                strncpy(p->username, r->username, sizeof(p->username)-1);
                strncpy(p->exten, r->contact, sizeof(p->exten) - 1);
-               /* Always bind to our IP if specified */
-               if (bindaddr.sin_addr.s_addr)
-                       memcpy(&p->ourip, &bindaddr.sin_addr, sizeof(p->ourip));
+
+               /*
+                 check which address we should use in our contact header 
+                 based on whether the remote host is on the external or
+                 internal network so we can register through nat
+                */
+               if ((hp = gethostbyname(r->hostname))) {
+                       if (ast_sip_ouraddrfor((struct in_addr *)hp->h_addr,
&p->ourip))
+                               memcpy(&p->ourip, &bindaddr.sin_addr,
sizeof(p->ourip));
+               }
                build_contact(p);
        }
 
@@ -5921,6 +5941,10 @@
        sip_prefs_free();
 
        memset(&bindaddr, 0, sizeof(bindaddr));
+       memset(&inside_net, 0, sizeof(inside_net));
+       memset(&inside_mask, 0, sizeof(inside_mask));
+       memset(&outside_addr, 0, sizeof(outside_addr));
+
        /* Initialize some reasonable defaults */
        strncpy(context, "default", sizeof(context) - 1);
        strcpy(language, "");
@@ -5979,6 +6003,21 @@
                        } else {
                                memcpy(&bindaddr.sin_addr, hp->h_addr,
sizeof(bindaddr.sin_addr));
                        }
+               } else if (!strcasecmp(v->name, "inside_net")) {
+                       if (!(hp = gethostbyname(v->value)))
+                               ast_log(LOG_WARNING, "Invalid INSIDE_NET:
%s\n", v->value);
+                       else 
+                               memcpy(&inside_net.sin_addr, hp->h_addr,
sizeof(inside_net.sin_addr));
+               } else if (!strcasecmp(v->name, "inside_mask")) {
+                       if (!(hp = gethostbyname(v->value)))
+                               ast_log(LOG_WARNING, "Invalid INSIDE_MASK:
%s\n", v->value);
+                       else
+                               memcpy(&inside_mask.sin_addr, hp->h_addr,
sizeof(inside_mask.sin_addr));
+               } else if (!strcasecmp(v->name, "outside_addr")) {
+                       if (!(hp = gethostbyname(v->value))) 
+                               ast_log(LOG_WARNING, "Invalid OUTSIDE_MASK:
%s\n", v->value);
+                       else
+                               memcpy(&outside_addr.sin_addr, hp->h_addr,
sizeof(outside_addr.sin_addr));
                } else if (!strcasecmp(v->name, "allow")) {
                        format = ast_getformatbyname(v->value);
                        if (format < 1)