Fixed a couple of bugs in handling of multicast sockets.

See comments in lib/socket.h for a detailed guide on how to use them.

TODO

@@ -37,6 +37,7 @@ Cleanup
 - check if all protocols set proper packet priorities and TTL's.
 - replace all NUM, IPA and expr tokens by constant filter expressions
 - try compiling with -Wunused
+- does everybody test return value of sk_open?
 
 Various ideas
 ~~~~~~~~~~~~~

lib/socket.h

@@ -55,8 +55,16 @@ void sk_dump_all(void);
 #define SK_TCP		2
 #define SK_UDP		3          /* ?  ?  -  -  -  ?   ?	*/
 #define SK_UDP_MC       4          /* ?  ?  *  *  *  *   -	*/
-#define SK_IP		5          /* ?  ?  -  *  -  ?   ?	*/
+#define SK_IP		5          /* ?  -  -  *  -  ?   ?	*/
-#define SK_IP_MC	6          /* ?  ?  *  *  *  *   -	*/
+#define SK_IP_MC	6          /* ?  -  *  *  *  *   -	*/
 #define SK_MAGIC	7	   /* Internal use by sysdep code */
 
+/*
+ *  Multicast sockets are slightly different from the other ones:
+ *  If you want to send packets only, just set the destination
+ *  address to the corresponding multicast group and iface to
+ *  the interface to be used. If you also want receiving, set
+ *  source address to the same multicast group as well.
+ */
+
 #endif

sysdep/unix/io.c

@@ -408,21 +408,18 @@ sk_open(sock *s)
     case SK_IP_MC:
       {
 #ifdef HAVE_IP_MREQN
+	/* FIXME: Define HAVE_IP_MREQN somewhere :) */
 	struct ip_mreqn mreq;
 #define mreq_add mreq
+	ASSERT(s->iface);
 	mreq.imr_ifindex = s->iface->index;
-	if (has_src)
+	set_inaddr(&mreq.imr_address, s->iface->ip);
-	  set_inaddr(&mreq.imr_address, s->saddr);
-	else
-	  set_inaddr(&mreq.imr_address, s->iface->ifa->ip);
 #else
 	struct in_addr mreq;
 	struct ip_mreq mreq_add;
-	if (has_src)
+	ASSERT(s->iface);
-	  set_inaddr(&mreq, s->saddr);
+	set_inaddr(&mreq, s->iface->ip);
-	else
+	mreq_add.imr_interface = mreq;
-	  set_inaddr(&mreq, s->iface->ip);
-	memcpy(&mreq_add.imr_interface, &mreq, sizeof(struct in_addr));
 #endif
 	set_inaddr(&mreq_add.imr_multiaddr, s->daddr);
 	if (has_dest)
@@ -439,9 +436,11 @@ sk_open(sock *s)
 #endif
 		setsockopt(fd, SOL_IP, IP_MULTICAST_LOOP, &zero, sizeof(zero)) < 0)
 	      ERR("IP_MULTICAST_LOOP");
+	    /* This defines where should we send _outgoing_ multicasts */
 	    if (setsockopt(fd, SOL_IP, IP_MULTICAST_IF, &mreq, sizeof(mreq)) < 0)
 	      ERR("IP_MULTICAST_IF");
 	}
+      /* And this one sets interface for _receiving_ multicasts from */
       if (has_src && setsockopt(fd, SOL_IP, IP_ADD_MEMBERSHIP, &mreq_add, sizeof(mreq_add)) < 0)
 	ERR("IP_ADD_MEMBERSHIP");
       break;