[Live-devel] multicast & linux information

[Piers Hawksley]

 >> It seems that kernel maintainers chose to keep the backward 
compatibility with a default that cause receiving data from all 
multicast groups and not only from joined multicast group.
 >> But they add since kernel 2.6.31 an option that allow to avoid this.

 > That's good to hear.  (I guess this is the closest they'll ever come 
to admitting that the default behavior is a bug :-)


 >> Do you think it could be possible to set this option in 
socketJoinGroup in a future release of live555 ?

 > Done!  I've just installed a new version (2013.10.03) of the "LIVE555 
Streaming Media" code that sets this option to 0 if it's defined.

Attached is the changes I made to Linux 2.6.29 to port the 
IP_MULTICAST_ALL socket option from 2.6.31.

Sorry for this being an svn diff - but it isn't a big change, only a few 
lines to 5 files.

Hopefully it is of interest and not too off-topic. I've tested it within 
the limits of what it is meant to do (and only on one (custom ARM) 
embedded Linux platform) so ymmv.

Cheers,

Piers Hawksley
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Index: include/net/inet_sock.h
===================================================================
--- include/net/inet_sock.h	(revision 5965)
+++ include/net/inet_sock.h	(working copy)
@@ -130,7 +130,8 @@
 				freebind:1,
 				hdrincl:1,
 				mc_loop:1,
-				transparent:1;
+				transparent:1,
+				mc_all:1;	// From 2.6.31
 	int			mc_index;
 	__be32			mc_addr;
 	struct ip_mc_socklist	*mc_list;
Index: include/linux/in.h
===================================================================
--- include/linux/in.h	(revision 5965)
+++ include/linux/in.h	(working copy)
@@ -107,6 +107,7 @@
 #define MCAST_JOIN_SOURCE_GROUP		46
 #define MCAST_LEAVE_SOURCE_GROUP	47
 #define MCAST_MSFILTER			48
+#define IP_MULTICAST_ALL		49	// From 2.6.31
 
 #define MCAST_EXCLUDE	0
 #define MCAST_INCLUDE	1
Index: net/ipv4/af_inet.c
===================================================================
--- net/ipv4/af_inet.c	(revision 5965)
+++ net/ipv4/af_inet.c	(working copy)
@@ -376,6 +376,7 @@
 	inet->uc_ttl	= -1;
 	inet->mc_loop	= 1;
 	inet->mc_ttl	= 1;
+	inet->mc_all    = 1;	// From 2.6.31
 	inet->mc_index	= 0;
 	inet->mc_list	= NULL;
 
Index: net/ipv4/ip_sockglue.c
===================================================================
--- net/ipv4/ip_sockglue.c	(revision 5965)
+++ net/ipv4/ip_sockglue.c	(working copy)
@@ -449,6 +449,7 @@
 			     (1<<IP_ROUTER_ALERT) | (1<<IP_FREEBIND) |
 			     (1<<IP_PASSSEC) | (1<<IP_TRANSPARENT))) ||
 	    optname == IP_MULTICAST_TTL ||
+	    optname == IP_MULTICAST_ALL ||	// From 2.6.31
 	    optname == IP_MULTICAST_LOOP ||
 	    optname == IP_RECVORIGDSTADDR) {
 		if (optlen >= sizeof(int)) {
@@ -895,6 +896,13 @@
 		kfree(gsf);
 		break;
 	}
+	case IP_MULTICAST_ALL:	// From 2.6.31
+		if (optlen < 1)
+			goto e_inval;
+		if (val != 0 && val != 1)
+			goto e_inval;
+		inet->mc_all = val;
+		break;
 	case IP_ROUTER_ALERT:
 		err = ip_ra_control(sk, val ? 1 : 0, NULL);
 		break;
@@ -1147,6 +1155,9 @@
 		release_sock(sk);
 		return err;
 	}
+	case IP_MULTICAST_ALL:	// From 2.6.31
+		val = inet->mc_all;
+		break;
 	case IP_PKTOPTIONS:
 	{
 		struct msghdr msg;
Index: net/ipv4/igmp.c
===================================================================
--- net/ipv4/igmp.c	(revision 5965)
+++ net/ipv4/igmp.c	(working copy)
@@ -2196,7 +2196,7 @@
 			break;
 	}
 	if (!pmc)
-		return 1;
+		return inet->mc_all;	// From 2.6.31
 	psl = pmc->sflist;
 	if (!psl)
 		return pmc->sfmode == MCAST_EXCLUDE;