ipv4: New multicast-all socket option

After some discussion offline with Christoph Lameter and David Stevens
regarding multicast behaviour in Linux, I'm submitting a slightly
modified patch from the one Christoph submitted earlier.

This patch provides a new socket option IP_MULTICAST_ALL.

In this case, default behaviour is _unchanged_ from the current
Linux standard. The socket option is set by default to provide
original behaviour. Sockets wishing to receive data only from
multicast groups they join explicitly will need to clear this
socket option.

Signed-off-by: Nivedita Singhvi <niv@us.ibm.com>
Signed-off-by: Christoph Lameter<cl@linux.com>
Acked-by: David Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/in.h

@@ -107,6 +107,7 @@ struct in_addr {
 #define MCAST_JOIN_SOURCE_GROUP		46
 #define MCAST_LEAVE_SOURCE_GROUP	47
 #define MCAST_MSFILTER			48
+#define IP_MULTICAST_ALL		49
 
 #define MCAST_EXCLUDE	0
 #define MCAST_INCLUDE	1

include/net/inet_sock.h

@@ -130,7 +130,8 @@ struct inet_sock {
 				freebind:1,
 				hdrincl:1,
 				mc_loop:1,
-				transparent:1;
+				transparent:1,
+				mc_all:1;
 	int			mc_index;
 	__be32			mc_addr;
 	struct ip_mc_socklist	*mc_list;

net/ipv4/af_inet.c

@@ -375,6 +375,7 @@ static int inet_create(struct net *net, struct socket *sock, int protocol)
 	inet->uc_ttl	= -1;
 	inet->mc_loop	= 1;
 	inet->mc_ttl	= 1;
+	inet->mc_all	= 1;
 	inet->mc_index	= 0;
 	inet->mc_list	= NULL;
 

net/ipv4/igmp.c

@@ -2196,7 +2196,7 @@ int ip_mc_sf_allow(struct sock *sk, __be32 loc_addr, __be32 rmt_addr, int dif)
 			break;
 	}
 	if (!pmc)
-		return 1;
+		return inet->mc_all;
 	psl = pmc->sflist;
 	if (!psl)
 		return pmc->sfmode == MCAST_EXCLUDE;

net/ipv4/ip_sockglue.c

@@ -453,6 +453,7 @@ static int do_ip_setsockopt(struct sock *sk, int level,
 			     (1<<IP_ROUTER_ALERT) | (1<<IP_FREEBIND) |
 			     (1<<IP_PASSSEC) | (1<<IP_TRANSPARENT))) ||
 	    optname == IP_MULTICAST_TTL ||
+	    optname == IP_MULTICAST_ALL ||
 	    optname == IP_MULTICAST_LOOP ||
 	    optname == IP_RECVORIGDSTADDR) {
 		if (optlen >= sizeof(int)) {
@@ -898,6 +899,13 @@ static int do_ip_setsockopt(struct sock *sk, int level,
 		kfree(gsf);
 		break;
 	}
+	case IP_MULTICAST_ALL:
+		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;
@@ -1151,6 +1159,9 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
 		release_sock(sk);
 		return err;
 	}
+	case IP_MULTICAST_ALL:
+		val = inet->mc_all;
+		break;
 	case IP_PKTOPTIONS:
 	{
 		struct msghdr msg;