[PATCH] Add a socketoption IPV6_MULTICAST_ALL analogue to the IPV4 version

[Andre Naujoks]

The socket option will be enabled by default to ensure current behaviour
is not changed. This is the same for the IPv4 version.

A socket bound to in6addr_any and a specific port will receive all traffic
on that port. Analogue to IP_MULTICAST_ALL, disable this behaviour, if
one or more multicast groups were joined (using said socket) and only
pass on multicast traffic from groups, which were explicitly joined via
this socket.

Without this option disabled a socket (system even) joined to multiple
multicast groups is very hard to get right. Filtering by destination
address has to take place in user space to avoid receiving multicast
traffic from other multicast groups, which might have traffic on the same
port.

The extension of the IP_MULTICAST_ALL socketoption to just apply to ipv6,
too, is not done to avoid changing the behaviour of current applications.

Signed-off-by: Andre Naujoks <nautsch2@xxxxxxxxx>
---
 include/linux/ipv6.h     |  3 ++-
 include/uapi/linux/in6.h |  1 +
 net/ipv6/af_inet6.c      |  1 +
 net/ipv6/ipv6_sockglue.c | 11 +++++++++++
 net/ipv6/mcast.c         |  2 +-
 5 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 8415bf1a9776..495e834c1367 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -274,7 +274,8 @@ struct ipv6_pinfo {
 						 */
 				dontfrag:1,
 				autoflowlabel:1,
-				autoflowlabel_set:1;
+				autoflowlabel_set:1,
+				mc_all:1;
 	__u8			min_hopcount;
 	__u8			tclass;
 	__be32			rcv_flowinfo;
diff --git a/include/uapi/linux/in6.h b/include/uapi/linux/in6.h
index ed291e55f024..71d82fe15b03 100644
--- a/include/uapi/linux/in6.h
+++ b/include/uapi/linux/in6.h
@@ -177,6 +177,7 @@ struct in6_flowlabel_req {
 #define IPV6_V6ONLY		26
 #define IPV6_JOIN_ANYCAST	27
 #define IPV6_LEAVE_ANYCAST	28
+#define IPV6_MULTICAST_ALL	29
 
 /* IPV6_MTU_DISCOVER values */
 #define IPV6_PMTUDISC_DONT		0
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 8da0b513f188..7844cd9d2f10 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -209,6 +209,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol,
 	np->hop_limit	= -1;
 	np->mcast_hops	= IPV6_DEFAULT_MCASTHOPS;
 	np->mc_loop	= 1;
+	np->mc_all	= 1;
 	np->pmtudisc	= IPV6_PMTUDISC_WANT;
 	np->repflow	= net->ipv6.sysctl.flowlabel_reflect;
 	sk->sk_ipv6only	= net->ipv6.sysctl.bindv6only;
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 4d780c7f0130..b2bc1942a2ee 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -664,6 +664,13 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 			retv = ipv6_sock_ac_drop(sk, mreq.ipv6mr_ifindex, &mreq.ipv6mr_acaddr);
 		break;
 	}
+	case IPV6_MULTICAST_ALL:
+		if (optlen < sizeof(int))
+			goto e_inval;
+		np->mc_all = valbool;
+		retv = 0;
+		break;
+
 	case MCAST_JOIN_GROUP:
 	case MCAST_LEAVE_GROUP:
 	{
@@ -1255,6 +1262,10 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		val = np->mcast_oif;
 		break;
 
+	case IPV6_MULTICAST_ALL:
+		val = np->mc_all;
+		break;
+
 	case IPV6_UNICAST_IF:
 		val = (__force int)htonl((__u32) np->ucast_oif);
 		break;
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 793159d77d8a..623ad00eb3c2 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -622,7 +622,7 @@ bool inet6_mc_check(struct sock *sk, const struct in6_addr *mc_addr,
 	}
 	if (!mc) {
 		rcu_read_unlock();
-		return true;
+		return np->mc_all;
 	}
 	read_lock(&mc->sflock);
 	psl = mc->sflist;
-- 
2.17.0