ipv6: lockless IPV6_MULTICAST_ALL implementation

Move np->mc_all to an atomic flags to fix data-races.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -255,7 +255,6 @@ struct ipv6_pinfo {
 				dontfrag:1,
 				autoflowlabel:1,
 				autoflowlabel_set:1,
-				mc_all:1,
 				rtalert_isolate:1;
 	__u8			min_hopcount;
 	__u8			tclass;

include/net/inet_sock.h

@@ -270,6 +270,7 @@ enum {
 	INET_FLAGS_DEFER_CONNECT = 19,
 	INET_FLAGS_MC6_LOOP	= 20,
 	INET_FLAGS_RECVERR6_RFC4884 = 21,
+	INET_FLAGS_MC6_ALL	= 22,
 };
 
 /* cmsg flags for inet */

net/ipv6/af_inet6.c

@@ -218,7 +218,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol,
 	np->hop_limit	= -1;
 	np->mcast_hops	= IPV6_DEFAULT_MCASTHOPS;
 	inet6_set_bit(MC6_LOOP, sk);
-	np->mc_all	= 1;
+	inet6_set_bit(MC6_ALL, sk);
 	np->pmtudisc	= IPV6_PMTUDISC_WANT;
 	np->repflow	= net->ipv6.sysctl.flowlabel_reflect & FLOWLABEL_REFLECT_ESTABLISHED;
 	sk->sk_ipv6only	= net->ipv6.sysctl.bindv6only;

net/ipv6/ipv6_sockglue.c

@@ -469,6 +469,11 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 			return -EINVAL;
 		inet6_assign_bit(RECVERR6_RFC4884, sk, valbool);
 		return 0;
+	case IPV6_MULTICAST_ALL:
+		if (optlen < sizeof(int))
+			return -EINVAL;
+		inet6_assign_bit(MC6_ALL, sk, valbool);
+		return 0;
 	}
 	if (needs_rtnl)
 		rtnl_lock();
@@ -890,13 +895,6 @@ 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:
 		if (in_compat_syscall())
@@ -1372,7 +1370,7 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case IPV6_MULTICAST_ALL:
-		val = np->mc_all;
+		val = inet6_test_bit(MC6_ALL, sk);
 		break;
 
 	case IPV6_UNICAST_IF:

net/ipv6/mcast.c

@@ -642,7 +642,7 @@ bool inet6_mc_check(const struct sock *sk, const struct in6_addr *mc_addr,
 	}
 	if (!mc) {
 		rcu_read_unlock();
-		return np->mc_all;
+		return inet6_test_bit(MC6_ALL, sk);
 	}
 	psl = rcu_dereference(mc->sflist);
 	if (!psl) {