net: ipv6: add socket option IPV6_ROUTER_ALERT_ISOLATE

By default IPv6 socket with IPV6_ROUTER_ALERT socket option set will
receive all IPv6 RA packets from all namespaces.
IPV6_ROUTER_ALERT_ISOLATE socket option restricts packets received by
the socket to be only from the socket's namespace.
Signed-off-by: Maxim Martynov <maxim@arista.com>
Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -281,7 +281,8 @@ struct ipv6_pinfo {
 				dontfrag:1,
 				autoflowlabel:1,
 				autoflowlabel_set:1,
-				mc_all:1;
+				mc_all:1,
+				rtalert_isolate:1;
 	__u8			min_hopcount;
 	__u8			tclass;
 	__be32			rcv_flowinfo;

include/uapi/linux/in6.h

@@ -178,6 +178,7 @@ struct in6_flowlabel_req {
 #define IPV6_JOIN_ANYCAST	27
 #define IPV6_LEAVE_ANYCAST	28
 #define IPV6_MULTICAST_ALL	29
+#define IPV6_ROUTER_ALERT_ISOLATE	30
 
 /* IPV6_MTU_DISCOVER values */
 #define IPV6_PMTUDISC_DONT		0

net/ipv6/ip6_output.c

@@ -300,6 +300,12 @@ static int ip6_call_ra_chain(struct sk_buff *skb, int sel)
 		if (sk && ra->sel == sel &&
 		    (!sk->sk_bound_dev_if ||
 		     sk->sk_bound_dev_if == skb->dev->ifindex)) {
+			struct ipv6_pinfo *np = inet6_sk(sk);
+
+			if (np && np->rtalert_isolate &&
+			    !net_eq(sock_net(sk), dev_net(skb->dev))) {
+				continue;
+			}
 			if (last) {
 				struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
 				if (skb2)

net/ipv6/ipv6_sockglue.c

@@ -787,6 +787,12 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 			goto e_inval;
 		retv = ip6_ra_control(sk, val);
 		break;
+	case IPV6_ROUTER_ALERT_ISOLATE:
+		if (optlen < sizeof(int))
+			goto e_inval;
+		np->rtalert_isolate = valbool;
+		retv = 0;
+		break;
 	case IPV6_MTU_DISCOVER:
 		if (optlen < sizeof(int))
 			goto e_inval;
@@ -1358,6 +1364,10 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		val = np->rxopt.bits.recvfragsize;
 		break;
 
+	case IPV6_ROUTER_ALERT_ISOLATE:
+		val = np->rtalert_isolate;
+		break;
+
 	default:
 		return -ENOPROTOOPT;
 	}