sctp: process sk_reuseport in sctp_get_port_local

When socks' sk_reuseport is set, the same port and address are allowed
to be bound into these socks who have the same uid.

Note that the difference from sk_reuse is that it allows multiple socks
to listen on the same port and address.
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -96,7 +96,9 @@ struct sctp_stream;
 
 struct sctp_bind_bucket {
 	unsigned short	port;
-	unsigned short	fastreuse;
+	signed char	fastreuse;
+	signed char	fastreuseport;
+	kuid_t		fastuid;
 	struct hlist_node	node;
 	struct hlist_head	owner;
 	struct net	*net;

net/sctp/socket.c

@@ -7644,8 +7644,10 @@ static struct sctp_bind_bucket *sctp_bucket_create(
 
 static long sctp_get_port_local(struct sock *sk, union sctp_addr *addr)
 {
-	bool reuse = (sk->sk_reuse || sctp_sk(sk)->reuse);
+	struct sctp_sock *sp = sctp_sk(sk);
+	bool reuse = (sk->sk_reuse || sp->reuse);
 	struct sctp_bind_hashbucket *head; /* hash list */
+	kuid_t uid = sock_i_uid(sk);
 	struct sctp_bind_bucket *pp;
 	unsigned short snum;
 	int ret;
@@ -7721,7 +7723,10 @@ static long sctp_get_port_local(struct sock *sk, union sctp_addr *addr)
 
 		pr_debug("%s: found a possible match\n", __func__);
 
-		if (pp->fastreuse && reuse && sk->sk_state != SCTP_SS_LISTENING)
+		if ((pp->fastreuse && reuse &&
+		     sk->sk_state != SCTP_SS_LISTENING) ||
+		    (pp->fastreuseport && sk->sk_reuseport &&
+		     uid_eq(pp->fastuid, uid)))
 			goto success;
 
 		/* Run through the list of sockets bound to the port
@@ -7735,16 +7740,18 @@ static long sctp_get_port_local(struct sock *sk, union sctp_addr *addr)
 		 * in an endpoint.
 		 */
 		sk_for_each_bound(sk2, &pp->owner) {
-			struct sctp_endpoint *ep2;
-			ep2 = sctp_sk(sk2)->ep;
+			struct sctp_sock *sp2 = sctp_sk(sk2);
+			struct sctp_endpoint *ep2 = sp2->ep;
 
 			if (sk == sk2 ||
-			    (reuse && (sk2->sk_reuse || sctp_sk(sk2)->reuse) &&
-			     sk2->sk_state != SCTP_SS_LISTENING))
+			    (reuse && (sk2->sk_reuse || sp2->reuse) &&
+			     sk2->sk_state != SCTP_SS_LISTENING) ||
+			    (sk->sk_reuseport && sk2->sk_reuseport &&
+			     uid_eq(uid, sock_i_uid(sk2))))
 				continue;
 
-			if (sctp_bind_addr_conflict(&ep2->base.bind_addr, addr,
-						 sctp_sk(sk2), sctp_sk(sk))) {
+			if (sctp_bind_addr_conflict(&ep2->base.bind_addr,
+						    addr, sp2, sp)) {
 				ret = (long)sk2;
 				goto fail_unlock;
 			}
@@ -7767,19 +7774,32 @@ static long sctp_get_port_local(struct sock *sk, union sctp_addr *addr)
 			pp->fastreuse = 1;
 		else
 			pp->fastreuse = 0;
-	} else if (pp->fastreuse &&
+
+		if (sk->sk_reuseport) {
+			pp->fastreuseport = 1;
+			pp->fastuid = uid;
+		} else {
+			pp->fastreuseport = 0;
+		}
+	} else {
+		if (pp->fastreuse &&
 		    (!reuse || sk->sk_state == SCTP_SS_LISTENING))
 			pp->fastreuse = 0;
 
+		if (pp->fastreuseport &&
+		    (!sk->sk_reuseport || !uid_eq(pp->fastuid, uid)))
+			pp->fastreuseport = 0;
+	}
+
 	/* We are set, so fill up all the data in the hash table
 	 * entry, tie the socket list information with the rest of the
 	 * sockets FIXME: Blurry, NPI (ipg).
 	 */
 success:
-	if (!sctp_sk(sk)->bind_hash) {
+	if (!sp->bind_hash) {
 		inet_sk(sk)->inet_num = snum;
 		sk_add_bind_node(sk, &pp->owner);
-		sctp_sk(sk)->bind_hash = pp;
+		sp->bind_hash = pp;
 	}
 	ret = 0;