mptcp: address lookup improvements

When looking-up a socket address in the endpoint list, we
must prefer port-based matches over address only match.

Ensure that port-based endpoints are listed first, using
head insertion for them. Additionally be sure that only
port-based endpoints carry a non zero port number.

Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm_netlink.c

@@ -413,7 +413,7 @@ static bool lookup_address_in_vec(const struct mptcp_addr_info *addrs, unsigned
 	int i;
 
 	for (i = 0; i < nr; i++) {
-		if (mptcp_addresses_equal(&addrs[i], addr, addr->port))
+		if (addrs[i].id == addr->id)
 			return true;
 	}
 
@@ -449,7 +449,8 @@ static unsigned int fill_remote_addresses_vec(struct mptcp_sock *msk, bool fullm
 		mptcp_for_each_subflow(msk, subflow) {
 			ssk = mptcp_subflow_tcp_sock(subflow);
 			remote_address((struct sock_common *)ssk, &addrs[i]);
-			if (deny_id0 && mptcp_addresses_equal(&addrs[i], &remote, false))
+			addrs[i].id = subflow->remote_id;
+			if (deny_id0 && !addrs[i].id)
 				continue;
 
 			if (!lookup_address_in_vec(addrs, i, &addrs[i]) &&
@@ -919,10 +920,11 @@ static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
 	/* do not insert duplicate address, differentiate on port only
 	 * singled addresses
 	 */
+	if (!address_use_port(entry))
+		entry->addr.port = 0;
 	list_for_each_entry(cur, &pernet->local_addr_list, list) {
 		if (mptcp_addresses_equal(&cur->addr, &entry->addr,
-					  address_use_port(entry) &&
-					  address_use_port(cur))) {
+					  cur->addr.port || entry->addr.port)) {
 			/* allow replacing the exiting endpoint only if such
 			 * endpoint is an implicit one and the user-space
 			 * did not provide an endpoint id
@@ -968,7 +970,10 @@ find_next:
 	}
 
 	pernet->addrs++;
-	list_add_tail_rcu(&entry->list, &pernet->local_addr_list);
+	if (!entry->addr.port)
+		list_add_tail_rcu(&entry->list, &pernet->local_addr_list);
+	else
+		list_add_rcu(&entry->list, &pernet->local_addr_list);
 	ret = entry->addr.id;
 
 out: