mptcp: reflect remote port (not 0) in ANNOUNCED events

Per RFC 8684, if no port is specified in an ADD_ADDR message, MPTCP
SHOULD attempt to connect to the specified address on the same port
as the port that is already in use by the subflow on which the
ADD_ADDR signal was sent.

To facilitate that, this change reflects the specific remote port in
use by that subflow in MPTCP_EVENT_ANNOUNCED events.

Signed-off-by: Kishen Maloor <kishen.maloor@intel.com>

net/mptcp/options.c

@@ -1123,7 +1123,7 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 		if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
 		    add_addr_hmac_valid(msk, &mp_opt)) {
 			if (!mp_opt.echo) {
-				mptcp_pm_add_addr_received(msk, &mp_opt.addr);
+				mptcp_pm_add_addr_received(msk, &mp_opt.addr, sk);
 				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
 			} else {
 				mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);

net/mptcp/pm.c

@@ -204,14 +204,15 @@ void mptcp_pm_subflow_check_next(struct mptcp_sock *msk, const struct sock *ssk,
 }
 
 void mptcp_pm_add_addr_received(struct mptcp_sock *msk,
-				const struct mptcp_addr_info *addr)
+				const struct mptcp_addr_info *addr,
+				const struct sock *ssk)
 {
 	struct mptcp_pm_data *pm = &msk->pm;
 
 	pr_debug("msk=%p remote_id=%d accept=%d", msk, addr->id,
 		 READ_ONCE(pm->accept_addr));
 
-	mptcp_event_addr_announced(msk, addr);
+	mptcp_event_addr_announced(msk, addr, ssk);
 
 	spin_lock_bh(&pm->lock);
 

net/mptcp/pm_netlink.c

@@ -1933,7 +1933,8 @@ void mptcp_event_addr_removed(const struct mptcp_sock *msk, uint8_t id)
 }
 
 void mptcp_event_addr_announced(const struct mptcp_sock *msk,
-				const struct mptcp_addr_info *info)
+				const struct mptcp_addr_info *info,
+				const struct sock *ssk)
 {
 	struct net *net = sock_net((const struct sock *)msk);
 	struct nlmsghdr *nlh;
@@ -1957,7 +1958,10 @@ void mptcp_event_addr_announced(const struct mptcp_sock *msk,
 	if (nla_put_u8(skb, MPTCP_ATTR_REM_ID, info->id))
 		goto nla_put_failure;
 
-	if (nla_put_be16(skb, MPTCP_ATTR_DPORT, info->port))
+	if (nla_put_be16(skb, MPTCP_ATTR_DPORT,
+			 info->port  == 0 ?
+			 ((struct inet_sock *)inet_sk(ssk))->inet_dport :
+			 info->port))
 		goto nla_put_failure;
 
 	switch (info->family) {

net/mptcp/protocol.h

@@ -752,7 +752,8 @@ bool mptcp_pm_nl_check_work_pending(struct mptcp_sock *msk);
 void mptcp_pm_subflow_check_next(struct mptcp_sock *msk, const struct sock *ssk,
 				 const struct mptcp_subflow_context *subflow);
 void mptcp_pm_add_addr_received(struct mptcp_sock *msk,
-				const struct mptcp_addr_info *addr);
+				const struct mptcp_addr_info *addr,
+				const struct sock *ssk);
 void mptcp_pm_add_addr_echoed(struct mptcp_sock *msk,
 			      struct mptcp_addr_info *addr);
 void mptcp_pm_add_addr_send_ack(struct mptcp_sock *msk);
@@ -780,7 +781,8 @@ int mptcp_pm_remove_subflow(struct mptcp_sock *msk, const struct mptcp_rm_list *
 
 void mptcp_event(enum mptcp_event_type type, const struct mptcp_sock *msk,
 		 const struct sock *ssk, gfp_t gfp);
-void mptcp_event_addr_announced(const struct mptcp_sock *msk, const struct mptcp_addr_info *info);
+void mptcp_event_addr_announced(const struct mptcp_sock *msk, const struct mptcp_addr_info *info,
+				const struct sock *ssk);
 void mptcp_event_addr_removed(const struct mptcp_sock *msk, u8 id);
 
 static inline bool mptcp_pm_should_add_signal(struct mptcp_sock *msk)