mptcp: fix ADD_ADDR and RM_ADDR maybe flush addr_signal each other

ADD_ADDR shares pm.addr_signal with RM_ADDR, so after RM_ADDR/ADD_ADDR
has done, we should not clean ADD_ADDR/RM_ADDR's addr_signal.

Co-developed-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/pm.c

@@ -261,6 +261,7 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, struct sk_buff *skb,
 			      bool *port, bool *drop_other_suboptions)
 {
 	int ret = false;
+	u8 add_addr;
 
 	spin_lock_bh(&msk->pm.lock);
 
@@ -284,7 +285,11 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, struct sk_buff *skb,
 		goto out_unlock;
 
 	*saddr = msk->pm.local;
-	WRITE_ONCE(msk->pm.addr_signal, 0);
+	if (*echo)
+		add_addr = msk->pm.addr_signal & ~BIT(MPTCP_ADD_ADDR_ECHO);
+	else
+		add_addr = msk->pm.addr_signal & ~BIT(MPTCP_ADD_ADDR_SIGNAL);
+	WRITE_ONCE(msk->pm.addr_signal, add_addr);
 	ret = true;
 
 out_unlock:
@@ -296,23 +301,25 @@ bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 			     struct mptcp_rm_list *rm_list)
 {
 	int ret = false, len;
+	u8 rm_addr;
 
 	spin_lock_bh(&msk->pm.lock);
 
 	/* double check after the lock is acquired */
 	if (!mptcp_pm_should_rm_signal(msk))
 		goto out_unlock;
 
+	rm_addr = msk->pm.addr_signal & ~BIT(MPTCP_RM_ADDR_SIGNAL);
 	len = mptcp_rm_addr_len(&msk->pm.rm_list_tx);
 	if (len < 0) {
-		WRITE_ONCE(msk->pm.addr_signal, 0);
+		WRITE_ONCE(msk->pm.addr_signal, rm_addr);
 		goto out_unlock;
 	}
 	if (remaining < len)
 		goto out_unlock;
 
 	*rm_list = msk->pm.rm_list_tx;
-	WRITE_ONCE(msk->pm.addr_signal, 0);
+	WRITE_ONCE(msk->pm.addr_signal, rm_addr);
 	ret = true;
 
 out_unlock: