mptcp: move drop_other_suboptions check under pm lock

This patch moved the drop_other_suboptions check from
mptcp_established_options_add_addr() into mptcp_pm_add_addr_signal(), do
it under the PM lock to avoid the race between this check and
mptcp_pm_add_addr_signal().

For this, added a new parameter for mptcp_pm_add_addr_signal() to get
the drop_other_suboptions value. And drop the other suboptions after the
option length check if drop_other_suboptions is true.

Additionally, always drop the other suboption for TCP pure ack:
that makes both the code simpler and the MPTCP behaviour more
consistent.

Co-developed-by: Geliang Tang <[email protected]>
Signed-off-by: Geliang Tang <[email protected]>
Co-developed-by: Paolo Abeni <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>
Signed-off-by: Yonglong Li <[email protected]>
Signed-off-by: Mat Martineau <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

1 files changed, 13 insertions, 2 deletions

diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 0ed3e565f8f8..24e2f6f6178b 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -251,8 +251,10 @@ void mptcp_pm_mp_prio_received(struct sock *sk, u8 bkup)
 
 /* path manager helpers */
 
-bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
-			      struct mptcp_addr_info *saddr, bool *echo, bool *port)
+bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, struct sk_buff *skb,
+			      unsigned int opt_size, unsigned int remaining,
+			      struct mptcp_addr_info *saddr, bool *echo,
+			      bool *port, bool *drop_other_suboptions)
 {
 	int ret = false;
 
@@ -262,6 +264,15 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 	if (!mptcp_pm_should_add_signal(msk))
 		goto out_unlock;
 
+	/* always drop every other options for pure ack ADD_ADDR; this is a
+	 * plain dup-ack from TCP perspective. The other MPTCP-relevant info,
+	 * if any, will be carried by the 'original' TCP ack
+	 */
+	if (skb && skb_is_tcp_pure_ack(skb)) {
+		remaining += opt_size;
+		*drop_other_suboptions = true;
+	}
+
 	*echo = mptcp_pm_should_add_signal_echo(msk);
 	*port = mptcp_pm_should_add_signal_port(msk);