[PATCH net-next] mptcp: send ADD_ADDR echo before create subflows

[PATCH net-next] mptcp: send ADD_ADDR echo before create subflows

[Mat Martineau]

From: Yonglong Li <liyonglong@chinatelecom.cn>

In some corner cases, the peer handing an incoming ADD_ADDR option, can
receive a retransmitted ADD_ADDR for the same address before the subflow
creation completes.

We can avoid the above issue by generating and sending the ADD_ADDR echo
before starting the MPJ subflow connection.

This slightly changes the behaviour of the packetdrill tests as the
ADD_ADDR echo packet is sent earlier.

Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 net/mptcp/pm_netlink.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 800515fe5e1d..b5e8de6f7507 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -650,7 +650,6 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 	unsigned int add_addr_accept_max;
 	struct mptcp_addr_info remote;
 	unsigned int subflows_max;
-	bool reset_port = false;
 	int i, nr;
 
 	add_addr_accept_max = mptcp_pm_get_add_addr_accept_max(msk);
@@ -661,14 +660,15 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 		 msk->pm.remote.family);
 
 	remote = msk->pm.remote;
+	mptcp_pm_announce_addr(msk, &remote, true);
+	mptcp_pm_nl_addr_send_ack(msk);
+
 	if (lookup_subflow_by_daddr(&msk->conn_list, &remote))
-		goto add_addr_echo;
+		return;
 
 	/* pick id 0 port, if none is provided the remote address */
-	if (!remote.port) {
-		reset_port = true;
+	if (!remote.port)
 		remote.port = sk->sk_dport;
-	}
 
 	/* connect to the specified remote address, using whatever
 	 * local address the routing configuration will pick.
@@ -684,14 +684,6 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 	for (i = 0; i < nr; i++)
 		__mptcp_subflow_connect(sk, &addrs[i], &remote);
 	spin_lock_bh(&msk->pm.lock);
-
-	/* be sure to echo exactly the received address */
-	if (reset_port)
-		remote.port = 0;
-
-add_addr_echo:
-	mptcp_pm_announce_addr(msk, &remote, true);
-	mptcp_pm_nl_addr_send_ack(msk);
 }
 
 void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)

base-commit: 1abea24af42c35c6eb537e4402836e2cde2a5b13
-- 
2.35.1

Re: [PATCH net-next] mptcp: send ADD_ADDR echo before create subflows

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 17 Mar 2022 15:14:44 -0700 you wrote:
> From: Yonglong Li <liyonglong@chinatelecom.cn>
> 
> In some corner cases, the peer handing an incoming ADD_ADDR option, can
> receive a retransmitted ADD_ADDR for the same address before the subflow
> creation completes.
> 
> We can avoid the above issue by generating and sending the ADD_ADDR echo
> before starting the MPJ subflow connection.
> 
> [...]

Here is the summary with links:
  - [net-next] mptcp: send ADD_ADDR echo before create subflows
    https://git.kernel.org/netdev/net-next/c/12a18341b5c3

You are awesome, thank you!
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