mptcp: continue marking the first subflow as UNCONNECTED

After the 'Fixes' commit mentioned below, which is a partial backport, the MPTCP worker was no longer marking the first subflow as "UNCONNECTED" when the socket was transitioning to TCP_CLOSE state.

As a result, in v6.1, it was no longer possible to reconnect to the just disconnected socket. Continue to do that like before, only for the first subflow.

A few refactoring have been done around the 'msk->subflow' in later versions, and it looks like this is not needed to do that there, but still needed in v6.1. Without that, the 'disconnect' tests from the mptcp_connect.sh selftest fail: they repeat the transfer 3 times by reconnecting to the server each time.

---
Notes:
- This is specific to the 6.1 version having the partial backport.

---
 net/mptcp/protocol.c | 2 ++
 1 file changed, 2 insertions(+)

index cdabb00648bd2..125825db642cc 100644
@@ -2440,6 +2440,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 	need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
 	if (!dispose_it) {
 		__mptcp_subflow_disconnect(ssk, subflow, flags);
+		if (msk->subflow && ssk == msk->subflow->sk)
+			msk->subflow->state = SS_UNCONNECTED;
 		release_sock(ssk);
 
 		goto out;

2.43.0

Hi Matthieu,

Thank you for your modifications, that's great!

But sadly, our CI spotted some issues with it when trying to build it.

You can find more details there:

https://patchwork.kernel.org/project/mptcp/patch/[email protected]/
https://github.com/multipath-tcp/mptcp_net-next/actions/runs/8084822552

Status: cancelled
Initiator: MPTCPimporter
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/2c89af223cba

Feel free to reply to this email if you cannot access logs, if you need some support to fix the error, if this doesn't seem to be caused by your modifications or if the error is a false positive one.

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)

All 6.1 backports now queued up, thanks!

greg k-h

This is a note to let you know that I've just added the patch titled

mptcp: continue marking the first subflow as UNCONNECTED

to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mptcp-continue-marking-the-first-subflow-as-unconnected.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From [email protected] Mon Mar 4 09:10:32 2024
From: "Matthieu Baerts (NGI0)" <[email protected]>
Date: Wed, 28 Feb 2024 18:21:21 +0100
Subject: mptcp: continue marking the first subflow as UNCONNECTED
To: [email protected], [email protected], [email protected]
Cc: MPTCP Upstream <[email protected]>, "Matthieu Baerts (NGI0)" <[email protected]>
Message-ID: <[email protected]>

From: "Matthieu Baerts (NGI0)" <[email protected]>

After the 'Fixes' commit mentioned below, which is a partial backport, the MPTCP worker was no longer marking the first subflow as "UNCONNECTED" when the socket was transitioning to TCP_CLOSE state.

As a result, in v6.1, it was no longer possible to reconnect to the just disconnected socket. Continue to do that like before, only for the first subflow.

A few refactoring have been done around the 'msk->subflow' in later versions, and it looks like this is not needed to do that there, but still needed in v6.1. Without that, the 'disconnect' tests from the mptcp_connect.sh selftest fail: they repeat the transfer 3 times by reconnecting to the server each time.

---
 net/mptcp/protocol.c | 2 ++
 1 file changed, 2 insertions(+)

index cdabb00648bd2..125825db642cc 100644
@@ -2440,6 +2440,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 	need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
 	if (!dispose_it) {
 		__mptcp_subflow_disconnect(ssk, subflow, flags);
+		if (msk->subflow && ssk == msk->subflow->sk)
+			msk->subflow->state = SS_UNCONNECTED;
 		release_sock(ssk);
 
 		goto out;

2.43.0



Patches currently in stable-queue which might be from [email protected] are

queue-5.4/mptcp-continue-marking-the-first-subflow-as-unconnected.patch

Oops, nope, my fault, this doesn't go to 5.4.y, sorry for the noise.

greg k-h

This is a note to let you know that I've just added the patch titled

mptcp: continue marking the first subflow as UNCONNECTED

to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mptcp-continue-marking-the-first-subflow-as-unconnected.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From [email protected] Mon Mar 4 09:10:32 2024
From: "Matthieu Baerts (NGI0)" <[email protected]>
Date: Wed, 28 Feb 2024 18:21:21 +0100
Subject: mptcp: continue marking the first subflow as UNCONNECTED
To: [email protected], [email protected], [email protected]
Cc: MPTCP Upstream <[email protected]>, "Matthieu Baerts (NGI0)" <[email protected]>
Message-ID: <[email protected]>

From: "Matthieu Baerts (NGI0)" <[email protected]>

After the 'Fixes' commit mentioned below, which is a partial backport, the MPTCP worker was no longer marking the first subflow as "UNCONNECTED" when the socket was transitioning to TCP_CLOSE state.

As a result, in v6.1, it was no longer possible to reconnect to the just disconnected socket. Continue to do that like before, only for the first subflow.

A few refactoring have been done around the 'msk->subflow' in later versions, and it looks like this is not needed to do that there, but still needed in v6.1. Without that, the 'disconnect' tests from the mptcp_connect.sh selftest fail: they repeat the transfer 3 times by reconnecting to the server each time.

---
 net/mptcp/protocol.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -2440,6 +2440,8 @@ static void __mptcp_close_ssk(struct soc
 	need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
 	if (!dispose_it) {
 		__mptcp_subflow_disconnect(ssk, subflow, flags);
+		if (msk->subflow && ssk == msk->subflow->sk)
+			msk->subflow->state = SS_UNCONNECTED;
 		release_sock(ssk);
 
 		goto out;

Patches currently in stable-queue which might be from [email protected] are

queue-6.1/mptcp-continue-marking-the-first-subflow-as-unconnected.patch queue-6.1/mptcp-fix-data-races-on-local_id.patch queue-6.1/mptcp-fix-duplicate-subflow-creation.patch queue-6.1/mptcp-fix-data-races-on-remote_id.patch