[PATCH net 0/6] mptcp: fixes for v6.2

[PATCH net 0/6] mptcp: fixes for v6.2

[Matthieu Baerts]

Patch 1 clears resources earlier if there is no more reasons to keep
MPTCP sockets alive.

Patches 2 and 3 fix some locking issues visible in some rare corner
cases: the linked issues should be quite hard to reproduce.

Patch 4 makes sure subflows are correctly cleaned after the end of a
connection.

Patch 5 and 6 improve the selftests stability when running in a slow
environment by transfering data for a longer period on one hand and by
stopping the tests when all expected events have been observed on the
other hand.

All these patches fix issues introduced before v6.2.

Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
Matthieu Baerts (1):
      selftests: mptcp: stop tests earlier

Paolo Abeni (5):
      mptcp: do not wait for bare sockets' timeout
      mptcp: fix locking for setsockopt corner-case
      mptcp: fix locking for in-kernel listener creation
      mptcp: be careful on subflow status propagation on errors
      selftests: mptcp: allow more slack for slow test-case

 net/mptcp/pm_netlink.c                          | 10 ++++++----
 net/mptcp/protocol.c                            |  9 +++++++++
 net/mptcp/sockopt.c                             | 11 +++++++++--
 net/mptcp/subflow.c                             | 12 ++++++++++--
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 22 +++++++++++++++++-----
 5 files changed, 51 insertions(+), 13 deletions(-)
---
base-commit: 811d581194f7412eda97acc03d17fc77824b561f
change-id: 20230207-upstream-net-20230207-various-fix-6-2-1848a75bbbe6

Best regards,
-- 
Matthieu Baerts <matthieu.baerts@tessares.net>

[PATCH net 1/6] mptcp: do not wait for bare sockets' timeout

[Matthieu Baerts]

From: Paolo Abeni <pabeni@redhat.com>

If the peer closes all the existing subflows for a given
mptcp socket and later the application closes it, the current
implementation let it survive until the timewait timeout expires.

While the above is allowed by the protocol specification it
consumes resources for almost no reason and additionally
causes sporadic self-tests failures.

Let's move the mptcp socket to the TCP_CLOSE state when there are
no alive subflows at close time, so that the allocated resources
will be freed immediately.

Fixes: e16163b6e2b7 ("mptcp: refactor shutdown and close")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
 net/mptcp/protocol.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8cd6cc67c2c5..bc6c1f62a690 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2897,6 +2897,7 @@ bool __mptcp_close(struct sock *sk, long timeout)
 	struct mptcp_subflow_context *subflow;
 	struct mptcp_sock *msk = mptcp_sk(sk);
 	bool do_cancel_work = false;
+	int subflows_alive = 0;
 
 	sk->sk_shutdown = SHUTDOWN_MASK;
 
@@ -2922,6 +2923,8 @@ bool __mptcp_close(struct sock *sk, long timeout)
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 		bool slow = lock_sock_fast_nested(ssk);
 
+		subflows_alive += ssk->sk_state != TCP_CLOSE;
+
 		/* since the close timeout takes precedence on the fail one,
 		 * cancel the latter
 		 */
@@ -2937,6 +2940,12 @@ bool __mptcp_close(struct sock *sk, long timeout)
 	}
 	sock_orphan(sk);
 
+	/* all the subflows are closed, only timeout can change the msk
+	 * state, let's not keep resources busy for no reasons
+	 */
+	if (subflows_alive == 0)
+		inet_sk_state_store(sk, TCP_CLOSE);
+
 	sock_hold(sk);
 	pr_debug("msk=%p state=%d", sk, sk->sk_state);
 	if (msk->token)

-- 
2.38.1

[PATCH net 2/6] mptcp: fix locking for setsockopt corner-case

[Matthieu Baerts]

From: Paolo Abeni <pabeni@redhat.com>

We need to call the __mptcp_nmpc_socket(), and later subflow socket
access under the msk socket lock, or e.g. a racing connect() could
change the socket status under the hood, with unexpected results.

Fixes: 54635bd04701 ("mptcp: add TCP_FASTOPEN_CONNECT socket option")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
 net/mptcp/sockopt.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index d4b1e6ec1b36..7f2c3727ab23 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -760,14 +760,21 @@ static int mptcp_setsockopt_v4(struct mptcp_sock *msk, int optname,
 static int mptcp_setsockopt_first_sf_only(struct mptcp_sock *msk, int level, int optname,
 					  sockptr_t optval, unsigned int optlen)
 {
+	struct sock *sk = (struct sock *)msk;
 	struct socket *sock;
+	int ret = -EINVAL;
 
 	/* Limit to first subflow, before the connection establishment */
+	lock_sock(sk);
 	sock = __mptcp_nmpc_socket(msk);
 	if (!sock)
-		return -EINVAL;
+		goto unlock;
 
-	return tcp_setsockopt(sock->sk, level, optname, optval, optlen);
+	ret = tcp_setsockopt(sock->sk, level, optname, optval, optlen);
+
+unlock:
+	release_sock(sk);
+	return ret;
 }
 
 static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,

-- 
2.38.1

[PATCH net 3/6] mptcp: fix locking for in-kernel listener creation

[Matthieu Baerts]

From: Paolo Abeni <pabeni@redhat.com>

For consistency, in mptcp_pm_nl_create_listen_socket(), we need to
call the __mptcp_nmpc_socket() under the msk socket lock.

Note that as a side effect, mptcp_subflow_create_socket() needs a
'nested' lockdep annotation, as it will acquire the subflow (kernel)
socket lock under the in-kernel listener msk socket lock.

The current lack of locking is almost harmless, because the relevant
socket is not exposed to the user space, but in future we will add
more complexity to the mentioned helper, let's play safe.

Fixes: 1729cf186d8a ("mptcp: create the listening socket for new port")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
 net/mptcp/pm_netlink.c | 10 ++++++----
 net/mptcp/subflow.c    |  2 +-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 2ea7eae43bdb..10fe9771a852 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -998,8 +998,8 @@ static int mptcp_pm_nl_create_listen_socket(struct sock *sk,
 {
 	int addrlen = sizeof(struct sockaddr_in);
 	struct sockaddr_storage addr;
-	struct mptcp_sock *msk;
 	struct socket *ssock;
+	struct sock *newsk;
 	int backlog = 1024;
 	int err;
 
@@ -1008,11 +1008,13 @@ static int mptcp_pm_nl_create_listen_socket(struct sock *sk,
 	if (err)
 		return err;
 
-	msk = mptcp_sk(entry->lsk->sk);
-	if (!msk)
+	newsk = entry->lsk->sk;
+	if (!newsk)
 		return -EINVAL;
 
-	ssock = __mptcp_nmpc_socket(msk);
+	lock_sock(newsk);
+	ssock = __mptcp_nmpc_socket(mptcp_sk(newsk));
+	release_sock(newsk);
 	if (!ssock)
 		return -EINVAL;
 
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index ec54413fb31f..a3e5026bee5b 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1679,7 +1679,7 @@ int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
 	if (err)
 		return err;
 
-	lock_sock(sf->sk);
+	lock_sock_nested(sf->sk, SINGLE_DEPTH_NESTING);
 
 	/* the newly created socket has to be in the same cgroup as its parent */
 	mptcp_attach_cgroup(sk, sf->sk);

-- 
2.38.1

[PATCH net 4/6] mptcp: be careful on subflow status propagation on errors

[Matthieu Baerts]

From: Paolo Abeni <pabeni@redhat.com>

Currently the subflow error report callback unconditionally
propagates the fallback subflow status to the owning msk.

If the msk is already orphaned, the above prevents the code
from correctly tracking the msk moving to the TCP_CLOSE state
and doing the appropriate cleanup.

All the above causes increasing memory usage over time and
sporadic self-tests failures.

There is a great deal of infrastructure trying to propagate
correctly the fallback subflow status to the owning mptcp socket,
e.g. via mptcp_subflow_eof() and subflow_sched_work_if_closed():
in the error propagation path we need only to cope with unorphaned
sockets.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/339
Fixes: 15cc10453398 ("mptcp: deliver ssk errors to msk")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
 net/mptcp/subflow.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index a3e5026bee5b..32904c76c6a1 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1399,6 +1399,7 @@ void __mptcp_error_report(struct sock *sk)
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 		int err = sock_error(ssk);
+		int ssk_state;
 
 		if (!err)
 			continue;
@@ -1409,7 +1410,14 @@ void __mptcp_error_report(struct sock *sk)
 		if (sk->sk_state != TCP_SYN_SENT && !__mptcp_check_fallback(msk))
 			continue;
 
-		inet_sk_state_store(sk, inet_sk_state_load(ssk));
+		/* We need to propagate only transition to CLOSE state.
+		 * Orphaned socket will see such state change via
+		 * subflow_sched_work_if_closed() and that path will properly
+		 * destroy the msk as needed.
+		 */
+		ssk_state = inet_sk_state_load(ssk);
+		if (ssk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DEAD))
+			inet_sk_state_store(sk, ssk_state);
 		sk->sk_err = -err;
 
 		/* This barrier is coupled with smp_rmb() in mptcp_poll() */

-- 
2.38.1

[PATCH net 5/6] selftests: mptcp: allow more slack for slow test-case

[Matthieu Baerts]

From: Paolo Abeni <pabeni@redhat.com>

A test-case is frequently failing on some extremely slow VMs.
The mptcp transfer completes before the script is able to do
all the required PM manipulation.

Address the issue in the simplest possible way, making the
transfer even more slow.

Additionally dump more info in case of failures, to help debugging
similar problems in the future and init dump_stats var.

Fixes: e274f7154008 ("selftests: mptcp: add subflow limits test-cases")
Cc: stable@vger.kernel.org
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/323
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index d11d3d566608..f8a969300ef4 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1694,6 +1694,7 @@ chk_subflow_nr()
 	local subflow_nr=$3
 	local cnt1
 	local cnt2
+	local dump_stats
 
 	if [ -n "${need_title}" ]; then
 		printf "%03u %-36s %s" "${TEST_COUNT}" "${TEST_NAME}" "${msg}"
@@ -1711,7 +1712,12 @@ chk_subflow_nr()
 		echo "[ ok ]"
 	fi
 
-	[ "${dump_stats}" = 1 ] && ( ss -N $ns1 -tOni ; ss -N $ns1 -tOni | grep token; ip -n $ns1 mptcp endpoint )
+	if [ "${dump_stats}" = 1 ]; then
+		ss -N $ns1 -tOni
+		ss -N $ns1 -tOni | grep token
+		ip -n $ns1 mptcp endpoint
+		dump_stats
+	fi
 }
 
 chk_link_usage()
@@ -3069,7 +3075,7 @@ endpoint_tests()
 		pm_nl_set_limits $ns1 1 1
 		pm_nl_set_limits $ns2 1 1
 		pm_nl_add_endpoint $ns2 10.0.2.2 id 2 dev ns2eth2 flags subflow
-		run_tests $ns1 $ns2 10.0.1.1 4 0 0 slow &
+		run_tests $ns1 $ns2 10.0.1.1 4 0 0 speed_20 &
 
 		wait_mpj $ns2
 		pm_nl_del_endpoint $ns2 2 10.0.2.2

-- 
2.38.1

[PATCH net 6/6] selftests: mptcp: stop tests earlier

[Matthieu Baerts]

These 'endpoint' tests from 'mptcp_join.sh' selftest start a transfer in
the background and check the status during this transfer.

Once the expected events have been recorded, there is no reason to wait
for the data transfer to finish. It can be stopped earlier to reduce the
execution time by more than half.

For these tests, the exchanged data were not verified. Errors, if any,
were ignored but that's fine, plenty of other tests are looking at that.
It is then OK to mute stderr now that we are sure errors will be printed
(and still ignored) because the transfer is stopped before the end.

Fixes: e274f7154008 ("selftests: mptcp: add subflow limits test-cases")
Cc: stable@vger.kernel.org
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index f8a969300ef4..079f8f46849d 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -498,6 +498,12 @@ kill_events_pids()
 	kill_wait $evts_ns2_pid
 }
 
+kill_tests_wait()
+{
+	kill -SIGUSR1 $(ip netns pids $ns2) $(ip netns pids $ns1)
+	wait
+}
+
 pm_nl_set_limits()
 {
 	local ns=$1
@@ -3055,7 +3061,7 @@ endpoint_tests()
 		pm_nl_set_limits $ns1 2 2
 		pm_nl_set_limits $ns2 2 2
 		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal
-		run_tests $ns1 $ns2 10.0.1.1 0 0 0 slow &
+		run_tests $ns1 $ns2 10.0.1.1 0 0 0 slow 2>/dev/null &
 
 		wait_mpj $ns1
 		pm_nl_check_endpoint 1 "creation" \
@@ -3068,14 +3074,14 @@ endpoint_tests()
 		pm_nl_add_endpoint $ns2 10.0.2.2 flags signal
 		pm_nl_check_endpoint 0 "modif is allowed" \
 			$ns2 10.0.2.2 id 1 flags signal
-		wait
+		kill_tests_wait
 	fi
 
 	if reset "delete and re-add"; then
 		pm_nl_set_limits $ns1 1 1
 		pm_nl_set_limits $ns2 1 1
 		pm_nl_add_endpoint $ns2 10.0.2.2 id 2 dev ns2eth2 flags subflow
-		run_tests $ns1 $ns2 10.0.1.1 4 0 0 speed_20 &
+		run_tests $ns1 $ns2 10.0.1.1 4 0 0 speed_20 2>/dev/null &
 
 		wait_mpj $ns2
 		pm_nl_del_endpoint $ns2 2 10.0.2.2
@@ -3085,7 +3091,7 @@ endpoint_tests()
 		pm_nl_add_endpoint $ns2 10.0.2.2 dev ns2eth2 flags subflow
 		wait_mpj $ns2
 		chk_subflow_nr "" "after re-add" 2
-		wait
+		kill_tests_wait
 	fi
 }
 

-- 
2.38.1

Re: [PATCH net 0/6] mptcp: fixes for v6.2

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Tue, 07 Feb 2023 14:04:12 +0100 you wrote:
> Patch 1 clears resources earlier if there is no more reasons to keep
> MPTCP sockets alive.
> 
> Patches 2 and 3 fix some locking issues visible in some rare corner
> cases: the linked issues should be quite hard to reproduce.
> 
> Patch 4 makes sure subflows are correctly cleaned after the end of a
> connection.
> 
> [...]

Here is the summary with links:
  - [net,1/6] mptcp: do not wait for bare sockets' timeout
    https://git.kernel.org/netdev/net/c/d4e85922e3e7
  - [net,2/6] mptcp: fix locking for setsockopt corner-case
    https://git.kernel.org/netdev/net/c/21e43569685d
  - [net,3/6] mptcp: fix locking for in-kernel listener creation
    https://git.kernel.org/netdev/net/c/ad2171009d96
  - [net,4/6] mptcp: be careful on subflow status propagation on errors
    https://git.kernel.org/netdev/net/c/1249db44a102
  - [net,5/6] selftests: mptcp: allow more slack for slow test-case
    https://git.kernel.org/netdev/net/c/a635a8c3df66
  - [net,6/6] selftests: mptcp: stop tests earlier
    https://git.kernel.org/netdev/net/c/070d6dafacba

You are awesome, thank you!
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