[PATCH net 0/2] mptcp: fix fallback MIB counter and wrong var in selftests

[PATCH net 0/2] mptcp: fix fallback MIB counter and wrong var in selftests

[Matthieu Baerts (NGI0)]

Here are two fixes related to MPTCP.

The first patch fixes when the MPTcpExtMPCapableFallbackACK MIB counter
is modified: it should only be incremented when a connection was using
MPTCP options, but then a fallback to TCP has been done. This patch also
checks the counter is not incremented by mistake during the connect
selftests. This counter was wrongly incremented since its introduction
in v5.7.

The second patch fixes a wrong parsing of the 'dev' endpoint options in
the selftests: the wrong variable was used. This option was not used
before, but it is going to be soon. This issue is visible since v5.18.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Davide Caratti (1):
      mptcp: don't account accept() of non-MPC client as fallback to TCP

Geliang Tang (1):
      selftests: mptcp: join: fix dev in check_endpoint

 net/mptcp/protocol.c                               | 2 --
 net/mptcp/subflow.c                                | 2 ++
 tools/testing/selftests/net/mptcp/mptcp_connect.sh | 9 +++++++++
 tools/testing/selftests/net/mptcp/mptcp_join.sh    | 4 +++-
 4 files changed, 14 insertions(+), 3 deletions(-)
---
base-commit: 0ba80d96585662299d4ea4624043759ce9015421
change-id: 20240329-upstream-net-20240329-fallback-mib-b0fec9c6189b

Best regards,
-- 
Matthieu Baerts (NGI0) <matttbe@kernel.org>

[PATCH net 1/2] mptcp: don't account accept() of non-MPC client as fallback to TCP

[Matthieu Baerts (NGI0)]

From: Davide Caratti <dcaratti@redhat.com>

Current MPTCP servers increment MPTcpExtMPCapableFallbackACK when they
accept non-MPC connections. As reported by Christoph, this is "surprising"
because the counter might become greater than MPTcpExtMPCapableSYNRX.

MPTcpExtMPCapableFallbackACK counter's name suggests it should only be
incremented when a connection was seen using MPTCP options, then a
fallback to TCP has been done. Let's do that by incrementing it when
the subflow context of an inbound MPC connection attempt is dropped.
Also, update mptcp_connect.sh kselftest, to ensure that the
above MIB does not increment in case a pure TCP client connects to a
MPTCP server.

Fixes: fc518953bc9c ("mptcp: add and use MIB counter infrastructure")
Cc: stable@vger.kernel.org
Reported-by: Christoph Paasch <cpaasch@apple.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/449
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c                               | 2 --
 net/mptcp/subflow.c                                | 2 ++
 tools/testing/selftests/net/mptcp/mptcp_connect.sh | 9 +++++++++
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 3a1967bc7bad..7e74b812e366 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3937,8 +3937,6 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 				mptcp_set_state(newsk, TCP_CLOSE);
 		}
 	} else {
-		MPTCP_INC_STATS(sock_net(ssk),
-				MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
 tcpfallback:
 		newsk->sk_kern_sock = kern;
 		lock_sock(newsk);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 1626dd20c68f..6042a47da61b 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -905,6 +905,8 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 	return child;
 
 fallback:
+	if (fallback)
+		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
 	mptcp_subflow_drop_ctx(child);
 	return child;
 }
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
index 4c4248554826..4131f3263a48 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
@@ -383,12 +383,14 @@ do_transfer()
 	local stat_cookierx_last
 	local stat_csum_err_s
 	local stat_csum_err_c
+	local stat_tcpfb_last_l
 	stat_synrx_last_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableSYNRX")
 	stat_ackrx_last_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableACKRX")
 	stat_cookietx_last=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesSent")
 	stat_cookierx_last=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesRecv")
 	stat_csum_err_s=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtDataCsumErr")
 	stat_csum_err_c=$(mptcp_lib_get_counter "${connector_ns}" "MPTcpExtDataCsumErr")
+	stat_tcpfb_last_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableFallbackACK")
 
 	timeout ${timeout_test} \
 		ip netns exec ${listener_ns} \
@@ -457,11 +459,13 @@ do_transfer()
 	local stat_cookietx_now
 	local stat_cookierx_now
 	local stat_ooo_now
+	local stat_tcpfb_now_l
 	stat_synrx_now_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableSYNRX")
 	stat_ackrx_now_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableACKRX")
 	stat_cookietx_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesSent")
 	stat_cookierx_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesRecv")
 	stat_ooo_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtTCPOFOQueue")
+	stat_tcpfb_now_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableFallbackACK")
 
 	expect_synrx=$((stat_synrx_last_l))
 	expect_ackrx=$((stat_ackrx_last_l))
@@ -508,6 +512,11 @@ do_transfer()
 		fi
 	fi
 
+	if [ ${stat_ooo_now} -eq 0 ] && [ ${stat_tcpfb_last_l} -ne ${stat_tcpfb_now_l} ]; then
+		mptcp_lib_pr_fail "unexpected fallback to TCP"
+		rets=1
+	fi
+
 	if [ $cookies -eq 2 ];then
 		if [ $stat_cookietx_last -ge $stat_cookietx_now ] ;then
 			extra+=" WARN: CookieSent: did not advance"

-- 
2.43.0

[PATCH net 2/2] selftests: mptcp: join: fix dev in check_endpoint

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

There's a bug in pm_nl_check_endpoint(), 'dev' didn't be parsed correctly.
If calling it in the 2nd test of endpoint_tests() too, it fails with an
error like this:

 creation  [FAIL] expected '10.0.2.2 id 2 subflow dev dev' \
                     found '10.0.2.2 id 2 subflow dev ns2eth2'

The reason is '$2' should be set to 'dev', not '$1'. This patch fixes it.

Fixes: 69c6ce7b6eca ("selftests: mptcp: add implicit endpoint test case")
Cc: stable@vger.kernel.org
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 5e9211e89825..e4403236f655 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -729,7 +729,7 @@ pm_nl_check_endpoint()
 			[ -n "$_flags" ]; flags="flags $_flags"
 			shift
 		elif [ $1 = "dev" ]; then
-			[ -n "$2" ]; dev="dev $1"
+			[ -n "$2" ]; dev="dev $2"
 			shift
 		elif [ $1 = "id" ]; then
 			_id=$2
@@ -3610,6 +3610,8 @@ endpoint_tests()
 		local tests_pid=$!
 
 		wait_mpj $ns2
+		pm_nl_check_endpoint "creation" \
+			$ns2 10.0.2.2 id 2 flags subflow dev ns2eth2
 		chk_subflow_nr "before delete" 2
 		chk_mptcp_info subflows 1 subflows 1
 

-- 
2.43.0

Re: [PATCH net 0/2] mptcp: fix fallback MIB counter and wrong var in selftests

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 29 Mar 2024 13:08:51 +0100 you wrote:
> Here are two fixes related to MPTCP.
> 
> The first patch fixes when the MPTcpExtMPCapableFallbackACK MIB counter
> is modified: it should only be incremented when a connection was using
> MPTCP options, but then a fallback to TCP has been done. This patch also
> checks the counter is not incremented by mistake during the connect
> selftests. This counter was wrongly incremented since its introduction
> in v5.7.
> 
> [...]

Here is the summary with links:
  - [net,1/2] mptcp: don't account accept() of non-MPC client as fallback to TCP
    https://git.kernel.org/netdev/net/c/7a1b3490f47e
  - [net,2/2] selftests: mptcp: join: fix dev in check_endpoint
    https://git.kernel.org/netdev/net/c/40061817d95b

You are awesome, thank you!
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