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 Link: https://lore.kernel.org/r/20240329-upstream-net-20240329-fallback-mib-v1-1-3... Signed-off-by: Jakub Kicinski kuba@kernel.org (cherry picked from commit 7a1b3490f47e88ec4cbde65f1a77a0f4bc972282) Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- Notes: - Conflicts in protocol.c: because commit 8e2b8a9fa512 ("mptcp: don't overwrite sock_ops in mptcp_is_tcpsk()") is not in this version, but it depends on new features, making it hard to be backported, while the conflict resolution is easy: just remove the MIB incrementation from the previous location. - Conflicts in subflow.c: because commit a88d0092b24b ("mptcp: simplify subflow_syn_recv_sock()") is not in this version, but it depends on new features, making it hard to be backported, while the conflict resolution is easy: just move the MIB incrementation where the subflow context is dropped (fallback to TCP). - Conflicts in mptcp_connect.sh: because commit e3aae1098f10 ("selftests: mptcp: connect: fix shellcheck warnings") and commit e7c42bf4d320 ("selftests: mptcp: use += operator to append strings") are not in this version. The dependency chain looks too long, while resolving the conflicts was not difficult: - using get_mib_counter() instead of the new mptcp_lib_get_counter() - writing the error message with 'printf' instead of the new mptcp_lib_pr_fail(). --- net/mptcp/protocol.c | 3 --- net/mptcp/subflow.c | 3 +++ tools/testing/selftests/net/mptcp/mptcp_connect.sh | 7 +++++++ 3 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 5db1c0142abb..cde62dafda49 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3018,9 +3018,6 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err, sock_hold(new_mptcp_sock); newsk = new_mptcp_sock; MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK); - } else { - MPTCP_INC_STATS(sock_net(sk), - MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK); }
out: diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 80230787554e..ff7239fe3d2c 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -725,6 +725,9 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk, goto dispose_child; }
+ if (fallback) + SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK); + subflow_drop_ctx(child); goto out; } diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh index 8efff3f9c52a..5a1277d17286 100755 --- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh @@ -451,6 +451,7 @@ do_transfer() local stat_cookierx_last=$(get_mib_counter "${listener_ns}" "TcpExtSyncookiesRecv") local stat_csum_err_s=$(get_mib_counter "${listener_ns}" "MPTcpExtDataCsumErr") local stat_csum_err_c=$(get_mib_counter "${connector_ns}" "MPTcpExtDataCsumErr") + local stat_tcpfb_last_l=$(get_mib_counter "${listener_ns}" "MPTcpExtMPCapableFallbackACK")
timeout ${timeout_test} \ ip netns exec ${listener_ns} \ @@ -516,6 +517,7 @@ do_transfer() local stat_cookietx_now=$(get_mib_counter "${listener_ns}" "TcpExtSyncookiesSent") local stat_cookierx_now=$(get_mib_counter "${listener_ns}" "TcpExtSyncookiesRecv") local stat_ooo_now=$(get_mib_counter "${listener_ns}" "TcpExtTCPOFOQueue") + local stat_tcpfb_now_l=$(get_mib_counter "${listener_ns}" "MPTcpExtMPCapableFallbackACK")
expect_synrx=$((stat_synrx_last_l)) expect_ackrx=$((stat_ackrx_last_l)) @@ -560,6 +562,11 @@ do_transfer() fi fi
+ if [ ${stat_ooo_now} -eq 0 ] && [ ${stat_tcpfb_last_l} -ne ${stat_tcpfb_now_l} ]; then + printf "[ FAIL ]\nunexpected fallback to TCP" + rets=1 + fi + if [ $retc -eq 0 ] && [ $rets -eq 0 ]; then printf "[ OK ]" fi