queue-6.1/mptcp-don-t-account-accept-of-non-mpc-client-as-fallback-to-tcp.patch

   1 From 7a1b3490f47e88ec4cbde65f1a77a0f4bc972282 Mon Sep 17 00:00:00 2001
   2 From: Davide Caratti <dcaratti@redhat.com>
   3 Date: Fri, 29 Mar 2024 13:08:52 +0100
   4 Subject: mptcp: don't account accept() of non-MPC client as fallback to TCP
   5
   6 From: Davide Caratti <dcaratti@redhat.com>
   7
   8 commit 7a1b3490f47e88ec4cbde65f1a77a0f4bc972282 upstream.
   9
  10 Current MPTCP servers increment MPTcpExtMPCapableFallbackACK when they
  11 accept non-MPC connections. As reported by Christoph, this is "surprising"
  12 because the counter might become greater than MPTcpExtMPCapableSYNRX.
  13
  14 MPTcpExtMPCapableFallbackACK counter's name suggests it should only be
  15 incremented when a connection was seen using MPTCP options, then a
  16 fallback to TCP has been done. Let's do that by incrementing it when
  17 the subflow context of an inbound MPC connection attempt is dropped.
  18 Also, update mptcp_connect.sh kselftest, to ensure that the
  19 above MIB does not increment in case a pure TCP client connects to a
  20 MPTCP server.
  21
  22 Fixes: fc518953bc9c ("mptcp: add and use MIB counter infrastructure")
  23 Cc: stable@vger.kernel.org
  24 Reported-by: Christoph Paasch <cpaasch@apple.com>
  25 Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/449
  26 Signed-off-by: Davide Caratti <dcaratti@redhat.com>
  27 Reviewed-by: Mat Martineau <martineau@kernel.org>
  28 Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
  29 Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
  30 Link: https://lore.kernel.org/r/20240329-upstream-net-20240329-fallback-mib-v1-1-324a8981da48@kernel.org
  31 Signed-off-by: Jakub Kicinski <kuba@kernel.org>
  32 Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
  33 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  34 ---
  35  net/mptcp/protocol.c                               |    3 ---
  36  net/mptcp/subflow.c                                |    2 ++
  37  tools/testing/selftests/net/mptcp/mptcp_connect.sh |    7 +++++++
  38  3 files changed, 9 insertions(+), 3 deletions(-)
  39
  40 --- a/net/mptcp/protocol.c
  41 +++ b/net/mptcp/protocol.c
  42 @@ -3349,9 +3349,6 @@ static struct sock *mptcp_accept(struct
  43
  44                 newsk = new_mptcp_sock;
  45                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
  46 -       } else {
  47 -               MPTCP_INC_STATS(sock_net(sk),
  48 -                               MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
  49         }
  50
  51  out:
  52 --- a/net/mptcp/subflow.c
  53 +++ b/net/mptcp/subflow.c
  54 @@ -816,6 +816,8 @@ dispose_child:
  55         return child;
  56
  57  fallback:
  58 +       if (fallback)
  59 +               SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
  60         mptcp_subflow_drop_ctx(child);
  61         return child;
  62  }
  63 --- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh
  64 +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
  65 @@ -439,6 +439,7 @@ do_transfer()
  66         local stat_cookierx_last=$(get_mib_counter "${listener_ns}" "TcpExtSyncookiesRecv")
  67         local stat_csum_err_s=$(get_mib_counter "${listener_ns}" "MPTcpExtDataCsumErr")
  68         local stat_csum_err_c=$(get_mib_counter "${connector_ns}" "MPTcpExtDataCsumErr")
  69 +       local stat_tcpfb_last_l=$(get_mib_counter "${listener_ns}" "MPTcpExtMPCapableFallbackACK")
  70
  71         timeout ${timeout_test} \
  72                 ip netns exec ${listener_ns} \
  73 @@ -504,6 +505,7 @@ do_transfer()
  74         local stat_cookietx_now=$(get_mib_counter "${listener_ns}" "TcpExtSyncookiesSent")
  75         local stat_cookierx_now=$(get_mib_counter "${listener_ns}" "TcpExtSyncookiesRecv")
  76         local stat_ooo_now=$(get_mib_counter "${listener_ns}" "TcpExtTCPOFOQueue")
  77 +       local stat_tcpfb_now_l=$(get_mib_counter "${listener_ns}" "MPTcpExtMPCapableFallbackACK")
  78
  79         expect_synrx=$((stat_synrx_last_l))
  80         expect_ackrx=$((stat_ackrx_last_l))
  81 @@ -548,6 +550,11 @@ do_transfer()
  82                 fi
  83         fi
  84
  85 +       if [ ${stat_ooo_now} -eq 0 ] && [ ${stat_tcpfb_last_l} -ne ${stat_tcpfb_now_l} ]; then
  86 +               printf "[ FAIL ]\nunexpected fallback to TCP"
  87 +               rets=1
  88 +       fi
  89 +
  90         if [ $retc -eq 0 ] && [ $rets -eq 0 ]; then
  91                 printf "[ OK ]"
  92         fi