The special C-flag case expects the ADD_ADDR to be received when switching to 'fully-established'. But for various reasons, the ADD_ADDR could be sent after the "4th ACK", and the special case doesn't work.

On NIPA, the new test validating this special case for the C-flag failed a few times, e.g.

102 default limits, server deny join id 0 syn rx [FAIL] got 0 JOIN[s] syn rx expected 2

Server ns stats (...) MPTcpExtAddAddrTx 1 MPTcpExtEchoAdd 1

Client ns stats (...) MPTcpExtAddAddr 1 MPTcpExtEchoAddTx 1

synack rx [FAIL] got 0 JOIN[s] synack rx expected 2 ack rx [FAIL] got 0 JOIN[s] ack rx expected 2 join Rx [FAIL] see above syn tx [FAIL] got 0 JOIN[s] syn tx expected 2 join Tx [FAIL] see above

I had a suspicion about what the issue could be: the ADD_ADDR might have been received after the switch to the 'fully-established' state. The issue was not easy to reproduce. The packet capture shown that the ADD_ADDR can indeed be sent with a delay, and the client would not try to establish subflows to it as expected.

A simple fix is not to mark the endpoints as 'used' in the C-flag case, when looking at creating subflows to the remote initial IP address and port. In this case, there is no need to try.

Note: newly added fullmesh endpoints will still continue to be used as expected, thanks to the conditions behind mptcp_pm_add_addr_c_flag_case.

Fixes: 4b1ff850e0c1 ("mptcp: pm: in-kernel: usable client side with C-flag") Cc: stable@vger.kernel.org Reviewed-by: Geliang Tang geliang@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/pm_kernel.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c index e0f44dc232aa..2ae95476dba3 100644 --- a/net/mptcp/pm_kernel.c +++ b/net/mptcp/pm_kernel.c @@ -370,6 +370,10 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk) }

subflow: + /* No need to try establishing subflows to remote id0 if not allowed */ + if (mptcp_pm_add_addr_c_flag_case(msk)) + goto exit; + /* check if should create a new subflow */ while (msk->pm.local_addr_used < endp_subflow_max && msk->pm.extra_subflows < limit_extra_subflows) { @@ -401,6 +405,8 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk) __mptcp_subflow_connect(sk, &local, &addrs[i]); spin_lock_bh(&msk->pm.lock); } + +exit: mptcp_pm_nl_check_work_pending(msk); }

The call to 'continue_if' was missing: it properly marks a subtest as 'skipped' if the attached condition is not valid.

Without that, the test is wrongly marked as passed on older kernels.

Fixes: 36c4127ae8dd ("selftests: mptcp: join: skip implicit tests if not supported") Cc: stable@vger.kernel.org Reviewed-by: Geliang Tang geliang@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- tools/testing/selftests/net/mptcp/mptcp_join.sh | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh index deba21ca5a97..d98f8f8905b9 100755 --- a/tools/testing/selftests/net/mptcp/mptcp_join.sh +++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh @@ -3939,7 +3939,7 @@ endpoint_tests() # subflow_rebuild_header is needed to support the implicit flag # userspace pm type prevents add_addr if reset "implicit EP" && - mptcp_lib_kallsyms_has "subflow_rebuild_header$"; then + continue_if mptcp_lib_kallsyms_has "subflow_rebuild_header$"; then 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 @@ -3964,7 +3964,7 @@ endpoint_tests() fi

if reset_with_tcp_filter "delete and re-add" ns2 10.0.3.2 REJECT OUTPUT && - mptcp_lib_kallsyms_has "subflow_rebuild_header$"; then + continue_if mptcp_lib_kallsyms_has "subflow_rebuild_header$"; then start_events pm_nl_set_limits $ns1 0 3 pm_nl_set_limits $ns2 0 3