Re: [PATCH bpf-next 0/4] monitor network traffic for flaky test cases

[Kui-Feng Lee <sinquersw@gmail.com>]

It fails on CI. Looks like we don't have tcpdump installed on CI!


On 7/12/24 22:55, Kui-Feng Lee wrote:
> Run tcpdump in the background for flaky test cases related to network
> features.
> 
> We have some flaky test cases that are difficult to debug without
> knowing what the traffic looks like. With the log printed by tcpdump,
> the CI log may help developers to fix these flaky test cases.
> 
> This patch set monitors a few test cases. Recently, they have been
> showing flaky behavior. If these test cases fail, they will report a
> traffic log.
> 
> At the beginning and the end of a traffic log, there are additional
> traffic packets used for synchronization between the test cases and
> the tcpdump process. These packets consist of UDP packets sent to
> 127.0.0.241:4321 and ICMP unreachable messages for this
> destination. For instance, the first two and the last two packets
> serve as synchronization packets in the following log.
> 
>      15:04:08.586368 lo    In  IP 127.0.0.1.58904 > 127.0.0.241.4321: UDP, length 5
>      15:04:08.586435 lo    In  IP 127.0.0.241 > 127.0.0.1: ICMP 127.0.0.241 udp port 4321 unreachable, length 41
>      15:04:08.704526 lo    In  IP6 ::1.52053 > ::1.45070: UDP, length 8
>      15:04:08.722785 lo    In  IP 127.0.0.1.51863 > 127.0.0.241.4321: UDP, length 15
>      15:04:08.722856 lo    In  IP 127.0.0.241 > 127.0.0.1: ICMP 127.0.0.241 udp port 4321 unreachable, length 51
> 
> The IP address 127.0.0.241 is used for synchronization, so the
> loopback interface "lo" should be up in the network namespace where
> the test is being conducted. While not ideal, this should suffice for
> testing purposes.
> 
> The following block is an example that monitors the network traffic of
> a test case. This test is running in the network namespace
> "testns". You can pass NULL to traffic_monitor_start() if the entire
> test, from traffic_monitor_start() to traffic_monitor_stop(), is
> running in the same namespace.
> 
>      struct tmonitor_ctx *tmon;
>      
>      ...
>      tmon = traffic_monitor_start("testns");
>      ASSERT_TRUE(tmon, "traffic_monitor_start");
>      
>      ... test ...
>      
>      /* Report the traffic log only if there is one or more errors. */
>      if (env.subtest_state->error_cnt)
>          traffic_monitor_report(tmon);
>      traffic_monitor_stop(tmon);
> 
> traffic_monitor_start() may fail, but we just ignore it since the
> failure doesn't affect the following test.  This tracking feature
> takes another 60ms for each test with qemu on my test environment.
> 
> Kui-Feng Lee (4):
>    selftests/bpf: Add traffic monitor functions.
>    selftests/bpf: Monitor traffic for tc_redirect/tc_redirect_dtime.
>    selftests/bpf: Monitor traffic for sockmap_listen.
>    selftests/bpf: Monitor traffic for select_reuseport.
> 
>   tools/testing/selftests/bpf/network_helpers.c | 244 ++++++++++++++++++
>   tools/testing/selftests/bpf/network_helpers.h |   5 +
>   .../bpf/prog_tests/select_reuseport.c         |   9 +
>   .../selftests/bpf/prog_tests/sockmap_listen.c |  10 +
>   .../selftests/bpf/prog_tests/tc_redirect.c    |   7 +
>   5 files changed, 275 insertions(+)
>