Re: [PATCH bpf-next v7 0/6] monitor network traffic for flaky test cases

[Stanislav Fomichev <sdf@fomichev.me>]

On 08/09, Kui-Feng Lee wrote:
> Capture packets 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. Capturing packets, the CI log and
> packet files may help developers to fix these flaky test cases.
> 
> This patch set monitors a few test cases. Recently, they have been
> showing flaky behavior.
> 
>     lo      In  IPv4 127.0.0.1:40265 > 127.0.0.1:55907: TCP, length 68, SYN
>     lo      In  IPv4 127.0.0.1:55907 > 127.0.0.1:40265: TCP, length 60, SYN, ACK
>     lo      In  IPv4 127.0.0.1:40265 > 127.0.0.1:55907: TCP, length 60, ACK
>     lo      In  IPv4 127.0.0.1:55907 > 127.0.0.1:40265: TCP, length 52, ACK
>     lo      In  IPv4 127.0.0.1:40265 > 127.0.0.1:55907: TCP, length 52, FIN, ACK
>     lo      In  IPv4 127.0.0.1:55907 > 127.0.0.1:40265: TCP, length 52, RST, ACK
>     Packet file: packets-2173-86-select_reuseport:sockhash_IPv4_TCP_LOOPBACK_test_detach_bpf-test.log
>     #280/87 select_reuseport/sockhash IPv4/TCP LOOPBACK test_detach_bpf:OK
> 
> The above block is the log of a test case. It shows every packet of a
> connection. The captured packets are stored in the file called
> packets-2173-86-select_reuseport:sockhash_IPv4_TCP_LOOPBACK_test_detach_bpf-test.log.
> 
> We have a set of high-level helpers and a test_progs option to
> simplify the process of enabling the traffic monitor. netns_new() and
> netns_free() are helpers used to create and delete namespaces while
> also enabling the traffic monitor for the namespace based on the
> patterns provided by the "-m" option of test_progs. The value of the
> "-m" option is a list of patterns used to enable the traffic monitor
> for a group of tests or a file containing patterns. CI can utilize
> this option to enable monitoring.
> 
> traffic_monitor_start() and traffic_monitor_stop() are low-level
> functions to start monitoring explicitly. You can have more controls,
> however high-level helpers are preferred.
> 
> The following block is an example that monitors the network traffic of
> a test case in a network namespace.
> 
>     struct netns_obj *netns;
>     
>     ...
>     netns = netns_new("test", true);
>     if (!ASSERT_TRUE(netns, "netns_new"))
>         goto err;
>     
>     ... test ...
>     
>     netns_free(netns);
> 
> netns_new() will create a network namespace named "test" and bring up
> "lo" in the namespace. By passing "true" as the 2nd argument, it will
> set the network namespace of the current process to
> "test".netns_free() will destroy the namespace, and the process will
> leave the "test" namespace if the struct netns_obj returned by
> netns_new() is created with "true" as the 2nd argument. If the name of
> the test matches the patterns given by the "-m" option, the traffic
> monitor will be enabled for the "test" namespace as well.
> 
> The packet files are located in the directory "/tmp/tmon_pcap/". The
> directory is intended to be compressed as a file so that developers
> can download it from the CI.
> 
> This feature is enabled only if libpcap is available when building
> selftests.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>