Re: [PATCH bpf-next v4 1/6] selftests/bpf: Add traffic monitor functions.

[Stanislav Fomichev <sdf@fomichev.me>]

On 07/31, Kui-Feng Lee wrote:
> Add functions that capture packets and print log in the background. They
> are supposed to be used for debugging flaky network test cases. A monitored
> test case should call traffic_monitor_start() to start a thread to capture
> packets in the background for a given namespace and call
> traffic_monitor_stop() to stop capturing. (Or, option '-m' implemented by
> the later patches.)
> 
>     IPv4 TCP packet: 127.0.0.1:48165 -> 127.0.0.1:36707, len 68, ifindex 1, SYN
>     IPv4 TCP packet: 127.0.0.1:36707 -> 127.0.0.1:48165, len 60, ifindex 1, SYN, ACK
>     IPv4 TCP packet: 127.0.0.1:48165 -> 127.0.0.1:36707, len 60, ifindex 1, ACK
>     IPv4 TCP packet: 127.0.0.1:36707 -> 127.0.0.1:48165, len 52, ifindex 1, ACK
>     IPv4 TCP packet: 127.0.0.1:48165 -> 127.0.0.1:36707, len 52, ifindex 1, FIN, ACK
>     IPv4 TCP packet: 127.0.0.1:36707 -> 127.0.0.1:48165, len 52, ifindex 1, RST, ACK
>     Packet file: packets-2172-86-select_reuseport:sockhash-test.log
>     #280/87 select_reuseport/sockhash IPv4/TCP LOOPBACK test_detach_bpf:OK
> 
> The above is the output of an example. It shows the packets of a connection
> and the name of the file that contains captured packets in the directory
> /tmp/tmon_pcap. The file can be loaded by tcpdump or wireshark.
> 
> This feature only works if TRAFFIC_MONITOR variable has been passed to
> build BPF selftests. For example,
> 
>   make TRAFFIC_MONITOR=1 -C tools/testing/selftests/bpf
> 
> This command will build BPF selftests with this feature enabled.
> 
> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
> ---
>  tools/testing/selftests/bpf/Makefile     |   5 +
>  tools/testing/selftests/bpf/test_progs.c | 432 +++++++++++++++++++++++
>  tools/testing/selftests/bpf/test_progs.h |  16 +
>  3 files changed, 453 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 774c6270e377..0a3108311be7 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -41,6 +41,11 @@ CFLAGS += -g $(OPT_FLAGS) -rdynamic					\
>  LDFLAGS += $(SAN_LDFLAGS)
>  LDLIBS += $(LIBELF_LIBS) -lz -lrt -lpthread
>  
> +ifneq ($(TRAFFIC_MONITOR),)
> +LDLIBS += -lpcap
> +CFLAGS += -DTRAFFIC_MONITOR=1
> +endif

Optionally: can make this more automagical with the following:

LDLIBS += $(shell pkg-config --libs 2>/dev/null)
CFLAGS += $(shell pkg-config --cflags 2>/dev/null)
CFLAGS += $(shell pkg-config --exists libpcap 2>/dev/null && echo "-DTRAFFIC_MONITOR=1")