tree 621b3473cdd11c8a66a8c0c4819cad3974c32896
parent 47d3d7ac656a1ffb9d0f0d3c845663ed6fd7e78d
author Song Liu <songliubraving@fb.com> 1509399695 -0700
committer David S. Miller <davem@davemloft.net> 1509671565 +0900

tcp: add tracepoint trace_tcp_retransmit_synack()

This tracepoint can be used to trace synack retransmits. It maintains
pointer to struct request_sock.

We cannot simply reuse trace_tcp_retransmit_skb() here, because the
sk here is the LISTEN socket. The IP addresses and ports should be
extracted from struct request_sock.

Note that, like many other tracepoints, this patch uses IS_ENABLED
in TP_fast_assign macro, which triggers sparse warning like:

./include/trace/events/tcp.h:274:1: error: directive in argument list
./include/trace/events/tcp.h:281:1: error: directive in argument list

However, there is no good solution to avoid these warnings. To the
best of our knowledge, these warnings are harmless.

Signed-off-by: Song Liu <songliubraving@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>