On Mon, 18 Dec 2017 17:12:15 +0900
Masami Hiramatsu <mhira...@kernel.org> wrote:
> Add SCTP ACK tracking trace event to trace the changes of SCTP
> association state in response to incoming packets.
> It is used for debugging SCTP congestion control algorithms,
> and will replace sctp_probe module.
>
> Note that this event a bit tricky. Since this consists of 2
> events (sctp_probe and sctp_probe_path) so you have to enable
> both events as below.
>
> # cd /sys/kernel/debug/tracing
> # echo 1 > events/sctp/sctp_probe/enable
> # echo 1 > events/sctp/sctp_probe_path/enable
>
> Or, you can enable all the events under sctp.
>
> # echo 1 > events/sctp/enable
>
> Since sctp_probe_path event is always invoked from sctp_probe
> event, you can not see any output if you only enable
> sctp_probe_path.
I have to ask, why did you do it this way?
> +#include <trace/define_trace.h>
> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> index 8f8ccded13e4..c5f92b2cc5c3 100644
> --- a/net/sctp/sm_statefuns.c
> +++ b/net/sctp/sm_statefuns.c
> @@ -59,6 +59,9 @@
> #include <net/sctp/sm.h>
> #include <net/sctp/structs.h>
>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/sctp.h>
> +
> static struct sctp_packet *sctp_abort_pkt_new(
> struct net *net,
> const struct sctp_endpoint *ep,
> @@ -3219,6 +3222,8 @@ enum sctp_disposition sctp_sf_eat_sack_6_2(struct net
> *net,
> struct sctp_sackhdr *sackh;
> __u32 ctsn;
>
> + trace_sctp_probe(ep, asoc, chunk);
What about doing this right after this probe:
if (trace_sctp_probe_path_enabled()) {
struct sctp_transport *sp;
list_for_each_entry(sp, &asoc->peer.transpor_addr_list,
transports) {
trace_sctp_probe_path(sp, asoc);
}
}
The "trace_sctp_probe_path_enabled()" is a static branch, which means
it's a nop just like a tracepoint is, and will not add any overhead if
the trace_sctp_probe_path is not enabled.
-- Steve
> +
> if (!sctp_vtag_verify(chunk, asoc))
> return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
>
