net: sctp: Add SCTP ACK tracking trace event

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.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/trace/events/sctp.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM sctp
+
+#if !defined(_TRACE_SCTP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SCTP_H
+
+#include <net/sctp/structs.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(sctp_probe_path,
+
+	TP_PROTO(struct sctp_transport *sp,
+		 const struct sctp_association *asoc),
+
+	TP_ARGS(sp, asoc),
+
+	TP_STRUCT__entry(
+		__field(__u64, asoc)
+		__field(__u32, primary)
+		__array(__u8, ipaddr, sizeof(union sctp_addr))
+		__field(__u32, state)
+		__field(__u32, cwnd)
+		__field(__u32, ssthresh)
+		__field(__u32, flight_size)
+		__field(__u32, partial_bytes_acked)
+		__field(__u32, pathmtu)
+	),
+
+	TP_fast_assign(
+		__entry->asoc = (unsigned long)asoc;
+		__entry->primary = (sp == asoc->peer.primary_path);
+		memcpy(__entry->ipaddr, &sp->ipaddr, sizeof(union sctp_addr));
+		__entry->state = sp->state;
+		__entry->cwnd = sp->cwnd;
+		__entry->ssthresh = sp->ssthresh;
+		__entry->flight_size = sp->flight_size;
+		__entry->partial_bytes_acked = sp->partial_bytes_acked;
+		__entry->pathmtu = sp->pathmtu;
+	),
+
+	TP_printk("asoc=%#llx%s ipaddr=%pISpc state=%u cwnd=%u ssthresh=%u "
+		  "flight_size=%u partial_bytes_acked=%u pathmtu=%u",
+		  __entry->asoc, __entry->primary ? "(*)" : "",
+		  __entry->ipaddr, __entry->state, __entry->cwnd,
+		  __entry->ssthresh, __entry->flight_size,
+		  __entry->partial_bytes_acked, __entry->pathmtu)
+);
+
+TRACE_EVENT(sctp_probe,
+
+	TP_PROTO(const struct sctp_endpoint *ep,
+		 const struct sctp_association *asoc,
+		 struct sctp_chunk *chunk),
+
+	TP_ARGS(ep, asoc, chunk),
+
+	TP_STRUCT__entry(
+		__field(__u64, asoc)
+		__field(__u32, mark)
+		__field(__u16, bind_port)
+		__field(__u16, peer_port)
+		__field(__u32, pathmtu)
+		__field(__u32, rwnd)
+		__field(__u16, unack_data)
+	),
+
+	TP_fast_assign(
+		struct sk_buff *skb = chunk->skb;
+
+		__entry->asoc = (unsigned long)asoc;
+		__entry->mark = skb->mark;
+		__entry->bind_port = ep->base.bind_addr.port;
+		__entry->peer_port = asoc->peer.port;
+		__entry->pathmtu = asoc->pathmtu;
+		__entry->rwnd = asoc->peer.rwnd;
+		__entry->unack_data = asoc->unack_data;
+
+		if (trace_sctp_probe_path_enabled()) {
+			struct sctp_transport *sp;
+
+			list_for_each_entry(sp, &asoc->peer.transport_addr_list,
+					    transports) {
+				trace_sctp_probe_path(sp, asoc);
+			}
+		}
+	),
+
+	TP_printk("asoc=%#llx mark=%#x bind_port=%d peer_port=%d pathmtu=%d "
+		  "rwnd=%u unack_data=%d",
+		  __entry->asoc, __entry->mark, __entry->bind_port,
+		  __entry->peer_port, __entry->pathmtu, __entry->rwnd,
+		  __entry->unack_data)
+);
+
+#endif /* _TRACE_SCTP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

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);
+
 	if (!sctp_vtag_verify(chunk, asoc))
 		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);