rxrpc: Trace protocol errors in received packets

Add a tracepoint (rxrpc_rx_proto) to record protocol errors in received
packets.  The following changes are made:

 (1) Add a function, __rxrpc_abort_eproto(), to note a protocol error on a
     call and mark the call aborted.  This is wrapped by
     rxrpc_abort_eproto() that makes the why string usable in trace.

 (2) Add trace_rxrpc_rx_proto() or rxrpc_abort_eproto() to protocol error
     generation points, replacing rxrpc_abort_call() with the latter.

 (3) Only send an abort packet in rxkad_verify_packet*() if we actually
     managed to abort the call.

Note that a trace event is also emitted if a kernel user (e.g. afs) tries
to send data through a call when it's not in the transmission phase, though
it's not technically a receive event.

Signed-off-by: David Howells <dhowells@redhat.com>

include/trace/events/rxrpc.h

@@ -1087,6 +1087,30 @@ TRACE_EVENT(rxrpc_improper_term,
 		      __entry->abort_code)
 	    );
 
+TRACE_EVENT(rxrpc_rx_eproto,
+	    TP_PROTO(struct rxrpc_call *call, rxrpc_serial_t serial,
+		     const char *why),
+
+	    TP_ARGS(call, serial, why),
+
+	    TP_STRUCT__entry(
+		    __field(struct rxrpc_call *,	call		)
+		    __field(rxrpc_serial_t,		serial		)
+		    __field(const char *,		why		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->call = call;
+		    __entry->serial = serial;
+		    __entry->why = why;
+			   ),
+
+	    TP_printk("c=%p EPROTO %08x %s",
+		      __entry->call,
+		      __entry->serial,
+		      __entry->why)
+	    );
+
 #endif /* _TRACE_RXRPC_H */
 
 /* This part must be outside protection */