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 <[email protected]>

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 */

net/rxrpc/ar-internal.h

@@ -739,6 +739,25 @@ static inline bool rxrpc_abort_call(const char *why, struct rxrpc_call *call,
 	return ret;
 }
 
+/*
+ * Abort a call due to a protocol error.
+ */
+static inline bool __rxrpc_abort_eproto(struct rxrpc_call *call,
+					struct sk_buff *skb,
+					const char *eproto_why,
+					const char *why,
+					u32 abort_code)
+{
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+
+	trace_rxrpc_rx_eproto(call, sp->hdr.serial, eproto_why);
+	return rxrpc_abort_call(why, call, sp->hdr.seq, abort_code, -EPROTO);
+}
+
+#define rxrpc_abort_eproto(call, skb, eproto_why, abort_why, abort_code) \
+	__rxrpc_abort_eproto((call), (skb), tracepoint_string(eproto_why), \
+			     (abort_why), (abort_code))
+
 /*
  * conn_client.c
  */

net/rxrpc/conn_event.c

@@ -281,8 +281,11 @@ static int rxrpc_process_event(struct rxrpc_connection *conn,
 
 	case RXRPC_PACKET_TYPE_ABORT:
 		if (skb_copy_bits(skb, sizeof(struct rxrpc_wire_header),
-				  &wtmp, sizeof(wtmp)) < 0)
+				  &wtmp, sizeof(wtmp)) < 0) {
+			trace_rxrpc_rx_eproto(NULL, sp->hdr.serial,
+					      tracepoint_string("bad_abort"));
 			return -EPROTO;
+		}
 		abort_code = ntohl(wtmp);
 		_proto("Rx ABORT %%%u { ac=%d }", sp->hdr.serial, abort_code);
 
@@ -327,7 +330,8 @@ static int rxrpc_process_event(struct rxrpc_connection *conn,
 		return 0;
 
 	default:
-		_leave(" = -EPROTO [%u]", sp->hdr.type);
+		trace_rxrpc_rx_eproto(NULL, sp->hdr.serial,
+				      tracepoint_string("bad_conn_pkt"));
 		return -EPROTO;
 	}
 }
@@ -422,6 +426,5 @@ void rxrpc_process_connection(struct work_struct *work)
 	if (rxrpc_abort_connection(conn, ret, abort_code) < 0)
 		goto requeue_and_leave;
 	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
-	_leave(" [EPROTO]");
 	goto out;
 }

net/rxrpc/input.c

@@ -1017,8 +1017,11 @@ int rxrpc_extract_header(struct rxrpc_skb_priv *sp, struct sk_buff *skb)
 	struct rxrpc_wire_header whdr;
 
 	/* dig out the RxRPC connection details */
-	if (skb_copy_bits(skb, 0, &whdr, sizeof(whdr)) < 0)
+	if (skb_copy_bits(skb, 0, &whdr, sizeof(whdr)) < 0) {
+		trace_rxrpc_rx_eproto(NULL, sp->hdr.serial,
+				      tracepoint_string("bad_hdr"));
 		return -EBADMSG;
+	}
 
 	memset(sp, 0, sizeof(*sp));
 	sp->hdr.epoch		= ntohl(whdr.epoch);

net/rxrpc/insecure.c

@@ -46,15 +46,21 @@ static int none_respond_to_challenge(struct rxrpc_connection *conn,
 				     struct sk_buff *skb,
 				     u32 *_abort_code)
 {
-	*_abort_code = RX_PROTOCOL_ERROR;
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+
+	trace_rxrpc_rx_eproto(NULL, sp->hdr.serial,
+			      tracepoint_string("chall_none"));
 	return -EPROTO;
 }
 
 static int none_verify_response(struct rxrpc_connection *conn,
 				struct sk_buff *skb,
 				u32 *_abort_code)
 {
-	*_abort_code = RX_PROTOCOL_ERROR;
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+
+	trace_rxrpc_rx_eproto(NULL, sp->hdr.serial,
+			      tracepoint_string("resp_none"));
 	return -EPROTO;
 }
 

net/rxrpc/recvmsg.c

@@ -682,9 +682,11 @@ int rxrpc_kernel_recv_data(struct socket *sock, struct rxrpc_call *call,
 	return ret;
 
 short_data:
+	trace_rxrpc_rx_eproto(call, 0, tracepoint_string("short_data"));
 	ret = -EBADMSG;
 	goto out;
 excess_data:
+	trace_rxrpc_rx_eproto(call, 0, tracepoint_string("excess_data"));
 	ret = -EMSGSIZE;
 	goto out;
 call_complete: