rxrpc: Record the Tx serial in the rxrpc_txbuf and retransmit trace

Each Rx protocol packet contains a per-connection monotonically increasing
serial number used to correlate outgoing messages with their replies -
something that can be used for RTT calculation.

Note this value in the rxrpc_txbuf struct in addition to the wire header
and then log it in the rxrpc_retransmit trace for reference.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org

include/trace/events/rxrpc.h

@@ -1506,25 +1506,29 @@ TRACE_EVENT(rxrpc_drop_ack,
 	    );
 
 TRACE_EVENT(rxrpc_retransmit,
-	    TP_PROTO(struct rxrpc_call *call, rxrpc_seq_t seq, s64 expiry),
+	    TP_PROTO(struct rxrpc_call *call, rxrpc_seq_t seq,
+		     rxrpc_serial_t serial, s64 expiry),
 
-	    TP_ARGS(call, seq, expiry),
+	    TP_ARGS(call, seq, serial, expiry),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,	call)
 		    __field(rxrpc_seq_t,	seq)
+		    __field(rxrpc_serial_t,	serial)
 		    __field(s64,		expiry)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->call = call->debug_id;
 		    __entry->seq = seq;
+		    __entry->serial = serial;
 		    __entry->expiry = expiry;
 			   ),
 
-	    TP_printk("c=%08x q=%x xp=%lld",
+	    TP_printk("c=%08x q=%x r=%x xp=%lld",
 		      __entry->call,
 		      __entry->seq,
+		      __entry->serial,
 		      __entry->expiry)
 	    );
 

net/rxrpc/ar-internal.h

@@ -794,6 +794,7 @@ struct rxrpc_txbuf {
 	ktime_t			last_sent;	/* Time at which last transmitted */
 	refcount_t		ref;
 	rxrpc_seq_t		seq;		/* Sequence number of this packet */
+	rxrpc_serial_t		serial;		/* Last serial number transmitted with */
 	unsigned int		call_debug_id;
 	unsigned int		debug_id;
 	unsigned int		len;		/* Amount of data in buffer */

net/rxrpc/call_event.c

@@ -160,7 +160,7 @@ void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
 			goto no_further_resend;
 
 		found_txb:
-			if (after(ntohl(txb->wire.serial), call->acks_highest_serial))
+			if (after(txb->serial, call->acks_highest_serial))
 				continue; /* Ack point not yet reached */
 
 			rxrpc_see_txbuf(txb, rxrpc_txbuf_see_unacked);
@@ -170,7 +170,7 @@ void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
 				set_bit(RXRPC_TXBUF_RESENT, &txb->flags);
 			}
 
-			trace_rxrpc_retransmit(call, txb->seq,
+			trace_rxrpc_retransmit(call, txb->seq, txb->serial,
 					       ktime_to_ns(ktime_sub(txb->last_sent,
 								     max_age)));
 
@@ -197,7 +197,7 @@ void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
 			break; /* Not transmitted yet */
 
 		if (ack && ack->reason == RXRPC_ACK_PING_RESPONSE &&
-		    before(ntohl(txb->wire.serial), ntohl(ack->serial)))
+		    before(txb->serial, ntohl(ack->serial)))
 			goto do_resend; /* Wasn't accounted for by a more recent ping. */
 
 		if (ktime_after(txb->last_sent, max_age)) {

net/rxrpc/output.c

@@ -189,7 +189,6 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 	struct rxrpc_connection *conn;
 	struct msghdr msg;
 	struct kvec iov[1];
-	rxrpc_serial_t serial;
 	size_t len, n;
 	int ret, rtt_slot = -1;
 	u16 rwind;
@@ -216,15 +215,15 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 	iov[0].iov_len	= sizeof(txb->wire) + sizeof(txb->ack) + n;
 	len = iov[0].iov_len;
 
-	serial = rxrpc_get_next_serial(conn);
-	txb->wire.serial = htonl(serial);
-	trace_rxrpc_tx_ack(call->debug_id, serial,
+	txb->serial = rxrpc_get_next_serial(conn);
+	txb->wire.serial = htonl(txb->serial);
+	trace_rxrpc_tx_ack(call->debug_id, txb->serial,
 			   ntohl(txb->ack.firstPacket),
 			   ntohl(txb->ack.serial), txb->ack.reason, txb->ack.nAcks,
 			   rwind);
 
 	if (txb->ack.reason == RXRPC_ACK_PING)
-		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_ping);
+		rtt_slot = rxrpc_begin_rtt_probe(call, txb->serial, rxrpc_rtt_tx_ping);
 
 	rxrpc_inc_stat(call->rxnet, stat_tx_ack_send);
 
@@ -235,7 +234,7 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 	ret = do_udp_sendmsg(conn->local->socket, &msg, len);
 	call->peer->last_tx_at = ktime_get_seconds();
 	if (ret < 0) {
-		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
+		trace_rxrpc_tx_fail(call->debug_id, txb->serial, ret,
 				    rxrpc_tx_point_call_ack);
 	} else {
 		trace_rxrpc_tx_packet(call->debug_id, &txb->wire,
@@ -247,7 +246,7 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 
 	if (!__rxrpc_call_is_complete(call)) {
 		if (ret < 0)
-			rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
+			rxrpc_cancel_rtt_probe(call, txb->serial, rtt_slot);
 		rxrpc_set_keepalive(call);
 	}
 
@@ -327,15 +326,14 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 	struct rxrpc_connection *conn = call->conn;
 	struct msghdr msg;
 	struct kvec iov[1];
-	rxrpc_serial_t serial;
 	size_t len;
 	int ret, rtt_slot = -1;
 
 	_enter("%x,{%d}", txb->seq, txb->len);
 
-	/* Each transmission of a Tx packet needs a new serial number */
-	serial = rxrpc_get_next_serial(conn);
-	txb->wire.serial = htonl(serial);
+	/* Each transmission of a Tx packet+ needs a new serial number */
+	txb->serial = rxrpc_get_next_serial(conn);
+	txb->wire.serial = htonl(txb->serial);
 
 	if (test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags) &&
 	    txb->seq == 1)
@@ -388,7 +386,7 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 		static int lose;
 		if ((lose++ & 7) == 7) {
 			ret = 0;
-			trace_rxrpc_tx_data(call, txb->seq, serial,
+			trace_rxrpc_tx_data(call, txb->seq, txb->serial,
 					    txb->wire.flags,
 					    test_bit(RXRPC_TXBUF_RESENT, &txb->flags),
 					    true);
@@ -396,7 +394,7 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 		}
 	}
 
-	trace_rxrpc_tx_data(call, txb->seq, serial, txb->wire.flags,
+	trace_rxrpc_tx_data(call, txb->seq, txb->serial, txb->wire.flags,
 			    test_bit(RXRPC_TXBUF_RESENT, &txb->flags), false);
 
 	/* Track what we've attempted to transmit at least once so that the
@@ -415,7 +413,7 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 
 	txb->last_sent = ktime_get_real();
 	if (txb->wire.flags & RXRPC_REQUEST_ACK)
-		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_data);
+		rtt_slot = rxrpc_begin_rtt_probe(call, txb->serial, rxrpc_rtt_tx_data);
 
 	/* send the packet by UDP
 	 * - returns -EMSGSIZE if UDP would have to fragment the packet
@@ -429,8 +427,8 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 
 	if (ret < 0) {
 		rxrpc_inc_stat(call->rxnet, stat_tx_data_send_fail);
-		rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
-		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
+		rxrpc_cancel_rtt_probe(call, txb->serial, rtt_slot);
+		trace_rxrpc_tx_fail(call->debug_id, txb->serial, ret,
 				    rxrpc_tx_point_call_data_nofrag);
 	} else {
 		trace_rxrpc_tx_packet(call->debug_id, &txb->wire,
@@ -489,7 +487,7 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 
 	txb->last_sent = ktime_get_real();
 	if (txb->wire.flags & RXRPC_REQUEST_ACK)
-		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_data);
+		rtt_slot = rxrpc_begin_rtt_probe(call, txb->serial, rxrpc_rtt_tx_data);
 
 	switch (conn->local->srx.transport.family) {
 	case AF_INET6:
@@ -508,8 +506,8 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 
 	if (ret < 0) {
 		rxrpc_inc_stat(call->rxnet, stat_tx_data_send_fail);
-		rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
-		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
+		rxrpc_cancel_rtt_probe(call, txb->serial, rtt_slot);
+		trace_rxrpc_tx_fail(call->debug_id, txb->serial, ret,
 				    rxrpc_tx_point_call_data_frag);
 	} else {
 		trace_rxrpc_tx_packet(call->debug_id, &txb->wire,

net/rxrpc/txbuf.c

@@ -34,6 +34,7 @@ struct rxrpc_txbuf *rxrpc_alloc_txbuf(struct rxrpc_call *call, u8 packet_type,
 		txb->flags		= 0;
 		txb->ack_why		= 0;
 		txb->seq		= call->tx_prepared + 1;
+		txb->serial		= 0;
 		txb->wire.epoch		= htonl(call->conn->proto.epoch);
 		txb->wire.cid		= htonl(call->cid);
 		txb->wire.callNumber	= htonl(call->call_id);