rxrpc: Track highest acked serial

Keep track of the highest DATA serial number that has been acked by the
peer for future purposes.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

net/rxrpc/ar-internal.h

@@ -690,6 +690,7 @@ struct rxrpc_call {
 	rxrpc_seq_t		acks_lowest_nak; /* Lowest NACK in the buffer (or ==tx_hard_ack) */
 	rxrpc_seq_t		acks_lost_top;	/* tx_top at the time lost-ack ping sent */
 	rxrpc_serial_t		acks_lost_ping;	/* Serial number of probe ACK */
+	rxrpc_serial_t		acks_highest_serial; /* Highest serial number ACK'd */
 };
 
 /*

net/rxrpc/input.c

@@ -967,6 +967,10 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 	call->acks_first_seq = first_soft_ack;
 	call->acks_prev_seq = prev_pkt;
 
+	if (buf.ack.reason != RXRPC_ACK_PING &&
+	    after(acked_serial, call->acks_highest_serial))
+		call->acks_highest_serial = acked_serial;
+
 	/* Parse rwind and mtu sizes if provided. */
 	if (buf.info.rxMTU)
 		rxrpc_input_ackinfo(call, skb, &buf.info);