[PATCH net 4/5] rxrpc: Don't let ack.previousPacket regress

[David Howells <dhowells@redhat.com>]

The previousPacket field in the rx ACK packet should never go backwards -
it's now the highest DATA sequence number received, not the last on
received (it used to be used for out of sequence detection).

Fixes: 248f219cb8bc ("rxrpc: Rewrite the data and ack handling code")
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 |    4 ++--
 net/rxrpc/input.c       |    4 +++-
 net/rxrpc/output.c      |    2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 9a9688c41d4d..8465985a4cb6 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -679,7 +679,7 @@ struct rxrpc_call {
 	/* Receive-phase ACK management (ACKs we send). */
 	u8			ackr_reason;	/* reason to ACK */
 	rxrpc_serial_t		ackr_serial;	/* serial of packet being ACK'd */
-	rxrpc_seq_t		ackr_prev_seq;	/* previous sequence number received */
+	rxrpc_seq_t		ackr_highest_seq; /* Higest sequence number received */
 	rxrpc_seq_t		ackr_consumed;	/* Highest packet shown consumed */
 	rxrpc_seq_t		ackr_seen;	/* Highest packet shown seen */
 
@@ -694,7 +694,7 @@ struct rxrpc_call {
 	/* Transmission-phase ACK management (ACKs we've received). */
 	ktime_t			acks_latest_ts;	/* Timestamp of latest ACK received */
 	rxrpc_seq_t		acks_first_seq;	/* first sequence number received */
-	rxrpc_seq_t		acks_prev_seq;	/* previous sequence number received */
+	rxrpc_seq_t		acks_prev_seq;	/* Highest previousPacket received */
 	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 */
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index f11673cda217..2e61545ad8ca 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -453,7 +453,6 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb)
 	    !rxrpc_receiving_reply(call))
 		goto unlock;
 
-	call->ackr_prev_seq = seq0;
 	hard_ack = READ_ONCE(call->rx_hard_ack);
 
 	nr_subpackets = sp->nr_subpackets;
@@ -534,6 +533,9 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb)
 			ack_serial = serial;
 		}
 
+		if (after(seq0, call->ackr_highest_seq))
+			call->ackr_highest_seq = seq0;
+
 		/* Queue the packet.  We use a couple of memory barriers here as need
 		 * to make sure that rx_top is perceived to be set after the buffer
 		 * pointer and that the buffer pointer is set after the annotation and
diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index a45c83f22236..46aae9b7006f 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -89,7 +89,7 @@ static size_t rxrpc_fill_out_ack(struct rxrpc_connection *conn,
 	pkt->ack.bufferSpace	= htons(8);
 	pkt->ack.maxSkew	= htons(0);
 	pkt->ack.firstPacket	= htonl(hard_ack + 1);
-	pkt->ack.previousPacket	= htonl(call->ackr_prev_seq);
+	pkt->ack.previousPacket	= htonl(call->ackr_highest_seq);
 	pkt->ack.serial		= htonl(serial);
 	pkt->ack.reason		= reason;
 	pkt->ack.nAcks		= top - hard_ack;