netdev - [PATCH net 4/6] rxrpc: Fix overlapping ACK accounting

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Date:   Fri, 20 May 2022 17:34:08 +0100
From:   David Howells <dhowells@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Jeffrey Altman <jaltman@...istor.com>,
        Marc Dionne <marc.dionne@...istor.com>,
        linux-afs@...ts.infradead.org, dhowells@...hat.com,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH net 4/6] rxrpc: Fix overlapping ACK accounting

Fix accidental overlapping of Rx-phase ACK accounting with Tx-phase ACK
accounting through variables shared between the two.  call->acks_* members
refer to ACKs received in the Tx phase and call->ackr_* members to ACKs
sent/to be sent during the Rx phase.

Fixes: 1a2391c30c0b ("rxrpc: Fix detection of out of order acks")
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Jeffrey Altman <jaltman@...istor.com>
cc: Marc Dionne <marc.dionne@...istor.com>
cc: linux-afs@...ts.infradead.org
---

 net/rxrpc/ar-internal.h |    7 ++++---
 net/rxrpc/input.c       |   16 ++++++++--------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 969e532f77a9..9a9688c41d4d 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -676,10 +676,9 @@ struct rxrpc_call {
 
 	spinlock_t		input_lock;	/* Lock for packet input to this call */
 
-	/* receive-phase ACK management */
+	/* 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_serial_t		ackr_first_seq;	/* first sequence number received */
 	rxrpc_seq_t		ackr_prev_seq;	/* previous sequence number received */
 	rxrpc_seq_t		ackr_consumed;	/* Highest packet shown consumed */
 	rxrpc_seq_t		ackr_seen;	/* Highest packet shown seen */
@@ -692,8 +691,10 @@ struct rxrpc_call {
 #define RXRPC_CALL_RTT_AVAIL_MASK	0xf
 #define RXRPC_CALL_RTT_PEND_SHIFT	8
 
-	/* transmission-phase ACK management */
+	/* 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_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 dc201363f2c4..f11673cda217 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -812,7 +812,7 @@ static void rxrpc_input_soft_acks(struct rxrpc_call *call, u8 *acks,
 static bool rxrpc_is_ack_valid(struct rxrpc_call *call,
 			       rxrpc_seq_t first_pkt, rxrpc_seq_t prev_pkt)
 {
-	rxrpc_seq_t base = READ_ONCE(call->ackr_first_seq);
+	rxrpc_seq_t base = READ_ONCE(call->acks_first_seq);
 
 	if (after(first_pkt, base))
 		return true; /* The window advanced */
@@ -820,7 +820,7 @@ static bool rxrpc_is_ack_valid(struct rxrpc_call *call,
 	if (before(first_pkt, base))
 		return false; /* firstPacket regressed */
 
-	if (after_eq(prev_pkt, call->ackr_prev_seq))
+	if (after_eq(prev_pkt, call->acks_prev_seq))
 		return true; /* previousPacket hasn't regressed. */
 
 	/* Some rx implementations put a serial number in previousPacket. */
@@ -906,8 +906,8 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 	/* Discard any out-of-order or duplicate ACKs (outside lock). */
 	if (!rxrpc_is_ack_valid(call, first_soft_ack, prev_pkt)) {
 		trace_rxrpc_rx_discard_ack(call->debug_id, ack_serial,
-					   first_soft_ack, call->ackr_first_seq,
-					   prev_pkt, call->ackr_prev_seq);
+					   first_soft_ack, call->acks_first_seq,
+					   prev_pkt, call->acks_prev_seq);
 		return;
 	}
 
@@ -922,14 +922,14 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 	/* Discard any out-of-order or duplicate ACKs (inside lock). */
 	if (!rxrpc_is_ack_valid(call, first_soft_ack, prev_pkt)) {
 		trace_rxrpc_rx_discard_ack(call->debug_id, ack_serial,
-					   first_soft_ack, call->ackr_first_seq,
-					   prev_pkt, call->ackr_prev_seq);
+					   first_soft_ack, call->acks_first_seq,
+					   prev_pkt, call->acks_prev_seq);
 		goto out;
 	}
 	call->acks_latest_ts = skb->tstamp;
 
-	call->ackr_first_seq = first_soft_ack;
-	call->ackr_prev_seq = prev_pkt;
+	call->acks_first_seq = first_soft_ack;
+	call->acks_prev_seq = prev_pkt;
 
 	/* Parse rwind and mtu sizes if provided. */
 	if (buf.info.rxMTU)