rxrpc: Pass the last Tx packet marker in the annotation buffer

When the last packet of data to be transmitted on a call is queued, tx_top
is set and then the RXRPC_CALL_TX_LAST flag is set.  Unfortunately, this
leaves a race in the ACK processing side of things because the flag affects
the interpretation of tx_top and also allows us to start receiving reply
data before we've finished transmitting.

To fix this, make the following changes:

 (1) rxrpc_queue_packet() now sets a marker in the annotation buffer
     instead of setting the RXRPC_CALL_TX_LAST flag.

 (2) rxrpc_rotate_tx_window() detects the marker and sets the flag in the
     same context as the routines that use it.

 (3) rxrpc_end_tx_phase() is simplified to just shift the call state.
     The Tx window must have been rotated before calling to discard the
     last packet.

 (4) rxrpc_receiving_reply() is added to handle the arrival of the first
     DATA packet of a reply to a client call (which is an implicit ACK of
     the Tx phase).

 (5) The last part of rxrpc_input_ack() is reordered to perform Tx
     rotation, then soft-ACK application and then to end the phase if we've
     rotated the last packet.  In the event of a terminal ACK, the soft-ACK
     application will be skipped as nAcks should be 0.

 (6) rxrpc_input_ackall() now has to rotate as well as ending the phase.

In addition:

 (7) Alter the transmit tracepoint to log the rotation of the last packet.

 (8) Remove the no-longer relevant queue_reqack tracepoint note.  The
     ACK-REQUESTED packet header flag is now set as needed when we actually
     transmit the packet and may vary by retransmission.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 9e3ba4dc9578..a494d56eb236 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -508,7 +508,9 @@ struct rxrpc_call {
 #define RXRPC_TX_ANNO_NAK	2
 #define RXRPC_TX_ANNO_RETRANS	3
 #define RXRPC_TX_ANNO_MASK	0x03
-#define RXRPC_TX_ANNO_RESENT	0x04
+#define RXRPC_TX_ANNO_LAST	0x04
+#define RXRPC_TX_ANNO_RESENT	0x08
+
 #define RXRPC_RX_ANNO_JUMBO	0x3f		/* Jumbo subpacket number + 1 if not zero */
 #define RXRPC_RX_ANNO_JLAST	0x40		/* Set if last element of a jumbo packet */
 #define RXRPC_RX_ANNO_VERIFIED	0x80		/* Set if verified and decrypted */
@@ -621,9 +623,10 @@ extern const char rxrpc_call_traces[rxrpc_call__nr_trace][4];
 enum rxrpc_transmit_trace {
 	rxrpc_transmit_wait,
 	rxrpc_transmit_queue,
-	rxrpc_transmit_queue_reqack,
 	rxrpc_transmit_queue_last,
 	rxrpc_transmit_rotate,
+	rxrpc_transmit_rotate_last,
+	rxrpc_transmit_await_reply,
 	rxrpc_transmit_end,
 	rxrpc_transmit__nr_trace
 };