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, 2 insertions, 1 deletions

diff --git a/net/rxrpc/misc.c b/net/rxrpc/misc.c
index 0d425e707f22..fe648711c2f7 100644
--- a/net/rxrpc/misc.c
+++ b/net/rxrpc/misc.c
@@ -155,9 +155,10 @@ const char rxrpc_client_traces[rxrpc_client__nr_trace][7] = {
 const char rxrpc_transmit_traces[rxrpc_transmit__nr_trace][4] = {
 	[rxrpc_transmit_wait]		= "WAI",
 	[rxrpc_transmit_queue]		= "QUE",
-	[rxrpc_transmit_queue_reqack]	= "QRA",
 	[rxrpc_transmit_queue_last]	= "QLS",
 	[rxrpc_transmit_rotate]		= "ROT",
+	[rxrpc_transmit_rotate_last]	= "RLS",
+	[rxrpc_transmit_await_reply]	= "AWR",
 	[rxrpc_transmit_end]		= "END",
 };