rxrpc: Switch to Congestion Avoidance mode at cwnd==ssthresh

Switch to Congestion Avoidance mode at cwnd == ssthresh rather than relying
on cwnd getting incremented beyond ssthresh and the window size, the mode
being shifted and then cwnd being corrected.

We need to make sure we switch into CA mode so that we stop marking every
packet for ACK.

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

net/rxrpc/input.c

@@ -57,7 +57,7 @@ static void rxrpc_congestion_management(struct rxrpc_call *call,
 		call->cong_ssthresh = max_t(unsigned int,
 					    summary->flight_size / 2, 2);
 		cwnd = 1;
-		if (cwnd > call->cong_ssthresh &&
+		if (cwnd >= call->cong_ssthresh &&
 		    call->cong_mode == RXRPC_CALL_SLOW_START) {
 			call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
 			call->cong_tstamp = skb->tstamp;
@@ -82,7 +82,7 @@ static void rxrpc_congestion_management(struct rxrpc_call *call,
 			goto packet_loss_detected;
 		if (summary->cumulative_acks > 0)
 			cwnd += 1;
-		if (cwnd > call->cong_ssthresh) {
+		if (cwnd >= call->cong_ssthresh) {
 			call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
 			call->cong_tstamp = skb->tstamp;
 		}
@@ -161,7 +161,7 @@ static void rxrpc_congestion_management(struct rxrpc_call *call,
 	call->cong_dup_acks = 0;
 	call->cong_extra = 0;
 	call->cong_tstamp = skb->tstamp;
-	if (cwnd <= call->cong_ssthresh)
+	if (cwnd < call->cong_ssthresh)
 		call->cong_mode = RXRPC_CALL_SLOW_START;
 	else
 		call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;