rxrpc: Allow tx_winsize to grow in response to an ACK

Allow tx_winsize to grow when the ACK info packet shows a larger receive
window at the other end rather than only permitting it to shrink.
Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/input.c

@@ -333,14 +333,16 @@ static void rxrpc_input_ackinfo(struct rxrpc_call *call, struct sk_buff *skb,
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct rxrpc_peer *peer;
 	unsigned int mtu;
+	u32 rwind = ntohl(ackinfo->rwind);
 
 	_proto("Rx ACK %%%u Info { rx=%u max=%u rwin=%u jm=%u }",
 	       sp->hdr.serial,
 	       ntohl(ackinfo->rxMTU), ntohl(ackinfo->maxMTU),
-	       ntohl(ackinfo->rwind), ntohl(ackinfo->jumbo_max));
+	       rwind, ntohl(ackinfo->jumbo_max));
 
-	if (call->tx_winsize > ntohl(ackinfo->rwind))
-		call->tx_winsize = ntohl(ackinfo->rwind);
+	if (rwind > RXRPC_RXTX_BUFF_SIZE - 1)
+		rwind = RXRPC_RXTX_BUFF_SIZE - 1;
+	call->tx_winsize = rwind;
 
 	mtu = min(ntohl(ackinfo->rxMTU), ntohl(ackinfo->maxMTU));