[TCP]: TCP_DEFER_ACCEPT updates - defer timeout conflicts with max_thresh

timeout associated with SO_DEFER_ACCEPT wasn't being honored if it was
less than the timeout allowed by the maximum syn-recv queue size
algorithm. Fix by using the SO_DEFER_ACCEPT value if the ack has
arrived.
Signed-off-by: NPatrick McManus <mcmanus@ducksong.com>
Acked-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/inet_connection_sock.c

@@ -461,8 +461,7 @@ void inet_csk_reqsk_queue_prune(struct sock *parent,
 		reqp=&lopt->syn_table[i];
 		while ((req = *reqp) != NULL) {
 			if (time_after_eq(now, req->expires)) {
-				if ((req->retrans < thresh ||
-				     (inet_rsk(req)->acked && req->retrans < max_retries))
+				if ((req->retrans < (inet_rsk(req)->acked ? max_retries : thresh))
 				    && !req->rsk_ops->rtx_syn_ack(parent, req)) {
 					unsigned long timeo;