From: Eric Dumazet <edumazet@google.com>
Date: Tue, 6 Oct 2015 21:49:58 +0000 (-0700)
Subject: tcp: ensure prior synack rtx behavior with small backlogs
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=acb4a6bfc80ddeea4c44074dd630f916259e909e;p=openwrt%2Fstaging%2Fblogic.git

tcp: ensure prior synack rtx behavior with small backlogs

Some applications use a listen() backlog of 1.

Prior kernels were silently enforcing a qlen_log of 4, so that we were
sending up to /proc/sys/net/ipv4/tcp_synack_retries SYNACK messages.

Fixes: ef547f2ac16b ("tcp: remove max_qlen_log")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 89eedfbd4ad5..514b9e910bd4 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -579,7 +579,7 @@ static void reqsk_timer_handler(unsigned long data)
 	 * ones are about to clog our table.
 	 */
 	qlen = reqsk_queue_len(queue);
-	if ((qlen << 1) > sk_listener->sk_max_ack_backlog) {
+	if ((qlen << 1) > max(8U, sk_listener->sk_max_ack_backlog)) {
 		int young = reqsk_queue_len_young(queue) << 1;
 
 		while (thresh > 2) {