Commit becb74f0 authored Mar 19, 2015 by Eric Dumazet Committed by David S. Miller Mar 20, 2015

net: increase sk_[max_]ack_backlog



sk_ack_backlog & sk_max_ack_backlog were 16bit fields, meaning
listen() backlog was limited to 65535.

It is time to increase the width to allow much bigger backlog,
if admins change /proc/sys/net/core/somaxconn &
/proc/sys/net/ipv4/tcp_max_syn_backlog default values.

Tested:

echo 5000000 >/proc/sys/net/core/somaxconn
echo 5000000 >/proc/sys/net/ipv4/tcp_max_syn_backlog

Ran a SYNFLOOD test against a listener using listen(fd, 5000000)

myhost~# grep request_sock_TCP /proc/slabinfo
request_sock_TCP  4185642 4411940    304   13    1 : tunables   54   27    8 : slabdata 339380 339380      0

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent fa76ce73

include/net/sock.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -405,8 +405,8 @@ struct sock {
		rwlock_t sk_callback_lock;
		int sk_err,
		sk_err_soft;
		unsigned short sk_ack_backlog;
		unsigned short sk_max_ack_backlog;
		u32 sk_ack_backlog;
		u32 sk_max_ack_backlog;
		__u32 sk_priority;
		#if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
		__u32 sk_cgrp_prioidx;

net/core/sysctl_net_core.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -24,7 +24,6 @@

		static int zero = 0;
		static int one = 1;
		static int ushort_max = USHRT_MAX;

		static int net_msg_warn; /* Unused, but still a sysctl */

		@@ -401,7 +400,6 @@ static struct ctl_table netns_core_table[] = {
		.maxlen = sizeof(int),
		.mode = 0644,
		.extra1 = &zero,
		.extra2 = &ushort_max,
		.proc_handler = proc_dointvec_minmax
		},
		{ }

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