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>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index e0360f5a53e9..3f9b8ce56948 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -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;