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>

diff --git a/include/net/sock.h b/include/net/sock.h
index e0360f5..3f9b8ce 100644 (file)
--- 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;

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 4334248..e1c85db 100644 (file)
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -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
        },
        { }