import PULS_20180308

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / net / ipv4 / tcp_input.c

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0d94fd91d988a377635d477d14db3e1a0bd2cdf4..f9dff6427a0be7af2c8be24d90bc7cfc311693e8 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -68,6 +68,7 @@
 #include <linux/module.h>
 #include <linux/sysctl.h>
 #include <linux/kernel.h>
+#include <linux/reciprocal_div.h>
 #include <net/dst.h>
 #include <net/tcp.h>
 #include <net/inet_common.h>
@@ -87,7 +88,7 @@ int sysctl_tcp_adv_win_scale __read_mostly = 1;
 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
 
 /* rfc5961 challenge ack rate limiting */
-int sysctl_tcp_challenge_ack_limit = 100;
+int sysctl_tcp_challenge_ack_limit = 1000;
 
 int sysctl_tcp_stdurg __read_mostly;
 int sysctl_tcp_rfc1337 __read_mostly;
@@ -3322,12 +3323,19 @@ static void tcp_send_challenge_ack(struct sock *sk)
        static u32 challenge_timestamp;
        static unsigned int challenge_count;
        u32 now = jiffies / HZ;
+       u32 count;
 
        if (now != challenge_timestamp) {
+               u32 half = (sysctl_tcp_challenge_ack_limit + 1) >> 1;
+
                challenge_timestamp = now;
-               challenge_count = 0;
+               ACCESS_ONCE(challenge_count) = half +
+                                       reciprocal_divide(prandom_u32(),
+                                                       sysctl_tcp_challenge_ack_limit);
        }
-       if (++challenge_count <= sysctl_tcp_challenge_ack_limit) {
+       count = ACCESS_ONCE(challenge_count);
+       if (count > 0) {
+               ACCESS_ONCE(challenge_count) = count - 1;
                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK);
                tcp_send_ack(sk);
        }