diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fc51b17858a13a2c8a76df53d5a4fe06887b6e5a..2f0e0f08f1173fd1f6cd4c2e33a3ec4b260c017c 100644
--- 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;
@@ -3289,12 +3290,19 @@ 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);
 	}