diff options
| -rw-r--r-- | net/ipv4/tcp_input.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index c91002f..5e16e92 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -66,6 +66,7 @@ #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; @@ -3649,12 +3650,19 @@ 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); } |