diff options
| -rw-r--r-- | net/ipv4/tcp_input.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 5e39dbe..1e81dd4 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -87,7 +87,7 @@ 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; @@ -3648,13 +3648,20 @@ static void tcp_send_challenge_ack(struct sock *sk) /* unprotected vars, we dont care of overwrites */ static u32 challenge_timestamp; static unsigned int challenge_count; - u32 now = jiffies / HZ; + u32 count, now = jiffies / HZ; if (now != challenge_timestamp) { + u32 half = (sysctl_tcp_challenge_ack_limit + 1) >> 1; + challenge_timestamp = now; - challenge_count = 0; - } - if (++challenge_count <= sysctl_tcp_challenge_ack_limit) { + ACCESS_ONCE(challenge_count) = + half + (u32)( + ((u64) random32() * sysctl_tcp_challenge_ack_limit) + >> 32); + } + 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); } |