diff options
| -rw-r--r-- | Documentation/networking/ip-sysctl.rst | 5 | ||||
| -rw-r--r-- | include/net/netns/ipv4.h | 2 | ||||
| -rw-r--r-- | net/ipv4/tcp_input.c | 21 | ||||
| -rw-r--r-- | net/ipv4/tcp_ipv4.c | 6 |
4 files changed, 21 insertions, 13 deletions
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 56cd4ea059b2..a759872a2883 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -1035,7 +1035,10 @@ tcp_limit_output_bytes - INTEGER tcp_challenge_ack_limit - INTEGER Limits number of Challenge ACK sent per second, as recommended in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) - Default: 1000 + Note that this per netns rate limit can allow some side channel + attacks and probably should not be enabled. + TCP stack implements per TCP socket limits anyway. + Default: INT_MAX (unlimited) UDP variables ============= diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index c7320ef356d9..6320a76cefdc 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -179,6 +179,8 @@ struct netns_ipv4 { unsigned int sysctl_tcp_fastopen_blackhole_timeout; atomic_t tfo_active_disable_times; unsigned long tfo_active_disable_stamp; + u32 tcp_challenge_timestamp; + u32 tcp_challenge_count; int sysctl_udp_wmem_min; int sysctl_udp_rmem_min; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index c184e15397a2..b85a9f755da4 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3614,12 +3614,9 @@ bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb, /* RFC 5961 7 [ACK Throttling] */ 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; struct tcp_sock *tp = tcp_sk(sk); struct net *net = sock_net(sk); - u32 count, now; + u32 count, now, ack_limit; /* First check our per-socket dupack rate limit. */ if (__tcp_oow_rate_limited(net, @@ -3627,18 +3624,22 @@ static void tcp_send_challenge_ack(struct sock *sk) &tp->last_oow_ack_time)) return; + ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit); + if (ack_limit == INT_MAX) + goto send_ack; + /* Then check host-wide RFC 5961 rate limit. */ now = jiffies / HZ; - if (now != READ_ONCE(challenge_timestamp)) { - u32 ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit); + if (now != READ_ONCE(net->ipv4.tcp_challenge_timestamp)) { u32 half = (ack_limit + 1) >> 1; - WRITE_ONCE(challenge_timestamp, now); - WRITE_ONCE(challenge_count, half + prandom_u32_max(ack_limit)); + WRITE_ONCE(net->ipv4.tcp_challenge_timestamp, now); + WRITE_ONCE(net->ipv4.tcp_challenge_count, half + prandom_u32_max(ack_limit)); } - count = READ_ONCE(challenge_count); + count = READ_ONCE(net->ipv4.tcp_challenge_count); if (count > 0) { - WRITE_ONCE(challenge_count, count - 1); + WRITE_ONCE(net->ipv4.tcp_challenge_count, count - 1); +send_ack: NET_INC_STATS(net, LINUX_MIB_TCPCHALLENGEACK); tcp_send_ack(sk); } diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 0c83780dc9bf..5b019ba2b9d2 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -3139,8 +3139,10 @@ static int __net_init tcp_sk_init(struct net *net) net->ipv4.sysctl_tcp_tso_win_divisor = 3; /* Default TSQ limit of 16 TSO segments */ net->ipv4.sysctl_tcp_limit_output_bytes = 16 * 65536; - /* rfc5961 challenge ack rate limiting */ - net->ipv4.sysctl_tcp_challenge_ack_limit = 1000; + + /* rfc5961 challenge ack rate limiting, per net-ns, disabled by default. */ + net->ipv4.sysctl_tcp_challenge_ack_limit = INT_MAX; + net->ipv4.sysctl_tcp_min_tso_segs = 2; net->ipv4.sysctl_tcp_tso_rtt_log = 9; /* 2^9 = 512 usec */ net->ipv4.sysctl_tcp_min_rtt_wlen = 300; |