diff options
| -rw-r--r-- | net/ipv4/tcp_input.c | 43 |
1 files changed, 25 insertions, 18 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index b75cb8554a7..aab8f089c89 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3703,6 +3703,24 @@ static int tcp_process_frto(struct sock *sk, int flag) return 0; } +/* 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; + u32 now = jiffies / HZ; + + if (now != challenge_timestamp) { + challenge_timestamp = now; + challenge_count = 0; + } + if (++challenge_count <= sysctl_tcp_challenge_ack_limit) { + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK); + tcp_send_ack(sk); + } +} + /* This routine deals with incoming acks, but not outgoing ones. */ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) { @@ -3721,8 +3739,14 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) /* If the ack is older than previous acks * then we can probably ignore it. */ - if (before(ack, prior_snd_una)) + if (before(ack, prior_snd_una)) { + /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */ + if (before(ack, prior_snd_una - tp->max_window)) { + tcp_send_challenge_ack(sk); + return -1; + } goto old_ack; + } /* If the ack includes data we haven't sent yet, discard * this segment (RFC793 Section 3.9). @@ -5243,23 +5267,6 @@ out: } #endif /* CONFIG_NET_DMA */ -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; - - if (now != challenge_timestamp) { - challenge_timestamp = now; - challenge_count = 0; - } - if (++challenge_count <= sysctl_tcp_challenge_ack_limit) { - NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK); - tcp_send_ack(sk); - } -} - /* Does PAWS and seqno based validation of an incoming segment, flags will * play significant role here. */ |