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Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c45
1 files changed, 26 insertions, 19 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 181fc8234a52..a13692560e63 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3552,6 +3552,24 @@ static bool tcp_process_frto(struct sock *sk, int flag)
return false;
}
+/* 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)
{
@@ -3571,8 +3589,14 @@ 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).
@@ -5244,23 +5268,6 @@ 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.
*/
@@ -5992,7 +5999,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
*/
if (req) {
tcp_synack_rtt_meas(sk, req);
- tp->total_retrans = req->retrans;
+ tp->total_retrans = req->num_retrans;
reqsk_fastopen_remove(sk, req, false);
} else {