@@ -5477,8 +5477,11 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
* an acknowledgment should be sent in reply (unless the RST
* bit is set, if so drop the segment and return)".
*/
- if (!th->rst)
+ if (!th->rst) {
+ if (th->syn)
+ goto syn_challenge;
tcp_send_dupack(sk, skb);
+ }
goto discard;
}
@@ -5508,6 +5511,7 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
* RFC 5691 4.2 : Send a challenge ack
*/
if (th->syn) {
+syn_challenge:
if (syn_inerr)
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);