tcp: drop SYN+FIN messages
Eric Dumazet [Fri, 2 Dec 2011 23:41:42 +0000 (23:41 +0000)]
Denys Fedoryshchenko reported that SYN+FIN attacks were bringing his
linux machines to their limits.

Dont call conn_request() if the TCP flags includes SYN flag

Reported-by: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

index 78dd38c..0cbb440 100644 (file)
@@ -5811,6 +5811,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                        goto discard;
 
                if (th->syn) {
+                       if (th->fin)
+                               goto discard;
                        if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
                                return 1;