syncookies: Make sure ECN is disabled

ecn_ok is not initialized when a connection is established by cookies.
The cookie syn-ack never sets ECN, so ecn_ok must be set to 0.

Spotted using ns-3/network simulation cradle simulator and valgrind.
Signed-off-by: NFlorian Westphal <fw@strlen.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/syncookies.c

@@ -299,6 +299,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 	ireq->rmt_port		= th->source;
 	ireq->loc_addr		= ip_hdr(skb)->daddr;
 	ireq->rmt_addr		= ip_hdr(skb)->saddr;
+	ireq->ecn_ok		= 0;
 	ireq->snd_wscale	= tcp_opt.snd_wscale;
 	ireq->rcv_wscale	= tcp_opt.rcv_wscale;
 	ireq->sack_ok		= tcp_opt.sack_ok;

net/ipv6/syncookies.c

@@ -223,6 +223,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 
 	req->expires = 0UL;
 	req->retrans = 0;
+	ireq->ecn_ok		= 0;
 	ireq->snd_wscale	= tcp_opt.snd_wscale;
 	ireq->rcv_wscale	= tcp_opt.rcv_wscale;
 	ireq->sack_ok		= tcp_opt.sack_ok;