syncookies: add support for ECN

Allows use of ECN when syncookies are in effect by encoding ecn_ok
into the syn-ack tcp timestamp.

While at it, remove a uneeded #ifdef CONFIG_SYN_COOKIES.
With CONFIG_SYN_COOKIES=nm want_cookie is ifdef'd to 0 and gcc
removes the "if (0)".

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index f87534569366..5ebc27ecebdc 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1269,7 +1269,7 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
         treq = inet6_rsk(req);
         ipv6_addr_copy(&treq->rmt_addr, &ipv6_hdr(skb)->saddr);
         ipv6_addr_copy(&treq->loc_addr, &ipv6_hdr(skb)->daddr);
-        if (!want_cookie)
+        if (!want_cookie || tmp_opt.tstamp_ok)
                 TCP_ECN_create_request(req, tcp_hdr(skb));
 
         if (!isn) {