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, 2 insertions, 4 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 2e41e6f92968..8fa32f5ae2ce 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1328,14 +1328,12 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
         if (security_inet_conn_request(sk, skb, req))
                 goto drop_and_free;
 
-        if (!want_cookie)
+        if (!want_cookie || tmp_opt.tstamp_ok)
                 TCP_ECN_create_request(req, tcp_hdr(skb));
 
         if (want_cookie) {
-#ifdef CONFIG_SYN_COOKIES
-                req->cookie_ts = tmp_opt.tstamp_ok;
-#endif
                 isn = cookie_v4_init_sequence(sk, skb, &req->mss);
+                req->cookie_ts = tmp_opt.tstamp_ok;
         } else if (!isn) {
                 struct inet_peer *peer = NULL;