tcp: Remove TCPCT

TCPCT uses option-number 253, reserved for experimental use and should
not be used in production environments.
Further, TCPCT does not fully implement RFC 6013.

As a nice side-effect, removing TCPCT increases TCP's performance for
very short flows:

Doing an apache-benchmark with -c 100 -n 100000, sending HTTP-requests
for files of 1KB size.

before this patch:
	average (among 7 runs) of 20845.5 Requests/Second
after:
	average (among 7 runs) of 21403.6 Requests/Second

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 2 deletions

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index ef54377fb11c..7f4a5cb8f8d0 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -267,7 +267,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
                              struct ip_options *opt)
 {
         struct tcp_options_received tcp_opt;
-        const u8 *hash_location;
         struct inet_request_sock *ireq;
         struct tcp_request_sock *treq;
         struct tcp_sock *tp = tcp_sk(sk);
@@ -294,7 +293,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 
         /* check for timestamp cookie support */
         memset(&tcp_opt, 0, sizeof(tcp_opt));
-        tcp_parse_options(skb, &tcp_opt, &hash_location, 0, NULL);
+        tcp_parse_options(skb, &tcp_opt, 0, NULL);
 
         if (!cookie_check_timestamp(&tcp_opt, sock_net(sk), &ecn_ok))
                 goto out;