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, 5 insertions, 35 deletions

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 4bdb09fca401..8f0234f8bb95 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -93,13 +93,12 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
                            const struct tcphdr *th)
 {
         struct tcp_options_received tmp_opt;
-        const u8 *hash_location;
         struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
         bool paws_reject = false;
 
         tmp_opt.saw_tstamp = 0;
         if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
-                tcp_parse_options(skb, &tmp_opt, &hash_location, 0, NULL);
+                tcp_parse_options(skb, &tmp_opt, 0, NULL);
 
                 if (tmp_opt.saw_tstamp) {
                         tmp_opt.rcv_tsecr       -= tcptw->tw_ts_offset;
@@ -388,32 +387,6 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
                 struct tcp_request_sock *treq = tcp_rsk(req);
                 struct inet_connection_sock *newicsk = inet_csk(newsk);
                 struct tcp_sock *newtp = tcp_sk(newsk);
-                struct tcp_sock *oldtp = tcp_sk(sk);
-                struct tcp_cookie_values *oldcvp = oldtp->cookie_values;
-
-                /* TCP Cookie Transactions require space for the cookie pair,
-                 * as it differs for each connection.  There is no need to
-                 * copy any s_data_payload stored at the original socket.
-                 * Failure will prevent resuming the connection.
-                 *
-                 * Presumed copied, in order of appearance:
-                 *      cookie_in_always, cookie_out_never
-                 */
-                if (oldcvp != NULL) {
-                        struct tcp_cookie_values *newcvp =
-                                kzalloc(sizeof(*newtp->cookie_values),
-                                        GFP_ATOMIC);
-
-                        if (newcvp != NULL) {
-                                kref_init(&newcvp->kref);
-                                newcvp->cookie_desired =
-                                                oldcvp->cookie_desired;
-                                newtp->cookie_values = newcvp;
-                        } else {
-                                /* Not Yet Implemented */
-                                newtp->cookie_values = NULL;
-                        }
-                }
 
                 /* Now setup tcp_sock */
                 newtp->pred_flags = 0;
@@ -422,8 +395,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
                 newtp->rcv_nxt = treq->rcv_isn + 1;
 
                 newtp->snd_sml = newtp->snd_una =
-                newtp->snd_nxt = newtp->snd_up =
-                        treq->snt_isn + 1 + tcp_s_data_size(oldtp);
+                newtp->snd_nxt = newtp->snd_up = treq->snt_isn + 1;
 
                 tcp_prequeue_init(newtp);
                 INIT_LIST_HEAD(&newtp->tsq_node);
@@ -460,8 +432,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
                 tcp_set_ca_state(newsk, TCP_CA_Open);
                 tcp_init_xmit_timers(newsk);
                 skb_queue_head_init(&newtp->out_of_order_queue);
-                newtp->write_seq = newtp->pushed_seq =
-                        treq->snt_isn + 1 + tcp_s_data_size(oldtp);
+                newtp->write_seq = newtp->pushed_seq = treq->snt_isn + 1;
 
                 newtp->rx_opt.saw_tstamp = 0;
 
@@ -538,7 +509,6 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
                            bool fastopen)
 {
         struct tcp_options_received tmp_opt;
-        const u8 *hash_location;
         struct sock *child;
         const struct tcphdr *th = tcp_hdr(skb);
         __be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
@@ -548,7 +518,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
 
         tmp_opt.saw_tstamp = 0;
         if (th->doff > (sizeof(struct tcphdr)>>2)) {
-                tcp_parse_options(skb, &tmp_opt, &hash_location, 0, NULL);
+                tcp_parse_options(skb, &tmp_opt, 0, NULL);
 
                 if (tmp_opt.saw_tstamp) {
                         tmp_opt.ts_recent = req->ts_recent;
@@ -648,7 +618,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
          */
         if ((flg & TCP_FLAG_ACK) && !fastopen &&
             (TCP_SKB_CB(skb)->ack_seq !=
-             tcp_rsk(req)->snt_isn + 1 + tcp_s_data_size(tcp_sk(sk))))
+             tcp_rsk(req)->snt_isn + 1))
                 return sk;
 
         /* Also, it would be not so bad idea to check rcv_tsecr, which