TCPCT part 1g: Responder Cookie => Initiator

Parse incoming TCP_COOKIE option(s).

Calculate <SYN,ACK> TCP_COOKIE option.

Send optional <SYN,ACK> data.

This is a significantly revised implementation of an earlier (year-old)
patch that no longer applies cleanly, with permission of the original
author (Adam Langley):

    http://thread.gmane.org/gmane.linux.network/102586

Requires:
   TCPCT part 1a: add request_values parameter for sending SYNACK
   TCPCT part 1b: generate Responder Cookie secret
   TCPCT part 1c: sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS
   TCPCT part 1d: define TCP cookie option, extend existing struct's
   TCPCT part 1e: implement socket option TCP_COOKIE_TRANSACTIONS
   TCPCT part 1f: Initiator Cookie => Responder

Signed-off-by: William.Allen.Simpson@gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 3146cc401748..26399ad2a289 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -253,6 +253,8 @@ EXPORT_SYMBOL(cookie_check_timestamp);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
                              struct ip_options *opt)
 {
+        struct tcp_options_received tcp_opt;
+        u8 *hash_location;
         struct inet_request_sock *ireq;
         struct tcp_request_sock *treq;
         struct tcp_sock *tp = tcp_sk(sk);
@@ -263,7 +265,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
         int mss;
         struct rtable *rt;
         __u8 rcv_wscale;
-        struct tcp_options_received tcp_opt;
 
         if (!sysctl_tcp_syncookies || !th->ack)
                 goto out;
@@ -341,7 +342,7 @@ 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, 0, &rt->u.dst);
+        tcp_parse_options(skb, &tcp_opt, &hash_location, 0, &rt->u.dst);
 
         if (tcp_opt.saw_tstamp)
                 cookie_check_timestamp(&tcp_opt);