tcp: simplify fast open cookie processing

Consolidate various cookie checking and generation code to simplify
the fast open processing. The main goal is to reduce code duplication
in tcp_v4_conn_request() for IPv6 support.

Removes two experimental sysctl flags TFO_SERVER_ALWAYS and
TFO_SERVER_COOKIE_NOT_CHKD used primarily for developmental debugging
purposes.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Daniel Lee <longinus00@gmail.com>
Signed-off-by: Jerry Chu <hkchu@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 7 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 032fcaee164a..5ea0949dadfd 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1273,7 +1273,6 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
         bool want_cookie = false;
         struct flowi4 fl4;
         struct tcp_fastopen_cookie foc = { .len = -1 };
-        struct tcp_fastopen_cookie valid_foc = { .len = -1 };
         struct sk_buff *skb_synack;
         int do_fastopen;
 
@@ -1381,7 +1380,8 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
                 if (dst == NULL)
                         goto drop_and_free;
         }
-        do_fastopen = tcp_fastopen_check(sk, skb, req, &foc, &valid_foc);
+        do_fastopen = !want_cookie &&
+                      tcp_fastopen_check(sk, skb, req, &foc);
 
         /* We don't call tcp_v4_send_synack() directly because we need
          * to make sure a child socket can be created successfully before
@@ -1394,8 +1394,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
          * latter to remove its dependency on the current implementation
          * of tcp_v4_send_synack()->tcp_select_initial_window().
          */
-        skb_synack = tcp_make_synack(sk, dst, req,
-            fastopen_cookie_present(&valid_foc) ? &valid_foc : NULL);
+        skb_synack = tcp_make_synack(sk, dst, req, &foc);
 
         if (skb_synack) {
                 __tcp_v4_send_check(skb_synack, ireq->ir_loc_addr, ireq->ir_rmt_addr);
@@ -1415,9 +1414,6 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
                 tcp_rsk(req)->listener = NULL;
                 /* Add the request_sock to the SYN table */
                 inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
-                if (fastopen_cookie_present(&foc) && foc.len != 0)
-                        NET_INC_STATS_BH(sock_net(sk),
-                            LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
         } else if (tcp_fastopen_create_child(sk, skb, skb_synack, req))
                 goto drop_and_release;