tcp: TCP Fast Open Server - support TFO listeners

This patch builds on top of the previous patch to add the support
for TFO listeners. This includes -

1. allocating, properly initializing, and managing the per listener
fastopen_queue structure when TFO is enabled

2. changes to the inet_csk_accept code to support TFO. E.g., the
request_sock can no longer be freed upon accept(), not until 3WHS
finishes

3. allowing a TCP_SYN_RECV socket to properly poll() and sendmsg()
if it's a TFO socket

4. properly closing a TFO listener, and a TFO socket before 3WHS
finishes

5. supporting TCP_FASTOPEN socket option

6. modifying tcp_check_req() to use to check a TFO socket as well
as request_sock

7. supporting TCP's TFO cookie option

8. adding a new SYN-ACK retransmit handler to use the timer directly
off the TFO socket rather than the listener socket. Note that TFO
server side will not retransmit anything other than SYN-ACK until
the 3WHS is completed.

The patch also contains an important function
"reqsk_fastopen_remove()" to manage the somewhat complex relation
between a listener, its request_sock, and the corresponding child
socket. See the comment above the function for the detail.

Signed-off-by: H.K. Jerry Chu <hkchu@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 13 deletions

diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index c3cdd6c9f448..b01d8dd9ee7c 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -226,19 +226,6 @@ static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue
 	return req;
 }
 
-static inline struct sock *reqsk_queue_get_child(struct request_sock_queue *queue,
-						 struct sock *parent)
-{
-	struct request_sock *req = reqsk_queue_remove(queue);
-	struct sock *child = req->sk;
-
-	WARN_ON(child == NULL);
-
-	sk_acceptq_removed(parent);
-	__reqsk_free(req);
-	return child;
-}
-
 static inline int reqsk_queue_removed(struct request_sock_queue *queue,
 				      struct request_sock *req)
 {