Merge branch 'tcp_fastopen_server'

Jerry Chu says:

====================
This patch series provides the server (passive open) side code
for TCP Fast Open. Together with the earlier client side patches
it completes the TCP Fast Open implementation.

The server side Fast Open code accepts data carried in the SYN
packet with a valid Fast Open cookie, and passes it to the
application right away, allowing application to send back response
data, all before TCP's 3-way handshake finishes.

A simple cookie scheme together with capping the number of
outstanding TFO requests (still in TCP_SYN_RECV state) to a limit
per listener forms the main line of defense against spoofed SYN
attacks.

For more details about TCP Fast Open see our IETF internet draft
at http://www.ietf.org/id/draft-ietf-tcpm-fastopen-01.txt
and a research paper at
http://conferences.sigcomm.org/co-next/2011/papers/1569470463.pdf

A prototype implementation was first developed by Sivasankar
Radhakrishnan (sivasankar@cs.ucsd.edu).

A patch based on an older version of Linux kernel has been
undergoing internal tests at Google for the past few months.

Jerry Chu (3):
  tcp: TCP Fast Open Server - header & support functions
  tcp: TCP Fast Open Server - support TFO listeners
  tcp: TCP Fast Open Server - main code path
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 50 insertions, 5 deletions

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 7f75f21d7b8..8464b79c493 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -283,7 +283,9 @@ static int inet_csk_wait_for_connect(struct sock *sk, long timeo)
 struct sock *inet_csk_accept(struct sock *sk, int flags, int *err)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct request_sock_queue *queue = &icsk->icsk_accept_queue;
 	struct sock *newsk;
+	struct request_sock *req;
 	int error;
 
 	lock_sock(sk);
@@ -296,7 +298,7 @@ struct sock *inet_csk_accept(struct sock *sk, int flags, int *err)
 		goto out_err;
 
 	/* Find already established connection */
-	if (reqsk_queue_empty(&icsk->icsk_accept_queue)) {
+	if (reqsk_queue_empty(queue)) {
 		long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);
 
 		/* If this is a non blocking socket don't sleep */
@@ -308,14 +310,32 @@ struct sock *inet_csk_accept(struct sock *sk, int flags, int *err)
 		if (error)
 			goto out_err;
 	}
+	req = reqsk_queue_remove(queue);
+	newsk = req->sk;
 
-	newsk = reqsk_queue_get_child(&icsk->icsk_accept_queue, sk);
-	WARN_ON(newsk->sk_state == TCP_SYN_RECV);
+	sk_acceptq_removed(sk);
+	if (sk->sk_type == SOCK_STREAM && queue->fastopenq != NULL) {
+		spin_lock_bh(&queue->fastopenq->lock);
+		if (tcp_rsk(req)->listener) {
+			/* We are still waiting for the final ACK from 3WHS
+			 * so can't free req now. Instead, we set req->sk to
+			 * NULL to signify that the child socket is taken
+			 * so reqsk_fastopen_remove() will free the req
+			 * when 3WHS finishes (or is aborted).
+			 */
+			req->sk = NULL;
+			req = NULL;
+		}
+		spin_unlock_bh(&queue->fastopenq->lock);
+	}
 out:
 	release_sock(sk);
+	if (req)
+		__reqsk_free(req);
 	return newsk;
 out_err:
 	newsk = NULL;
+	req = NULL;
 	*err = error;
 	goto out;
 }
@@ -720,13 +740,14 @@ EXPORT_SYMBOL_GPL(inet_csk_listen_start);
 void inet_csk_listen_stop(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct request_sock_queue *queue = &icsk->icsk_accept_queue;
 	struct request_sock *acc_req;
 	struct request_sock *req;
 
 	inet_csk_delete_keepalive_timer(sk);
 
 	/* make all the listen_opt local to us */
-	acc_req = reqsk_queue_yank_acceptq(&icsk->icsk_accept_queue);
+	acc_req = reqsk_queue_yank_acceptq(queue);
 
 	/* Following specs, it would be better either to send FIN
 	 * (and enter FIN-WAIT-1, it is normal close)
@@ -736,7 +757,7 @@ void inet_csk_listen_stop(struct sock *sk)
 	 * To be honest, we are not able to make either
 	 * of the variants now.			--ANK
 	 */
-	reqsk_queue_destroy(&icsk->icsk_accept_queue);
+	reqsk_queue_destroy(queue);
 
 	while ((req = acc_req) != NULL) {
 		struct sock *child = req->sk;
@@ -754,6 +775,19 @@ void inet_csk_listen_stop(struct sock *sk)
 
 		percpu_counter_inc(sk->sk_prot->orphan_count);
 
+		if (sk->sk_type == SOCK_STREAM && tcp_rsk(req)->listener) {
+			BUG_ON(tcp_sk(child)->fastopen_rsk != req);
+			BUG_ON(sk != tcp_rsk(req)->listener);
+
+			/* Paranoid, to prevent race condition if
+			 * an inbound pkt destined for child is
+			 * blocked by sock lock in tcp_v4_rcv().
+			 * Also to satisfy an assertion in
+			 * tcp_v4_destroy_sock().
+			 */
+			tcp_sk(child)->fastopen_rsk = NULL;
+			sock_put(sk);
+		}
 		inet_csk_destroy_sock(child);
 
 		bh_unlock_sock(child);
@@ -763,6 +797,17 @@ void inet_csk_listen_stop(struct sock *sk)
 		sk_acceptq_removed(sk);
 		__reqsk_free(req);
 	}
+	if (queue->fastopenq != NULL) {
+		/* Free all the reqs queued in rskq_rst_head. */
+		spin_lock_bh(&queue->fastopenq->lock);
+		acc_req = queue->fastopenq->rskq_rst_head;
+		queue->fastopenq->rskq_rst_head = NULL;
+		spin_unlock_bh(&queue->fastopenq->lock);
+		while ((req = acc_req) != NULL) {
+			acc_req = req->dl_next;
+			__reqsk_free(req);
+		}
+	}
 	WARN_ON(sk->sk_ack_backlog);
 }
 EXPORT_SYMBOL_GPL(inet_csk_listen_stop);