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>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2109ff4..df83d74 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -486,8 +486,9 @@
if (sk->sk_shutdown & RCV_SHUTDOWN)
mask |= POLLIN | POLLRDNORM | POLLRDHUP;
- /* Connected? */
- if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV)) {
+ /* Connected or passive Fast Open socket? */
+ if (sk->sk_state != TCP_SYN_SENT &&
+ (sk->sk_state != TCP_SYN_RECV || tp->fastopen_rsk != NULL)) {
int target = sock_rcvlowat(sk, 0, INT_MAX);
if (tp->urg_seq == tp->copied_seq &&
@@ -840,10 +841,15 @@
ssize_t copied;
long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
- /* Wait for a connection to finish. */
- if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
+ /* Wait for a connection to finish. One exception is TCP Fast Open
+ * (passive side) where data is allowed to be sent before a connection
+ * is fully established.
+ */
+ if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
+ !tcp_passive_fastopen(sk)) {
if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
goto out_err;
+ }
clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
@@ -1042,10 +1048,15 @@
timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
- /* Wait for a connection to finish. */
- if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
+ /* Wait for a connection to finish. One exception is TCP Fast Open
+ * (passive side) where data is allowed to be sent before a connection
+ * is fully established.
+ */
+ if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
+ !tcp_passive_fastopen(sk)) {
if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
goto do_error;
+ }
if (unlikely(tp->repair)) {
if (tp->repair_queue == TCP_RECV_QUEUE) {
@@ -2144,6 +2155,10 @@
* they look as CLOSING or LAST_ACK for Linux)
* Probably, I missed some more holelets.
* --ANK
+ * XXX (TFO) - To start off we don't support SYN+ACK+FIN
+ * in a single packet! (May consider it later but will
+ * probably need API support or TCP_CORK SYN-ACK until
+ * data is written and socket is closed.)
*/
tcp_send_fin(sk);
}
@@ -2215,8 +2230,16 @@
}
}
- if (sk->sk_state == TCP_CLOSE)
+ if (sk->sk_state == TCP_CLOSE) {
+ struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
+ /* We could get here with a non-NULL req if the socket is
+ * aborted (e.g., closed with unread data) before 3WHS
+ * finishes.
+ */
+ if (req != NULL)
+ reqsk_fastopen_remove(sk, req, false);
inet_csk_destroy_sock(sk);
+ }
/* Otherwise, socket is reprieved until protocol close. */
out:
@@ -2688,6 +2711,14 @@
else
icsk->icsk_user_timeout = msecs_to_jiffies(val);
break;
+
+ case TCP_FASTOPEN:
+ if (val >= 0 && ((1 << sk->sk_state) & (TCPF_CLOSE |
+ TCPF_LISTEN)))
+ err = fastopen_init_queue(sk, val);
+ else
+ err = -EINVAL;
+ break;
default:
err = -ENOPROTOOPT;
break;
@@ -3501,11 +3532,15 @@
void tcp_done(struct sock *sk)
{
+ struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
+
if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
tcp_set_state(sk, TCP_CLOSE);
tcp_clear_xmit_timers(sk);
+ if (req != NULL)
+ reqsk_fastopen_remove(sk, req, false);
sk->sk_shutdown = SHUTDOWN_MASK;