Commit 168a8f58 authored by Jerry Chu's avatar Jerry Chu Committed by David S. Miller

tcp: TCP Fast Open Server - main code path

This patch adds the main processing path to complete the TFO server
patches.

A TFO request (i.e., SYN+data packet with a TFO cookie option) first
gets processed in tcp_v4_conn_request(). If it passes the various TFO
checks by tcp_fastopen_check(), a child socket will be created right
away to be accepted by applications, rather than waiting for the 3WHS
to finish.

In additon to the use of TFO cookie, a simple max_qlen based scheme
is put in place to fend off spoofed TFO attack.

When a valid ACK comes back to tcp_rcv_state_process(), it will cause
the state of the child socket to switch from either TCP_SYN_RECV to
TCP_ESTABLISHED, or TCP_FIN_WAIT1 to TCP_FIN_WAIT2. At this time
retransmission will resume for any unack'ed (data, FIN,...) segments.
Signed-off-by: default avatarH.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: default avatarDavid S. Miller <davem@davemloft.net>
parent 8336886f
......@@ -3127,6 +3127,12 @@ void tcp_rearm_rto(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
/* If the retrans timer is currently being used by Fast Open
* for SYN-ACK retrans purpose, stay put.
*/
if (tp->fastopen_rsk)
return;
if (!tp->packets_out) {
inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
} else {
......@@ -5895,7 +5901,9 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
tcp_send_synack(sk);
#if 0
/* Note, we could accept data and URG from this segment.
* There are no obstacles to make this.
* There are no obstacles to make this (except that we must
* either change tcp_recvmsg() to prevent it from returning data
* before 3WHS completes per RFC793, or employ TCP Fast Open).
*
* However, if we ignore data in ACKless segments sometimes,
* we have no reasons to accept it sometimes.
......@@ -5935,6 +5943,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
{
struct tcp_sock *tp = tcp_sk(sk);
struct inet_connection_sock *icsk = inet_csk(sk);
struct request_sock *req;
int queued = 0;
tp->rx_opt.saw_tstamp = 0;
......@@ -5990,7 +5999,14 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
return 0;
}
if (!tcp_validate_incoming(sk, skb, th, 0))
req = tp->fastopen_rsk;
if (req != NULL) {
BUG_ON(sk->sk_state != TCP_SYN_RECV &&
sk->sk_state != TCP_FIN_WAIT1);
if (tcp_check_req(sk, skb, req, NULL, true) == NULL)
goto discard;
} else if (!tcp_validate_incoming(sk, skb, th, 0))
return 0;
/* step 5: check the ACK field */
......@@ -6000,7 +6016,22 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
switch (sk->sk_state) {
case TCP_SYN_RECV:
if (acceptable) {
/* Once we leave TCP_SYN_RECV, we no longer
* need req so release it.
*/
if (req) {
reqsk_fastopen_remove(sk, req, false);
} else {
/* Make sure socket is routed, for
* correct metrics.
*/
icsk->icsk_af_ops->rebuild_header(sk);
tcp_init_congestion_control(sk);
tcp_mtup_init(sk);
tcp_init_buffer_space(sk);
tp->copied_seq = tp->rcv_nxt;
}
smp_mb();
tcp_set_state(sk, TCP_ESTABLISHED);
sk->sk_state_change(sk);
......@@ -6022,23 +6053,27 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
if (tp->rx_opt.tstamp_ok)
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
/* Make sure socket is routed, for
* correct metrics.
if (req) {
/* Re-arm the timer because data may
* have been sent out. This is similar
* to the regular data transmission case
* when new data has just been ack'ed.
*
* (TFO) - we could try to be more
* aggressive and retranmitting any data
* sooner based on when they were sent
* out.
*/
icsk->icsk_af_ops->rebuild_header(sk);
tcp_rearm_rto(sk);
} else
tcp_init_metrics(sk);
tcp_init_congestion_control(sk);
/* Prevent spurious tcp_cwnd_restart() on
* first data packet.
*/
tp->lsndtime = tcp_time_stamp;
tcp_mtup_init(sk);
tcp_initialize_rcv_mss(sk);
tcp_init_buffer_space(sk);
tcp_fast_path_on(tp);
} else {
return 1;
......@@ -6046,6 +6081,16 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
break;
case TCP_FIN_WAIT1:
/* If we enter the TCP_FIN_WAIT1 state and we are a
* Fast Open socket and this is the first acceptable
* ACK we have received, this would have acknowledged
* our SYNACK so stop the SYNACK timer.
*/
if (acceptable && req != NULL) {
/* We no longer need the request sock. */
reqsk_fastopen_remove(sk, req, false);
tcp_rearm_rto(sk);
}
if (tp->snd_una == tp->write_seq) {
struct dst_entry *dst;
......
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