tcp: TCP Fast Open Server - take SYNACK RTT after completing 3WHS
When taking SYNACK RTT samples for servers using TCP Fast Open, fix
the code to ensure that we only call tcp_valid_rtt_meas() after we
receive the ACK that completes the 3-way handshake.
Previously we were always taking an RTT sample in
tcp_v4_syn_recv_sock(). However, for TCP Fast Open connections
tcp_v4_conn_req_fastopen() calls tcp_v4_syn_recv_sock() at the time we
receive the SYN. So for TFO we must wait until tcp_rcv_state_process()
to take the RTT sample.
To fix this, we wait until after TFO calls tcp_v4_syn_recv_sock()
before we set the snt_synack timestamp, since tcp_synack_rtt_meas()
already ensures that we only take a SYNACK RTT sample if snt_synack is
non-zero. To be careful, we only take a snt_synack timestamp when
a SYNACK transmit or retransmit succeeds.
Signed-off-by: Neal Cardwell <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index a718d0e..6feeccd 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1125,6 +1125,7 @@
req->cookie_ts = 0;
tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+ tcp_rsk(req)->snt_synack = 0;
req->mss = rx_opt->mss_clamp;
req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
ireq->tstamp_ok = rx_opt->tstamp_ok;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e2bec81..bb32668 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5983,6 +5983,7 @@
* need req so release it.
*/
if (req) {
+ tcp_synack_rtt_meas(sk, req);
reqsk_fastopen_remove(sk, req, false);
} else {
/* Make sure socket is routed, for
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 1e66f7f..0a7e020 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -868,6 +868,8 @@
ireq->rmt_addr,
ireq->opt);
err = net_xmit_eval(err);
+ if (!tcp_rsk(req)->snt_synack && !err)
+ tcp_rsk(req)->snt_synack = tcp_time_stamp;
}
return err;
@@ -1382,6 +1384,7 @@
struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
const struct inet_request_sock *ireq = inet_rsk(req);
struct sock *child;
+ int err;
req->retrans = 0;
req->sk = NULL;
@@ -1393,8 +1396,11 @@
kfree_skb(skb_synack);
return -1;
}
- ip_build_and_send_pkt(skb_synack, sk, ireq->loc_addr,
- ireq->rmt_addr, ireq->opt);
+ err = ip_build_and_send_pkt(skb_synack, sk, ireq->loc_addr,
+ ireq->rmt_addr, ireq->opt);
+ err = net_xmit_eval(err);
+ if (!err)
+ tcp_rsk(req)->snt_synack = tcp_time_stamp;
/* XXX (TFO) - is it ok to ignore error and continue? */
spin_lock(&queue->fastopenq->lock);
@@ -1612,7 +1618,6 @@
isn = tcp_v4_init_sequence(skb);
}
tcp_rsk(req)->snt_isn = isn;
- tcp_rsk(req)->snt_synack = tcp_time_stamp;
if (dst == NULL) {
dst = inet_csk_route_req(sk, &fl4, req);
@@ -1650,6 +1655,7 @@
if (err || want_cookie)
goto drop_and_free;
+ tcp_rsk(req)->snt_synack = tcp_time_stamp;
tcp_rsk(req)->listener = NULL;
/* Add the request_sock to the SYN table */
inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index cfeeeb7..d6212d6b 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1169,7 +1169,6 @@
}
have_isn:
tcp_rsk(req)->snt_isn = isn;
- tcp_rsk(req)->snt_synack = tcp_time_stamp;
if (security_inet_conn_request(sk, skb, req))
goto drop_and_release;
@@ -1180,6 +1179,7 @@
want_cookie)
goto drop_and_free;
+ tcp_rsk(req)->snt_synack = tcp_time_stamp;
tcp_rsk(req)->listener = NULL;
inet6_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
return 0;
