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 <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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623df484a7
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@ -1125,6 +1125,7 @@ static inline void tcp_openreq_init(struct request_sock *req,
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req->cookie_ts = 0;
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tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
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tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
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tcp_rsk(req)->snt_synack = 0;
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req->mss = rx_opt->mss_clamp;
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req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
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ireq->tstamp_ok = rx_opt->tstamp_ok;
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@ -5983,6 +5983,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
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* need req so release it.
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*/
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if (req) {
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tcp_synack_rtt_meas(sk, req);
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reqsk_fastopen_remove(sk, req, false);
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} else {
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/* Make sure socket is routed, for
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@ -868,6 +868,8 @@ static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst,
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ireq->rmt_addr,
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ireq->opt);
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err = net_xmit_eval(err);
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if (!tcp_rsk(req)->snt_synack && !err)
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tcp_rsk(req)->snt_synack = tcp_time_stamp;
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}
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return err;
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@ -1382,6 +1384,7 @@ static int tcp_v4_conn_req_fastopen(struct sock *sk,
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struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
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const struct inet_request_sock *ireq = inet_rsk(req);
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struct sock *child;
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int err;
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req->retrans = 0;
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req->sk = NULL;
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@ -1393,8 +1396,11 @@ static int tcp_v4_conn_req_fastopen(struct sock *sk,
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kfree_skb(skb_synack);
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return -1;
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}
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ip_build_and_send_pkt(skb_synack, sk, ireq->loc_addr,
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ireq->rmt_addr, ireq->opt);
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err = ip_build_and_send_pkt(skb_synack, sk, ireq->loc_addr,
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ireq->rmt_addr, ireq->opt);
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err = net_xmit_eval(err);
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if (!err)
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tcp_rsk(req)->snt_synack = tcp_time_stamp;
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/* XXX (TFO) - is it ok to ignore error and continue? */
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spin_lock(&queue->fastopenq->lock);
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@ -1612,7 +1618,6 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
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isn = tcp_v4_init_sequence(skb);
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}
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tcp_rsk(req)->snt_isn = isn;
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tcp_rsk(req)->snt_synack = tcp_time_stamp;
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if (dst == NULL) {
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dst = inet_csk_route_req(sk, &fl4, req);
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@ -1650,6 +1655,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
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if (err || want_cookie)
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goto drop_and_free;
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tcp_rsk(req)->snt_synack = tcp_time_stamp;
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tcp_rsk(req)->listener = NULL;
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/* Add the request_sock to the SYN table */
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inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
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@ -1169,7 +1169,6 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
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}
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have_isn:
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tcp_rsk(req)->snt_isn = isn;
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tcp_rsk(req)->snt_synack = tcp_time_stamp;
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if (security_inet_conn_request(sk, skb, req))
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goto drop_and_release;
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@ -1180,6 +1179,7 @@ have_isn:
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want_cookie)
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goto drop_and_free;
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tcp_rsk(req)->snt_synack = tcp_time_stamp;
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tcp_rsk(req)->listener = NULL;
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inet6_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
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return 0;
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