1 files changed, 25 insertions, 9 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a16b01b537ba..068c8fb0d158 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2856,7 +2856,8 @@ static inline bool tcp_ack_update_rtt(struct sock *sk, const int flag,
          * left edge of the send window.
          * See draft-ietf-tcplw-high-performance-00, section 3.3.
          */
-        if (seq_rtt < 0 && tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
+        if (seq_rtt < 0 && tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
+            flag & FLAG_ACKED)
                 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
 
         if (seq_rtt < 0)
@@ -2871,14 +2872,19 @@ static inline bool tcp_ack_update_rtt(struct sock *sk, const int flag,
 }
 
 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
-static void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req)
+static void tcp_synack_rtt_meas(struct sock *sk, const u32 synack_stamp)
 {
         struct tcp_sock *tp = tcp_sk(sk);
         s32 seq_rtt = -1;
 
-        if (tp->lsndtime && !tp->total_retrans)
-                seq_rtt = tcp_time_stamp - tp->lsndtime;
-        tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, seq_rtt, -1);
+        if (synack_stamp && !tp->total_retrans)
+                seq_rtt = tcp_time_stamp - synack_stamp;
+
+        /* If the ACK acks both the SYNACK and the (Fast Open'd) data packets
+         * sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack()
+         */
+        if (!tp->srtt)
+                tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, seq_rtt, -1);
 }
 
 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
@@ -2981,6 +2987,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
         s32 seq_rtt = -1;
         s32 ca_seq_rtt = -1;
         ktime_t last_ackt = net_invalid_timestamp();
+        bool rtt_update;
 
         while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
                 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
@@ -3057,14 +3064,13 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
         if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
                 flag |= FLAG_SACK_RENEGING;
 
-        if (tcp_ack_update_rtt(sk, flag, seq_rtt, sack_rtt) ||
-            (flag & FLAG_ACKED))
-                tcp_rearm_rto(sk);
+        rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt, sack_rtt);
 
         if (flag & FLAG_ACKED) {
                 const struct tcp_congestion_ops *ca_ops
                         = inet_csk(sk)->icsk_ca_ops;
 
+                tcp_rearm_rto(sk);
                 if (unlikely(icsk->icsk_mtup.probe_size &&
                              !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
                         tcp_mtup_probe_success(sk);
@@ -3103,6 +3109,13 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 
                         ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
                 }
+        } else if (skb && rtt_update && sack_rtt >= 0 &&
+                   sack_rtt > (s32)(now - TCP_SKB_CB(skb)->when)) {
+                /* Do not re-arm RTO if the sack RTT is measured from data sent
+                 * after when the head was last (re)transmitted. Otherwise the
+                 * timeout may continue to extend in loss recovery.
+                 */
+                tcp_rearm_rto(sk);
         }
 
 #if FASTRETRANS_DEBUG > 0
@@ -5587,6 +5600,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
         struct request_sock *req;
         int queued = 0;
         bool acceptable;
+        u32 synack_stamp;
 
         tp->rx_opt.saw_tstamp = 0;
 
@@ -5669,9 +5683,11 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                  * so release it.
                  */
                 if (req) {
+                        synack_stamp = tcp_rsk(req)->snt_synack;
                         tp->total_retrans = req->num_retrans;
                         reqsk_fastopen_remove(sk, req, false);
                 } else {
+                        synack_stamp = tp->lsndtime;
                         /* Make sure socket is routed, for correct metrics. */
                         icsk->icsk_af_ops->rebuild_header(sk);
                         tcp_init_congestion_control(sk);
@@ -5694,7 +5710,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
                 tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
                 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
-                tcp_synack_rtt_meas(sk, req);
+                tcp_synack_rtt_meas(sk, synack_stamp);
 
                 if (tp->rx_opt.tstamp_ok)
                         tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;