Merge branch 'tcp-RACK-loss-recovery-bug-fixes'

Yuchung Cheng says:

====================
tcp: RACK loss recovery bug fixes

This patch set has four minor bug fixes in TCP RACK loss recovery.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 14 insertions, 15 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 075c559570e6..9550cc42de2d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2329,6 +2329,7 @@ static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss)
         }
         tp->snd_cwnd_stamp = tcp_jiffies32;
         tp->undo_marker = 0;
+        tp->rack.advanced = 1; /* Force RACK to re-exam losses */
 }
 
 static inline bool tcp_may_undo(const struct tcp_sock *tp)
diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
index d3ea89020c69..3a81720ac0c4 100644
--- a/net/ipv4/tcp_recovery.c
+++ b/net/ipv4/tcp_recovery.c
@@ -55,7 +55,8 @@ static void tcp_rack_detect_loss(struct sock *sk, u32 *reo_timeout)
          * to queuing or delayed ACKs.
          */
         reo_wnd = 1000;
-        if ((tp->rack.reord || !tp->lost_out) && min_rtt != ~0U) {
+        if ((tp->rack.reord || inet_csk(sk)->icsk_ca_state < TCP_CA_Recovery) &&
+            min_rtt != ~0U) {
                 reo_wnd = max((min_rtt >> 2) * tp->rack.reo_wnd_steps, reo_wnd);
                 reo_wnd = min(reo_wnd, tp->srtt_us >> 3);
         }
@@ -79,12 +80,12 @@ static void tcp_rack_detect_loss(struct sock *sk, u32 *reo_timeout)
                  */
                 remaining = tp->rack.rtt_us + reo_wnd -
                             tcp_stamp_us_delta(tp->tcp_mstamp, skb->skb_mstamp);
-                if (remaining < 0) {
+                if (remaining <= 0) {
                         tcp_rack_mark_skb_lost(sk, skb);
                         list_del_init(&skb->tcp_tsorted_anchor);
                 } else {
-                        /* Record maximum wait time (+1 to avoid 0) */
-                        *reo_timeout = max_t(u32, *reo_timeout, 1 + remaining);
+                        /* Record maximum wait time */
+                        *reo_timeout = max_t(u32, *reo_timeout, remaining);
                 }
         }
 }
@@ -116,13 +117,8 @@ void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
 {
         u32 rtt_us;
 
-        if (tp->rack.mstamp &&
-            !tcp_rack_sent_after(xmit_time, tp->rack.mstamp,
-                                 end_seq, tp->rack.end_seq))
-                return;
-
         rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time);
-        if (sacked & TCPCB_RETRANS) {
+        if (rtt_us < tcp_min_rtt(tp) && (sacked & TCPCB_RETRANS)) {
                 /* If the sacked packet was retransmitted, it's ambiguous
                  * whether the retransmission or the original (or the prior
                  * retransmission) was sacked.
@@ -133,13 +129,15 @@ void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
                  * so it's at least one RTT (i.e., retransmission is at least
                  * an RTT later).
                  */
-                if (rtt_us < tcp_min_rtt(tp))
-                        return;
+                return;
         }
-        tp->rack.rtt_us = rtt_us;
-        tp->rack.mstamp = xmit_time;
-        tp->rack.end_seq = end_seq;
         tp->rack.advanced = 1;
+        tp->rack.rtt_us = rtt_us;
+        if (tcp_rack_sent_after(xmit_time, tp->rack.mstamp,
+                                end_seq, tp->rack.end_seq)) {
+                tp->rack.mstamp = xmit_time;
+                tp->rack.end_seq = end_seq;
+        }
 }
 
 /* We have waited long enough to accommodate reordering. Mark the expired