netdev - [PATCH net-next] tcp: account total lost packets properly

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Message-Id: <20201001210518.92495-1-ycheng@google.com>
Date:   Thu,  1 Oct 2020 14:05:18 -0700
From:   Yuchung Cheng <ycheng@...gle.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, ncardwell@...gle.com,
        Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH net-next] tcp: account total lost packets properly

The retransmission refactoring patch
686989700cab ("tcp: simplify tcp_mark_skb_lost")
does not properly update the total lost packet counter which may
break the policer mode in BBR. This patch fixes it.

Fixes: 686989700cab ("tcp: simplify tcp_mark_skb_lost")
Reported-by: Neal Cardwell <ncardwell@...gle.com>
Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp_input.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f7b3e37d2198..20f89078fa8d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1020,6 +1020,14 @@ static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
 		tp->retransmit_skb_hint = skb;
 }
 
+/* Sum the number of packets on the wire we have marked as lost, and
+ * notify the congestion control module that the given skb was marked lost.
+ */
+static void tcp_notify_skb_loss_event(struct tcp_sock *tp, const struct sk_buff *skb)
+{
+	tp->lost += tcp_skb_pcount(skb);
+}
+
 void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb)
 {
 	__u8 sacked = TCP_SKB_CB(skb)->sacked;
@@ -1036,10 +1044,12 @@ void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb)
 			tp->retrans_out -= tcp_skb_pcount(skb);
 			NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT,
 				      tcp_skb_pcount(skb));
+			tcp_notify_skb_loss_event(tp, skb);
 		}
 	} else {
 		tp->lost_out += tcp_skb_pcount(skb);
 		TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+		tcp_notify_skb_loss_event(tp, skb);
 	}
 }
 
-- 
2.28.0.709.gb0816b6eb0-goog