From 678550c651aee051d66112933c87894f129b9355 Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Fri, 27 Jan 2017 16:24:39 -0800 Subject: [PATCH] tcp: include locally failed retries in retransmission stats Currently the retransmission stats are not incremented if the retransmit fails locally. But we always increment the other packet counters that track total packet/bytes sent. Awkwardly while we don't count these failed retransmits in RETRANSSEGS, we do count them in FAILEDRETRANS. If the qdisc is dropping many packets this could under-estimate TCP retransmission rate substantially from both SNMP or per-socket TCP_INFO stats. This patch changes this by always incrementing retransmission stats on retransmission attempts and failures. Another motivation is to properly track retransmists in SCM_TIMESTAMPING_OPT_STATS. Since SCM_TSTAMP_SCHED collection is triggered in tcp_transmit_skb(), If tp->total_retrans is incremented after the function, we'll always mis-count by the amount of the latest retransmission. Signed-off-by: Yuchung Cheng Signed-off-by: Soheil Hassas Yeganeh Acked-by: Neal Cardwell Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 671c695..7b2d876 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2771,6 +2771,13 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN) tcp_ecn_clear_syn(sk, skb); + /* Update global and local TCP statistics. */ + segs = tcp_skb_pcount(skb); + TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs); + if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); + tp->total_retrans += segs; + /* make sure skb->data is aligned on arches that require it * and check if ack-trimming & collapsing extended the headroom * beyond what csum_start can cover. @@ -2788,14 +2795,9 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) } if (likely(!err)) { - segs = tcp_skb_pcount(skb); - TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS; - /* Update global TCP statistics. */ - TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs); - if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) - __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); - tp->total_retrans += segs; + } else if (err != -EBUSY) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL); } return err; } @@ -2818,8 +2820,6 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) if (!tp->retrans_stamp) tp->retrans_stamp = tcp_skb_timestamp(skb); - } else if (err != -EBUSY) { - NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL); } if (tp->undo_retrans < 0) -- 2.7.4