Konstantin Demin
8cbaf1dea2
3rd patchs (in alphabetical order): - bbr3 - ntsync5 - openwrt - pf-kernel - xanmod - zen no configuration changes for now
98 lines
3.9 KiB
Diff
98 lines
3.9 KiB
Diff
From a4d44bce49f61f8755f558dc40edff5f8958b7c6 Mon Sep 17 00:00:00 2001
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From: Neal Cardwell <ncardwell@google.com>
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Date: Wed, 1 May 2019 20:16:25 -0400
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Subject: [PATCH 08/19] net-tcp_bbr: v2: adjust skb tx.in_flight upon split in
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tcp_fragment()
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When we fragment an skb that has already been sent, we need to update
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the tx.in_flight for the first skb in the resulting pair ("buff").
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Because we were not updating the tx.in_flight, the tx.in_flight value
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was inconsistent with the pcount of the "buff" skb (tx.in_flight would
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be too high). That meant that if the "buff" skb was lost, then
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bbr2_inflight_hi_from_lost_skb() would calculate an inflight_hi value
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that is too high. This could result in longer queues and higher packet
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loss.
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Packetdrill testing verified that without this commit, when the second
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half of an skb is SACKed and then later the first half of that skb is
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marked lost, the calculated inflight_hi was incorrect.
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Effort: net-tcp_bbr
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Origin-9xx-SHA1: 385f1ddc610798fab2837f9f372857438b25f874
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Origin-9xx-SHA1: a0eb099690af net-tcp_bbr: v2: fix tcp_fragment() tx.in_flight recomputation [prod feb 8 2021; use as a fixup]
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Origin-9xx-SHA1: 885503228153ff0c9114e net-tcp_bbr: v2: introduce tcp_skb_tx_in_flight_is_suspicious() helper for warnings
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Change-Id: I617f8cab4e9be7a0b8e8d30b047bf8645393354d
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Signed-off-by: Alexandre Frade <kernel@xanmod.org>
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---
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include/net/tcp.h | 15 +++++++++++++++
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net/ipv4/tcp_output.c | 26 +++++++++++++++++++++++++-
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2 files changed, 40 insertions(+), 1 deletion(-)
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--- a/include/net/tcp.h
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+++ b/include/net/tcp.h
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@@ -1283,6 +1283,21 @@ static inline bool tcp_skb_sent_after(u6
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return t1 > t2 || (t1 == t2 && after(seq1, seq2));
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}
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+/* If a retransmit failed due to local qdisc congestion or other local issues,
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+ * then we may have called tcp_set_skb_tso_segs() to increase the number of
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+ * segments in the skb without increasing the tx.in_flight. In all other cases,
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+ * the tx.in_flight should be at least as big as the pcount of the sk_buff. We
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+ * do not have the state to know whether a retransmit failed due to local qdisc
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+ * congestion or other local issues, so to avoid spurious warnings we consider
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+ * that any skb marked lost may have suffered that fate.
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+ */
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+static inline bool tcp_skb_tx_in_flight_is_suspicious(u32 skb_pcount,
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+ u32 skb_sacked_flags,
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+ u32 tx_in_flight)
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+{
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+ return (skb_pcount > tx_in_flight) && !(skb_sacked_flags & TCPCB_LOST);
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+}
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+
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/* These functions determine how the current flow behaves in respect of SACK
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* handling. SACK is negotiated with the peer, and therefore it can vary
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* between different flows.
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--- a/net/ipv4/tcp_output.c
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+++ b/net/ipv4/tcp_output.c
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@@ -1601,7 +1601,7 @@ int tcp_fragment(struct sock *sk, enum t
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{
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struct tcp_sock *tp = tcp_sk(sk);
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struct sk_buff *buff;
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- int old_factor;
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+ int old_factor, inflight_prev;
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long limit;
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int nlen;
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u8 flags;
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@@ -1676,6 +1676,30 @@ int tcp_fragment(struct sock *sk, enum t
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if (diff)
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tcp_adjust_pcount(sk, skb, diff);
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+
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+ inflight_prev = TCP_SKB_CB(skb)->tx.in_flight - old_factor;
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+ if (inflight_prev < 0) {
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+ WARN_ONCE(tcp_skb_tx_in_flight_is_suspicious(
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+ old_factor,
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+ TCP_SKB_CB(skb)->sacked,
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+ TCP_SKB_CB(skb)->tx.in_flight),
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+ "inconsistent: tx.in_flight: %u "
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+ "old_factor: %d mss: %u sacked: %u "
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+ "1st pcount: %d 2nd pcount: %d "
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+ "1st len: %u 2nd len: %u ",
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+ TCP_SKB_CB(skb)->tx.in_flight, old_factor,
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+ mss_now, TCP_SKB_CB(skb)->sacked,
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+ tcp_skb_pcount(skb), tcp_skb_pcount(buff),
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+ skb->len, buff->len);
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+ inflight_prev = 0;
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+ }
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+ /* Set 1st tx.in_flight as if 1st were sent by itself: */
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+ TCP_SKB_CB(skb)->tx.in_flight = inflight_prev +
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+ tcp_skb_pcount(skb);
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+ /* Set 2nd tx.in_flight with new 1st and 2nd pcounts: */
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+ TCP_SKB_CB(buff)->tx.in_flight = inflight_prev +
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+ tcp_skb_pcount(skb) +
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+ tcp_skb_pcount(buff);
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}
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/* Link BUFF into the send queue. */
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