[PATCH v3 net 1/5] tcp: feed correct number of pkts acked to cc modules also in recovery
flat view
STALE3123d
From: Ilpo Järvinen <hidden>
Date: 2018-03-13 10:25:25
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
Revision v3 of 3 in this series.
Revisions (3)
- v1 [diff vs current]
- v2 [diff vs current]
- v3 current
A miscalculation for the number of acknowledged packets occurs during RTO recovery whenever SACK is not enabled and a cumulative ACK covers any non-retransmitted skbs. The reason is that pkts_acked value calculated in tcp_clean_rtx_queue is not correct for slow start after RTO as it may include segments that were not lost and therefore did not need retransmissions in the slow start following the RTO. Then tcp_slow_start will add the excess into cwnd bloating it and triggering a burst. Instead, we want to pass only the number of retransmitted segments that were covered by the cumulative ACK (and potentially newly sent data segments too if the cumulative ACK covers that far). Signed-off-by: Ilpo Järvinen <redacted> --- net/ipv4/tcp_input.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9a1b3c1..4a26c09 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c@@ -3027,6 +3027,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack, long seq_rtt_us = -1L; long ca_rtt_us = -1L; u32 pkts_acked = 0; + u32 rexmit_acked = 0; + u32 newdata_acked = 0; u32 last_in_flight = 0; bool rtt_update; int flag = 0;
@@ -3056,8 +3058,10 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack, } if (unlikely(sacked & TCPCB_RETRANS)) { - if (sacked & TCPCB_SACKED_RETRANS) + if (sacked & TCPCB_SACKED_RETRANS) { tp->retrans_out -= acked_pcount; + rexmit_acked += acked_pcount; + } flag |= FLAG_RETRANS_DATA_ACKED; } else if (!(sacked & TCPCB_SACKED_ACKED)) { last_ackt = skb->skb_mstamp;
@@ -3070,6 +3074,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack, reord = start_seq; if (!after(scb->end_seq, tp->high_seq)) flag |= FLAG_ORIG_SACK_ACKED; + else + newdata_acked += acked_pcount; } if (sacked & TCPCB_SACKED_ACKED) {
@@ -3151,6 +3157,14 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack, } if (tcp_is_reno(tp)) { + /* Due to discontinuity on RTO in the artificial + * sacked_out calculations, TCP must restrict + * pkts_acked without SACK to rexmits and new data + * segments + */ + if (icsk->icsk_ca_state == TCP_CA_Loss) + pkts_acked = rexmit_acked + newdata_acked; + tcp_remove_reno_sacks(sk, pkts_acked); } else { int delta;
--
2.7.4