git: e4ee2a39ade5 - stable/13 - tcp: Add PRR cwnd reduction for non-SACK loss
Richard Scheffenegger
rscheff at FreeBSD.org
Mon Aug 2 12:18:48 UTC 2021
The branch stable/13 has been updated by rscheff:
URL: https://cgit.FreeBSD.org/src/commit/?id=e4ee2a39ade5d6be38aed21f2fe1224c77f61af2
commit e4ee2a39ade5d6be38aed21f2fe1224c77f61af2
Author: Richard Scheffenegger <rscheff at FreeBSD.org>
AuthorDate: 2021-06-19 17:06:48 +0000
Commit: Richard Scheffenegger <rscheff at FreeBSD.org>
CommitDate: 2021-08-02 11:59:23 +0000
tcp: Add PRR cwnd reduction for non-SACK loss
This completes PRR cwnd reduction in all circumstances
for the base TCP stack (SACK loss recovery, ECN window reduction,
non-SACK loss recovery), preventing the arriving ACKs to
clock out new data at the old, too high rate. This
reduces the chance to induce additional losses while
recovering from loss (during congested network conditions).
For non-SACK loss recovery, each ACK is assumed to have
one MSS delivered. In order to prevent ACK-split attacks,
only one window worth of ACKs is considered to actually
have delivered new data.
MFC after: 6 weeks
Reviewed By: rrs, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29441
(cherry picked from commit 74d7fc8753a76851db6db556ff0f09de1fbb26d5)
---
sys/netinet/tcp_input.c | 56 ++++++++++++++++++++++++++++++++++++-------------
1 file changed, 41 insertions(+), 15 deletions(-)
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 6d86e43f07dd..f7ca4ce05200 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -2605,8 +2605,7 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
cc_ack_received(tp, th, nsegs,
CC_DUPACK);
if (V_tcp_do_prr &&
- IN_FASTRECOVERY(tp->t_flags) &&
- (tp->t_flags & TF_SACK_PERMIT)) {
+ IN_FASTRECOVERY(tp->t_flags)) {
tcp_do_prr_ack(tp, th, &to);
} else if ((tp->t_flags & TF_SACK_PERMIT) &&
(to.to_flags & TOF_SACK) &&
@@ -2682,8 +2681,16 @@ enter_recovery:
* snd_ssthresh is already updated by
* cc_cong_signal.
*/
- tp->sackhint.prr_delivered =
- tp->sackhint.sacked_bytes;
+ if ((tp->t_flags & TF_SACK_PERMIT) &&
+ (to.to_flags & TOF_SACK)) {
+ tp->sackhint.prr_delivered =
+ tp->sackhint.sacked_bytes;
+ } else {
+ tp->sackhint.prr_delivered =
+ imin(tp->snd_max - tp->snd_una,
+ imin(INT_MAX / 65536,
+ tp->t_dupacks) * maxseg);
+ }
tp->sackhint.recover_fs = max(1,
tp->snd_nxt - tp->snd_una);
}
@@ -3961,11 +3968,23 @@ tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
* (del_data) and an estimate of how many bytes are in the
* network.
*/
- del_data = tp->sackhint.delivered_data;
- if (V_tcp_do_rfc6675_pipe)
- pipe = tcp_compute_pipe(tp);
- else
- pipe = (tp->snd_nxt - tp->snd_fack) + tp->sackhint.sack_bytes_rexmit;
+ if (((tp->t_flags & TF_SACK_PERMIT) &&
+ (to->to_flags & TOF_SACK)) ||
+ (IN_CONGRECOVERY(tp->t_flags) &&
+ !IN_FASTRECOVERY(tp->t_flags))) {
+ del_data = tp->sackhint.delivered_data;
+ if (V_tcp_do_rfc6675_pipe)
+ pipe = tcp_compute_pipe(tp);
+ else
+ pipe = (tp->snd_nxt - tp->snd_fack) +
+ tp->sackhint.sack_bytes_rexmit;
+ } else {
+ if (tp->sackhint.prr_delivered < (tcprexmtthresh * maxseg +
+ tp->snd_recover - tp->snd_una))
+ del_data = maxseg;
+ pipe = imax(0, tp->snd_max - tp->snd_una -
+ imin(INT_MAX / 65536, tp->t_dupacks) * maxseg);
+ }
tp->sackhint.prr_delivered += del_data;
/*
* Proportional Rate Reduction
@@ -3978,9 +3997,9 @@ tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
tp->snd_ssthresh, tp->sackhint.recover_fs) -
tp->sackhint.prr_out;
} else {
- if (V_tcp_do_prr_conservative)
+ if (V_tcp_do_prr_conservative || (del_data == 0))
limit = tp->sackhint.prr_delivered -
- tp->sackhint.prr_out;
+ tp->sackhint.prr_out;
else
limit = imax(tp->sackhint.prr_delivered -
tp->sackhint.prr_out, del_data) +
@@ -3994,11 +4013,18 @@ tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
* accordingly.
*/
if (IN_FASTRECOVERY(tp->t_flags)) {
- tp->snd_cwnd = imax(maxseg, tp->snd_nxt - tp->snd_recover +
- tp->sackhint.sack_bytes_rexmit + (snd_cnt * maxseg));
+ if ((tp->t_flags & TF_SACK_PERMIT) &&
+ (to->to_flags & TOF_SACK)) {
+ tp->snd_cwnd = tp->snd_nxt - tp->snd_recover +
+ tp->sackhint.sack_bytes_rexmit +
+ (snd_cnt * maxseg);
+ } else {
+ tp->snd_cwnd = (tp->snd_max - tp->snd_una) +
+ (snd_cnt * maxseg);
+ }
} else if (IN_CONGRECOVERY(tp->t_flags))
- tp->snd_cwnd = imax(maxseg, pipe - del_data +
- (snd_cnt * maxseg));
+ tp->snd_cwnd = pipe - del_data + (snd_cnt * maxseg);
+ tp->snd_cwnd = imax(maxseg, tp->snd_cwnd);
}
/*
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