git: 9155d4b273ff - main - tcp: retire do_newsack - always adhere to RFC6675 SACK
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Date: Fri, 05 Dec 2025 13:10:59 UTC
The branch main has been updated by rscheff:
URL: https://cgit.FreeBSD.org/src/commit/?id=9155d4b273ffc07e81e2cb0bcedfac570d14a303
commit 9155d4b273ffc07e81e2cb0bcedfac570d14a303
Author: Richard Scheffenegger <rscheff@FreeBSD.org>
AuthorDate: 2025-12-05 11:29:15 +0000
Commit: Richard Scheffenegger <rscheff@FreeBSD.org>
CommitDate: 2025-12-05 13:10:37 +0000
tcp: retire do_newsack - always adhere to RFC6675 SACK
Depreciation notice for net.inet.tcp.newsack is in 15.0.
Remove this tunable for HEAD, streamlining the code slightly.
Reviewed by: tuexen, cc, nickbanks_netflix.com, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D54072
---
sys/netinet/tcp_input.c | 11 +++--------
sys/netinet/tcp_sack.c | 41 +----------------------------------------
sys/netinet/tcp_stacks/rack.c | 4 ++--
sys/netinet/tcp_var.h | 2 --
4 files changed, 6 insertions(+), 52 deletions(-)
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 0036a07384ae..c015995ffc7a 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -2535,8 +2535,7 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
}
if (th->th_ack == tp->snd_una) {
/* Check if this is a duplicate ACK. */
- if ((tp->t_flags & TF_SACK_PERMIT) &&
- V_tcp_do_newsack) {
+ if (tp->t_flags & TF_SACK_PERMIT) {
/*
* If SEG.ACK == SND.UNA, RFC 6675 requires a
* duplicate ACK to selectively acknowledge
@@ -2613,7 +2612,6 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
goto drop;
} else if (tp->t_dupacks == tcprexmtthresh ||
(tp->t_flags & TF_SACK_PERMIT &&
- V_tcp_do_newsack &&
tp->sackhint.sacked_bytes >
(tcprexmtthresh - 1) * maxseg)) {
enter_recovery:
@@ -2780,8 +2778,7 @@ enter_recovery:
* from the left side. Such partial ACKs should not be
* counted as dupacks here.
*/
- if (V_tcp_do_newsack &&
- tcp_is_sack_recovery(tp, &to) &&
+ if (tcp_is_sack_recovery(tp, &to) &&
(((tp->t_rxtshift == 0) && (sack_changed != SACK_NOCHANGE)) ||
((tp->t_rxtshift > 0) && (sack_changed == SACK_NEWLOSS))) &&
(tp->snd_nxt == tp->snd_max)) {
@@ -4120,13 +4117,11 @@ tcp_compute_pipe(struct tcpcb *tp)
if (tp->t_fb->tfb_compute_pipe != NULL) {
pipe = (*tp->t_fb->tfb_compute_pipe)(tp);
- } else if (V_tcp_do_newsack) {
+ } else {
pipe = tp->snd_max - tp->snd_una +
tp->sackhint.sack_bytes_rexmit -
tp->sackhint.sacked_bytes -
tp->sackhint.lost_bytes;
- } else {
- pipe = tp->snd_nxt - tp->snd_fack + tp->sackhint.sack_bytes_rexmit;
}
return (imax(pipe, 0));
}
diff --git a/sys/netinet/tcp_sack.c b/sys/netinet/tcp_sack.c
index 13cc7b0de157..f31e88eda41a 100644
--- a/sys/netinet/tcp_sack.c
+++ b/sys/netinet/tcp_sack.c
@@ -126,28 +126,6 @@ SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(tcp_do_sack), 0,
"Enable/Disable TCP SACK support");
-VNET_DEFINE(int, tcp_do_newsack) = 1;
-
-static int
-sysctl_net_inet_tcp_sack_revised(SYSCTL_HANDLER_ARGS)
-{
- int error;
- int new;
-
- new = V_tcp_do_newsack;
- error = sysctl_handle_int(oidp, &new, 0, req);
- if (error == 0 && req->newptr) {
- V_tcp_do_newsack = new;
- gone_in(16, "net.inet.tcp.sack.revised will be deprecated."
- " net.inet.tcp.sack.enable will always follow RFC6675 SACK.\n");
- }
- return (error);
-}
-
-SYSCTL_PROC(_net_inet_tcp_sack, OID_AUTO, revised, CTLFLAG_VNET | CTLFLAG_RW | CTLTYPE_INT,
- &VNET_NAME(tcp_do_newsack), 0, sysctl_net_inet_tcp_sack_revised, "CU",
- "Use revised SACK loss recovery per RFC 6675");
-
VNET_DEFINE(int, tcp_do_lrd) = 1;
SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, lrd, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(tcp_do_lrd), 1,
@@ -1013,8 +991,7 @@ tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th, u_int *maxsegp)
* the trailing packets of a window are lost and no further data
* is available for sending.
*/
- if ((V_tcp_do_newsack) &&
- SEQ_LT(th->th_ack, tp->snd_recover) &&
+ if (SEQ_LT(th->th_ack, tp->snd_recover) &&
TAILQ_EMPTY(&tp->snd_holes) &&
(tp->sackhint.delivered_data > 0)) {
/*
@@ -1079,22 +1056,6 @@ tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt)
}
KASSERT(SEQ_LT(hole->start, hole->end),
("%s: SEQ_GEQ(hole.start, hole.end)", __func__));
- if (!(V_tcp_do_newsack)) {
- KASSERT(SEQ_LT(hole->start, tp->snd_fack),
- ("%s: SEG_GEQ(hole.start, snd.fack)", __func__));
- KASSERT(SEQ_LT(hole->end, tp->snd_fack),
- ("%s: SEG_GEQ(hole.end, snd.fack)", __func__));
- KASSERT(SEQ_LT(hole->rxmit, tp->snd_fack),
- ("%s: SEQ_GEQ(hole.rxmit, snd.fack)", __func__));
- if (SEQ_GEQ(hole->start, hole->end) ||
- SEQ_GEQ(hole->start, tp->snd_fack) ||
- SEQ_GEQ(hole->end, tp->snd_fack) ||
- SEQ_GEQ(hole->rxmit, tp->snd_fack)) {
- log(LOG_CRIT,"tcp: invalid SACK hole (%u-%u,%u) vs fwd ack %u, ignoring.\n",
- hole->start, hole->end, hole->rxmit, tp->snd_fack);
- return (NULL);
- }
- }
return (hole);
}
diff --git a/sys/netinet/tcp_stacks/rack.c b/sys/netinet/tcp_stacks/rack.c
index 9ed26d5a617b..76bf8f2e3b17 100644
--- a/sys/netinet/tcp_stacks/rack.c
+++ b/sys/netinet/tcp_stacks/rack.c
@@ -5393,7 +5393,7 @@ rack_ack_received(struct tcpcb *tp, struct tcp_rack *rack, uint32_t th_ack, uint
log.u_bbr.flex4 = tp->t_ccv.nsegs;
log.u_bbr.flex5 = labc_to_use;
log.u_bbr.flex6 = prior_cwnd;
- log.u_bbr.flex7 = V_tcp_do_newsack;
+ log.u_bbr.flex7 = 1; /* always doing RFC6675 SACK */
log.u_bbr.flex8 = 1;
lgb = tcp_log_event(tp, NULL, NULL, NULL, BBR_LOG_CWND, 0,
0, &log, false, NULL, __func__, __LINE__,&tv);
@@ -5508,7 +5508,7 @@ rack_post_recovery(struct tcpcb *tp, uint32_t th_ack)
log.u_bbr.flex4 = tp->t_ccv.nsegs;
log.u_bbr.flex5 = V_tcp_abc_l_var;
log.u_bbr.flex6 = orig_cwnd;
- log.u_bbr.flex7 = V_tcp_do_newsack;
+ log.u_bbr.flex7 = 1; /* always doing RFC6675 SACK */
log.u_bbr.pkts_out = rack->r_ctl.rc_prr_sndcnt;
log.u_bbr.flex8 = 2;
tcp_log_event(tp, NULL, NULL, NULL, BBR_LOG_CWND, 0,
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index f9297be46af7..7f836f5a1df4 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -1308,7 +1308,6 @@ VNET_DECLARE(int, tcp_tolerate_missing_ts);
VNET_DECLARE(int, tcp_do_rfc3042);
VNET_DECLARE(int, tcp_do_rfc3390);
VNET_DECLARE(int, tcp_do_rfc3465);
-VNET_DECLARE(int, tcp_do_newsack);
VNET_DECLARE(int, tcp_do_sack);
VNET_DECLARE(int, tcp_do_tso);
VNET_DECLARE(int, tcp_ecn_maxretries);
@@ -1359,7 +1358,6 @@ VNET_DECLARE(struct inpcbinfo, tcbinfo);
#define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042)
#define V_tcp_do_rfc3390 VNET(tcp_do_rfc3390)
#define V_tcp_do_rfc3465 VNET(tcp_do_rfc3465)
-#define V_tcp_do_newsack VNET(tcp_do_newsack)
#define V_tcp_do_sack VNET(tcp_do_sack)
#define V_tcp_do_tso VNET(tcp_do_tso)
#define V_tcp_ecn_maxretries VNET(tcp_ecn_maxretries)