* [PATCH net 1/2] rxrpc: Fix the comments saying RFC8958 to be RFC8985
2026-09-25 19:15 [PATCH net 0/2] rxrpc: RACK-TLP fixes David Howells
@ 2026-09-25 19:15 ` David Howells
2026-09-25 19:15 ` [PATCH net 2/2] rxrpc: Fix RACK-TLP implementation David Howells
1 sibling, 0 replies; 3+ messages in thread
From: David Howells @ 2026-09-25 19:15 UTC (permalink / raw)
To: netdev
Cc: David Howells, Marc Dionne, Jakub Kicinski, David S. Miller,
Eric Dumazet, Paolo Abeni, Simon Horman, linux-afs, linux-kernel,
Jeffrey Altman, stable
Fix the comments saying RFC8958 to be RFC8985 - ie. The RACK-TLP Loss
Detection Algorithm for TCP.
Fixes: 7c482665931b ("rxrpc: Implement RACK/TLP to deal with transmission stalls [RFC8985]")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Eric Dumazet <edumazet@google.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@vger.kernel.org
---
net/rxrpc/ar-internal.h | 2 +-
net/rxrpc/input_rack.c | 20 ++++++++++----------
2 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 865f05fe37ab..f0c8cbcc5dd5 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -1264,7 +1264,7 @@ void rxrpc_tlp_send_probe(struct rxrpc_call *call);
void rxrpc_tlp_process_ack(struct rxrpc_call *call, struct rxrpc_ack_summary *summary);
void rxrpc_rack_timer_expired(struct rxrpc_call *call, ktime_t overran_by);
-/* Initialise TLP state [RFC8958 7.1]. */
+/* Initialise TLP state [RFC8985 7.1]. */
static inline void rxrpc_tlp_init(struct rxrpc_call *call)
{
call->tlp_serial = 0;
diff --git a/net/rxrpc/input_rack.c b/net/rxrpc/input_rack.c
index 9eb109ffba56..072e1d9ecb2e 100644
--- a/net/rxrpc/input_rack.c
+++ b/net/rxrpc/input_rack.c
@@ -1,5 +1,5 @@
// SPDX-License-Identifier: GPL-2.0-or-later
-/* RACK-TLP [RFC8958] Implementation
+/* RACK-TLP [RFC8985] Implementation
*
* Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
@@ -57,7 +57,7 @@ static unsigned long rxrpc_tq_nacks(const struct rxrpc_txqueue *tq)
/*
* Update the RACK state for the most recently sent packet that has been
- * delivered [RFC8958 6.2 Step 2].
+ * delivered [RFC8985 6.2 Step 2].
*/
static void rxrpc_rack_update(struct rxrpc_call *call,
struct rxrpc_ack_summary *summary,
@@ -98,7 +98,7 @@ static void rxrpc_rack_update(struct rxrpc_call *call,
}
/*
- * Detect data segment reordering [RFC8958 6.2 Step 3].
+ * Detect data segment reordering [RFC8985 6.2 Step 3].
*/
static void rxrpc_rack_detect_reordering(struct rxrpc_call *call,
struct rxrpc_ack_summary *summary,
@@ -143,7 +143,7 @@ void rxrpc_input_rack(struct rxrpc_call *call,
}
/*
- * Update the reordering window [RFC8958 6.2 Step 4]. Returns the updated
+ * Update the reordering window [RFC8985 6.2 Step 4]. Returns the updated
* duration of the reordering window.
*
* Note that the Rx protocol doesn't have a 'DSACK option' per se, but ACKs can
@@ -192,7 +192,7 @@ static ktime_t rxrpc_rack_update_reo_wnd(struct rxrpc_call *call,
}
/*
- * Detect losses [RFC8958 6.2 Step 5].
+ * Detect losses [RFC8985 6.2 Step 5].
*/
static ktime_t rxrpc_rack_detect_loss(struct rxrpc_call *call,
struct rxrpc_ack_summary *summary)
@@ -239,7 +239,7 @@ static ktime_t rxrpc_rack_detect_loss(struct rxrpc_call *call,
}
/*
- * Detect losses and set a timer to retry the detection [RFC8958 6.2 Step 5].
+ * Detect losses and set a timer to retry the detection [RFC8985 6.2 Step 5].
*/
void rxrpc_rack_detect_loss_and_arm_timer(struct rxrpc_call *call,
struct rxrpc_ack_summary *summary)
@@ -255,7 +255,7 @@ void rxrpc_rack_detect_loss_and_arm_timer(struct rxrpc_call *call,
}
/*
- * Handle RACK-TLP RTO expiration [RFC8958 6.3].
+ * Handle RACK-TLP RTO expiration [RFC8985 6.3].
*/
static void rxrpc_rack_mark_losses_on_rto(struct rxrpc_call *call)
{
@@ -285,7 +285,7 @@ static void rxrpc_rack_mark_losses_on_rto(struct rxrpc_call *call)
}
/*
- * Calculate the TLP loss probe timeout (PTO) [RFC8958 7.2].
+ * Calculate the TLP loss probe timeout (PTO) [RFC8985 7.2].
*/
ktime_t rxrpc_tlp_calc_pto(struct rxrpc_call *call, ktime_t now)
{
@@ -309,7 +309,7 @@ ktime_t rxrpc_tlp_calc_pto(struct rxrpc_call *call, ktime_t now)
}
/*
- * Send a TLP loss probe on PTO expiration [RFC8958 7.3].
+ * Send a TLP loss probe on PTO expiration [RFC8985 7.3].
*/
void rxrpc_tlp_send_probe(struct rxrpc_call *call)
{
@@ -356,7 +356,7 @@ void rxrpc_tlp_send_probe(struct rxrpc_call *call)
}
/*
- * Detect losses using the ACK of a TLP loss probe [RFC8958 7.4].
+ * Detect losses using the ACK of a TLP loss probe [RFC8985 7.4].
*/
void rxrpc_tlp_process_ack(struct rxrpc_call *call, struct rxrpc_ack_summary *summary)
{
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH net 2/2] rxrpc: Fix RACK-TLP implementation
2026-09-25 19:15 [PATCH net 0/2] rxrpc: RACK-TLP fixes David Howells
2026-09-25 19:15 ` [PATCH net 1/2] rxrpc: Fix the comments saying RFC8958 to be RFC8985 David Howells
@ 2026-09-25 19:15 ` David Howells
1 sibling, 0 replies; 3+ messages in thread
From: David Howells @ 2026-09-25 19:15 UTC (permalink / raw)
To: netdev
Cc: David Howells, Marc Dionne, Jakub Kicinski, David S. Miller,
Eric Dumazet, Paolo Abeni, Simon Horman, linux-afs, linux-kernel,
Jeffrey Altman, stable
Fix the RACK-TLP implementation in the following ways:
(1) Move the "in/exiting Fast or RTO recovery" flags to the rxrpc_call
struct rather than rxrpc_ack_summary so that they persist beyond ACK
parsing to the next time rxrpc_congestion_management() happens (when
the next ACK is parsed). This allows those values to be accessed by
RACK-TLP when invoked by the Reorder timer expiring.
(2) In rxrpc_input_call_event(), rearm the RTO timer before the function
returns if no other timer is running and if DATA packets have been
sent but not yet ACK'd. This prevents us not having a timer set to
drive retransmission.
(3) In rxrpc_congestion_management(), initialise the TLP state when
entering the FAST_RETRANSMIT congestion control state, not every time
we process that state - otherwise TLP doesn't happen in that state.
(4) Don't reset segment_xmit_ts in rxrpc_rack_mark_lost() as that's called
from two places, one of which shouldn't do that. Instead, do it in
rxrpc_rack_detect_loss().
(5) In rxrpc_tlp_calc_pto(), check flight_size is at most one jumbo
packet's worth of subpackets in size, not just any non-zero value
(RFC8985 7.2 has a comparison against 1, so this is approximated
because we'll be sending jumbo packets if possible).
(6) In rxrpc_prepare_data_packet(), only increment call->tx_nr_resent if
the DATA packet being retransmitted was not previously transmitted
otherwise tx_nr_resent will keep getting bigger and cause RACK-TLP to
malfunction (the value is used in the in-flight calculation).
tx_nr_resent is decremented when a packet that has been retransmitted
is discarded - but only by 1 per packet.
Fixes: 7c482665931b ("rxrpc: Implement RACK/TLP to deal with transmission stalls [RFC8985]")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: Eric Dumazet <edumazet@google.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@vger.kernel.org
---
net/rxrpc/ar-internal.h | 4 ++--
net/rxrpc/call_event.c | 13 +++++++++++++
net/rxrpc/input.c | 10 ++++++----
net/rxrpc/input_rack.c | 8 ++++----
net/rxrpc/output.c | 4 ++--
5 files changed, 27 insertions(+), 12 deletions(-)
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index f0c8cbcc5dd5..9c7b2e0817e7 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -818,6 +818,8 @@ struct rxrpc_call {
u16 cong_dup_acks; /* Count of ACKs showing missing packets */
u16 cong_cumul_acks; /* Cumulative ACK count */
ktime_t cong_tstamp; /* Last time cwnd was changed */
+ bool cong_in_recovery:1; /* If we're in Fast/RTO recovery */
+ bool cong_exiting_recovery:1; /* If we're leaving Fast/RTO recovery */
/* RACK-TLP [RFC8985] state. */
ktime_t rack_xmit_ts; /* Latest transmission timestamp */
@@ -896,8 +898,6 @@ struct rxrpc_ack_summary {
bool retrans_timeo:1; /* T if reTx due to timeout happened */
bool need_retransmit:1; /* T if we need transmission */
bool rtt_sample_avail:1; /* T if RTT sample available */
- bool in_fast_or_rto_recovery:1;
- bool exiting_fast_or_rto_recovery:1;
bool tlp_probe_acked:1; /* T if the TLP probe seq was acked */
u8 /*enum rxrpc_congest_change*/ change;
};
diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index 21be9c86d7a7..07e9aac42163 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -440,6 +440,19 @@ bool rxrpc_input_call_event(struct rxrpc_call *call)
rxrpc_propose_ack_input_data);
}
+ /* Need to rearm the RTO timer if we don't start the TLP-PTO
+ * timer [RFC8985 7.3].
+ */
+ if (call->rack_timer_mode == RXRPC_CALL_RACKTIMER_OFF &&
+ rxrpc_tx_in_flight(call) > 0) {
+ ktime_t rto = rxrpc_get_rto_backoff(call, true);
+
+ call->rack_timer_mode = RXRPC_CALL_RACKTIMER_RTO;
+ call->rack_timo_at = ktime_add(ktime_get_real(), rto);
+ trace_rxrpc_rack_timer(call, rto, false);
+ trace_rxrpc_timer_set(call, rto, rxrpc_timer_trace_rack_rto);
+ }
+
/* Make sure the timer is restarted */
if (!__rxrpc_call_is_complete(call)) {
ktime_t next = READ_ONCE(call->expect_term_by), delay;
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 73cafe6bfa9f..0e9f6a1e9f00 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -34,6 +34,8 @@ static void rxrpc_congestion_management(struct rxrpc_call *call,
{
summary->change = rxrpc_cong_no_change;
summary->in_flight = rxrpc_tx_in_flight(call);
+ call->cong_in_recovery = false;
+ call->cong_exiting_recovery = false;
if (test_and_clear_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags)) {
summary->retrans_timeo = true;
@@ -106,12 +108,12 @@ static void rxrpc_congestion_management(struct rxrpc_call *call,
call->cong_extra = 0;
call->cong_dup_acks = 0;
summary->need_retransmit = true;
- summary->in_fast_or_rto_recovery = true;
+ call->cong_in_recovery = true;
+ rxrpc_tlp_init(call);
goto out;
case RXRPC_CA_FAST_RETRANSMIT:
- rxrpc_tlp_init(call);
- summary->in_fast_or_rto_recovery = true;
+ call->cong_in_recovery = true;
if (!summary->new_low_snack) {
if (summary->nr_new_sacks == 0)
call->cong_cwnd += 1;
@@ -125,7 +127,7 @@ static void rxrpc_congestion_management(struct rxrpc_call *call,
summary->change = rxrpc_cong_progress;
call->cong_cwnd = call->cong_ssthresh;
if (call->acks_nr_snacks == 0) {
- summary->exiting_fast_or_rto_recovery = true;
+ call->cong_exiting_recovery = true;
goto resume_normality;
}
}
diff --git a/net/rxrpc/input_rack.c b/net/rxrpc/input_rack.c
index 072e1d9ecb2e..66ef2fc6d3d9 100644
--- a/net/rxrpc/input_rack.c
+++ b/net/rxrpc/input_rack.c
@@ -29,7 +29,6 @@ static void rxrpc_rack_mark_lost(struct rxrpc_call *call,
} else {
call->tx_nr_lost++;
}
- tq->segment_xmit_ts[ix] = UINT_MAX;
}
/*
@@ -174,14 +173,14 @@ static ktime_t rxrpc_rack_update_reo_wnd(struct rxrpc_call *call,
call->rack_dsack_round = snd_nxt;
call->rack_reo_wnd_mult++;
call->rack_reo_wnd_persist = 16;
- } else if (summary->exiting_fast_or_rto_recovery) {
+ } else if (call->cong_exiting_recovery) {
call->rack_reo_wnd_persist--;
if (call->rack_reo_wnd_persist <= 0)
call->rack_reo_wnd_mult = 1;
}
if (!call->rack_reordering_seen) {
- if (summary->in_fast_or_rto_recovery)
+ if (call->cong_in_recovery)
return 0;
if (call->acks_nr_sacks >= dup_thresh)
return 0;
@@ -227,6 +226,7 @@ static ktime_t rxrpc_rack_detect_loss(struct rxrpc_call *call,
remaining = ktime_sub(ktime_add(xmit_ts, lost_after), now);
if (remaining <= 0) {
rxrpc_rack_mark_lost(call, tq, ix);
+ tq->segment_xmit_ts[ix] = UINT_MAX;
trace_rxrpc_rack_detect_loss(call, summary, seq);
} else {
timeout = max(remaining, timeout);
@@ -297,7 +297,7 @@ ktime_t rxrpc_tlp_calc_pto(struct rxrpc_call *call, ktime_t now)
if (call->rtt_count > 0) {
/* Use 2*SRTT as the timeout. */
pto = ns_to_ktime(call->srtt_us * NSEC_PER_USEC / 4);
- if (flight_size)
+ if (flight_size <= call->peer->pmtud_jumbo)
pto = ktime_add(pto, call->tlp_max_ack_delay);
} else {
pto = NSEC_PER_SEC;
diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 88cad087f13b..9e082f740331 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -576,8 +576,8 @@ static size_t rxrpc_prepare_data_packet(struct rxrpc_call *call,
call->tx_nr_lost--;
if (req->retrans) {
__set_bit(ix, &tq->ever_retransmitted);
- __set_bit(ix, &tq->segment_retransmitted);
- call->tx_nr_resent++;
+ if (!__test_and_set_bit(ix, &tq->segment_retransmitted))
+ call->tx_nr_resent++;
} else {
call->tx_nr_sent++;
start_tlp = true;
^ permalink raw reply [flat|nested] 3+ messages in thread