tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp->prior_cwnd) added
in commit 8b8a321ff72c ("tcp: fix zero cwnd in tcp_cwnd_reduction")
can trigger, and without a repro we would have to spend
considerable time finding the bug.

Instead of complaining too late, we want to catch where
and when tp->snd_cwnd is set to an illegal value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Link: https://lore.kernel.org/r/20220405233538.947344-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp->prior_cwnd) added
in commit 8b8a321ff72c ("tcp: fix zero cwnd in tcp_cwnd_reduction")
can trigger, and without a repro we would have to spend
considerable time finding the bug.

Instead of complaining too late, we want to catch where
and when tp->snd_cwnd is set to an illegal value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Link: https://lore.kernel.org/r/20220405233538.947344-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp->prior_cwnd) added
in commit 8b8a321ff72c ("tcp: fix zero cwnd in tcp_cwnd_reduction")
can trigger, and without a repro we would have to spend
considerable time finding the bug.

Instead of complaining too late, we want to catch where
and when tp->snd_cwnd is set to an illegal value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Link: https://lore.kernel.org/r/20220405233538.947344-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp->prior_cwnd) added
in commit 8b8a321ff72c ("tcp: fix zero cwnd in tcp_cwnd_reduction")
can trigger, and without a repro we would have to spend
considerable time finding the bug.

Instead of complaining too late, we want to catch where
and when tp->snd_cwnd is set to an illegal value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Link: https://lore.kernel.org/r/20220405233538.947344-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp->prior_cwnd) added
in commit 8b8a321ff72c ("tcp: fix zero cwnd in tcp_cwnd_reduction")
can trigger, and without a repro we would have to spend
considerable time finding the bug.

Instead of complaining too late, we want to catch where
and when tp->snd_cwnd is set to an illegal value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Link: https://lore.kernel.org/r/20220405233538.947344-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

Replace HTTP links with HTTPS ones: IPv*

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each

Replace HTTP links with HTTPS ones: IPv*

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
If not .svg:
For each line:
If doesn't contain `\bxmlns\b`:
For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
If both the HTTP and HTTPS versions
return 200 OK and serve the same content:
Replace HTTP with HTTPS.

Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

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treewide: Add SPDX license identifier for more missed files

Add SPDX license identifiers to all files which:

- Have no license information of any form

- Have MODULE_LICENCE("GPL*") inside which

treewide: Add SPDX license identifier for more missed files

Add SPDX license identifiers to all files which:

- Have no license information of any form

- Have MODULE_LICENCE("GPL*") inside which was used in the initial
scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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tcp: consolidate congestion control undo functions

Most TCP congestion controls are using identical logic to undo
cwnd except BBR. This patch consolidates these similar functions
to the one used cur

tcp: consolidate congestion control undo functions

Most TCP congestion controls are using identical logic to undo
cwnd except BBR. This patch consolidates these similar functions
to the one used currently by Reno and others.

Suggested-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

tcp: add cwnd_undo functions to various tcp cc algorithms

congestion control algorithms that do not halve cwnd in their .ssthresh
should provide a .cwnd_undo rather than rely on current fallback whi

tcp: add cwnd_undo functions to various tcp cc algorithms

congestion control algorithms that do not halve cwnd in their .ssthresh
should provide a .cwnd_undo rather than rely on current fallback which
assumes reno halving (and thus doubles the cwnd).

All of these do 'something else' in their .ssthresh implementation, thus
store the cwnd on loss and provide .undo_cwnd to restore it again.

A followup patch will remove the fallback and all algorithms will
need to provide a .cwnd_undo function.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

tcp: add tcp_in_slow_start helper

Add a helper to test the slow start condition in various congestion
control modules and other places. This is to prepare a slight improvement
in policy as to exactl

tcp: add tcp_in_slow_start helper

Add a helper to test the slow start condition in various congestion
control modules and other places. This is to prepare a slight improvement
in policy as to exactly when to slow start.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Nandita Dukkipati <nanditad@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

tcp: whitespace fixes

Fix places where there is space before tab, long lines, and
awkward if(){, double spacing etc. Add blank line after declaration/initialization.

Signed-off-by: Stephen Hemminge

tcp: whitespace fixes

Fix places where there is space before tab, long lines, and
awkward if(){, double spacing etc. Add blank line after declaration/initialization.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

tcp: remove in_flight parameter from cong_avoid() methods

Commit e114a710aa505 ("tcp: fix cwnd limited checking to improve
congestion control") obsoleted in_flight parameter from
tcp_is_cwnd_limited

tcp: remove in_flight parameter from cong_avoid() methods

Commit e114a710aa505 ("tcp: fix cwnd limited checking to improve
congestion control") obsoleted in_flight parameter from
tcp_is_cwnd_limited() and its callers.

This patch does the removal as promised.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

tcp: remove unused min_cwnd member of tcp_congestion_ops

Commit 684bad110757 "tcp: use PRR to reduce cwin in CWR state" removed all
calls to min_cwnd, so we can safely remove it.
Also, remove tcp_re

tcp: remove unused min_cwnd member of tcp_congestion_ops

Commit 684bad110757 "tcp: use PRR to reduce cwin in CWR state" removed all
calls to min_cwnd, so we can safely remove it.
Also, remove tcp_reno_min_cwnd because it was only used for min_cwnd.

Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

tcp: properly handle stretch acks in slow start

Slow start now increases cwnd by 1 if an ACK acknowledges some packets,
regardless the number of packets. Consequently slow start performance
is highl

tcp: properly handle stretch acks in slow start

Slow start now increases cwnd by 1 if an ACK acknowledges some packets,
regardless the number of packets. Consequently slow start performance
is highly dependent on the degree of the stretch ACKs caused by
receiver or network ACK compression mechanisms (e.g., delayed-ACK,
GRO, etc). But slow start algorithm is to send twice the amount of
packets of packets left so it should process a stretch ACK of degree
N as if N ACKs of degree 1, then exits when cwnd exceeds ssthresh. A
follow up patch will use the remainder of the N (if greater than 1)
to adjust cwnd in the congestion avoidance phase.

In addition this patch retires the experimental limited slow start
(LSS) feature. LSS has multiple drawbacks but questionable benefit. The
fractional cwnd increase in LSS requires a loop in slow start even
though it's rarely used. Configuring such an increase step via a global
sysctl on different BDPS seems hard. Finally and most importantly the
slow start overshoot concern is now better covered by the Hybrid slow
start (hystart) enabled by default.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

tcp: mark tcp_congestion_ops read_mostly

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

[TCP]: Cong.ctrl modules: remove unused good_ack from cong_avoid

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David

[TCP]: Cong.ctrl modules: remove unused good_ack from cong_avoid

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

[TCP]: remove unused argument to cong_avoid op

None of the existing TCP congestion controls use the rtt value pased
in the ca_ops->cong_avoid interface. Which is lucky because seq_rtt
could have be

[TCP]: remove unused argument to cong_avoid op

None of the existing TCP congestion controls use the rtt value pased
in the ca_ops->cong_avoid interface. Which is lucky because seq_rtt
could have been -1 when handling a duplicate ack.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

[TCP] Highspeed: Limited slow-start is nowadays in tcp_slow_start

Reuse limited slow-start (RFC3742) included into tcp_cong instead
of having another implementation in High Speed TCP.

Signed-off-by

[TCP] Highspeed: Limited slow-start is nowadays in tcp_slow_start

Reuse limited slow-start (RFC3742) included into tcp_cong instead
of having another implementation in High Speed TCP.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

[NET] IPV4: Fix whitespace errors.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

[TCP] Congestion control (modulo lp, bic): use BUILD_BUG_ON

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

[TCP] tcp_highspeed: Fix AI updates.

I think there is still a problem with the AIMD parameter update in
HighSpeed TCP code.

Line 125~138 of the code (net/ipv4/tcp_highspeed.c):

/* Update AIMD par

[TCP] tcp_highspeed: Fix AI updates.

I think there is still a problem with the AIMD parameter update in
HighSpeed TCP code.

Line 125~138 of the code (net/ipv4/tcp_highspeed.c):

/* Update AIMD parameters */
if (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd) {
while (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd &&
ca->ai < HSTCP_AIMD_MAX - 1)
ca->ai++;
} else if (tp->snd_cwnd < hstcp_aimd_vals[ca->ai].cwnd) {
while (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd &&
ca->ai > 0)
ca->ai--;

In fact, the second part (decreasing ca->ai) never decreases since the
while loop's inequality is in the reverse direction. This leads to
unfairness with multiple flows (once a flow happens to enjoy a higher
ca->ai, it keeps enjoying that even its cwnd decreases)

Here is a tentative fix (I also added a comment, trying to keep the
change clear):

Acked-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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Remove obsolete #include <linux/config.h>

Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

[TCP]: Limited slow start for Highspeed TCP

Implementation of RFC3742 limited slow start. Added as part
of the TCP highspeed congestion control module.

Signed-off-by: Stephen Hemminger <shemminger@

[TCP]: Limited slow start for Highspeed TCP

Implementation of RFC3742 limited slow start. Added as part
of the TCP highspeed congestion control module.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

[TCP] tcp_highspeed: Fix problem observed by Xiaoliang (David) Wei

When snd_cwnd is smaller than 38 and the connection is in
congestion avoidance phase (snd_cwnd > snd_ssthresh), the snd_cwnd
seems

[TCP] tcp_highspeed: Fix problem observed by Xiaoliang (David) Wei

When snd_cwnd is smaller than 38 and the connection is in
congestion avoidance phase (snd_cwnd > snd_ssthresh), the snd_cwnd
seems to stop growing.

The additive increase was confused because C array's are 0 based.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

[TCP]: Fix snd_cwnd adjustments in tcp_highspeed.c

Xiaoliang (David) Wei wrote:
> Hi gurus,
>
> I am reading the code of tcp_highspeed.c in the kernel and have a
> question on the hstcp_cong_avo

[TCP]: Fix snd_cwnd adjustments in tcp_highspeed.c

Xiaoliang (David) Wei wrote:
> Hi gurus,
>
> I am reading the code of tcp_highspeed.c in the kernel and have a
> question on the hstcp_cong_avoid function, specifically the following
> AI part (line 136~143 in net/ipv4/tcp_highspeed.c ):
>
> /* Do additive increase */
> if (tp->snd_cwnd < tp->snd_cwnd_clamp) {
> tp->snd_cwnd_cnt += ca->ai;
> if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
> tp->snd_cwnd++;
> tp->snd_cwnd_cnt -= tp->snd_cwnd;
> }
> }
>
> In this part, when (tp->snd_cwnd_cnt == tp->snd_cwnd),
> snd_cwnd_cnt will be -1... snd_cwnd_cnt is defined as u16, will this
> small chance of getting -1 becomes a problem?
> Shall we change it by reversing the order of the cwnd++ and cwnd_cnt -=
> cwnd?

Absolutely correct. Thanks.

Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...