linux-stable.git/Documentation/networking/ip-sysctl.txt, branch linux-5.4.y

Documentation: fix sctp_wmem in ip-sysctl.rst

2022-08-03T09:59:40+00:00

[ Upstream commit aa709da0e032cee7c202047ecd75f437bb0126ed ]

Since commit 1033990ac5b2 ("sctp: implement memory accounting on tx path"),
SCTP has supported memory accounting on tx path where 'sctp_wmem' is used
by sk_wmem_schedule(). So we should fix the description for this option in
ip-sysctl.rst accordingly.

v1->v2:
  - Improve the description as Marcelo suggested.

Fixes: 1033990ac5b2 ("sctp: implement memory accounting on tx path")
Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Signed-off-by: David S. Miller 
Signed-off-by: Sasha Levin

ipv4: Fix data-races around sysctl_ip_dynaddr.

2022-07-21T18:59:22+00:00

[ Upstream commit e49e4aff7ec19b2d0d0957ee30e93dade57dab9e ]

While reading sysctl_ip_dynaddr, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima 
Signed-off-by: David S. Miller 
Signed-off-by: Sasha Levin

cipso: Fix data-races around sysctl.

2022-07-21T18:59:20+00:00

[ Upstream commit dd44f04b9214adb68ef5684ae87a81ba03632250 ]

While reading cipso sysctl variables, they can be changed concurrently.
So, we need to add READ_ONCE() to avoid data-races.

Fixes: 446fda4f2682 ("[NetLabel]: CIPSOv4 engine")
Signed-off-by: Kuniyuki Iwashima 
Acked-by: Paul Moore 
Signed-off-by: David S. Miller 
Signed-off-by: Sasha Levin

icmp: randomize the global rate limiter

2020-10-29T08:57:27+00:00

[ Upstream commit b38e7819cae946e2edf869e604af1e65a5d241c5 ]

Keyu Man reported that the ICMP rate limiter could be used
by attackers to get useful signal. Details will be provided
in an upcoming academic publication.

Our solution is to add some noise, so that the attackers
no longer can get help from the predictable token bucket limiter.

Fixes: 4cdf507d5452 ("icmp: add a global rate limitation")
Signed-off-by: Eric Dumazet 
Reported-by: Keyu Man 
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

tcp: increase tcp_max_syn_backlog max value

2019-10-31T21:02:01+00:00

tcp_max_syn_backlog default value depends on memory size
and TCP ehash size. Before this patch, the max value
was 2048 [1], which is considered too small nowadays.

Increase it to 4096 to match the recent SOMAXCONN change.

[1] This is with TCP ehash size being capped to 524288 buckets.

Signed-off-by: Eric Dumazet 
Cc: Willy Tarreau 
Cc: Yue Cao 
Signed-off-by: David S. Miller

net: increase SOMAXCONN to 4096

2019-10-31T21:01:40+00:00

SOMAXCONN is /proc/sys/net/core/somaxconn default value.

It has been defined as 128 more than 20 years ago.

Since it caps the listen() backlog values, the very small value has
caused numerous problems over the years, and many people had
to raise it on their hosts after beeing hit by problems.

Google has been using 1024 for at least 15 years, and we increased
this to 4096 after TCP listener rework has been completed, more than
4 years ago. We got no complain of this change breaking any
legacy application.

Many applications indeed setup a TCP listener with listen(fd, -1);
meaning they let the system select the backlog.

Raising SOMAXCONN lowers chance of the port being unavailable under
even small SYNFLOOD attack, and reduces possibilities of side channel
vulnerabilities.

Signed-off-by: Eric Dumazet 
Cc: Willy Tarreau 
Cc: Yue Cao 
Signed-off-by: David S. Miller

tcp: add new tcp_mtu_probe_floor sysctl

2019-08-09T20:03:30+00:00

The current implementation of TCP MTU probing can considerably
underestimate the MTU on lossy connections allowing the MSS to get down to
48. We have found that in almost all of these cases on our networks these
paths can handle much larger MTUs meaning the connections are being
artificially limited. Even though TCP MTU probing can raise the MSS back up
we have seen this not to be the case causing connections to be "stuck" with
an MSS of 48 when heavy loss is present.

Prior to pushing out this change we could not keep TCP MTU probing enabled
b/c of the above reasons. Now with a reasonble floor set we've had it
enabled for the past 6 months.

The new sysctl will still default to TCP_MIN_SND_MSS (48), but gives
administrators the ability to control the floor of MSS probing.

Signed-off-by: Josh Hunt 
Signed-off-by: Eric Dumazet 
Acked-by: Neal Cardwell 
Signed-off-by: David S. Miller

docs: admin-guide: move sysctl directory to it

2019-07-15T14:03:01+00:00

The stuff under sysctl describes /sys interface from userspace
point of view. So, add it to the admin-guide and remove the
:orphan: from its index file.

Signed-off-by: Mauro Carvalho Chehab

docs: sysctl: convert to ReST

2019-07-15T12:20:26+00:00

Rename the /proc/sys/ documentation files to ReST, using the
README file as a template for an index.rst, adding the other
files there via TOC markup.

Despite being written on different times with different
styles, try to make them somewhat coherent with a similar
look and feel, ensuring that they'll look nice as both
raw text file and as via the html output produced by the
Sphinx build system.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab

ipv6: Support multipath hashing on inner IP pkts

2019-07-08T23:37:29+00:00

Make the same support as commit 363887a2cdfe ("ipv4: Support multipath
hashing on inner IP pkts for GRE tunnel") for outer IPv6. The hashing
considers both IPv4 and IPv6 pkts when they are tunneled by IPv6 GRE.

Signed-off-by: Stephen Suryaputra 
Signed-off-by: David S. Miller