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Paolo Abeni 4f65ee7e0c Merge branch 'hsr-implement-more-robust-duplicate-discard-algorithm'
Felix Maurer says:

====================
hsr: Implement more robust duplicate discard algorithm

The duplicate discard algorithms for PRP and HSR do not work reliably
with certain link faults. Especially with packet loss on one link, the
duplicate discard algorithms drop valid packets. For a more thorough
description see patches 4 (for PRP) and 6 (for HSR).

This patchset replaces the current algorithms (based on a drop window
for PRP and highest seen sequence number for HSR) with a single new one
that tracks the received sequence numbers individually (descriptions
again in patches 4 and 6).

The changes will lead to higher memory usage and more work to do for
each packet. But I argue that this is an acceptable trade-off to make
for a more robust PRP and HSR behavior with faulty links. After all,
both protocols are to be used in environments where redundancy is needed
and people are willing to setup special network topologies to achieve
that.

Some more reasoning on the overhead and expected scale of the deployment
from the RFC discussion:

> As for the expected scale, there are two dimensions: the number of nodes
> in the network and the data rate with which they send.
>
> The number of nodes in the network affect the memory usage because each
> node now has the block buffer. For PRP that's 64 blocks * 32 byte =
> 2kbyte for each node in the node table. A PRP network doesn't have an
> explicit limit for the number of nodes. However, the whole network is a
> single layer-2 segment which shouldn't grow too large anyways. Even if
> one really tries to put 1000 nodes into the PRP network, the memory
> overhead (2Mbyte) is acceptable in my opinion.
>
> For HSR, the blocks would be larger because we need to track the
> sequence numbers per port. I expect 64 blocks * 80 byte = 5kbyte per
> node in the node table. There is no explicit limit for the size of an
> HSR ring either. But I expect them to be of limited size because the
> forwarding delays add up throughout the ring. I've seen vendors limiting
> the ring size to 50 nodes with 100Mbit/s links and 300 with 1Gbit/s
> links. In both cases I consider the memory overhead acceptable.
>
> The data rates are harder to reason about. In general, the data rates
> for HSR and PRP are limited because too high packet rates would lead to
> very fast re-use of the 16bit sequence numbers. The IEC 62439-3:2021
> mentions 100Mbit/s links and 1Gbit/s links. I don't expect HSR or PRP
> networks to scale out to, e.g., 10Gbit/s links with the current
> specification as this would mean that sequence numbers could repeat as
> often as every ~4ms. The default constants in the IEC standard, which we
> also use, are oriented at a 100Mbit/s network.
>
> In my tests with veth pairs, the CPU overhead didn't lead to
> significantly lower data rates. The main factor limiting the data rate
> at the moment, I assume, is the per-node spinlock that is taken for each
> received packet. IMHO, there is a lot more to gain in terms of CPU
> overhead from making this lock smaller or getting rid of it, than we
> loose with the more accurate duplicate discard algorithm in this patchset.
>
> The CPU overhead of the algorithm benefits from the fact that in high
> packet rate scenarios (where it really matters) many packets will have
> sequence numbers in already initialized blocks. These packets just have
> additionally: one xarray lookup, one comparison, and one bit setting. If
> a block needs to be initialized (once every 128 packets plus their 128
> duplicates if all sequence numbers are seen), we will have: one
> xa_erase, a bunch of memory writes, and one xa_store.
>
> In theory, all packets could end up in the slow path if a node sends
> every 128th packet to us. If this is sent from a well behaving node, the
> packet rate wouldn't be an issue anymore, though.

Signed-off-by: Felix Maurer <fmaurer@redhat.com>
====================

Link: https://patch.msgid.link/cover.1770299429.git.fmaurer@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2026-02-10 12:02:32 +01:00
Documentation dt-bindings: net: dsa: lantiq,gswip: reference common PHY properties 2026-02-10 09:09:26 +01:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2026-02-05 09:54:08 -08:00
block block-6.19-20260122 2026-01-23 12:53:56 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-20 14:38:48 +08:00
drivers net: fec: add AF_XDP zero-copy support 2026-02-10 10:58:20 +01:00
fs two client memory leak fixes 2026-02-03 16:20:59 -08:00
include net/ipv6: Remove HBH helpers 2026-02-06 20:50:13 -08:00
init Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
io_uring io_uring-6.19-20260122 2026-01-23 12:51:00 -08:00
ipc Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
kernel 5 hotfixes. 2 are cc:stable, 2 are for MM. 2026-02-04 16:04:00 -08:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2026-02-05 09:54:08 -08:00
mm 5 hotfixes. 2 are cc:stable, 2 are for MM. 2026-02-04 16:04:00 -08:00
net hsr: Implement more robust duplicate discard for HSR 2026-02-10 12:02:29 +01:00
rust Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2026-02-05 09:54:08 -08:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2025-12-31 15:19:25 +08:00
scripts Miscellaneous objtool fixes: 2026-02-01 10:27:43 -08:00
security lsm: preserve /proc/sys/vm/mmap_min_addr when !CONFIG_SECURITY 2026-01-29 13:56:53 -05:00
sound ASoC: Fixes for v6.19 2026-01-29 13:58:06 +01:00
tools selftests: hsr: Add more link fault tests for HSR 2026-02-10 12:02:29 +01:00
usr initramfs: add gen_init_cpio to hostprogs unconditionally 2025-11-26 21:55:40 +01:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-01-14 13:17:14 -08:00
.clang-format s390/pci: Fix cyclic dead-lock in zpci_zdev_put() and zpci_scan_devices() 2025-12-14 11:03:58 +01:00
.clippy.toml rust: clean Rust 1.88.0's warning about `clippy::disallowed_macros` configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: kbuild: add proc macro library support 2025-11-24 17:15:36 +01:00
.mailmap 5 hotfixes. 2 are cc:stable, 2 are for MM. 2026-02-04 16:04:00 -08:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml
COPYING
CREDITS net: ethernet: neterion: s2io: remove unused driver 2026-01-28 20:08:07 -08:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS MAINTAINERS: Assign hsr selftests to HSR 2026-02-10 12:02:29 +01:00
Makefile Linux 6.19-rc8 2026-02-01 14:01:13 -08:00
README README: restructure with role-based documentation and guidelines 2025-11-29 08:40:33 -07:00

README

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst



Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst