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Danielle Ratson d07d7c3dd9 selftests: net: Add kernel selftest for RFC 4884
RFC 4884 extended certain ICMP messages with a length attribute that
encodes the length of the "original datagram" field. This is needed so
that new information could be appended to these messages without
applications thinking that it is part of the "original datagram" field.

In version 5.9, the kernel was extended with two new socket options
(SOL_IP/IP_RECVERR_4884 and SOL_IPV6/IPV6_RECVERR_RFC4884) that allow
user space to retrieve this length which is basically the offset to the
ICMP Extension Structure at the end of the ICMP message. This is
required by user space applications that need to parse the information
contained in the ICMP Extension Structure. For example, the RFC 5837
extension for tracepath.

Add a selftest that verifies correct handling of the RFC 4884 length
field for both IPv4 and IPv6, with and without extension structures,
and validates that malformed extensions are correctly reported as invalid.

For each address family, the test creates:
  - a raw socket used to send locally crafted ICMP error packets to the
    loopback address, and
  - a datagram socket used to receive the encapsulated original datagram
    and associated error metadata from the kernel error queue.

ICMP packets are constructed entirely in user space rather than relying
on kernel-generated errors. This allows the test to exercise invalid
scenarios (such as corrupted checksums and incorrect length fields) and
verify that the SO_EE_RFC4884_FLAG_INVALID flag is set as expected.

Output Example:

$ ./icmp_rfc4884
Starting 18 tests from 18 test cases.
  RUN           rfc4884.ipv4_ext_small_payload.rfc4884 ...
            OK  rfc4884.ipv4_ext_small_payload.rfc4884
ok 1 rfc4884.ipv4_ext_small_payload.rfc4884
  RUN           rfc4884.ipv4_ext.rfc4884 ...
            OK  rfc4884.ipv4_ext.rfc4884
ok 2 rfc4884.ipv4_ext.rfc4884
  RUN           rfc4884.ipv4_ext_large_payload.rfc4884 ...
            OK  rfc4884.ipv4_ext_large_payload.rfc4884
ok 3 rfc4884.ipv4_ext_large_payload.rfc4884
  RUN           rfc4884.ipv4_no_ext_small_payload.rfc4884 ...
            OK  rfc4884.ipv4_no_ext_small_payload.rfc4884
ok 4 rfc4884.ipv4_no_ext_small_payload.rfc4884
  RUN           rfc4884.ipv4_no_ext_min_payload.rfc4884 ...
            OK  rfc4884.ipv4_no_ext_min_payload.rfc4884
ok 5 rfc4884.ipv4_no_ext_min_payload.rfc4884
  RUN           rfc4884.ipv4_no_ext_large_payload.rfc4884 ...
            OK  rfc4884.ipv4_no_ext_large_payload.rfc4884
ok 6 rfc4884.ipv4_no_ext_large_payload.rfc4884
  RUN           rfc4884.ipv4_invalid_ext_checksum.rfc4884 ...
            OK  rfc4884.ipv4_invalid_ext_checksum.rfc4884
ok 7 rfc4884.ipv4_invalid_ext_checksum.rfc4884
  RUN           rfc4884.ipv4_invalid_ext_length_small.rfc4884 ...
            OK  rfc4884.ipv4_invalid_ext_length_small.rfc4884
ok 8 rfc4884.ipv4_invalid_ext_length_small.rfc4884
  RUN           rfc4884.ipv4_invalid_ext_length_large.rfc4884 ...
            OK  rfc4884.ipv4_invalid_ext_length_large.rfc4884
ok 9 rfc4884.ipv4_invalid_ext_length_large.rfc4884
  RUN           rfc4884.ipv6_ext_small_payload.rfc4884 ...
            OK  rfc4884.ipv6_ext_small_payload.rfc4884
ok 10 rfc4884.ipv6_ext_small_payload.rfc4884
  RUN           rfc4884.ipv6_ext.rfc4884 ...
            OK  rfc4884.ipv6_ext.rfc4884
ok 11 rfc4884.ipv6_ext.rfc4884
  RUN           rfc4884.ipv6_ext_large_payload.rfc4884 ...
            OK  rfc4884.ipv6_ext_large_payload.rfc4884
ok 12 rfc4884.ipv6_ext_large_payload.rfc4884
  RUN           rfc4884.ipv6_no_ext_small_payload.rfc4884 ...
            OK  rfc4884.ipv6_no_ext_small_payload.rfc4884
ok 13 rfc4884.ipv6_no_ext_small_payload.rfc4884
  RUN           rfc4884.ipv6_no_ext_min_payload.rfc4884 ...
            OK  rfc4884.ipv6_no_ext_min_payload.rfc4884
ok 14 rfc4884.ipv6_no_ext_min_payload.rfc4884
  RUN           rfc4884.ipv6_no_ext_large_payload.rfc4884 ...
            OK  rfc4884.ipv6_no_ext_large_payload.rfc4884
ok 15 rfc4884.ipv6_no_ext_large_payload.rfc4884
  RUN           rfc4884.ipv6_invalid_ext_checksum.rfc4884 ...
            OK  rfc4884.ipv6_invalid_ext_checksum.rfc4884
ok 16 rfc4884.ipv6_invalid_ext_checksum.rfc4884
  RUN           rfc4884.ipv6_invalid_ext_length_small.rfc4884 ...
            OK  rfc4884.ipv6_invalid_ext_length_small.rfc4884
ok 17 rfc4884.ipv6_invalid_ext_length_small.rfc4884
  RUN           rfc4884.ipv6_invalid_ext_length_large.rfc4884 ...
            OK  rfc4884.ipv6_invalid_ext_length_large.rfc4884
ok 18 rfc4884.ipv6_invalid_ext_length_large.rfc4884
 PASSED: 18 / 18 tests passed.
 Totals: pass:18 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260121114644.2863640-1-danieller@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-01-22 18:29:49 -08:00
arch net: remove HIPPI support and RoadRunner HIPPI driver 2026-01-20 19:12:06 -08:00
block block-6.19-20260109 2026-01-09 15:42:46 -10:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: seqiv - Do not use req->iv after crypto_aead_encrypt 2025-12-19 14:47:06 +08:00
Documentation dt-bindings: net: pcs: mediatek,sgmiisys: deprecate "mediatek,pnswap" 2026-01-21 19:46:58 -08:00
drivers net: stmmac: dwmac-imx: keep preamble before sfd on i.MX8MP 2026-01-22 18:27:33 -08:00
fs gfs2 revert 2026-01-13 10:04:34 -08:00
include tcp: move tcp_rate_check_app_limited() to tcp.c 2026-01-22 18:28:48 -08:00
init Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
io_uring io_uring-6.19-20260109 2026-01-09 15:21:15 -10:00
ipc Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
kernel bpf-fixes 2026-01-13 21:21:13 -08:00
lib Crypto library fixes for v6.19-rc5 2026-01-11 15:07:56 -10:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm mm/ksm: fix pte_unmap_unlock of wrong address in break_ksm_pmd_entry 2025-12-23 11:23:17 -08:00
net tcp: move tcp_rate_check_app_limited() to tcp.c 2026-01-22 18:28:48 -08:00
rust net: remove HIPPI support and RoadRunner HIPPI driver 2026-01-20 19:12:06 -08:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2025-12-31 15:19:25 +08:00
scripts Crypto library fixes for v6.19-rc5 2026-01-11 15:07:56 -10:00
security kernel/kexec: change the prototype of kimage_map_segment() 2025-12-23 11:23:13 -08:00
sound ALSA: hda/realtek: add HP Laptop 15s-eq1xxx mute LED quirk 2026-01-02 14:34:23 +01:00
tools selftests: net: Add kernel selftest for RFC 4884 2026-01-22 18:29:49 -08:00
usr initramfs: add gen_init_cpio to hostprogs unconditionally 2025-11-26 21:55:40 +01:00
virt KVM fixes for 6.19-rc1 2025-12-18 18:38:45 +01:00
.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 treewide: Update email address 2026-01-11 06:09:11 -10:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS net: remove HIPPI support and RoadRunner HIPPI driver 2026-01-20 19:12:06 -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 net: remove HIPPI support and RoadRunner HIPPI driver 2026-01-20 19:12:06 -08:00
Makefile Linux 6.19-rc5 2026-01-11 17:03:14 -10:00
README README: restructure with role-based documentation and guidelines 2025-11-29 08:40:33 -07:00

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