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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>
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
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| .clang-format | ||
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| COPYING | ||
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| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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