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Ilya Maximets 03f374ac12 net: netlink: don't set nsid on local notifications 
[ Upstream commit 88b126b39f ]

In most cases, notifications on sockets with NETLINK_LISTEN_ALL_NSID
do not contain NSID in their ancillary data in case the event is local
to the listener.

However, when a self-referential NSID is allocated for a namespace,
every local notification starts sending this ID to the user space.

This is problematic, because the listener cannot tell if those
notifications are local or not anymore without making extra requests
to figure out if the provided NSID is local or not.  The listener
can also not figure out the local NSID beforehand as it can be
allocated at any point in time by other processes, changing the
structure of the future notifications for everyone.

The value is practically not useful, since it's the namespace's own
ID that the application has to obtain from other sources in order to
figure out if it's the same or not.  So, for the application it's
just an extra busy work with no benefits.  Moreover, applications
that do not know about this quirk may be mishandling notifications
with NSID set as notifications from remote namespaces.  This is the
case for ovs-vswitchd and the iproute2's 'ip monitor' that stops
printing 'current' and starts printing the nsid number mid-session.

Lack of clear documentation for this behavior is also not helping.

A search though open-source projects doesn't reveal any projects
that use NETNSA_NSID_NOT_ASSIGNED and rely on metadata to contain
self-referential NSIDs (expected, since the value is not useful).
Quite the opposite, as already mentioned, there are few applications
that rely on NSID to not be present in local events.

Since the value is not useful and actively harmful in some cases,
let's not report it for local events, making the notifications more
consistent.

Also adding some blank lines for readability.

Fixes: 59324cf35a ("netlink: allow to listen "all" netns")
Reported-by: Matteo Perin <matteo.perin@canonical.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Link: https://patch.msgid.link/20260520172317.175168-3-i.maximets@ovn.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-06-19 13:33:23 +02:00
arch ARM: integrator: Fix early initialization 2026-06-01 17:35:49 +02:00
block blk-mq: use quiesced elevator switch when reinitializing queues 2026-06-01 17:35:09 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: af_alg - Cap AEAD AD length to 0x80000000 2026-06-01 17:35:44 +02:00
Documentation Documentation: fix a hugetlbfs reservation statement 2026-06-01 17:35:32 +02:00
drivers tun: free page on short-frame rejection in tun_xdp_one() 2026-06-19 13:33:23 +02:00
fs sysfs: don't remove existing directory on update failure 2026-06-01 17:35:46 +02:00
include drm: Remove plane hsub/vsub alignment requirement for core helpers 2026-06-19 13:33:22 +02:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:21:45 +02:00
io_uring io_uring: prevent opcode speculation 2026-06-01 17:35:45 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:05:26 +01:00
kernel tracing: Avoid NULL return from hist_field_name() on truncation 2026-06-01 17:35:51 +02:00
lib kunit: config: KUNIT_DEBUGFS should depend on DEBUG_FS 2026-06-01 17:35:49 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() 2026-06-01 17:35:08 +02:00
net net: netlink: don't set nsid on local notifications 2026-06-19 13:33:23 +02:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts scripts/dtc: Remove unused dts_version in dtc-lexer.l 2026-06-01 17:35:12 +02:00
security ima: check return value of crypto_shash_final() in boot aggregate 2026-06-01 17:35:34 +02:00
sound ALSA: asihpi: Fix potential OOB array access at reading cache 2026-06-01 17:35:46 +02:00
tools perf util: Kill die() prototype, dead for a long time 2026-06-01 17:35:35 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Reject wrapped offset in kvm_reset_dirty_gfn() 2026-06-01 17:35:44 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:09:36 +09:00
Makefile Linux 5.15.209 2026-06-01 17:35:51 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.