15ffa8ec6f
When we recibe a Netlink message with a "route change" event, normally
we just ignore it if it's a route that we don't track (i.e. because of
the route protocol).
However, it's not that easy if it has the NLM_F_REPLACE flag because
that means that it might be replacing another route. If the kernel has
similar routes which are candidates for the replacement, it's hard for
NM to guess which one of those is being replaced (as the kernel doesn't
have a "route ID" or similar field to indicate it). Moreover, the kernel
might choose to replace a route that we don't have on cache, so we know
nothing about it.
It is important to note that we cannot just discard Netlink messages of
routes that we don't track if they has the NLM_F_REPLACE. For example,
if we are tracking a route with proto=static, we might receive a replace
message, changing that route to proto=other_proto_that_we_dont_track. We
need to process that message and remove the route from our cache.
As NM doesn't know what route is being replaced, trying to guess will
lead to errors that will leave the cache in an inconsistent state.
Because of that, it just do a cache resync for the routes.
For IPv4 there was an optimization to this: if we don't have in the
cache any route candidate for the replacement there are only 2 possible
options: either add the new route to the cache or discard it if we are
not interested on it. We don't need a resync for that.
This commit is extending that optimization to IPv6 routes. There is no
reason why it shouldn't work in the same way than with IPv4. This
optimization will only work well as long as we find potential candidate
routes in the same way than the kernel (comparing the same fields). NM
calls to this "comparing by WEAK_ID". But this can also happen with IPv4
routes.
It is worth it to enable this optimization because there are routing
daemons using custom routing protocols that makes tens or hundreds of
updates per second. If they use NLM_F_REPLACE, this caused NM to do a
resync hundreds of times per second leading to a 100% CPU usage:
https://issues.redhat.com/browse/RHEL-26195
An additional but smaller optimization is done in this commit: if we
receive a route message for routes that we don't track AND doesn't have
the NLM_F_REPLACE flag, we can ignore the entire message, thus avoiding
the memory allocation of the nmp_object. That nmp_object was going to be
ignored later, anyway, so better to avoid these allocations that, with
the routing daemon of the above's example, can happen hundreds of times
per second.
With this changes, the CPU usage doing `ip route replace` 300 times/s
drops from 100% to 1%. Doing `ip route replace` as fast as possible,
without any rate limitting, still keeps NM with a 3% CPU usage in the
system that I have used to test.
(cherry picked from commit
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| data | ||
| docs | ||
| examples | ||
| introspection | ||
| m4 | ||
| man | ||
| po | ||
| src | ||
| tools | ||
| vapi | ||
| .clang-format | ||
| .dir-locals.el | ||
| .git-blame-ignore-revs | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .mailmap | ||
| .triage-policies.yml | ||
| AUTHORS | ||
| autogen.sh | ||
| ChangeLog | ||
| config-extra.h.meson | ||
| config-extra.h.mk | ||
| config.h.meson | ||
| configure.ac | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| COPYING.GFDL | ||
| COPYING.LGPL | ||
| linker-script-binary.ver | ||
| linker-script-devices.ver | ||
| linker-script-settings.ver | ||
| lsan.suppressions | ||
| MAINTAINERS | ||
| MAINTAINERS.md | ||
| Makefile.am | ||
| Makefile.examples | ||
| Makefile.glib | ||
| Makefile.vapigen | ||
| meson.build | ||
| meson_options.txt | ||
| NEWS | ||
| README.md | ||
| RELICENSE.md | ||
| TODO | ||
| valgrind.suppressions | ||
NetworkManager
Networking that Just Works
NetworkManager attempts to keep an active network connection available at all times. The point of NetworkManager is to make networking configuration and setup as painless and automatic as possible. NetworkManager is intended to replace default route, replace other routes, set IP addresses, and in general configure networking as NM sees fit (with the possibility of manual override as necessary). In effect, the goal of NetworkManager is to make networking Just Work with a minimum of user hassle, but still allow customization and a high level of manual network control. If you have special needs, we'd like to hear about them, but understand that NetworkManager is not intended for every use-case.
NetworkManager will attempt to keep every network device in the system up and active, as long as the device is available for use (has a cable plugged in, the killswitch isn't turned on, etc). Network connections can be set to 'autoconnect', meaning that NetworkManager will make that connection active whenever it and the hardware is available.
"Settings services" store lists of user- or administrator-defined "connections", which contain all the settings and parameters required to connect to a specific network. NetworkManager will never activate a connection that is not in this list, or that the user has not directed NetworkManager to connect to.
How it works
The NetworkManager daemon runs as a privileged service (since it must access and control hardware), but provides a D-Bus interface on the system bus to allow for fine-grained control of networking. NetworkManager does not store connections or settings, it is only the mechanism by which those connections are selected and activated.
To store pre-defined network connections, two separate services, the "system settings service" and the "user settings service" store connection information and provide these to NetworkManager, also via D-Bus. Each settings service can determine how and where it persistently stores the connection information; for example, the GNOME applet stores its configuration in GConf, and the system settings service stores its config in distro-specific formats, or in a distro- agnostic format, depending on user/administrator preference.
A variety of other system services are used by NetworkManager to provide network functionality: wpa_supplicant for wireless connections and 802.1x wired connections, pppd for PPP and mobile broadband connections, DHCP clients for dynamic IP addressing, dnsmasq for proxy nameserver and DHCP server functionality for internet connection sharing, and avahi-autoipd for IPv4 link-local addresses. Most communication with these daemons occurs, again, via D-Bus.
How to use it
Install NetworkManager with your distribution's package manager.
As NetworkManager is actually a daemon that runs in the background, you need to use one of the many existing client programs to interact with it.
Terminal clients:
nmcli: advanced command line client that gives you full control over all the aspects of NetworkManager, developed as part of the NetworkManager project.nmtui: text-based user interface (TUI) client. Also for the terminal, but interactive and more user friendly, also part of the NetworkManager project.nmstate: declarative network API and command line tool that uses NetworkManager as backend.- Ansible: use the network-role in your playbooks
GUI clients
nm-connection-editorandnm-applet: basic GUI interfaces developed by the NetworkManager project.- GNOME shell: interacts with NetworkManager via its default settings panel
gnome-control-center - KDE Plasma: interacts with NetworkManager via its default settings panel
and
plasma-nm
Why doesn't my network Just Work?
Driver problems are the #1 cause of why NetworkManager sometimes fails to connect to wireless networks. Often, the driver simply doesn't behave in a consistent manner, or is just plain buggy. NetworkManager supports only those drivers that are shipped with the upstream Linux kernel, because only those drivers can be easily fixed and debugged. ndiswrapper, vendor binary drivers, or other out-of-tree drivers may or may not work well with NetworkManager, precisely because they have not been vetted and improved by the open-source community, and because problems in these drivers usually cannot be fixed.
Sometimes, command-line tools like 'iwconfig' will work, but NetworkManager will fail. This is again often due to buggy drivers, because these drivers simply aren't expecting the dynamic requests that NetworkManager and wpa_supplicant make. Driver bugs should be filed in the bug tracker of the distribution being run, since often distributions customize their kernel and drivers.
Sometimes, it really is NetworkManager's fault. If you think that's the case, please file a bug at:
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/issues
Attaching NetworkManager debug logs from the journal (or wherever your distribution directs syslog's 'daemon' facility output, as /var/log/messages or /var/log/daemon.log) is often very helpful, and (if you can get) a working wpa_supplicant config file helps enormously. See the logging section of file contrib/fedora/rpm/NetworkManager.conf for how to enable debug logging in NetworkManager.
Documentation
Updated documentation can be found at https://networkmanager.dev/docs
Users can consult the man pages. Most relevant pages for normal users are:
- NetworkManager daemon:
NetworkManager (8),NetworkManager.conf (5) - nmcli:
nmcli (1),nmcli-examples (5),nm-settings-nmcli (5) - nmtui:
nmtui (1)
Get in touch
To connect with the community, get help or get involved see the available communication channels at https://networkmanager.dev/community/
Report bugs or feature request in our issue tracker. See Report issues for details about how to do it.
To get involved, see CONTRIBUTING.md
License
NetworkManager is free software under GPL-2.0-or-later and LGPL-2.1-or-later. See CONTRIBUTING.md#legal and RELICENSE.md for details.