cfd696cc3c
The "ipv4.dhcp-client-id" is configurable per-profile and the default
value can be overwritten via connection defaults in NetworkManager.conf.
For "dhclient" DHCP plugin, the ultimate default for "ipv4.dhcp-client-id"
is determined by dhclient itself, or possibly by user configuration from
"/etc/dhcp".
For the "internal" DHCP plugin, the default must be decided by
NetworkManager. Also, the default here is important, as we preferably
won't change it anymore. That is because a changing the client-id
will result in different IP addresses after upgrade of NetworkManager
version. That should be avoided.
Still, change it now. If a downstream does not want this, it either needs
to patch the sources or add a configuration snippet like:
[connection-internal-dhcp-client-id-duid]
match-device=dhcp-plugin:internal
ipv4.dhcp-client-id=duid
The reason to change from the previous default "duid" to "mac" are the
following:
- "duid" is an RFC 4361 compatible client-id ([1]) and "mac" is defined
in RFC 2132.
- "duid" cannot (easily) be predicated a-priori as it is a hash of the
interface-name and "/etc/machine-id". In particular in cloud and server
environments, admins often prefer "mac" as they do know the MAC address
and pre-configure the DHCP server accordingly.
- with "dhclient" plugin, the default is decided by dhclient package or
user configuration in "/etc/dhcp". However, in fact the default is often
"client-identifier hardware" (for example on RHEL/CentOS).
- for RHEL/CentOS we require a way to select "mac" as default. That was
done by installing a configuration snippet via the NetworkManager-config-server
package. It's confusing to have the default depend on a package. Avoid
that. Also, users required "mac" in certain scenarios, but no users
explicitly asked for "duid" as default.
- our "duid" implementation generates a 32 bit IAID based on a hash of the
interface-name, and only 8 bytes entropy that contains a hash
of "/etc/machine-id". The point is, that is not a lot of entropy to
avoid conflicting client-ids. Another point is, that the choosen algorithm
for "duid" is suitable for RFC 4361, but it's only one of many possibly
implementations. Granted, each possibility has up and downsides but selecting
one of them as default seems wrong (given that it has obvious downsides
already). For "mac" there is only one straight-forward way to implement
it.
- RFC 7844 (Anonymity Profiles for DHCP Clients) is not yet supported by
NetworkManager. But we should not select a default client-id which
counteracts anonymit. Choosing "mac" does not reveal information which
is not already exposed.
[1] https://tools.ietf.org/html/rfc4361#section-4
https://bugzilla.redhat.com/show_bug.cgi?id=1661165
****************** 2008-12-11: NetworkManager core daemon has moved to git.freedesktop.org! git clone git://git.freedesktop.org/git/NetworkManager/NetworkManager.git ****************** 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. 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.