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NML3Cfg is stateful, that means it remembers which address/route it configured earlier. That is important because the API users of NML3Cfg only say what the want to configure now, and NML3Cfg needs to remove addresses/routes that it configured earlier but are no longer to be present. Also, NetworkManager wants to allow the user to add addresses/routes externally with `ip addr|route add` and NetworkManager not removing it. This is a common use case for dispatcher scripts, but in general, we want to allow other components to add addresses/routes. We try something similar with the removal of routes/addresses managed by NetworkManager. When NetworkManager adds a route/address, which later disappears, then we assume that the user intentionally removed the address/route and take the hint to not re-add it. However, it doesn't work. It is problematic for two reasons: - kernel can automatically remove routes. For example, deleting an IPv4 address that is the prefsrc of a route, will cause kernel to delete that route. Sure, we may be unable to re-configure the route at this moment, but we shouldn't remember indefinitely that the route is supposed to be absent. Rather, we should re-add it when possible. - kernel is a pain with validating consistencies of routes. For example, when a route has a nexthop gateway, then the gateway must be onlink (directly reachable), or kernel refuses to add it with "Nexthop has invalid gateway". Of course, when removing the onlink route kernel is fine leaving the gateway route behind, which it would otherwise refuse to add. Anyway. Such interdependencies for when kernel rejects adding a route with "Nexthop has invalid gateway" are non-trivial. We try to work around that by always adding the necessary onlink routes. See nm_l3_config_data_add_dependent_onlink_routes(). But if the user externally removed the dependent onlink route, and NetworkManager remembers to not re-adding it, then the efforts from nm_l3_config_data_add_dependent_onlink_routes() are ignored. This causes ripple effects and NetworkManager will also be unable to add the nexthop route. Trying to preserve absence of routes that NetworkManager would like to configure is not tenable. Don't do it anymore. There was anyway no guarantee that on the next update NetworkManager wouldn't try to re-add the route in question. For example, if the route came from DHCP, and the lease temporarily went away and came back, then NetworkManager probably would have (correctly) forgotten that the user wished that the route be absent. This did not work reliably and it just causes problems. |
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NetworkManager core daemon has moved to gitlab.freedesktop.org!
git clone https://gitlab.freedesktop.org/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.