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07262b165d
When we write a connection profile to ifcfg-rh file, we first load the possibly existing file and modify it. The purpose is to preserve variables that we don't know about, keep comments and preserve the order of the variables. Note that the writer sets a bunch of variables according to the profile's setting. At various places the writer would explicitly clear variables with svUnsetValue(). However, that was problematic: - we would not unset all variables that we care about. We really should not leave previous variables if they make no sense anymore for the profile. The only thing we want to preserve are entirely unknown keys and comments. Note that when the writer omits to clear an unset variable, it usually does so assuming that the reader would anyway ignore the key, become some other key renders it irrelevant. Given the complexity of the reader and writer, that is often not the case and hard to ensure. We might have simply forgotten a svUnsetValue(), which was an easy to make mistake and hard to find (because you'd have to test with a pre-existing profile that happens to contain that key, which leaves countless combinations for testing. That means, a profile written by the writter might be interpreted differently by the reader depending on which pre-existing keys were set. - it was cumbersome to explicitly call svUnsetValue(). Note that for numbered tags in particular we would iterate the keys trying to unset them. For example for addresses (like "IPADDR5") we would iterate over the first 256 IPADDR keys, trying to unset them. That is horrible. For one, it doesn't cover the case where there might be more than 256 addresses. Also, it adds a significant overhead every time. While writing a ifcfg file currently is O(n^2) because setting one key is O(l), with l being the number of keys/lines. So, if you set n keys in a file with l lines, you get O(n*l). Which is basically O(n^2), because the number of lines and the number of keys to set usually corresponds. So when setting 256 times IPADDR, the overall complexity was still O(n^2 + 256 * n) and didn't change. However, the 256 factor here can be very significant. We should not explicitly unset variables, we should always unset all known variables that we don't explicitly set. The svUnsetValue() calls are still there. They will be dropped next. |
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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.