57d226d3f0
Usually we anyway require systemd-resolved to resolve the hostname for connectivity checking. Only systemd-resolved provides a per-interface API. Without it, connectivity check (together with bumping the route metric) has problems. Anyway. If we had no systemd-resolved or it failed, we would just call libcurl. That would then try to resolve the name, using whatever resolver libcurl has enabled. Often that is the threaded resolver, which calls libc's blocking getaddrinfo() API on a thread. libcurl has a bug ([1]) that can cause the process to block, waiting to join the resolver thread: #0 0x00007ffff781fb27 in __pthread_timedjoin_ex () at /lib64/libpthread.so.0 #1 0x00007ffff7c0ac9a in Curl_thread_join () at /lib64/libcurl.so.4 #2 0x00007ffff7c0d693 in thread_wait_resolv () at /lib64/libcurl.so.4 #3 0x00007ffff7bf9284 in multi_done () at /lib64/libcurl.so.4 #4 0x00007ffff7bfb588 in curl_multi_remove_handle () at /lib64/libcurl.so.4 #5 0x000055555574adc3 in cb_data_complete That's not acceptable. Resolve the name ourselves using glib's implementation (which also does getaddrinfo() in a thread). If we fail, we no longer call to libcurl. [1] https://github.com/curl/curl/issues/8515 https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/312 https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/404 https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/934 https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/970 https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1176
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.