mirror of
https://gitlab.freedesktop.org/NetworkManager/NetworkManager.git
synced 2026-04-07 08:50:40 +02:00
39ab38a04d
Kernel recently got support for exposing TUN/TAP information on netlink [1], [2], [3]. Add support for it to the platform cache. The advantage of using netlink is that querying sysctl bypasses the order of events of the netlink socket. It is out of sync and racy. For example, platform cache might still think that a tun device exists, but a subsequent lookup at sysfs might fail because the device was deleted in the meantime. Another point is, that we don't get change notifications via sysctl and that it requires various extra syscalls to read the device information. If the tun information is present on netlink, put it into the cache. This bypasses checking sysctl while we keep looking at sysctl for backward compatibility until we require support from kernel. Notes: - we had two link types NM_LINK_TYPE_TAP and NM_LINK_TYPE_TUN. This deviates from the model of how kernel treats TUN/TAP devices, which makes it more complicated. The link type of a NMPlatformLink instance should match what kernel thinks about the device. Point in case, when parsing RTM_NETLINK messages, we very early need to determine the link type (_linktype_get_type()). However, to determine the type of a TUN/TAP at that point, we need to look into nested netlink attributes which in turn depend on the type (IFLA_INFO_KIND and IFLA_INFO_DATA), or even worse, we would need to look into sysctl for older kernel vesions. Now, the TUN/TAP type is a property of the link type NM_LINK_TYPE_TUN, instead of determining two different link types. - various parts of the API (both kernel's sysctl vs. netlink) and NMDeviceTun vs. NMSettingTun disagree whether the PI is positive (NM_SETTING_TUN_PI, IFLA_TUN_PI, NMPlatformLnkTun.pi) or inverted (NM_DEVICE_TUN_NO_PI, IFF_NO_PI). There is no consistent way, but prefer the positive form for internal API at NMPlatformLnkTun.pi. - previously NMDeviceTun.mode could not change after initializing the object. Allow for that to happen, because forcing some properties that are reported by kernel to not change is wrong, in case they might change. Of course, in practice kernel doesn't allow the device to ever change its type, but the type property of the NMDeviceTun should not make that assumption, because, if it actually changes, what would it mean? - note that as of now, new netlink API is not yet merged to mainline Linus tree. Shortcut _parse_lnk_tun() to not accidentally use unstable API for now. [1] https://bugzilla.redhat.com/show_bug.cgi?id=1277457 [2] https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=1ec010e705934c8acbe7dbf31afc81e60e3d828b [3] https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/commit/?id=118eda77d6602616bc523a17ee45171e879d1818 https://bugzilla.redhat.com/show_bug.cgi?id=1547213 https://github.com/NetworkManager/NetworkManager/pull/77 |
||
|---|---|---|
| .. | ||
| meson.build | ||
| test-arping.c | ||
| test-lldp.c | ||