Hm. udevd applies MTU property from the link file in the link_config_apply() function, which is called by builtin_net_setup_link(), from the net_setup_link builtin.
Reading the conditions for builtin_net_setup_link_init() and builtin_set_setup_link_validate(), the link configuration context is never recreated; but paths_check_timestamp(link_dirs, &ctx->link_dirs_ts_usec, false) is used to determine if things need to be reloaded. It verifies the time of last modification (st_mtim) on the directories that hold the link files. However, udevd only calls validate on the builtins at most every 3 seconds (see udevd.c). Thus if one changes link files (e.g. modification time on the directory less than 3 seconds since the last udev scan), and one triggers to run 80-net-setup-link, the link files will not be re- read and nothing new will happen. >From the original logs, it seems like everything happens within the same second on boot. Hence the race. It would be interesting to boot the bad instances with udev debugging enabled, to observe the messages related to realoding net link configuration and/or applying it, e.g. the interesting messages are: Created link configuration context. Unloaded link configuration context. Check if link configuration needs reloading. Udev debugging can be set by changing /etc/udev/udev.conf and use udev_log="debug", or by booting with udev.log-priority=debug on the kernel command line. Also it would be interesting to see, if we can sleep for 3 seconds, before triggering udevadm add. I understand that hardcoding 3 second sleep is sub-optimal, this is purely to establish if the above analysis is a complete red-herring or not =) -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1669564 Title: udevadm trigger subsystem-match=net doesn't always run rules Status in systemd package in Ubuntu: New Bug description: 1. root@ubuntu:~# lsb_release -rd Description: Ubuntu Zesty Zapus (development branch) Release: 17.04 2. root@ubuntu:~# apt-cache policy udev udev: Installed: 232-18ubuntu1 Candidate: 232-18ubuntu1 Version table: *** 232-18ubuntu1 500 500 http://archive.ubuntu.com/ubuntu zesty/main amd64 Packages 100 /var/lib/dpkg/status 3. udevadm trigger --verbose --subsystem-match=net --action=add will run and read .link files from /run/systemd/network/10-netplan-interface1.link and apply MTU settings 4. during system boot running (3) does not set the MTU; running (3) after boot has completed MTU is set correctly. Here'a log during boot where cloud-init generates a netplan config, invokes `netplan generate` which writes the networkd config out and then udevadm trigger (3). Upon logging in interface1 has an MTU of 1500. Re-running udevadm trigger now runs the rules/link files and updates the MTU. Note that, if you run udevadm test /sys/class/net/interface1; this also will apply the MTU (test probably shouldn't change the interface, I'll file a bug for that as well). # journalctl -o short-precise --no-pager -b | grep WARK Mar 02 19:17:19.839797 ubuntu cloud-init[647]: WARK: ['netplan', '--debug', 'generate']: Mar 02 19:17:19.839797 ubuntu cloud-init[647]: WARK: ['stat', '/run/systemd/network/10-netplan-interface1.link']: Mar 02 19:17:19.839797 ubuntu cloud-init[647]: WARK: ['cat', '/run/systemd/network/10-netplan-interface1.link']: Mar 02 19:17:19.839797 ubuntu cloud-init[647]: WARK: ['systemctl', 'start', '--no-block', 'systemd-udev-trigger.service']: Mar 02 19:17:19.839797 ubuntu cloud-init[647]: WARK: ['udevadm', 'trigger', '--verbose', '--subsystem-match=net', '--action=add']: root@ubuntu:~# cat /run/systemd/network/10-netplan-interface1.link [Match] MACAddress=52:54:00:12:34:02 [Link] Name=interface1 WakeOnLan=off MTUBytes=1492 root@ubuntu:~# ifconfig interface1 interface1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 10.0.2.100 netmask 255.255.255.0 broadcast 10.0.2.255 inet6 fe80::5054:ff:fe12:3402 prefixlen 64 scopeid 0x20<link> inet6 fec0::5054:ff:fe12:3402 prefixlen 64 scopeid 0x40<site> ether 52:54:00:12:34:02 txqueuelen 1000 (Ethernet) RX packets 16 bytes 5053 (5.0 KB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 35 bytes 3287 (3.2 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 root@ubuntu:~# udevadm trigger --verbose --subsystem-match=net --action=add /sys/devices/pci0000:00/0000:00:04.0/virtio1/net/interface1 /sys/devices/pci0000:00/0000:00:05.0/virtio2/net/interface2 ys/devices/pci0000:00/0000:00:06.0/virtio3/net/interface0 /sys/devices/virtual/net/lo root@ubuntu:~# ifconfig interface1 interface1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1492 inet 10.0.2.100 netmask 255.255.255.0 broadcast 10.0.2.255 inet6 fe80::5054:ff:fe12:3402 prefixlen 64 scopeid 0x20<link> inet6 fec0::5054:ff:fe12:3402 prefixlen 64 scopeid 0x40<site> ether 52:54:00:12:34:02 txqueuelen 1000 (Ethernet) RX packets 16 bytes 5053 (5.0 KB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 37 bytes 3504 (3.5 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 ProblemType: Bug DistroRelease: Ubuntu 17.04 Package: udev 232-18ubuntu1 ProcVersionSignature: Ubuntu 4.10.0-8.10-generic 4.10.0-rc8 Uname: Linux 4.10.0-8-generic x86_64 ApportVersion: 2.20.4-0ubuntu2 Architecture: amd64 Date: Thu Mar 2 19:22:14 2017 Lsusb: Error: command ['lsusb'] failed with exit code 1: MachineType: QEMU Standard PC (i440FX + PIIX, 1996) ProcEnviron: TERM=vt220 PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.10.0-8-generic root=UUID=8bbb84fe-91e8-4a9a-bd91-f6af4793727e ro console=ttyS0 SourcePackage: systemd UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 04/01/2014 dmi.bios.vendor: SeaBIOS dmi.bios.version: 1.10.1-1ubuntu1 dmi.chassis.type: 1 dmi.chassis.vendor: QEMU dmi.chassis.version: pc-i440fx-zesty dmi.modalias: dmi:bvnSeaBIOS:bvr1.10.1-1ubuntu1:bd04/01/2014:svnQEMU:pnStandardPC(i440FX+PIIX,1996):pvrpc-i440fx-zesty:cvnQEMU:ct1:cvrpc-i440fx-zesty: dmi.product.name: Standard PC (i440FX + PIIX, 1996) dmi.product.version: pc-i440fx-zesty dmi.sys.vendor: QEMU To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1669564/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
