[Bug 1792168] Re: ifupdown hotplug dhcp fails due to udevadm RestrictAddressFamilies

[Scott Moser]

This is invalid.
It actually all still works because:
 udev hook /lib/udev/rules.d/80-ifupdown.rules calls /lib/udev/ifupdown-hotplug
 which calls
   systemctl --no-block start $(systemd-escape --template ifup at .service $INTERFACE)

Then the ifup at .service is what actually brings up the device.

That service is then not beholden to the udevadm restrcitions.


** Changed in: ifupdown (Ubuntu)
       Status: New => Invalid

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Title:
  ifupdown hotplug dhcp fails due to udevadm RestrictAddressFamilies

Status in ifupdown package in Ubuntu:
  Invalid

Bug description:
  I haven't verified this, but I believe that ifupdown works through udevadm hooks.
  So udevadm hotplug event -> ifup eth0.
  Any subprocesses of a udevadm hook will be restricted by the systemd-udevd.service
  restrictions, which currently are
     RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6

  We found this when playing with udevamd hooks to bring up network
  devices on cosmic (netplan).

  root at b1:~# systemctl cat udev.service
  # /lib/systemd/system/systemd-udevd.service
  #  SPDX-License-Identifier: LGPL-2.1+
  #
  #  This file is part of systemd.
  #
  #  systemd is free software; you can redistribute it and/or modify it
  #  under the terms of the GNU Lesser General Public License as published by
  #  the Free Software Foundation; either version 2.1 of the License, or
  #  (at your option) any later version.

  [Unit]
  Description=udev Kernel Device Manager
  Documentation=man:systemd-udevd.service(8) man:udev(7)
  DefaultDependencies=no
  After=systemd-sysusers.service systemd-hwdb-update.service
  Before=sysinit.target
  ConditionPathIsReadWrite=/sys

  [Service]
  Type=notify
  OOMScoreAdjust=-1000
  Sockets=systemd-udevd-control.socket systemd-udevd-kernel.socket
  Restart=always
  RestartSec=0
  ExecStart=/lib/systemd/systemd-udevd
  KillMode=mixed
  WatchdogSec=3min
  TasksMax=infinity
  MountFlags=slave
  MemoryDenyWriteExecute=yes
  RestrictRealtime=yes
  RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6
  SystemCallArchitectures=native
  LockPersonality=yes
  IPAddressDeny=any

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ifupdown 0.8.17ubuntu1.1
  ProcVersionSignature: Ubuntu 4.17.0-9.10-generic 4.17.17
  Uname: Linux 4.17.0-9-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.3
  Architecture: amd64
  Date: Wed Sep 12 15:09:01 2018
  ProcEnviron:
   TERM=screen.xterm-256color
   PATH=(custom, no user)
   LANG=C.UTF-8
  SourcePackage: ifupdown
  UpgradeStatus: No upgrade log present (probably fresh install)

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