[Bug 1633619] Re: dhclient -1 exits 0 when no lease found

[Scott Moser]

Steve,
Good sleuthing.

Bug 974284 has good info in it.

This is definitely tricky.
I think we have the following cases to consider and may be at odds.
a.) dhclient -1 should exit failure as documented.
b.) we need a reliable point in boot where all static networking is configured.
c.) Ill timed reboot (or recovery from lab power failure)
    a system is configured for dhcp is rebooted while the dhcp server is unavailable.
    It seems better for this system to keep trying to get an IP address as otherwise
    the system will be offline forever.  
d.) Any dhcp server downtime and failed lease renewal.
    a system is configured for dhcp and initially succeeds, but while re-trying a lease
    the dhcp server is down for scheduled maintenance.  A failure to release here
    results in system offline if dhclient takes down the interface.
    This is mentioned at https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/838968/comments/11

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Title:
  dhclient -1 exits 0 when no lease found

Status in isc-dhcp package in Ubuntu:
  Confirmed

Bug description:
  I've tried this in containers of xenial, trusty and yakkety.

  i've created a lxc network that does not have dhcp4.

  See https://github.com/lxc/lxd/issues/2481 for some info on how to do
  that.

  Then, I launch an instance:

  $ lxc launch ubuntu-daily:xenial --profile=sm-test-profile2 x1
  % killall dhclient
  % dhclient -r eth0
  % dhclient -1 -v eth0
  Internet Systems Consortium DHCP Client 4.3.3
  Copyright 2004-2015 Internet Systems Consortium.
  All rights reserved.
  For info, please visit https://www.isc.org/software/dhcp/

  Listening on LPF/eth0/00:16:3e:b8:e6:70
  Sending on   LPF/eth0/00:16:3e:b8:e6:70
  Sending on   Socket/fallback
  DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3 (xid=0xc08cb53c)

  DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 4 (xid=0xc08cb53c)
  DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 9 (xid=0xc08cb53c)
  DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 19 (xid=0xc08cb53c)
  DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 7 (xid=0xc08cb53c)
  DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 12 (xid=0xc08cb53c)
  ..
  No DHCPOFFERS received.
  No working leases in persistent database - sleeping.

  % echo $?
  0
  % ps axw | grep dhcl
    356 ?        Ss     0:00 dhclient -1 -v eth0

  
  the man page says of the '-1' option:
         -1     Try to get a lease once.  On  failure  exit  with  code  2.   In
                DHCPv6 this sets the maximum duration of the initial exchange to
                timeout (from dhclient.conf with a default of sixty seconds).

  ProblemType: Bug
  DistroRelease: Ubuntu 16.10
  Package: isc-dhcp-client 4.3.3-5ubuntu15
  ProcVersionSignature: Ubuntu 4.8.0-22.24-generic 4.8.0
  Uname: Linux 4.8.0-22-generic x86_64
  NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
  ApportVersion: 2.20.3-0ubuntu8
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Fri Oct 14 16:59:45 2016
  DhclientLeases:

  EcryptfsInUse: Yes
  InstallationDate: Installed on 2015-07-23 (449 days ago)
  InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Alpha amd64 (20150722.1)
  SourcePackage: isc-dhcp
  UpgradeStatus: No upgrade log present (probably fresh install)

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