[Bug 974284] Re: invoking dhclient3 with -1 causes issue if no dhcp server available

[Scott Moser]

On Thu, 5 Apr 2012, Stéphane Graber wrote:

> 16:58 < smoser> ie, to safeguard for the power failure case, where 5 minutes wasn't enough, but 5 minutes and 3 seconds would have been.
> 16:59 < stgraber> so we want dhclient to try for $TIMEOUT, if it gets a lease during that time, background itself and get into a renewal/retry loop, if it doesn't, then ???
> 16:59 < stgraber> for ??? I tend to prefer failing as I really don't want to run the ifupdown hooks unless we have a working connection
> 17:00 < stgraber> but you clearly prefer continuing regardless that'll make all the upstart jobs trigger as well as all upstart hooks (even though you don't have network access)

Well, I don't know that I prefer that. Sorry I didn't see that earlier.
Obviously, triggering jobs that expect network when network isn't up isn't
a great solution.

What about exiting failure after $TIMEOUT, but forking into retry loop?

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https://bugs.launchpad.net/bugs/974284

Title:
  invoking dhclient3 with -1 causes issue if no dhcp server available

Status in “isc-dhcp” package in Ubuntu:
  Confirmed

Bug description:
  In bug 838968, we modified ifupdown to invoke dhclient3 with '-1' as a
  parameter [1], and subsequently changed the default timeout of
  dhclient in isc-dhcp3 to from 60 seconds to 300 seconds [2].

  The reason for this is that we now have a reliable "static-networking-
  up" event that can be used for upstart jobs to start on, when static
  networking is up.  Here, static is any networking with an entry in
  /etc/network/interfaces.

  That event is used by cloud-init and other things that depend on
  network.

  The fallout of this is that if for some reason a server (or cloud-
  instance, or anything really), boots and does not obtain a dhcp
  address in 5 minutes, then it will give up forever.  The previous
  behavior is that it would try forever.

  This scenario isn't terribly unrealistic.  A power fail could take out
  a dchp server, cause a fsck, while the server came up 5 minutes before
  the dhcp server was up.

  Issue was originally raised in #openstack-dev by rmk around
  2012-04-05T06:42:19 [3]

  --
  [1] http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/precise/ifupdown/precise/revision/56
  [2] http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/precise/isc-dhcp/precise/revision/32
  [3] http://eavesdrop.openstack.org/irclogs/%23openstack-dev/%23openstack-dev.2012-04-05.log

  Releated bugs:
    * bug 838968: static-network-up event does not wait for interfaces to have an address

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