[Bug 892233] [NEW] dhclient on server install CD hangs forever trying to get an IPv6 lease

[Nick]

Public bug reported:

Attempting to install from the Ubuntu Server CD ISO (
http://mirror.bytemark.co.uk/ubuntu-releases/11.10/ubuntu-11.10-server-
amd64.iso ) on a Bytemark (BigV) virtual machine, dhclient waits forever
trying to get an IPv6 lease.

I'm not sure if our network can be more helpful in terms of allowing the
IPv6 lease to be gotten (at the moment, we don't run a DHCPv6 server at
all, and RAs are lacking), but the current behaviour is surely a bug.

The installer is hung on running:

[9316] udpkg --configure --force-configure netcfg
[9317] netcfg
[9354] dhclient -6 -S -cf /var/lib/netcfg/dhclient6.conf -s

The screen on Alt+F1 is just a plain blue, with no information about
what's happening. On Alt+F4, I see the following:

dhclient: XMT: Info-Request on eth0, interval 930ms
dhclient: XMT: Info-Request on eth0, interval 1800ms
dhclient: XMT: Info-Request on eth0, interval 3510ms
dhclient: XMT: Info-Request on eth0, interval 7250ms
dhclient: XMT: Info-Request on eth0, interval 14940ms
dhclient: XMT: Info-Request on eth0, interval 30240ms
dhclient: XMT: Info-Request on eth0, interval 63100ms
dhclient: XMT: Info-Request on eth0, interval 125080ms
dhclient: XMT: Info-Request on eth0, interval 124300ms
[at this point, I ran kill 9354]


Given that there simply isn't a DHCPv6 server running on the network, this level of persistence is wrong. Once I killed the process, I installed from IPv4 without any further issues.

Prior to the dhclient attempt, there was an attempt to use rdisc6. This
discovered a router, and was given what it considered to be an invalid
prefix (we assign a /56 per VLAN, which is advertised, and assign each
machine within that VLAN a /64, but currently it needs to be manually
configured by the user). Those routes all ended up in the route table.

Suggested fix: fail and fall back to IPv4 after 4 attempts or so? man
dhclient.conf suggests the default timeout is 300 seconds - five minutes
- which is an awfully long time to be looking at a blank screen.
However, I waited for ~350 seconds and it didn't seem to timeout itself
automatically, so maybe the default is different in -6 mode, or perhaps
it needs setting explicitly and the manpage is wrong.

** Affects: netcfg (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: d-i dhcp dhcpv6 installer ipv6

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https://bugs.launchpad.net/bugs/892233

Title:
  dhclient on server install CD hangs forever trying to get an IPv6
  lease

Status in “netcfg” package in Ubuntu:
  New

Bug description:
  Attempting to install from the Ubuntu Server CD ISO (
  http://mirror.bytemark.co.uk/ubuntu-releases/11.10/ubuntu-11.10
  -server-amd64.iso ) on a Bytemark (BigV) virtual machine, dhclient
  waits forever trying to get an IPv6 lease.

  I'm not sure if our network can be more helpful in terms of allowing
  the IPv6 lease to be gotten (at the moment, we don't run a DHCPv6
  server at all, and RAs are lacking), but the current behaviour is
  surely a bug.

  The installer is hung on running:

  [9316] udpkg --configure --force-configure netcfg
  [9317] netcfg
  [9354] dhclient -6 -S -cf /var/lib/netcfg/dhclient6.conf -s

  The screen on Alt+F1 is just a plain blue, with no information about
  what's happening. On Alt+F4, I see the following:

  dhclient: XMT: Info-Request on eth0, interval 930ms
  dhclient: XMT: Info-Request on eth0, interval 1800ms
  dhclient: XMT: Info-Request on eth0, interval 3510ms
  dhclient: XMT: Info-Request on eth0, interval 7250ms
  dhclient: XMT: Info-Request on eth0, interval 14940ms
  dhclient: XMT: Info-Request on eth0, interval 30240ms
  dhclient: XMT: Info-Request on eth0, interval 63100ms
  dhclient: XMT: Info-Request on eth0, interval 125080ms
  dhclient: XMT: Info-Request on eth0, interval 124300ms
  [at this point, I ran kill 9354]

  
  Given that there simply isn't a DHCPv6 server running on the network, this level of persistence is wrong. Once I killed the process, I installed from IPv4 without any further issues.

  Prior to the dhclient attempt, there was an attempt to use rdisc6.
  This discovered a router, and was given what it considered to be an
  invalid prefix (we assign a /56 per VLAN, which is advertised, and
  assign each machine within that VLAN a /64, but currently it needs to
  be manually configured by the user). Those routes all ended up in the
  route table.

  Suggested fix: fail and fall back to IPv4 after 4 attempts or so? man
  dhclient.conf suggests the default timeout is 300 seconds - five
  minutes - which is an awfully long time to be looking at a blank
  screen.  However, I waited for ~350 seconds and it didn't seem to
  timeout itself automatically, so maybe the default is different in -6
  mode, or perhaps it needs setting explicitly and the manpage is wrong.

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