[Bug 1621507] Re: initramfs-tools configure_networking() fails to dhcp ipv6 addresses

[Robie Basak]

I've been working on reviewing this over the last few days. Thanks to
everyone for your help and patience, especially Mathieu, LaMont and
Scott for your in-person interactive responses.

We've had various review feedback loops and settled on using the MPs for
coordination. When everyone (including me, for ~ubuntu-sru) is happy, we
can upload and accept from the unapproved queue all at once.

>From a code review perspective, I'm done, though am waiting for the
agreed fixes to come through (and be checked by everyone relevant).

>From a QA review perspective, I would like a comprehensive test plan for
existing ip= use cases given the previous regressions that we've had.
There isn't currently anything on this in the bug description.

As we've been delayed enough already, I think it's OK to accept the
agreed changes into xenial-proposed now, provided that we agree on a
regression test plan and perform it before marking verification-done.

For everyone, here's the current status for Xenial.

Needed before accepting into xenial-proposed:

[cyphermox] initramfs-tools MP, and reviews from everyone
[smoser] isc-dhcp MP: Scott's review

[not rbasak] initramfs-tools upload from MP (blocked on MP and reviews)
[not rbasak] isc-dhcp upload from MP (blocked on MP review)
[rbasak] Check and accept from Xenial unapproved (blocked on above except for open-iscsi; might as well do all three together when ready)

Needed before accepting into xenial-updates:

Write a comprehensive test plan for existing ip= use cases given the previous regressions.
[rbasak or another ~ubuntu-sru] Agree on test plan.

All SRU review bugfixes incorporated into Zesty.

Standard test case verification for the problem we're fixing (ip6=
function).

Mark verification-done (blocked on all of the above).

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https://bugs.launchpad.net/bugs/1621507

Title:
  initramfs-tools configure_networking() fails to dhcp ipv6 addresses

Status in MAAS:
  Fix Committed
Status in initramfs-tools package in Ubuntu:
  Fix Released
Status in isc-dhcp package in Ubuntu:
  Fix Released
Status in klibc package in Ubuntu:
  Won't Fix
Status in open-iscsi package in Ubuntu:
  In Progress
Status in initramfs-tools source package in Xenial:
  Fix Committed
Status in isc-dhcp source package in Xenial:
  Fix Committed
Status in klibc source package in Xenial:
  Won't Fix
Status in open-iscsi source package in Xenial:
  Fix Released
Status in initramfs-tools source package in Yakkety:
  Fix Committed
Status in isc-dhcp source package in Yakkety:
  Fix Committed
Status in klibc source package in Yakkety:
  Won't Fix
Status in open-iscsi source package in Yakkety:
  Fix Released
Status in klibc package in Debian:
  New

Bug description:
  initramfs' configure_networking function uses ipconfig to configure the network.
  ipconfig does not support dhcpv6.  See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=627164

  Related bugs:
    * bug 1229458: grub2 needed changes
    * bug 1621615: network not configured when ipv6 netbooted into cloud-init
    * bug 1635716: Can't bring up a machine on a dual network (ipv4 and ipv6)

  Bugs related to uploads for this specific SRU:

  cloud-init:
  bug 1460715: different fix unrelated to this SRU
  bug 1639930: ip6= on kernel command line
  bug 1642679: different fix unrelated to this SRU
  bug 1644043: different fix unrelated to this SRU

  ifupdown:
  bug 1629972: networking.service takes down lo on stop

  initramfs-tools:
  bug 1621507: no IPv6 DHCP support in early boot
  bug 1628306: regression-update (failure when ip="")
  bug 1631474: regression-update (failure when ip=:::::eth0:dhcp)

  isc-dhcp:
  bug 1621507: no IPv6 DHCP support in early boot
  bug 1633479: dhclient does not wait for IPv6 DAD

  open-iscsi:
  bug 1621507: no IPv6 DHCP support in early boot

  
  [Impact]

  It is not possible to netboot Ubuntu with a network-based root
  filesystem in an ipv6-only environment.  Anyone wanting to netboot in
  an ipv6-only environment is affected.

  [Stable Fix]

  These uploads add "ip6=" to the command line syntax to configure ipv6
  using the defacto isc-dhcp-client.  IPv4 configuration (and "ip="
  syntax) remain unchanged.

  Valid format for the ip6= command line option is:
     ip6=none (or ip6=off or ip6=) -- do not configure ipv6
     ip6=DEVICE  -- run IPv6 dhclient on device DEVICE.

  [Test Case]

  See Bug 1229458.  Configure radvd, dhcpd, and tftpd for your ipv6-only
  netbooting world.  Pass the boot process an ipv6 address to talk to,
  and see it fail to configure the network.

  [Regression Potential]

  1) This increases the uncompressed initramfs size by approximately 500KB, since isc-dhcp-client is added, but klibc is still needed for some other things, and is therefore present.  On systems with a very small /boot partition, this could result in failure to upgrade the initramfs.
  2) In at least some cases, DHCP network configuration shifts from klibc's ipconfig to isc-dhcp-client's dhclient.  This should be of minimal risk, as isc-dhcp-client is in very very widespread use.  In the event of a regression, network boot would fail, but the prior kernel should still be bootable.

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