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

[LaMont Jones]

After looking into this more (and working on Bug #1629972 some), there
are couple of issues with the new configure_networking:

1. since it checks only for the existence of /run/net-${DEVICE}.conf,
and the dhclient scripts ALWAYS (even on failure) create it, it will try
to get a lease exactly once before bailing out.  Ideally, if both ipv4
and ipv6 are present on the vlan, then both would be configured and (as
is done) present in the net-$DEV.conf file.

2. Since router-advertisements are needed for the on-link indication
(and routes), ipv6 configuration via dhcp should wait until such time as
there is at least a (non-fe80) route for some ipv6 cidr on $DEVICE
(which RA should create).  This will eliminate the iscsi-timeout errors
that we see when configure_networking() returns before RA configures
routing.  Note that a default route is not necessary.  Note also that it
should timeout on the RA if it doesn't show up in a reasonable time,
complain that it got no RA, and then _not_ bring up ipv6 on the
interface (RA is required, as per Bug #1609898)

** Tags removed: verification-pending
** Tags added: verification-failed

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

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

Status in MAAS:
  Fix Released
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:
  Fix Released
Status in initramfs-tools source package in Xenial:
  Fix Released
Status in isc-dhcp source package in Xenial:
  Fix Released
Status in klibc source package in Xenial:
  Won't Fix
Status in open-iscsi source package in Xenial:
  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

  [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.

  These uploads address this by replacing the one-off klibc dhcp client
  (IPv4-only) with the defacto standard isc-dhcp-client, and thereby
  provide both ipv6 and ipv4 DHCP configuration.

  [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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