[Bug 713385] Re: netcfg/choose_interface=auto fails to find the right interface

[Colin Watson]

I'm told out of band that the fix for bug 56679 should be sufficient to
resolve this in practice.  The link detection bug hasn't gone away, so
I'm going to leave this bug open, but I'm unassigning it since it
doesn't sound as though it needs to be treated with any particular
priority.  Leave a comment if I'm wrong ...

** Changed in: netcfg (Ubuntu)
       Status: New => Confirmed

** Changed in: netcfg (Ubuntu)
   Importance: Undecided => Medium

** Changed in: netcfg (Ubuntu)
     Assignee: Canonical Foundations Team (canonical-foundations) => (unassigned)

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https://bugs.launchpad.net/bugs/713385

Title:
  netcfg/choose_interface=auto fails to find the right interface

Status in “netcfg” package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: netcfg

  Under some circumstances, netcfg may not be able to find the right
  interface to run dhclient on when netcfg/choose_interface is set to
  auto.  It looks like the way choose_interface=auto works is that
  ethtool finds the lowest numbered interface that reports a link, and
  runs dhclient on that interface.  If no interface with a link is
  found, it tries only eth0.

  I'm hitting a problem on a number of servers that have one or two
  Broadcom BCM5708 interfaces *and* two Intel gigabit interfaces.  If
  the network connection is plugged in to the BCM5708, the install will
  often fail to find a network with netcfg/choose_interface=auto.

  The problem is that the BCM5708 doesn't report link up until you try
  to send traffic over it.  So none of the interfaces on the server
  report having a link, and netcfg tries dhcp on just eth0.  Depending
  on the order the network modules have been loaded, eth0 may be the
  BCM5708 or it may be the Intel.  If eth0 is the Intel, d-i attempts to
  run dhclient on the wrong interface, and it fails.

  I think a reasonable solution to this problem would be for netcfg to
  attempt dhclient on all interfaces until one succeeds.  Or perhaps it
  should do this only when no interfaces report a link.  Either way, I
  don't think we can rely entirely on link status, because not all NIC
  report this correctly.

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