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

[Nicholas Digati]

I can also confirm this bug is still happening with the Ubuntu 18.04.2
installer. Using BOOTIF and "netcfg/choose_interface=auto" the installer
defaults to using eno1 (first interface in the list). These machines all
have an external network card they use the PXE boot.

I see the following messages in the installer syslog which makes it seem
like it knows which interface to use but ignores it afterwards and uses
a different interface:

Mar  6 03:46:42 netcfg[1195]: INFO: Starting netcfg v.1.142ubuntu7
Mar  6 03:46:42 netcfg[1195]: WARNING **: Couldn't read Wpasupplicant pid file, not trying to kill.
Mar  6 03:46:42 netcfg[1195]: DEBUG: Flusing addresses and routes on interface: eno1
Mar  6 03:46:42 netcfg[1195]: DEBUG: Flusing addresses and routes on interface: eno2
Mar  6 03:46:42 netcfg[1195]: DEBUG: Flusing addresses and routes on interface: eno3
Mar  6 03:46:42 netcfg[1195]: DEBUG: Flusing addresses and routes on interface: eno4
Mar  6 03:46:42 netcfg[1195]: DEBUG: Flusing addresses and routes on interface: enp4s0
Mar  6 03:46:42 netcfg[1195]: INFO: Found interface enp4s0 with link-layer address
Mar  6 03:46:42 netcfg[1195]: INFO: Taking down interface eno1
Mar  6 03:46:42 netcfg[1195]: INFO: Taking down interface eno2
Mar  6 03:46:42 netcfg[1195]: INFO: Taking down interface eno3
Mar  6 03:46:42 netcfg[1195]: INFO: Taking down interface eno4
Mar  6 03:46:42 netcfg[1195]: INFO: Taking down interface enp4s0
Mar  6 03:46:42 netcfg[1195]: INFO: Taking down interface lo
Mar  6 03:46:42 netcfg[1195]: INFO: Activating interface eno1
Mar  6 03:46:42 netcfg[1195]: INFO: Waiting time set to 3
Mar  6 03:46:42 netcfg[1195]: INFO: ethtool-lite: eno1: carrier down
... (repeats message for 3 seconds)
Mar  6 03:46:45 netcfg[1195]: INFO: Reached timeout for link detection on eno1
Mar  6 03:46:45 netcfg[1195]: DEBUG: Commencing network autoconfiguration on eno1


Some of the machines I've tested on it appears to have worked and some don't work at all (like the one with logs above). On the machines where it appears to work the internal interfaces are getting different names (enp6s0f0, enp6s0f1) so the external card comes first in the list (with the name enp5s0). So it just seems like it works when it's still just using the first interface in the list.

We worked around this for now by disabling the internal network
card/interfaces in the BIOS so it only detects the external card.

(P.S sorry for information type updates above clicked too many times)

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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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