[Bug 1561096] Comment bridged from LTC Bugzilla

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------- Comment From ruddk at us.ibm.com 2016-04-05 10:26 EDT-------
(In reply to comment #16)
> > This creates a name-slip problem for these ibmveth devices depending on the timing of other devices (where another NIC will temporarily be assigned a name like eth0 before it is renamed by udev).
>
> Can you please explain this further? The kernel should always pick a new
> eth* name and avoid name clashes with existing eth* devices, and udev (since
> Ubuntu 15.04) will never assign a name like "eth*" which potentially
> collides with the kernel default names. At least that's the current
> assumption, if that is invalid and you actually see a device being *re*named
> to "eth*", this is what we need to fix.

At the time of the install, only one network device existed (the ibmveth device).  This was assigned the name eth0, and this is what the installer recorded in the interfaces file.  After the install, additional physical NICs were added to the system.  Upon boot, one of the new NIC's driver loaded first and temporarily grabbed the eth0 name.  When the ibmveth driver loaded, it grabbed eth1 (since eth0 was taken at the time).  Eth0 was subsequently renamed (as you noticed in the logs), but the ibmveth device name had already slipped, and now there was no longer an eth0 device to go with the configuration in the interfaces file.
> I'm a bit confused why there are two different device drivers claiming the
> same device, though.

As noted, network device additions post-boot.

> After booting, what does "ip a" show, i. e. which ethernet devices do you
> actually have?  It would also be helpful to attach the output of "udevadm
> info --export-db" to show me which information udev collected about the
> ethernet devices.

This information should be contained in the sosreport attached.
> Did you manually put "eth0" into /etc/network/interfaces, or was that done
> by the installer? The latter would mean that the installer environment names
> devices differently than the installed OS (that'd be a major bug indeed).

Done by the installer due to the installation being done while there was
only the ibmveth device.

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https://bugs.launchpad.net/bugs/1561096

Title:
  STC850:Brazos:Br16:Br16p05: Network ethernet port name changed under
  Ubuntu 16.04 with added adapters (ibmveth)

Status in systemd package in Ubuntu:
  Incomplete
Status in systemd source package in Xenial:
  Incomplete

Bug description:
  Problem Description : I had installed a fresh install of Ubuntu 16.04
  from an ISO image and had set up the partition as directed in the
  Wiki. I had set up the networking as directed in the WIKI and was able
  to ping "iofnim" and was able to perform updates and upgrades to the
  Ubuntu installation without issue.

  I had checked to make sure (by adding them to an existing AIX
  partition) that the Mason and Travis_EN adapters to be added were at
  the latest microcode levels.  I assigned them to the partition to be
  used (br16p05) and then shut down the partition and restarted it to
  allow the partition to activate the adapters.

  After the partition restarted, I attempted to build the network using
  build_net and during its run noticed that the output for the adapters
  was returning "Network is unreachable".  After it completed, I
  attempted to mount iofnim using the command:

  "mount iofnim.aus.stglabs.ibm.com:/nim/build_net /root/test -o nolock"

  which returned a "Failed" error message.

  I then ran "ifconfig -a" to check on the state of the network which
  had been working until I rebooted the partition after adding the
  adapters.

  I found the unconventional names for both the Mason and the Travis_EN
  adapters contained in the output from "ifconfig -a" but also found
  that "eth0", with which I had originally set up the network access for
  the partition during setupp, was no longer listed but instead "eth1"
  was now listed and none of the networking data including IP's reported
  from "ifconfig -a" were set.

  I consulted with Thiru and he asked I write it up and include a tar
  file created from /var/log which I have attached to the defect.

  As an additional note, I was able to go back into
  /etc/network/interfaces and modify the settings for "eth0" to now be
  set to "eth1" and after bringing the port down and back up, was able
  to again ping out and access the network.

  Please advise.

  == Comment: #7 - Kevin W. Rudd  - 2016-02-11 12:32:49 ==
  Thank you for the additional info.  This is not quite the same as the bug I referenced earlier.  It is actually a match for bug 122308 . 

  Canonical:

  This is the same basic issue as originally worked in LP Bug 1437375

  The ibmveth based devices are not associated with PCI bus locations,
  and still rely on the legacy eth? naming.  The problem here is that
  the 75-persistent-net-generator.rules file that used to set up the 70
  -persistent-net.rules file for these devices has been removed in 16.04

  This creates a name-slip problem for these ibmveth devices depending
  on the timing of other devices (where another NIC will temporarily be
  assigned a name like eth0 before it is renamed by udev).

  Please add back persistent-net-generator support for non-PCI-based
  devices like this.

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