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[Eric Desrochers <eric.desrochers@xxxxxxxxxxxxx>]

** Also affects: linux (Ubuntu Trusty)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu Trusty)
       Status: New => In Progress

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

** Changed in: linux (Ubuntu Trusty)
     Assignee: (unassigned) => Eric Desrochers (slashd)

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https://bugs.launchpad.net/bugs/1761534

Title:
  "ip a" command on a guest VM shows UNKNOWN status

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Trusty:
  In Progress
Status in linux source package in Xenial:
  In Progress
Status in linux source package in Artful:
  In Progress
Status in linux source package in Bionic:
  In Progress

Bug description:
  It has been brought to my attention the following :

  ------------------------------------------------
  Environment: The guest VM is using a canonical ubuntu image, and the eth0 is a virtio-net adaptor, running on DPDK.

  Background: "ip a" command relies on the operstate variable of the
  net_device structure maintained by the kernel. This is based on the
  operational state as defined in the IF MIB (RFC 2863). Device drivers
  are expected to update this member. But many older drivers don’t seem
  to be using this. So in general, IF_OPER_UP and IF_OPER_UNKNOWN are
  treated as equal, in some sense, to maintain backward compatibility.
  Even if we look at https://elixir.free-
  electrons.com/linux/v4.15-rc2/source/include/linux/netdevice.h#L3468,
  the function to check if interface is up, is written as follows, which
  says that OPER_UNKNOWN is not something to be alarmed about, and just
  reflective of a state that some drivers don’t care to update about.

  static inline bool netif_oper_up(const struct net_device *dev)
  {
  return (dev->operstate == IF_OPER_UP ||
  dev->operstate == IF_OPER_UNKNOWN /* backward compat */);
  }

  Code Ref:

  1. https://elixir.free-electrons.com/linux/v4.15-rc2/source/include/linux/netdevice.h#L1739
  2. https://elixir.free-electrons.com/linux/v4.15-rc2/source/include/linux/netdevice.h#L3468
  3. https://www.kernel.org/doc/Documentation/networking/operstates.txt

  Now, for traditional kernel mode network adapter drivers, this state is supposed to be manipulated by the driver. And we can safely assume that most current kernel model drivers do keep this updated.
  ------------------------------------------------

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