The following patch fixes the bug :
-------------------
commit bda7fab54828bbef2164bb23c0f6b1a7d05cc718
Author: Jay Vosburgh <[email protected]>
Date: Thu Mar 22 14:42:41 2018 +0000
virtio-net: Fix operstate for virtio when no VIRTIO_NET_F_STATUS
The operstate update logic will leave an interface in the
default UNKNOWN operstate if the interface carrier state never changes
from the default carrier up state set at creation. This includes the
case of an explicit call to netif_carrier_on, as the carrier on to on
transition has no effect on operstate.
This affects virtio-net for the case that the virtio peer does
not support VIRTIO_NET_F_STATUS (the feature that provides carrier state
updates). Without this feature, the virtio specification states that
"the link should be assumed active," so, logically, the operstate should
be UP instead of UNKNOWN. This has impact on user space applications
that use the operstate to make availability decisions for the interface.
Resolve this by changing the virtio probe logic slightly to call
netif_carrier_off for both the "with" and "without" VIRTIO_NET_F_STATUS
cases, and then the existing call to netif_carrier_on for the "without"
case will cause an operstate transition.
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Jason Wang <[email protected]>
Cc: Ben Hutchings <[email protected]>
Signed-off-by: Jay Vosburgh <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
-------------------
** Changed in: linux (Ubuntu)
Assignee: (unassigned) => Eric Desrochers (slashd)
** Changed in: linux (Ubuntu)
Status: New => In Progress
** Changed in: linux (Ubuntu)
Importance: Undecided => Medium
** Also affects: linux (Ubuntu Bionic)
Importance: Medium
Assignee: Eric Desrochers (slashd)
Status: In Progress
** Also affects: linux (Ubuntu Xenial)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Artful)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Artful)
Assignee: (unassigned) => Eric Desrochers (slashd)
** Changed in: linux (Ubuntu Xenial)
Assignee: (unassigned) => Eric Desrochers (slashd)
** Changed in: linux (Ubuntu Artful)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Xenial)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Artful)
Status: New => In Progress
** Changed in: linux (Ubuntu Xenial)
Status: New => In Progress
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You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
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 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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