https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=250749
Bug ID: 250749
Summary: /etc/network.subr: Mitigate absence of LINK_UP
notification when VIRTIO_NET_F_STATUS is not
negotiated
Product: Base System
Version: CURRENT
Hardware: Any
OS: Any
Status: New
Severity: Affects Some People
Priority: ---
Component: misc
Assignee: b...@freebsd.org
Reporter: samy.mahmo...@gmail.com
Created attachment 219229
--> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=219229&action=edit
Patch file
Hi,
On some virtual machines (e.g. on VirtualBox, on the cloud platform Vultr,
etc.), restarting a vtnet interface configured with DHCP fails to restart
dhclient.
Because the driver 'if_vtnet' follows the driver requirements of the VIRTIO
specification [1], LINK_UP is notified at most once (most probably during the
boot process) when VIRTIO_NET_F_STATUS is not negotiated. As a result, dhclient
can not be restarted via devd.
For a similar reason, it might be possible that LINK_UP is not emitted at the
interface restart even in a variant scenario where VIRTIO_NET_F_STATUS is
negotiated (I do not have access to a bhyve-capable computer right now so I am
unable to test).
If SYNCDHCP is used to configure the interface, dhclient is restarted via
netif/network.subr.
The attached patch makes dhclient start from two different ways (devd and
netif/network.subr) when the interface is configured with DHCP. In that regard,
DHCP would behave exactly like SYNCDHCP and inherit the same race that
currently happens with SYNCDHCP when an interface is restarted [2].
• Mitigate the absence of LINK_UP notification to restart dhclient, at least
when VIRTIO_NET_F_STATUS is not negotiated
• Remove a comment note (success of wpaif does imply interface configuration
and wpa_supplicant does bring up the interface)
• Remove a trailing whitespace
[1]
https://docs.oasis-open.org/virtio/virtio/v1.1/csprd01/virtio-v1.1-csprd01.html
(5.1.4.2 Driver Requirements, second paragraph)
[2] This race does not happen during the boot process because devd has not yet
been started when netif runs). It is reproductible on a computer by configuring
an interface with SYNCDHCP and executing, e.g., 'service netif restart wlan0' a
dozen of times, or even more easily with a lagg interface by executing, e.g.,
'service netif restart wlan0 lagg0'. It has no functional impact, but it makes
one seriously wonder why 'dhclient is already running' whereas one just
restarted one's interface...
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