[libvirt] [PATCH 1 of 4] [LXC] Detect support for NETNS in lxc driver initialization

Dan Smith danms at us.ibm.com
Wed Jun 25 15:22:17 UTC 2008

DL> You call

DL> When this call fails, you 'assume' netns is not compiled in.

No, actually, I do this:


Where extra_flags=0 for the LXC detection and extra_flags=CLONE_NEWNET
for the NETNS detection.  See the lxcCheckContainerSupport() calls in
lxcProbe() and lxcCheckNetNsSupport().

DL> In your code, you launch the ip command and if it fails with a
DL> particular exit code, you 'assume' netns is not supported. Another
DL> assumption

The ip command returns a different error code for an invalid
subcommand than for a failure of a known subcommand.  That seems like
a pretty reasonable sentinel (and certainly better than scraping the
help output), IMHO.

DL> ... IMHO you should rely on the package dependencies/command
DL> version. Or if you absolutely want to detect that at startup,
DL> perhaps doing "ip link help | grep netns" is more secure :)

DV has already said he'd like to see it done dynamically at the driver
probe stage.  I'll let him comment on his preferred way of doing that.

Dan Smith
IBM Linux Technology Center
Open Hypervisor Team
email: danms at us.ibm.com
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