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

DL> You call DL> clone(CLONE_NEWPID|CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWUSER|CLONE_NEWIPC|SIGCHLD|CLONE_NEWNET) DL> When this call fails, you 'assume' netns is not compiled in. No, actually, I do this: int flags = CLONE_NEWPID|CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWUSER| CLONE_NEWIPC|SIGCHLD|extra_flags; 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(a)us.ibm.com