Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces

On Tue, Jul 26, 2016 at 11:32:25AM -0700, W. Trevor King wrote:

On Tue, Jul 26, 2016 at 11:25:24AM -0700, Andrew Vagin wrote:

quoted

Sure. If a process wants to compare two namespaces, it needs to get file
descriptors for them (open /proc/PID/ns/XXX, use new ioctl-s, find a
process which has them),
and then it calls kcmp(pid1, pid2, KCMP_NSFD, ns_fd1, ns_fd2)

If you use the new ioctl-s to get ns_fd2, do you walk your local /proc
to find pid2?

If you use the new ioctl-s to get nf_fd2, you will have it in the
current process, so pid2 will be getpid().

pidX identifies a process where to find fdX.

man 2 kcmp:
 The kcmp() system call can be used to check whether the  two processes
 identified  by  pid1  and  pid2 share a kernel resource such as virtual
 memory, file descriptors, and so on.

Cheers,
Trevor

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