Re: [PATCH 06/15] build: syscalls: Add setns syscall wrapper.

[Ludovic Courtès]

David Thompson <address@hidden> skribis:

> From: David Thompson <address@hidden>
>
> * guix/build/syscalls.scm (setns): New procedure.
> * tests/syscalls.scm: Test it.

[...]

> +    (lambda (fdes nstype)
> +      "Reassociate the current process with the namespace specified by FDES.

“... by FDES, a file descriptor obtained by opening a /proc/PID/ns/*
files.”

> +(test-assert "setns"
> +  (match (clone (logior CLONE_NEWUSER))
> +    (0 (primitive-exit 0))
> +    (clone-pid
> +     (match (pipe)
> +       ((in . out)
> +        (match (primitive-fork)
> +          (0
> +           (close in)
> +           (call-with-input-file (user-namespace clone-pid)
> +             (lambda (port)
> +               (setns (port->fdes port) 0)))
> +           (write 'done out)
> +           (close out)
> +           (primitive-exit 0))
> +          (fork-pid
> +           (close out)
> +           ;; Wait for the child process to join the namespace.
> +           (read in)
> +           (equal? (readlink (user-namespace clone-pid))
> +                   (readlink (user-namespace fork-pid))))))))))

Add a waipid call for both CLONE-PID and FORK-PID to make sure nothing’s
left behind.

OK with these changes!

Ludo’.