Re: [PATCH 2/9 v2] Introduce nat/linux-namespaces.[ch]

Pedro Alves
2015-05-21T14:56:45Z

On 04/30/2015 01:05 PM, Gary Benson wrote:

...

> + For avoidance of doubt, if the helper process receives a
> + message it doesn't handle it will reply with MNSH_MSG_ERROR.
> + If the main process receives MNSH_MSG_ERROR at any time then
> + it will call internal_error. If internal_error causes the
> + main process to exit, the helper will notice this and also
> + exit. The helper will not exit until the main process
> + terminates, so if the user continues through internal_error
> + the helper will still be there awaiting requests from the
> + main process.

...

> +/* Mount namespace helper message types. */
> +
> +enum mnsh_msg_type
> + {
> + /* An unrecoverable communication error occurred.

I think "unrecoverable" here sounds a bit confusing, as it
contradicts the comment above that explains that the helper
is still awaiting requests if the user decides to continue
after internal_error.

> + Receipt of this message by either end will cause
> + an assertion failure in the main process. */
> + MNSH_MSG_ERROR,

> + /* A request that the helper call unlink. The single
> + argument (the filename) should be passed in BUF, and
> + should include a terminating NUL character. Helper
> + should respond with a MNSH_RET_INT. */
> + MNSH_REQ_UNLINK,
> +
> + /* A request that the helper call readlink. The single
> + argument (the filename) should be passed in BUF, and
> + should include a terminating NUL character. The helper

Missing double-space.

> +static void
> +mnsh_main (int sock)
> +{
> + while (1)
> + {
> + enum mnsh_msg_type type;
> + int fd, int1, int2;
> + char buf[PATH_MAX];
> + ssize_t size, response = -1;
> +
> + size = mnsh_recv_message (sock, &type,
> + &fd, &int1, &int2,
> + buf, sizeof (buf));
> +
> + if (size >= 0 && size < sizeof (buf))
> + {
> + switch (type)
> + {
> + case MNSH_REQ_SETNS:
> + if (fd > 0)
> + response = mnsh_handle_setns (sock, fd, int1);
> + break;
> +
> + case MNSH_REQ_OPEN:
> + if (buf[size - 1] == '\0')

Why these == '\0' checks? To protect against bugs? In
that case, I guess this should be:

if (size > 0 && buf[size - 1] == '\0')

> + response = mnsh_handle_open (sock, buf, int1, int2);
> + break;

And that's it. Really all looks good to me. :-)

Thanks,
Pedro Alves