[Libguestfs] [nbdkit PATCH] captive: Support $uri in --run

[Richard W.M. Jones]

On Tue, Jun 25, 2019 at 09:35:11PM -0500, Eric Blake wrote:
> The existing --run '$nbd' outputs an older form that differs between
> libguestfs and qemu, and which is not always a valid URI.  For
> historical compatibility, we probably can't change that; but we can
> instead add a new '$uri' that outputs a valid URI.  Note that the
> libguestfs '$nbd' TCP form is already a valid URI, but that libguestfs
> still needs to be taught about the nbd+unix:// scheme, so for there,
> you are still better off using '$nbd'; but for qemu, using '$uri'
> already works since qemu v1.3.0 in 2012.
> 
> Note that the NBD project has not actually yet posted a link for the
> preferred URI syntax; once Rich is happy with his work on that
> project, we can touch this up to link to that page.
> 
> Reported-by: Martin Kletzander <mkletzan at redhat.com>
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
>  docs/nbdkit-captive.pod |  8 +++++++-
>  server/captive.c        | 14 +++++++++++++-
>  2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/nbdkit-captive.pod b/docs/nbdkit-captive.pod
> index 6f69cca5..59df6690 100644
> --- a/docs/nbdkit-captive.pod
> +++ b/docs/nbdkit-captive.pod
> @@ -42,9 +42,15 @@ The following shell variables are available in the I<--run> argument:
> 
>  =over 4
> 
> +=item C<$uri>
> +
> +A URI that refers to the nbdkit port or socket in the preferred form
> +documented by the NBD project.
> +
>  =item C<$nbd>
> 
> -A URL that refers to the nbdkit port or socket.
> +An older URL that refers to the nbdkit port or socket in a manner
> +specific to certain tools.
> 
>  Note there is some magic here, since qemu and guestfish URLs have a
>  different format, so nbdkit tries to guess which you are running.  If
> diff --git a/server/captive.c b/server/captive.c
> index 6971af2e..c5274f65 100644
> --- a/server/captive.c
> +++ b/server/captive.c
> @@ -66,7 +66,19 @@ run_command (void)
>      exit (EXIT_FAILURE);
>    }
> 
> -  /* Construct $nbd "URL".  Unfortunately guestfish and qemu take
> +  /* Construct $uri. */
> +  fprintf (fp, "uri=");
> +  if (port) {
> +    fprintf (fp, "nbd://localhost:");
> +    shell_quote (port, fp);
> +  }
> +  else if (unixsocket) {
> +    fprintf (fp, "nbd+unix://\\?socket=");
> +    shell_quote (unixsocket, fp);
> +  }
> +  fprintf (fp, "\n");
> +
> +  /* Construct older $nbd "URL".  Unfortunately guestfish and qemu take
>     * different syntax, so try to guess which one we need.
>     */
>    fprintf (fp, "nbd=");

Looks reasonable, although I guess we may one day find we need more
quoting of unixsocket (both shell quoting and URI quoting, urrgh).
Anyway:

ACK

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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