Re: [Qemu-devel] [PATCH v3 2/2] qemu-bridge-helper: Use stateless configuration for bridge.conf

[Eduardo Habkost]

On Tue, May 26, 2015 at 01:54:07PM +0100, Ikey Doherty wrote:
> The goal of stateless, and thus this change, is to separate OS configuration
> from system administrator configuration. With this change we will read the
> default configuration data from /usr/share/defaults/qemu, in the absence of
> an overriding site administrator configuration in /etc/qemu.
> 
> A key advantage of this change is enabling a sane and immutable default OS
> configuration, that is resiliant to upgrades. Ultimate power is still left
> to the system administrator, with the ability to override the defaults if
> required. Lastly, given that the sane defaults are always available, the
> administrator may simply remove their site-config files to reset the
> configuration to the "factory defaults" (i.e. OS configuration).
> 
> Signed-off-by: Ikey Doherty <address@hidden>
> ---
>  configure            |  2 ++
>  qemu-bridge-helper.c | 15 +++++++++------
>  2 files changed, 11 insertions(+), 6 deletions(-)
> 
[...]
> -#define DEFAULT_ACL_FILE CONFIG_QEMU_CONFDIR "/bridge.conf"
> +#define DEFAULT_ACL_FILE CONFIG_QEMU_DEFAULTDIR "/bridge.conf"
> +#define SITE_ACL_FILE    CONFIG_QEMU_CONFDIR    "/bridge.conf"
>  
>  enum {
>      ACL_ALLOW = 0,
> @@ -272,11 +273,13 @@ int main(int argc, char **argv)
>  
>      /* parse default acl file */
>      QSIMPLEQ_INIT(&acl_list);
> -    if (parse_acl_file(DEFAULT_ACL_FILE, &acl_list) == -1) {
> -        fprintf(stderr, "failed to parse default acl file `%s'\n",
> -                DEFAULT_ACL_FILE);
> -        ret = EXIT_FAILURE;
> -        goto cleanup;
> +    if (parse_acl_file(SITE_ACL_FILE, &acl_list) == -1) {
> +        if (parse_acl_file(DEFAULT_ACL_FILE, &acl_list) == -1) {
> +            fprintf(stderr, "failed to parse default acl file `%s'\n",
> +                    DEFAULT_ACL_FILE);
> +            ret = EXIT_FAILURE;
> +            goto cleanup;
> +        }
>      }

This will make syntax errors on SITE_ACL_FILE cause partial loading of
the rules on SITE_ACL_FILE, and trigger loading of DEFAULT_ACL_FILE,
instead of aborting bridge-helper.

Wouldn't it be better to fallback to DEFAULT_ACL_FILE if and only if
SITE_ACL_FILE is missing?

-- 
Eduardo