On 12/22/2010 11:58 AM, Laine Stump wrote:
> Later patches will add the possibility to define a network's netmask
> as a prefix (0-32, or 0-128 in the case of IPv6). To make it easier to
> deal with definition of both kinds (prefix or netmask), add two new
> functions:
>
> virNetworkDefNetmask: return a copy of the netmask into a
> virSocketAddr. If no netmask was specified in the XML, create a
> default netmask based on the network class of the virNetworkDef's IP
> address.
>
> virNetworkDefPrefix: return the netmask as numeric prefix (or the
> default prefix for the network class of the virNetworkDef's IP
> address, if no netmask was specified in the XML)
> +int virNetworkDefPrefix(const virNetworkDefPtr def)
> +{
> + if (VIR_SOCKET_HAS_ADDR(&def->netmask)) {
> + return virSocketGetNumNetmaskBits(&def->netmask);
> + } else if (VIR_SOCKET_IS_FAMILY(&def->ipAddress, AF_INET)) {
> + /* Return the natural prefix for the network's ip address.
> + * On Linux we could use the IN_CLASSx() macros, but those
> + * aren't guaranteed on all platforms, so we just deal with
> + * the bits ourselves.
> + */
> + const unsigned char *octets
> + = (const unsigned char *)(&def->ipAddress.data.inet4.sin_addr.s_addr);
Is this type-punning guaranteed to work on both big- and little-endian
systems? Or are you better off doing:
unsigned char octet
= ntohl(def->ipAddress.data.inet4.sin_addr.s_addr) >> 24;
and use octet instead of octets[0]?
--
Eric Blake eblake@xxxxxxxxxx +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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