network: add netmask to dhcp range of dnsmasq conf file for IPv4
dnsmasq documentation says that the *IPv4* prefix/network address/broadcast address sent to dhcp clients will be automatically determined by dnsmasq by looking at the interface it's listening on, so the original libvirt code did not add a netmask to the dnsmasq commandline (or later, the dnsmasq conf file). For *IPv6* however, dnsmasq apparently cannot automatically determine the prefix (functionally the same as a netmask), and it must be explicitly provided in the conf file (as a part of the dhcp-range option). So many years after IPv4 DHCP support had been added, when IPv6 dhcp support was added the prefix was included at the end of the dhcp-range setting, but only for IPv6. A user had reported a bug on a host where one of the interfaces was a superset of the libvirt network where dhcp is needed (e.g., the host's ethernet is 10.0.0.20/8, and the libvirt network is 10.10.0.1/24). For some reason dnsmasq was supplying the netmask for the /8 network to clients requesting an address on the /24 interface. This seems like a bug in dnsmasq, but even if/when it gets fixed there, it looks like there is no harm in just always adding the netmask to all IPv4 dhcp-range options similar to how prefix is added to all IPv6 dhcp-range options. Signed-off-by: NLaine Stump <laine@laine.org> Reviewed-by: NJohn Ferlan <jferlan@redhat.com>
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