--add-subnet[[=[<IPv4 address>/]<IPv4 prefix length>][,[<IPv6 address>/]<IPv6 prefix length>]]
Add a subnet address to the DNS queries which are forwarded
upstream. If an address is specified in the flag, it will be used,
otherwise, the address of the requestor will be used. The amount of
the address forwarded depends on the prefix length parameter: 32 (128
for IPv6) forwards the whole address, zero forwards none of it but
still marks the request so that no upstream nameserver will add client
address information either. The default is zero for both IPv4 and
IPv6. Note that upstream nameservers may be configured to return
different results based on this information, but the dnsmasq cache
does not take account. Caching is therefore disabled for such replies,
unless the subnet address being added is constant.
For example,
--add-subnet=24,96
will add the /24 and /96 subnets of the requestor for IPv4 and IPv6 requestors, respectively.
--add-subnet=1.2.3.4/24
will add 1.2.3.0/24 for IPv4 requestors and ::/0 for IPv6 requestors.
--add-subnet=1.2.3.4/24,1.2.3.4/24
will add 1.2.3.0/24 for both IPv4 and IPv6 requestors.