Motivation:
RFC7871 defines an extension which allows to request responses for a given subset.
Modifications:
- Add DnsOptPseudoRrRecord which can act as base class for extensions based on EDNS(0) as defined in RFC6891
- Add DnsOptEcsRecord to support the Client Subnet in DNS Queries extension
- Add tests
Result:
Client Subnet in DNS Queries extension is now supported.