returns unique strings in n not in s as new array.

TODO: Move to dnsx?.

GetBlocklistStampHeaderKey returns the http-header key for blocklists stamp.

GetBlocklistStampHeaderKey1 returns the http-header key for region set by rdns upstream on Fly.

GetBlocklistStampHeaderKey2 returns the http-header key for region set by rdns upstream on Cloudflare.

whether the given msg (ans/query) has a AAAA question section.

whether the given msg (ans/query) has a a/aaaa question section.

whether the given msg (ans/query) has a A question section.

whether the given msg (ans/query) has a https question section.

whether the given msg (ans/query) has a svcb question section.

whether the qtype code is a aaaa qtype.

whether the qtype code is a A qtype.

whether question q is a https question.

whether the qtype code is a https qtype.

whether the qtype code is a svcb qtype.

whether question q is a svcb question.

MaybeToQuadA translates an A record to a AAAA record if the prefix is not nil.

Net2ProxyID splits network string into proto and pid; proto is the network protocol and pid is the proxy ID.

NetAndProxyID joins proto and pid into a network string.

TODO: merge this with doh.Accept.

Servfail returns a SERVFAIL response to the query q.

65k, ought to be enough for everybody.