[dnsext] need new flag bit in EDNS, "do me no favours" (DMNF)

[Paul Vixie <[e-mail]>]

i'm thinking we need a flag bit in edns to allow a client to opt out of
things like "web error redirection" (dns ad insertion).  the semantics
of it would just be, if server policy allows "clear path" dns for this
query, then the server is requested to provide same.

if server policy does not allow, for example if dns ad insertion isn't
optional or if the non-clear-path dns is for security reasons (blocking
malware C&C names), then "clear path" dns would not be provided.

so this would be opt-out rather than opt-in, to make it noncontroversial.
(those of us who previously wanted opt-in have learned that opt-in is
considered controversial by the companies already doing dns ad insertion
or similar non-clear-path dns.)

opin?  i can write a short i-d on it before beijing.