Allow underscores in DNS names

[M. Warner Losh]

In message: <xzpel4phrcs.fsf at flood.ping.uio.no>
            des at ofug.org (Dag-Erling Smørgrav) writes:
: "M. Warner Losh" <imp at bsdimp.com> writes:
: > True.  However, they are still relevant today.  '_' is illegal in DNS
: > names
: 
: Says the RFC.  IIRC, BIND traditionally did not enforce this, though
: it does now for A records in master zones unless you change the
: "check-names" setting (it seems to allow it for TXT records though).

Bind 4 didn't enforce this until about 1998 or so.  Like I explained
in the other post, the reason it was changed was so that bind would
only accept welll formed packets so that it could help reduce the
liklihood that one could write an 'egg' for the payload for a buffer
overflow.  Bind 8 and bind 9 do enforce it for those RR that it is
well defined.  TXT records are well defined as allowing anything in
them.

Warner