func OPT(bufsize int, do bool) *dns.OPT {
o := new(dns.OPT)
o.Hdr.Name = "."
o.Hdr.Rrtype = dns.TypeOPT
o.SetVersion(0)
o.SetUDPSize(uint16(bufsize))
if do {
o.SetDo()
}
return o
}
// Edns0Version checks the EDNS version in the request. If error
// is nil everything is OK and we can invoke the middleware. If non-nil, the
// returned Msg is valid to be returned to the client (and should). For some
// reason this response should not contain a question RR in the question section.
func Edns0Version(req *dns.Msg) (*dns.Msg, error) {
opt := req.IsEdns0()
if opt == nil {
return nil, nil
}
if opt.Version() == 0 {
return nil, nil
}
m := new(dns.Msg)
m.SetReply(req)
// zero out question section, wtf.
m.Question = nil
o := new(dns.OPT)
o.Hdr.Name = "."
o.Hdr.Rrtype = dns.TypeOPT
o.SetVersion(0)
o.SetExtendedRcode(dns.RcodeBadVers)
m.Extra = []dns.RR{o}
return m, errors.New("EDNS0 BADVERS")
}