diff options
Diffstat (limited to 'plugin/pkg/edns/edns.go')
-rw-r--r-- | plugin/pkg/edns/edns.go | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/plugin/pkg/edns/edns.go b/plugin/pkg/edns/edns.go new file mode 100644 index 000000000..3f0ea5e16 --- /dev/null +++ b/plugin/pkg/edns/edns.go @@ -0,0 +1,46 @@ +// Package edns provides function useful for adding/inspecting OPT records to/in messages. +package edns + +import ( + "errors" + + "github.com/miekg/dns" +) + +// Version checks the EDNS version in the request. If error +// is nil everything is OK and we can invoke the plugin. 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 Version(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") +} + +// Size returns a normalized size based on proto. +func Size(proto string, size int) int { + if proto == "tcp" { + return dns.MaxMsgSize + } + if size < dns.MinMsgSize { + return dns.MinMsgSize + } + return size +} |