1 files changed, 110 insertions, 0 deletions
diff --git a/internal/dns/rr.go b/internal/dns/rr.go
new file mode 100644
index 0000000..38f467c
--- /dev/null
+++ b/internal/dns/rr.go
@@ -0,0 +1,110 @@
+package dns
+
+import "fmt"
+
+type RData interface {
+	Type() uint16
+	Pack(p *packer) error
+	Unpack(u *unpacker, length uint16) error
+	String() string
+}
+
+type RR struct {
+	Name  Name
+	Type  uint16
+	Class uint16
+	TTL   uint32
+	Data  RData
+}
+
+func unpackRR(u *unpacker) (RR, error) {
+	var rr RR
+	var err error
+	rr.Name, err = u.readName()
+	if err != nil {
+		return rr, err
+	}
+	rr.Type, err = u.readUint16()
+	if err != nil {
+		return rr, err
+	}
+	rr.Class, err = u.readUint16()
+	if err != nil {
+		return rr, err
+	}
+	rr.TTL, err = u.readUint32()
+	if err != nil {
+		return rr, err
+	}
+	rdlength, err := u.readUint16()
+	if err != nil {
+		return rr, err
+	}
+
+	rdStart := u.off
+	if u.off+int(rdlength) > len(u.buf) {
+		return rr, fmt.Errorf("dns: short rdata")
+	}
+
+	switch rr.Type {
+	case TypeA:
+		rr.Data = &A{}
+	case TypeNS:
+		rr.Data = &NS{}
+	case TypeCNAME:
+		rr.Data = &CNAME{}
+	case TypeSOA:
+		rr.Data = &SOA{}
+	case TypePTR:
+		rr.Data = &PTR{}
+	case TypeMX:
+		rr.Data = &MX{}
+	case TypeTXT:
+		rr.Data = &TXT{}
+	case TypeAAAA:
+		rr.Data = &AAAA{}
+	case TypeOPT:
+		opt := &OPT{
+			UDPSize: rr.Class,
+		}
+		opt.ExtRCode = uint8(rr.TTL >> 24)
+		opt.Version = uint8(rr.TTL >> 16)
+		// https://datatracker.ietf.org/doc/html/rfc3225
+		// https://datatracker.ietf.org/doc/html/rfc4035
+		opt.DO = rr.TTL&0x8000 != 0
+		opt.Z = uint16(rr.TTL & 0x7FFF)
+		rr.Data = opt
+	default:
+		rr.Data = &Unknown{RRType: rr.Type}
+	}
+
+	if err := rr.Data.Unpack(u, rdlength); err != nil {
+		return rr, err
+	}
+	if u.off != rdStart+int(rdlength) {
+		return rr, fmt.Errorf("dns: rdata length mismatch")
+	}
+	return rr, nil
+}
+
+func (rr *RR) pack(p *packer) error {
+	if err := p.writeName(rr.Name); err != nil {
+		return err
+	}
+	p.writeUint16(rr.Type)
+	p.writeUint16(rr.Class)
+	p.writeUint32(rr.TTL)
+
+	rdlenOff := len(p.buf)
+	p.buf = append(p.buf, 0, 0)
+	rdStart := len(p.buf)
+
+	if err := rr.Data.Pack(p); err != nil {
+		return err
+	}
+
+	rdlen := uint16(len(p.buf) - rdStart)
+	p.buf[rdlenOff] = byte(rdlen >> 8)
+	p.buf[rdlenOff+1] = byte(rdlen)
+	return nil
+}