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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
}
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