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package dns
import "strconv"
const (
year68 = 1 << 31 // For RFC1982 (Serial Arithmetic) calculations in 32 bits.
defaultTtl = 3600 // Default internal TTL.
// DefaultMsgSize is the standard default for messages larger than 512 bytes.
DefaultMsgSize = 4096
// MinMsgSize is the minimal size of a DNS packet.
MinMsgSize = 512
// MaxMsgSize is the largest possible DNS packet.
MaxMsgSize = 65535
)
// Error represents a DNS error.
type Error struct{ err string }
func (e *Error) Error() string {
if e == nil {
return "dns: <nil>"
}
return "dns: " + e.err
}
// An RR represents a resource record.
type RR interface {
// Header returns the header of an resource record. The header contains
// everything up to the rdata.
Header() *RR_Header
// String returns the text representation of the resource record.
String() string
// copy returns a copy of the RR
copy() RR
// len returns the length (in octets) of the uncompressed RR in wire format.
len() int
// pack packs an RR into wire format.
pack([]byte, int, map[string]int, bool) (int, error)
}
// RR_Header is the header all DNS resource records share.
type RR_Header struct {
Name string `dns:"cdomain-name"`
Rrtype uint16
Class uint16
Ttl uint32
Rdlength uint16 // Length of data after header.
}
// Header returns itself. This is here to make RR_Header implements the RR interface.
func (h *RR_Header) Header() *RR_Header { return h }
// Just to implement the RR interface.
func (h *RR_Header) copy() RR { return nil }
func (h *RR_Header) copyHeader() *RR_Header {
r := new(RR_Header)
r.Name = h.Name
r.Rrtype = h.Rrtype
r.Class = h.Class
r.Ttl = h.Ttl
r.Rdlength = h.Rdlength
return r
}
func (h *RR_Header) String() string {
var s string
if h.Rrtype == TypeOPT {
s = ";"
// and maybe other things
}
s += sprintName(h.Name) + "\t"
s += strconv.FormatInt(int64(h.Ttl), 10) + "\t"
s += Class(h.Class).String() + "\t"
s += Type(h.Rrtype).String() + "\t"
return s
}
func (h *RR_Header) len() int {
l := len(h.Name) + 1
l += 10 // rrtype(2) + class(2) + ttl(4) + rdlength(2)
return l
}
// ToRFC3597 converts a known RR to the unknown RR representation from RFC 3597.
func (rr *RFC3597) ToRFC3597(r RR) error {
buf := make([]byte, r.len()*2)
off, err := PackRR(r, buf, 0, nil, false)
if err != nil {
return err
}
buf = buf[:off]
if int(r.Header().Rdlength) > off {
return ErrBuf
}
rfc3597, _, err := unpackRFC3597(*r.Header(), buf, off-int(r.Header().Rdlength))
if err != nil {
return err
}
*rr = *rfc3597.(*RFC3597)
return nil
}
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