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package dns
import (
"fmt"
"strings"
)
// PrivateRdata is an interface used for implementing "Private Use" RR types, see
// RFC 6895. This allows one to experiment with new RR types, without requesting an
// official type code. Also see dns.PrivateHandle and dns.PrivateHandleRemove.
type PrivateRdata interface {
// String returns the text presentaton of the Rdata of the Private RR.
String() string
// Parse parses the Rdata of the private RR.
Parse([]string) error
// Pack is used when packing a private RR into a buffer.
Pack([]byte) (int, error)
// Unpack is used when unpacking a private RR from a buffer.
// TODO(miek): diff. signature than Pack, see edns0.go for instance.
Unpack([]byte) (int, error)
// Copy copies the Rdata.
Copy(PrivateRdata) error
// Len returns the length in octets of the Rdata.
Len() int
}
// PrivateRR represents an RR that uses a PrivateRdata user-defined type.
// It mocks normal RRs and implements dns.RR interface.
type PrivateRR struct {
Hdr RR_Header
Data PrivateRdata
}
func mkPrivateRR(rrtype uint16) *PrivateRR {
// Panics if RR is not an instance of PrivateRR.
rrfunc, ok := TypeToRR[rrtype]
if !ok {
panic(fmt.Sprintf("dns: invalid operation with Private RR type %d", rrtype))
}
anyrr := rrfunc()
switch rr := anyrr.(type) {
case *PrivateRR:
return rr
}
panic(fmt.Sprintf("dns: RR is not a PrivateRR, TypeToRR[%d] generator returned %T", rrtype, anyrr))
}
// Header return the RR header of r.
func (r *PrivateRR) Header() *RR_Header { return &r.Hdr }
func (r *PrivateRR) String() string { return r.Hdr.String() + r.Data.String() }
// Private len and copy parts to satisfy RR interface.
func (r *PrivateRR) len() int { return r.Hdr.len() + r.Data.Len() }
func (r *PrivateRR) copy() RR {
// make new RR like this:
rr := mkPrivateRR(r.Hdr.Rrtype)
rr.Hdr = r.Hdr
err := r.Data.Copy(rr.Data)
if err != nil {
panic("dns: got value that could not be used to copy Private rdata")
}
return rr
}
func (r *PrivateRR) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
off, err := r.Hdr.pack(msg, off, compression, compress)
if err != nil {
return off, err
}
headerEnd := off
n, err := r.Data.Pack(msg[off:])
if err != nil {
return len(msg), err
}
off += n
r.Header().Rdlength = uint16(off - headerEnd)
return off, nil
}
// PrivateHandle registers a private resource record type. It requires
// string and numeric representation of private RR type and generator function as argument.
func PrivateHandle(rtypestr string, rtype uint16, generator func() PrivateRdata) {
rtypestr = strings.ToUpper(rtypestr)
TypeToRR[rtype] = func() RR { return &PrivateRR{RR_Header{}, generator()} }
TypeToString[rtype] = rtypestr
StringToType[rtypestr] = rtype
typeToUnpack[rtype] = func(h RR_Header, msg []byte, off int) (RR, int, error) {
if noRdata(h) {
return &h, off, nil
}
var err error
rr := mkPrivateRR(h.Rrtype)
rr.Hdr = h
off1, err := rr.Data.Unpack(msg[off:])
off += off1
if err != nil {
return rr, off, err
}
return rr, off, err
}
setPrivateRR := func(h RR_Header, c chan lex, o, f string) (RR, *ParseError, string) {
rr := mkPrivateRR(h.Rrtype)
rr.Hdr = h
var l lex
text := make([]string, 0, 2) // could be 0..N elements, median is probably 1
Fetch:
for {
// TODO(miek): we could also be returning _QUOTE, this might or might not
// be an issue (basically parsing TXT becomes hard)
switch l = <-c; l.value {
case zNewline, zEOF:
break Fetch
case zString:
text = append(text, l.token)
}
}
err := rr.Data.Parse(text)
if err != nil {
return nil, &ParseError{f, err.Error(), l}, ""
}
return rr, nil, ""
}
typeToparserFunc[rtype] = parserFunc{setPrivateRR, true}
}
// PrivateHandleRemove removes defenitions required to support private RR type.
func PrivateHandleRemove(rtype uint16) {
rtypestr, ok := TypeToString[rtype]
if ok {
delete(TypeToRR, rtype)
delete(TypeToString, rtype)
delete(typeToparserFunc, rtype)
delete(StringToType, rtypestr)
delete(typeToUnpack, rtype)
}
return
}
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