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