1package dns
2
3import "strconv"
4
5const (
6	year68     = 1 << 31 // For RFC1982 (Serial Arithmetic) calculations in 32 bits.
7	defaultTtl = 3600    // Default internal TTL.
8
9	// DefaultMsgSize is the standard default for messages larger than 512 bytes.
10	DefaultMsgSize = 4096
11	// MinMsgSize is the minimal size of a DNS packet.
12	MinMsgSize = 512
13	// MaxMsgSize is the largest possible DNS packet.
14	MaxMsgSize = 65535
15)
16
17// Error represents a DNS error.
18type Error struct{ err string }
19
20func (e *Error) Error() string {
21	if e == nil {
22		return "dns: <nil>"
23	}
24	return "dns: " + e.err
25}
26
27// An RR represents a resource record.
28type RR interface {
29	// Header returns the header of an resource record. The header contains
30	// everything up to the rdata.
31	Header() *RR_Header
32	// String returns the text representation of the resource record.
33	String() string
34
35	// copy returns a copy of the RR
36	copy() RR
37
38	// len returns the length (in octets) of the compressed or uncompressed RR in wire format.
39	//
40	// If compression is nil, the uncompressed size will be returned, otherwise the compressed
41	// size will be returned and domain names will be added to the map for future compression.
42	len(off int, compression map[string]struct{}) int
43
44	// pack packs the records RDATA into wire format. The header will
45	// already have been packed into msg.
46	pack(msg []byte, off int, compression compressionMap, compress bool) (off1 int, err error)
47
48	// unpack unpacks an RR from wire format.
49	//
50	// This will only be called on a new and empty RR type with only the header populated. It
51	// will only be called if the record's RDATA is non-empty.
52	unpack(msg []byte, off int) (off1 int, err error)
53
54	// parse parses an RR from zone file format.
55	//
56	// This will only be called on a new and empty RR type with only the header populated.
57	parse(c *zlexer, origin string) *ParseError
58
59	// isDuplicate returns whether the two RRs are duplicates.
60	isDuplicate(r2 RR) bool
61}
62
63// RR_Header is the header all DNS resource records share.
64type RR_Header struct {
65	Name     string `dns:"cdomain-name"`
66	Rrtype   uint16
67	Class    uint16
68	Ttl      uint32
69	Rdlength uint16 // Length of data after header.
70}
71
72// Header returns itself. This is here to make RR_Header implements the RR interface.
73func (h *RR_Header) Header() *RR_Header { return h }
74
75// Just to implement the RR interface.
76func (h *RR_Header) copy() RR { return nil }
77
78func (h *RR_Header) String() string {
79	var s string
80
81	if h.Rrtype == TypeOPT {
82		s = ";"
83		// and maybe other things
84	}
85
86	s += sprintName(h.Name) + "\t"
87	s += strconv.FormatInt(int64(h.Ttl), 10) + "\t"
88	s += Class(h.Class).String() + "\t"
89	s += Type(h.Rrtype).String() + "\t"
90	return s
91}
92
93func (h *RR_Header) len(off int, compression map[string]struct{}) int {
94	l := domainNameLen(h.Name, off, compression, true)
95	l += 10 // rrtype(2) + class(2) + ttl(4) + rdlength(2)
96	return l
97}
98
99func (h *RR_Header) pack(msg []byte, off int, compression compressionMap, compress bool) (off1 int, err error) {
100	// RR_Header has no RDATA to pack.
101	return off, nil
102}
103
104func (h *RR_Header) unpack(msg []byte, off int) (int, error) {
105	panic("dns: internal error: unpack should never be called on RR_Header")
106}
107
108func (h *RR_Header) parse(c *zlexer, origin string) *ParseError {
109	panic("dns: internal error: parse should never be called on RR_Header")
110}
111
112// ToRFC3597 converts a known RR to the unknown RR representation from RFC 3597.
113func (rr *RFC3597) ToRFC3597(r RR) error {
114	buf := make([]byte, Len(r)*2)
115	headerEnd, off, err := packRR(r, buf, 0, compressionMap{}, false)
116	if err != nil {
117		return err
118	}
119	buf = buf[:off]
120
121	*rr = RFC3597{Hdr: *r.Header()}
122	rr.Hdr.Rdlength = uint16(off - headerEnd)
123
124	if noRdata(rr.Hdr) {
125		return nil
126	}
127
128	_, err = rr.unpack(buf, headerEnd)
129	if err != nil {
130		return err
131	}
132
133	return nil
134}
135