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 = 4096  // DefaultMsgSize is the standard default for messages larger than 512 bytes.
10	MinMsgSize     = 512   // MinMsgSize is the minimal size of a DNS packet.
11	MaxMsgSize     = 65535 // MaxMsgSize is the largest possible DNS packet.
12)
13
14// Error represents a DNS error.
15type Error struct{ err string }
16
17func (e *Error) Error() string {
18	if e == nil {
19		return "dns: <nil>"
20	}
21	return "dns: " + e.err
22}
23
24// An RR represents a resource record.
25type RR interface {
26	// Header returns the header of an resource record. The header contains
27	// everything up to the rdata.
28	Header() *RR_Header
29	// String returns the text representation of the resource record.
30	String() string
31
32	// copy returns a copy of the RR
33	copy() RR
34	// len returns the length (in octets) of the uncompressed RR in wire format.
35	len() int
36	// pack packs an RR into wire format.
37	pack([]byte, int, map[string]int, bool) (int, error)
38}
39
40// RR_Header is the header all DNS resource records share.
41type RR_Header struct {
42	Name     string `dns:"cdomain-name"`
43	Rrtype   uint16
44	Class    uint16
45	Ttl      uint32
46	Rdlength uint16 // Length of data after header.
47}
48
49// Header returns itself. This is here to make RR_Header implements the RR interface.
50func (h *RR_Header) Header() *RR_Header { return h }
51
52// Just to implement the RR interface.
53func (h *RR_Header) copy() RR { return nil }
54
55func (h *RR_Header) copyHeader() *RR_Header {
56	r := new(RR_Header)
57	r.Name = h.Name
58	r.Rrtype = h.Rrtype
59	r.Class = h.Class
60	r.Ttl = h.Ttl
61	r.Rdlength = h.Rdlength
62	return r
63}
64
65func (h *RR_Header) String() string {
66	var s string
67
68	if h.Rrtype == TypeOPT {
69		s = ";"
70		// and maybe other things
71	}
72
73	s += sprintName(h.Name) + "\t"
74	s += strconv.FormatInt(int64(h.Ttl), 10) + "\t"
75	s += Class(h.Class).String() + "\t"
76	s += Type(h.Rrtype).String() + "\t"
77	return s
78}
79
80func (h *RR_Header) len() int {
81	l := len(h.Name) + 1
82	l += 10 // rrtype(2) + class(2) + ttl(4) + rdlength(2)
83	return l
84}
85
86// ToRFC3597 converts a known RR to the unknown RR representation from RFC 3597.
87func (rr *RFC3597) ToRFC3597(r RR) error {
88	buf := make([]byte, r.len()*2)
89	off, err := PackRR(r, buf, 0, nil, false)
90	if err != nil {
91		return err
92	}
93	buf = buf[:off]
94	if int(r.Header().Rdlength) > off {
95		return ErrBuf
96	}
97
98	rfc3597, _, err := unpackRFC3597(*r.Header(), buf, off-int(r.Header().Rdlength))
99	if err != nil {
100		return err
101	}
102	*rr = *rfc3597.(*RFC3597)
103	return nil
104}
105