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