forked from TrueCloudLab/distribution
105 lines
2.5 KiB
Go
105 lines
2.5 KiB
Go
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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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defaultTtl = 3600 // Default internal TTL.
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DefaultMsgSize = 4096 // DefaultMsgSize is the standard default for messages larger than 512 bytes.
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MinMsgSize = 512 // MinMsgSize is the minimal size of a DNS packet.
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MaxMsgSize = 65535 // MaxMsgSize is the largest possible DNS packet.
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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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// pack packs an RR into wire format.
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pack([]byte, int, map[string]int, bool) (int, error)
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}
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// RR_Header is the header all DNS resource records share.
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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 implements the RR interface.
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func (h *RR_Header) Header() *RR_Header { return h }
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// Just to implement 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 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 := PackRR(r, buf, 0, nil, false)
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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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if int(r.Header().Rdlength) > off {
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return ErrBuf
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}
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rfc3597, _, err := unpackRFC3597(*r.Header(), buf, off-int(r.Header().Rdlength))
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if err != nil {
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return err
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}
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*rr = *rfc3597.(*RFC3597)
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return nil
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}
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