55 lines
1.4 KiB
Go
55 lines
1.4 KiB
Go
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package resolver
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import (
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"errors"
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"github.com/miekg/dns"
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)
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// The Decoder decodes a DNS reply into A or AAAA entries. It will use the
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// provided qtype and only look for mathing entries. It will return error if
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// there are no entries for the requested qtype inside the reply.
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type Decoder interface {
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Decode(qtype uint16, data []byte) ([]string, error)
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}
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// MiekgDecoder uses github.com/miekg/dns to implement the Decoder.
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type MiekgDecoder struct{}
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// Decode implements Decoder.Decode.
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func (d MiekgDecoder) Decode(qtype uint16, data []byte) ([]string, error) {
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reply := new(dns.Msg)
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if err := reply.Unpack(data); err != nil {
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return nil, err
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}
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// TODO(bassosimone): map more errors to net.DNSError names
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switch reply.Rcode {
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case dns.RcodeSuccess:
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case dns.RcodeNameError:
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return nil, errors.New("ooniresolver: no such host")
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default:
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return nil, errors.New("ooniresolver: query failed")
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}
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var addrs []string
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for _, answer := range reply.Answer {
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switch qtype {
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case dns.TypeA:
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if rra, ok := answer.(*dns.A); ok {
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ip := rra.A
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addrs = append(addrs, ip.String())
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}
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case dns.TypeAAAA:
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if rra, ok := answer.(*dns.AAAA); ok {
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ip := rra.AAAA
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addrs = append(addrs, ip.String())
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}
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}
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}
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if len(addrs) <= 0 {
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return nil, errors.New("ooniresolver: no response returned")
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}
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return addrs, nil
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}
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var _ Decoder = MiekgDecoder{}
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