6d3a4f1db8
When preparing a tutorial for netxlite, I figured it is easier to tell people "hey, this is the package you should use for all low-level networking stuff" rather than introducing people to a set of packages working together where some piece of functionality is here and some other piece is there. Part of https://github.com/ooni/probe/issues/1591
94 lines
2.2 KiB
Go
94 lines
2.2 KiB
Go
package netxlite
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import "github.com/miekg/dns"
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// The DNSDecoder decodes DNS replies.
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type DNSDecoder interface {
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// DecodeLookupHost decodes an A or AAAA reply.
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DecodeLookupHost(qtype uint16, data []byte) ([]string, error)
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// DecodeHTTPS decodes an HTTPS reply.
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DecodeHTTPS(data []byte) (*HTTPSSvc, error)
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}
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// DNSDecoderMiekg uses github.com/miekg/dns to implement the Decoder.
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type DNSDecoderMiekg struct{}
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func (d *DNSDecoderMiekg) parseReply(data []byte) (*dns.Msg, 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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// TODO(bassosimone): add support for lame referral.
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switch reply.Rcode {
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case dns.RcodeSuccess:
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return reply, nil
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case dns.RcodeNameError:
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return nil, ErrOODNSNoSuchHost
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case dns.RcodeRefused:
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return nil, ErrOODNSRefused
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default:
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return nil, ErrOODNSMisbehaving
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}
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}
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func (d *DNSDecoderMiekg) DecodeHTTPS(data []byte) (*HTTPSSvc, error) {
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reply, err := d.parseReply(data)
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if err != nil {
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return nil, err
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}
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out := &HTTPSSvc{}
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for _, answer := range reply.Answer {
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switch avalue := answer.(type) {
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case *dns.HTTPS:
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for _, v := range avalue.Value {
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switch extv := v.(type) {
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case *dns.SVCBAlpn:
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out.ALPN = extv.Alpn
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case *dns.SVCBIPv4Hint:
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for _, ip := range extv.Hint {
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out.IPv4 = append(out.IPv4, ip.String())
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}
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case *dns.SVCBIPv6Hint:
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for _, ip := range extv.Hint {
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out.IPv6 = append(out.IPv6, ip.String())
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}
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}
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}
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}
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}
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if len(out.ALPN) <= 0 {
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return nil, ErrOODNSNoAnswer
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}
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return out, nil
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}
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func (d *DNSDecoderMiekg) DecodeLookupHost(qtype uint16, data []byte) ([]string, error) {
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reply, err := d.parseReply(data)
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if err != nil {
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return nil, err
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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, ErrOODNSNoAnswer
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}
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return addrs, nil
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}
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var _ DNSDecoder = &DNSDecoderMiekg{}
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