68 lines
1.4 KiB
Go
68 lines
1.4 KiB
Go
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package shared
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import (
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"fmt"
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"os"
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"strconv"
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"time"
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"github.com/miekg/dns"
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)
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type DNSClient struct {
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timeout time.Duration
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}
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func NewDNSClient(timeout time.Duration) *DNSClient {
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return &DNSClient{timeout: timeout}
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}
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func (d DNSClient) SOACall(fqdn, nameserver string) (*dns.SOA, error) {
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m := new(dns.Msg)
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m.SetQuestion(fqdn, dns.TypeSOA)
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m.SetEdns0(4096, false)
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in, err := d.sendDNSQuery(m, nameserver)
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if err != nil {
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return nil, err
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}
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if len(in.Answer) == 0 {
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if len(in.Ns) > 0 {
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if soa, ok := in.Ns[0].(*dns.SOA); ok && fqdn != soa.Hdr.Name {
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return d.SOACall(soa.Hdr.Name, nameserver)
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}
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}
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return nil, fmt.Errorf("empty answer for %s in %s", fqdn, nameserver)
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}
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for _, rr := range in.Answer {
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if soa, ok := rr.(*dns.SOA); ok {
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return soa, nil
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}
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}
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return nil, fmt.Errorf("SOA not found for %s in %s", fqdn, nameserver)
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}
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func (d DNSClient) sendDNSQuery(m *dns.Msg, ns string) (*dns.Msg, error) {
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if ok, _ := strconv.ParseBool(os.Getenv("LEGO_EXPERIMENTAL_DNS_TCP_ONLY")); ok {
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tcp := &dns.Client{Net: "tcp", Timeout: d.timeout}
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in, _, err := tcp.Exchange(m, ns)
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return in, err
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}
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udp := &dns.Client{Net: "udp", Timeout: d.timeout}
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in, _, err := udp.Exchange(m, ns)
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if in != nil && in.Truncated {
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tcp := &dns.Client{Net: "tcp", Timeout: d.timeout}
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// If the TCP request succeeds, the err will reset to nil
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in, _, err = tcp.Exchange(m, ns)
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}
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return in, err
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}
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