79 lines
1.5 KiB
Go
79 lines
1.5 KiB
Go
package main
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import (
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"fmt"
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"github.com/miekg/dns"
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"log"
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"net"
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"time"
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)
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const TSIG_FUDGE_SECONDS = 300
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type TSIGAlgorithm string
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func (t *TSIGAlgorithm) UnmarshalFlag(value string) error {
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switch value {
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case "hmac-md5", "md5":
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*t = dns.HmacMD5
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case "hmac-sha1", "sha1":
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*t = dns.HmacSHA1
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case "hmac-sha256", "sha256":
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*t = dns.HmacSHA256
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case "hmac-sha512", "sha512":
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*t = dns.HmacSHA512
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default:
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return fmt.Errorf("Invalid --tsig-algorithm=%v", value)
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}
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return nil
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}
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func query(query *dns.Msg) (*dns.Msg, error) {
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clientConfig, err := dns.ClientConfigFromFile("/etc/resolv.conf")
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if err != nil {
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return nil, err
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}
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timeout := time.Duration(clientConfig.Timeout * int(time.Second))
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var client = new(dns.Client)
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client.DialTimeout = timeout
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client.ReadTimeout = timeout
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client.WriteTimeout = timeout
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for _, server := range clientConfig.Servers {
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addr := net.JoinHostPort(server, "53")
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if answer, _, err := client.Exchange(query, addr); err != nil {
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log.Printf("query %v: %v", server, err)
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continue
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} else {
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return answer, nil
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}
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}
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return nil, fmt.Errorf("DNS query failed")
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}
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// Discover likely master NS for zone
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func discoverZoneServer(zone string) (string, error) {
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var q = new(dns.Msg)
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q.SetQuestion(zone, dns.TypeSOA)
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r, err := query(q)
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if err != nil {
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return "", err
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}
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for _, rr := range r.Answer {
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if soa, ok := rr.(*dns.SOA); ok {
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return soa.Ns, nil
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}
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}
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return "", fmt.Errorf("No SOA response")
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}
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