62 lines
1.3 KiB
Go
62 lines
1.3 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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"strings"
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"time"
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)
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type ResolvError struct {
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qname string
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nameservers []string
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}
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func (e ResolvError) Error() string {
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errmsg := fmt.Sprintf("%s resolv failed on %s", e.qname, strings.Join(e.nameservers, "; "))
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return errmsg
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}
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type Resolver struct {
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config *dns.ClientConfig
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}
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func (r *Resolver) Lookup(net string, req *dns.Msg) (message *dns.Msg, err error) {
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c := &dns.Client{
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Net: net,
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ReadTimeout: r.Timeout(),
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WriteTimeout: r.Timeout(),
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}
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qname := req.Question[0].Name
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for _, nameserver := range r.Nameservers() {
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r, rtt, err := c.Exchange(req, nameserver)
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if err != nil {
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Debug("%s socket error on %s", qname, nameserver)
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Debug("error:%s", err.Error())
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continue
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}
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if r != nil && r.Rcode != dns.RcodeSuccess {
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Debug("%s failed to get an valid answer on %s", qname, nameserver)
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continue
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}
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Debug("%s resolv on %s ttl: %d", qname, nameserver, rtt)
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return r, nil
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}
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return nil, ResolvError{qname, r.Nameservers()}
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}
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func (r *Resolver) Nameservers() (ns []string) {
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for _, server := range r.config.Servers {
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nameserver := server + ":" + r.config.Port
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ns = append(ns, nameserver)
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}
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return
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}
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func (r *Resolver) Timeout() time.Duration {
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return time.Duration(r.config.Timeout) * time.Second
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}
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