godns/resolver.go

62 lines
1.3 KiB
Go
Raw Normal View History

2013-07-23 11:10:38 +00:00
package main
import (
"fmt"
"github.com/miekg/dns"
2013-07-23 16:37:38 +00:00
"strings"
2013-07-23 11:10:38 +00:00
"time"
)
2013-07-23 16:37:38 +00:00
type ResolvError struct {
qname string
nameservers []string
}
func (e ResolvError) Error() string {
errmsg := fmt.Sprintf("%s resolv failed on %s", e.qname, strings.Join(e.nameservers, "; "))
return errmsg
}
2013-07-23 11:10:38 +00:00
type Resolver struct {
config *dns.ClientConfig
}
2013-07-23 16:37:38 +00:00
func (r *Resolver) Lookup(net string, req *dns.Msg) (message *dns.Msg, err error) {
2013-07-23 11:10:38 +00:00
c := &dns.Client{
Net: net,
ReadTimeout: r.Timeout(),
WriteTimeout: r.Timeout(),
}
2013-07-23 16:37:38 +00:00
qname := req.Question[0].Name
2013-07-23 11:10:38 +00:00
2013-07-23 16:37:38 +00:00
for _, nameserver := range r.Nameservers() {
r, rtt, err := c.Exchange(req, nameserver)
if err != nil {
Debug("%s socket error on %s", qname, nameserver)
Debug("error:%s", err.Error())
continue
}
if r != nil && r.Rcode != dns.RcodeSuccess {
Debug("%s failed to get an valid answer on %s", qname, nameserver)
continue
}
Debug("%s resolv on %s ttl: %d", qname, nameserver, rtt)
return r, nil
2013-07-23 11:10:38 +00:00
}
2013-07-23 16:37:38 +00:00
return nil, ResolvError{qname, r.Nameservers()}
2013-07-23 11:10:38 +00:00
}
func (r *Resolver) Nameservers() (ns []string) {
for _, server := range r.config.Servers {
nameserver := server + ":" + r.config.Port
ns = append(ns, nameserver)
}
return
}
func (r *Resolver) Timeout() time.Duration {
return time.Duration(r.config.Timeout) * time.Second
}