godns/resolver.go
Tamás Gulácsi f2449642b7 Allow non-standard namserver ports
For example Consul uses port 8600.
With this patch, I can add
  nameserver 127.0.0.1#8600
to my godns-specific resolv.conf.
2015-02-12 07:27:12 +01:00

69 lines
1.5 KiB
Go

package main
import (
"fmt"
"strings"
"time"
"github.com/miekg/dns"
)
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
}
type Resolver struct {
config *dns.ClientConfig
}
func (r *Resolver) Lookup(net string, req *dns.Msg) (message *dns.Msg, err error) {
c := &dns.Client{
Net: net,
ReadTimeout: r.Timeout(),
WriteTimeout: r.Timeout(),
}
qname := req.Question[0].Name
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", UnFqdn(qname), nameserver, rtt)
return r, nil
}
return nil, ResolvError{qname, r.Nameservers()}
}
// Namservers return the array of nameservers, with port number appended.
// '#' in the name is treated as port separator, as with dnsmasq.
func (r *Resolver) Nameservers() (ns []string) {
for _, server := range r.config.Servers {
if i := strings.IndexByte(server, '#'); i > 0 {
server = server[:i] + ":" + server[i+1:]
} else {
server = server + ":" + r.config.Port
}
ns = append(ns, server)
}
return
}
func (r *Resolver) Timeout() time.Duration {
return time.Duration(r.config.Timeout) * time.Second
}