145 lines
3.4 KiB
Go
145 lines
3.4 KiB
Go
// Copyright 2011 Miek Gieben. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// DNS resolver client: see RFC 1035.
|
|
|
|
package dns
|
|
|
|
import (
|
|
"os"
|
|
"net"
|
|
"time"
|
|
)
|
|
|
|
// Todo(MG) put in dns.go
|
|
const ErrPack = "Failed to pack message"
|
|
const ErrUnpack = ""
|
|
const ErrServ = "No servers could be reached"
|
|
const ErrTsigKey = ""
|
|
const ErrTsigTime = ""
|
|
const ErrTsig = ""
|
|
|
|
type Resolver struct {
|
|
Servers []string // servers to use
|
|
Search []string // suffixes to append to local name
|
|
Port string // what port to use
|
|
Ndots int // number of dots in name to trigger absolute lookup -- TODO
|
|
Timeout int // seconds before giving up on packet
|
|
Attempts int // lost packets before giving up on server
|
|
Tcp bool // use TCP
|
|
Mangle func([]byte) []byte // mangle the packet
|
|
Rtt map[string]int64 // Store round trip times
|
|
Rrb int // Last used server (for round robin)
|
|
}
|
|
|
|
// Send a query to the nameserver using the res.
|
|
func (res *Resolver) Query(q *Msg) (d *Msg, err os.Error) {
|
|
return res.QueryTsig(q, nil)
|
|
}
|
|
|
|
// Send a query to the nameserver using res, but perform TSIG validation.
|
|
func (res *Resolver) QueryTsig(q *Msg, tsig *Tsig) (d *Msg, err os.Error) {
|
|
var c net.Conn
|
|
var inb []byte
|
|
in := new(Msg)
|
|
port, err := check(res, q)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
sending, ok := q.Pack()
|
|
if !ok {
|
|
return nil, &Error{Error: ErrPack}
|
|
}
|
|
if res.Mangle != nil {
|
|
sending = res.Mangle(sending)
|
|
}
|
|
|
|
for i := 0; i < len(res.Servers); i++ {
|
|
d := new(Conn)
|
|
server := res.Servers[i] + ":" + port
|
|
t := time.Nanoseconds()
|
|
if res.Tcp {
|
|
c, err = net.Dial("tcp", "", server)
|
|
if err != nil {
|
|
continue
|
|
}
|
|
d.TCP = c.(*net.TCPConn)
|
|
d.Addr = d.TCP.RemoteAddr()
|
|
} else {
|
|
c, err = net.Dial("udp", "", server)
|
|
if err != nil {
|
|
continue
|
|
}
|
|
d.UDP = c.(*net.UDPConn)
|
|
d.Addr = d.UDP.RemoteAddr()
|
|
}
|
|
|
|
d.Tsig = tsig
|
|
inb, err = d.Exchange(sending, false)
|
|
if err != nil {
|
|
continue
|
|
}
|
|
in.Unpack(inb) // Discard error.
|
|
res.Rtt[server] = time.Nanoseconds() - t
|
|
c.Close()
|
|
break
|
|
}
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return in, nil
|
|
}
|
|
|
|
func (res *Resolver) Xfr(q *Msg, m chan Xfr) {
|
|
res.XfrTsig(q, nil, m)
|
|
}
|
|
|
|
func (res *Resolver) XfrTsig(q *Msg, t *Tsig, m chan Xfr) {
|
|
port, err := check(res, q)
|
|
if err != nil {
|
|
return
|
|
}
|
|
sending, ok := q.Pack()
|
|
if !ok {
|
|
return
|
|
}
|
|
|
|
Server:
|
|
for i := 0; i < len(res.Servers); i++ {
|
|
server := res.Servers[i] + ":" + port
|
|
c, err := net.Dial("tcp", "", server)
|
|
if err != nil {
|
|
continue Server
|
|
}
|
|
d := new(Conn)
|
|
d.TCP = c.(*net.TCPConn)
|
|
d.Addr = d.TCP.RemoteAddr()
|
|
d.Tsig = t
|
|
|
|
_, err = d.Write(sending)
|
|
if err != nil {
|
|
continue Server
|
|
}
|
|
d.XfrRead(q, m) // check
|
|
}
|
|
return
|
|
}
|
|
|
|
// Some assorted checks on the resolver
|
|
func check(res *Resolver, q *Msg) (port string, err os.Error) {
|
|
if res.Port == "" {
|
|
port = "53"
|
|
} else {
|
|
port = res.Port
|
|
}
|
|
if res.Rtt == nil {
|
|
res.Rtt = make(map[string]int64)
|
|
}
|
|
if q.Id == 0 {
|
|
q.Id = Id()
|
|
}
|
|
return
|
|
}
|