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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Read system DNS config from /etc/resolv.conf
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package dns
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import (
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"os"
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"bufio"
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"strconv"
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"strings"
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"net"
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)
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// See resolv.conf(5) on a Linux machine.
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// Set the resolver configuration from a /etc/resolv.conf like file.
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func (r *Resolver) FromFile(conf string) os.Error {
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file, err := os.Open(conf, os.O_RDONLY, 0)
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defer file.Close()
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if err != nil {
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return err
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}
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b := bufio.NewReader(file)
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r.Servers = make([]string, 3)[0:0] // small, but the standard limit
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r.Search = make([]string, 0)
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r.Ndots = 1
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r.Timeout = 5
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r.Attempts = 2
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for line, ok := b.ReadString('\n'); ok == nil; line, ok = b.ReadString('\n') {
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f := strings.Fields(line)
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if len(f) < 1 {
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continue
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}
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switch f[0] {
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case "nameserver": // add one name server
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a := r.Servers
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n := len(a)
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if len(f) > 1 && n < cap(a) {
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// One more check: make sure server name is
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// just an IP address. Otherwise we need DNS
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// to look it up.
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name := f[1]
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switch len(net.ParseIP(name)) {
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case 16:
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name = "[" + name + "]"
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fallthrough
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case 4:
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a = a[0 : n+1]
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a[n] = name
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r.Servers = a
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}
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}
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case "domain": // set search path to just this domain
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if len(f) > 1 {
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r.Search = make([]string, 1)
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r.Search[0] = f[1]
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} else {
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r.Search = make([]string, 0)
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}
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case "search": // set search path to given servers
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r.Search = make([]string, len(f)-1)
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for i := 0; i < len(r.Search); i++ {
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r.Search[i] = f[i+1]
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}
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case "options": // magic options
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for i := 1; i < len(f); i++ {
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s := f[i]
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switch {
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case len(s) >= 6 && s[:6] == "ndots:":
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n, _ := strconv.Atoi(s[6:])
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if n < 1 {
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n = 1
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}
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r.Ndots = n
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case len(s) >= 8 && s[:8] == "timeout:":
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n, _ := strconv.Atoi(s[8:])
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if n < 1 {
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n = 1
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}
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r.Timeout = n
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case len(s) >= 8 && s[:9] == "attempts:":
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n, _ := strconv.Atoi(s[9:])
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if n < 1 {
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n = 1
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}
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r.Attempts = n
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case s == "rotate":
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/* not imp */
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}
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}
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}
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}
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return nil
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}
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