107 lines
2.6 KiB
Go
107 lines
2.6 KiB
Go
// 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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// +build darwin freebsd linux netbsd openbsd
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// Read system DNS config from /etc/resolv.conf
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package net
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type dnsConfig struct {
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servers []string // servers to use
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search []string // suffixes to append to local name
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ndots int // number of dots in name to trigger absolute lookup
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timeout int // seconds before giving up on packet
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attempts int // lost packets before giving up on server
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rotate bool // round robin among servers
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}
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// See resolv.conf(5) on a Linux machine.
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// TODO(rsc): Supposed to call uname() and chop the beginning
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// of the host name to get the default search domain.
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// We assume it's in resolv.conf anyway.
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func dnsReadConfig() (*dnsConfig, error) {
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file, err := open("/etc/resolv.conf")
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if err != nil {
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return nil, &DNSConfigError{err}
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}
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conf := new(dnsConfig)
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conf.servers = make([]string, 3)[0:0] // small, but the standard limit
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conf.search = make([]string, 0)
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conf.ndots = 1
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conf.timeout = 5
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conf.attempts = 2
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conf.rotate = false
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for line, ok := file.readLine(); ok; line, ok = file.readLine() {
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f := getFields(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 := conf.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(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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conf.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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conf.search = make([]string, 1)
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conf.search[0] = f[1]
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} else {
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conf.search = make([]string, 0)
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}
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case "search": // set search path to given servers
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conf.search = make([]string, len(f)-1)
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for i := 0; i < len(conf.search); i++ {
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conf.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[0:6] == "ndots:":
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n, _, _ := dtoi(s, 6)
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if n < 1 {
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n = 1
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}
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conf.ndots = n
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case len(s) >= 8 && s[0:8] == "timeout:":
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n, _, _ := dtoi(s, 8)
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if n < 1 {
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n = 1
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}
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conf.timeout = n
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case len(s) >= 8 && s[0:9] == "attempts:":
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n, _, _ := dtoi(s, 9)
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if n < 1 {
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n = 1
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}
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conf.attempts = n
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case s == "rotate":
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conf.rotate = true
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}
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}
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}
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}
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file.close()
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return conf, nil
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}
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