| // Copyright 2009 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // +build darwin dragonfly freebsd linux netbsd openbsd solaris |
| |
| // Read system DNS config from /etc/resolv.conf |
| |
| package net |
| |
| var defaultNS = []string{"127.0.0.1", "::1"} |
| |
| type dnsConfig struct { |
| servers []string // servers to use |
| search []string // suffixes to append to local name |
| ndots int // number of dots in name to trigger absolute lookup |
| timeout int // seconds before giving up on packet |
| attempts int // lost packets before giving up on server |
| rotate bool // round robin among servers |
| unknownOpt bool // anything unknown was encountered |
| lookup []string // OpenBSD top-level database "lookup" order |
| err error // any error that occurs during open of resolv.conf |
| } |
| |
| // See resolv.conf(5) on a Linux machine. |
| // TODO(rsc): Supposed to call uname() and chop the beginning |
| // of the host name to get the default search domain. |
| func dnsReadConfig(filename string) *dnsConfig { |
| conf := &dnsConfig{ |
| ndots: 1, |
| timeout: 5, |
| attempts: 2, |
| } |
| file, err := open(filename) |
| if err != nil { |
| conf.servers = defaultNS |
| conf.err = err |
| return conf |
| } |
| defer file.close() |
| for line, ok := file.readLine(); ok; line, ok = file.readLine() { |
| if len(line) > 0 && (line[0] == ';' || line[0] == '#') { |
| // comment. |
| continue |
| } |
| f := getFields(line) |
| if len(f) < 1 { |
| continue |
| } |
| switch f[0] { |
| case "nameserver": // add one name server |
| if len(f) > 1 && len(conf.servers) < 3 { // small, but the standard limit |
| // One more check: make sure server name is |
| // just an IP address. Otherwise we need DNS |
| // to look it up. |
| if parseIPv4(f[1]) != nil { |
| conf.servers = append(conf.servers, f[1]) |
| } else if ip, _ := parseIPv6(f[1], true); ip != nil { |
| conf.servers = append(conf.servers, f[1]) |
| } |
| } |
| |
| case "domain": // set search path to just this domain |
| if len(f) > 1 { |
| conf.search = []string{f[1]} |
| } |
| |
| case "search": // set search path to given servers |
| conf.search = make([]string, len(f)-1) |
| for i := 0; i < len(conf.search); i++ { |
| conf.search[i] = f[i+1] |
| } |
| |
| case "options": // magic options |
| for _, s := range f[1:] { |
| switch { |
| case hasPrefix(s, "ndots:"): |
| n, _, _ := dtoi(s, 6) |
| if n < 1 { |
| n = 1 |
| } |
| conf.ndots = n |
| case hasPrefix(s, "timeout:"): |
| n, _, _ := dtoi(s, 8) |
| if n < 1 { |
| n = 1 |
| } |
| conf.timeout = n |
| case hasPrefix(s, "attempts:"): |
| n, _, _ := dtoi(s, 9) |
| if n < 1 { |
| n = 1 |
| } |
| conf.attempts = n |
| case s == "rotate": |
| conf.rotate = true |
| default: |
| conf.unknownOpt = true |
| } |
| } |
| |
| case "lookup": |
| // OpenBSD option: |
| // http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man5/resolv.conf.5 |
| // "the legal space-separated values are: bind, file, yp" |
| conf.lookup = f[1:] |
| |
| default: |
| conf.unknownOpt = true |
| } |
| } |
| if len(conf.servers) == 0 { |
| conf.servers = defaultNS |
| } |
| return conf |
| } |
| |
| func hasPrefix(s, prefix string) bool { |
| return len(s) >= len(prefix) && s[:len(prefix)] == prefix |
| } |
