| // 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. |
| |
| // Read static host/IP entries from /etc/hosts. |
| |
| package net |
| |
| import ( |
| "os" |
| "sync" |
| ) |
| |
| const cacheMaxAge = int64(300) // 5 minutes. |
| |
| // hostsPath points to the file with static IP/address entries. |
| var hostsPath = "/etc/hosts" |
| |
| // Simple cache. |
| var hosts struct { |
| sync.Mutex |
| byName map[string][]string |
| byAddr map[string][]string |
| time int64 |
| path string |
| } |
| |
| func readHosts() { |
| now, _, _ := os.Time() |
| hp := hostsPath |
| if len(hosts.byName) == 0 || hosts.time+cacheMaxAge <= now || hosts.path != hp { |
| hs := make(map[string][]string) |
| is := make(map[string][]string) |
| var file *file |
| if file, _ = open(hp); file == nil { |
| return |
| } |
| for line, ok := file.readLine(); ok; line, ok = file.readLine() { |
| if i := byteIndex(line, '#'); i >= 0 { |
| // Discard comments. |
| line = line[0:i] |
| } |
| f := getFields(line) |
| if len(f) < 2 || ParseIP(f[0]) == nil { |
| continue |
| } |
| for i := 1; i < len(f); i++ { |
| h := f[i] |
| hs[h] = append(hs[h], f[0]) |
| is[f[0]] = append(is[f[0]], h) |
| } |
| } |
| // Update the data cache. |
| hosts.time, _, _ = os.Time() |
| hosts.path = hp |
| hosts.byName = hs |
| hosts.byAddr = is |
| file.close() |
| } |
| } |
| |
| // lookupStaticHosts looks up the addresses for the given host from /etc/hosts. |
| func lookupStaticHost(host string) []string { |
| hosts.Lock() |
| defer hosts.Unlock() |
| readHosts() |
| if len(hosts.byName) != 0 { |
| if ips, ok := hosts.byName[host]; ok { |
| return ips |
| } |
| } |
| return nil |
| } |
| |
| // rlookupStaticHosts looks up the hosts for the given address from /etc/hosts. |
| func lookupStaticAddr(addr string) []string { |
| hosts.Lock() |
| defer hosts.Unlock() |
| readHosts() |
| if len(hosts.byAddr) != 0 { |
| if hosts, ok := hosts.byAddr[addr]; ok { |
| return hosts |
| } |
| } |
| return nil |
| } |