mirror of
https://github.com/golang/go
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79 lines
1.6 KiB
Go
79 lines
1.6 KiB
Go
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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 static host/IP entries from /etc/hosts.
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package net
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import (
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"os"
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"sync"
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)
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const cacheMaxAge = int64(300) // 5 minutes.
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// hostsPath points to the file with static IP/address entries.
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var hostsPath = "/etc/hosts"
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// Simple cache.
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var hosts struct {
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sync.Mutex
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data map[string][]string
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time int64
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path string
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}
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func readHosts() {
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now, _, _ := os.Time()
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hp := hostsPath
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if len(hosts.data) == 0 || hosts.time+cacheMaxAge <= now || hosts.path != hp {
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hs := make(map[string][]string)
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var file *file
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file, _ = open(hp)
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for line, ok := file.readLine(); ok; line, ok = file.readLine() {
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if i := byteIndex(line, '#'); i >= 0 {
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// Discard comments.
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line = line[0:i]
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}
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f := getFields(line)
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if len(f) < 2 || ParseIP(f[0]) == nil {
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continue
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}
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h := f[1]
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old, _ := hs[h]
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hs[h] = appendHost(old, f[0])
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}
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// Update the data cache.
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hosts.time, _, _ = os.Time()
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hosts.path = hp
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hosts.data = hs
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file.close()
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}
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}
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func appendHost(hosts []string, address string) []string {
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n := len(hosts)
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if n+1 > cap(hosts) { // reallocate
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a := make([]string, n, 2*n+1)
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copy(a, hosts)
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hosts = a
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}
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hosts = hosts[0 : n+1]
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hosts[n] = address
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return hosts
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}
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// lookupStaticHosts looks up the addresses for the given host from /etc/hosts.
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func lookupStaticHost(host string) []string {
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hosts.Lock()
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defer hosts.Unlock()
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readHosts()
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if len(hosts.data) != 0 {
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if ips, ok := hosts.data[host]; ok {
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return ips
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}
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}
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return nil
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}
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