87 lines
1.8 KiB
Go
87 lines
1.8 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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// Read static host/IP entries from /etc/hosts.
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package net
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import (
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"sync"
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"time"
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)
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const cacheMaxAge = 5 * time.Minute
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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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byName map[string][]string
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byAddr map[string][]string
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expire time.Time
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path string
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}
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func readHosts() {
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now := time.Now()
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hp := hostsPath
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if len(hosts.byName) == 0 || now.After(hosts.expire) || hosts.path != hp {
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hs := make(map[string][]string)
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is := make(map[string][]string)
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var file *file
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if file, _ = open(hp); file == nil {
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return
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}
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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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for i := 1; i < len(f); i++ {
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h := f[i]
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hs[h] = append(hs[h], f[0])
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is[f[0]] = append(is[f[0]], h)
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}
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}
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// Update the data cache.
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hosts.expire = time.Now().Add(cacheMaxAge)
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hosts.path = hp
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hosts.byName = hs
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hosts.byAddr = is
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file.close()
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}
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}
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// lookupStaticHost 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.byName) != 0 {
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if ips, ok := hosts.byName[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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// lookupStaticAddr looks up the hosts for the given address from /etc/hosts.
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func lookupStaticAddr(addr 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.byAddr) != 0 {
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if hosts, ok := hosts.byAddr[addr]; ok {
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return hosts
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}
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}
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return nil
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}
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