// 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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package net
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import (
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"internal/bytealg"
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"sync"
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"time"
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)
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const cacheMaxAge = 5 * time.Second
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func parseLiteralIP(addr string) string {
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var ip IP
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var zone string
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ip = parseIPv4(addr)
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if ip == nil {
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ip, zone = parseIPv6Zone(addr)
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}
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if ip == nil {
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return ""
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}
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if zone == "" {
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return ip.String()
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}
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return ip.String() + "%" + zone
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}
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// hosts contains known host entries.
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var hosts struct {
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sync.Mutex
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// Key for the list of literal IP addresses must be a host
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// name. It would be part of DNS labels, a FQDN or an absolute
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// FQDN.
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// For now the key is converted to lower case for convenience.
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byName map[string][]string
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// Key for the list of host names must be a literal IP address
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// including IPv6 address with zone identifier.
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// We don't support old-classful IP address notation.
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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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mtime time.Time
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size int64
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}
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func readHosts() {
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now := time.Now()
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hp := testHookHostsPath
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if now.Before(hosts.expire) && hosts.path == hp && len(hosts.byName) > 0 {
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return
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}
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mtime, size, err := stat(hp)
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if err == nil && hosts.path == hp && hosts.mtime.Equal(mtime) && hosts.size == size {
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hosts.expire = now.Add(cacheMaxAge)
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return
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}
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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 := bytealg.IndexByteString(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 {
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continue
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}
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addr := parseLiteralIP(f[0])
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if addr == "" {
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continue
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}
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for i := 1; i < len(f); i++ {
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name := absDomainName([]byte(f[i]))
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h := []byte(f[i])
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lowerASCIIBytes(h)
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key := absDomainName(h)
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hs[key] = append(hs[key], addr)
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is[addr] = append(is[addr], name)
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}
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}
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// Update the data cache.
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hosts.expire = 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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hosts.mtime = mtime
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hosts.size = size
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file.close()
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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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// TODO(jbd,bradfitz): avoid this alloc if host is already all lowercase?
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// or linear scan the byName map if it's small enough?
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lowerHost := []byte(host)
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lowerASCIIBytes(lowerHost)
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if ips, ok := hosts.byName[absDomainName(lowerHost)]; ok {
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ipsCp := make([]string, len(ips))
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copy(ipsCp, ips)
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return ipsCp
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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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addr = parseLiteralIP(addr)
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if addr == "" {
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return nil
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}
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if len(hosts.byAddr) != 0 {
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if hosts, ok := hosts.byAddr[addr]; ok {
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hostsCp := make([]string, len(hosts))
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copy(hostsCp, hosts)
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return hostsCp
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}
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}
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return nil
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}
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