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Use /etc/hosts when resolving names.
http://code.google.com/p/go/issues/detail?id=313 This conflics with Chris' patch at: https://golang.org/cl/181063 But I believe this is more complete since it has a simple caching and proper tests. R=cw, rsc CC=golang-dev https://golang.org/cl/183066
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01b4f2dd23
commit
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@ -11,6 +11,7 @@ GOFILES=\
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dnsmsg.go\
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fd.go\
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fd_$(GOOS).go\
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hosts.go\
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ip.go\
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ipsock.go\
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net.go\
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@ -224,7 +224,7 @@ func isDomainName(s string) bool {
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return ok
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}
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// LookupHost looks up the host name using the local DNS resolver.
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// LookupHost looks for name using the local hosts file and DNS resolver.
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// It returns the canonical name for the host and an array of that
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// host's addresses.
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func LookupHost(name string) (cname string, addrs []string, err os.Error) {
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@ -236,7 +236,12 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
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err = dnserr
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return
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}
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// Use entries from /etc/hosts if they match.
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addrs = lookupStaticHost(name)
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if len(addrs) > 0 {
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cname = name
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return
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}
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// If name is rooted (trailing dot) or has enough dots,
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// try it by itself first.
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rooted := len(name) > 0 && name[len(name)-1] == '.'
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78
src/pkg/net/hosts.go
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78
src/pkg/net/hosts.go
Normal file
@ -0,0 +1,78 @@
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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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48
src/pkg/net/hosts_test.go
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48
src/pkg/net/hosts_test.go
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@ -0,0 +1,48 @@
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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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package net
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import (
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"testing"
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)
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type hostTest struct {
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host string
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ips []IP
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}
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var hosttests = []hostTest{
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hostTest{"odin", []IP{
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IPv4(127, 0, 0, 2),
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IPv4(127, 0, 0, 3),
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ParseIP("::2"),
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}},
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hostTest{"thor", []IP{
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IPv4(127, 1, 1, 1),
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}},
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hostTest{"loki", []IP{}},
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}
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func TestLookupStaticHost(t *testing.T) {
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p := hostsPath
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hostsPath = "hosts_testdata"
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for i := 0; i < len(hosttests); i++ {
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tt := hosttests[i]
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ips := lookupStaticHost(tt.host)
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if len(ips) != len(tt.ips) {
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t.Errorf("# of hosts = %v; want %v",
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len(ips), len(tt.ips))
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return
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}
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for k, v := range ips {
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if tt.ips[k].String() != v {
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t.Errorf("lookupStaticHost(%q) = %v; want %v",
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tt.host, v, tt.ips[k])
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}
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}
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}
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hostsPath = p
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}
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10
src/pkg/net/hosts_testdata
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10
src/pkg/net/hosts_testdata
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@ -0,0 +1,10 @@
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255.255.255.255 broadcasthost
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127.0.0.2 odin
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127.0.0.3 odin # inline comment
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::2 odin
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127.1.1.1 thor
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# Bogus entries that must be ignored.
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123.123.123 loki
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321.321.321.321
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# TODO(yvesj): Should we be able to parse this? From a Darwin system.
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fe80::1%lo0 localhost
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@ -278,6 +278,10 @@ func parseIPv4(s string) IP {
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var p [IPv4len]byte
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i := 0
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for j := 0; j < IPv4len; j++ {
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if i >= len(s) {
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// Missing octets.
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return nil
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}
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if j > 0 {
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if s[i] != '.' {
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return nil
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