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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
This commit is contained in:
Yves Junqueira 2010-01-15 13:43:14 -08:00 committed by Russ Cox
parent 01b4f2dd23
commit d6054fcd88
6 changed files with 148 additions and 2 deletions

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@ -11,6 +11,7 @@ GOFILES=\
dnsmsg.go\
fd.go\
fd_$(GOOS).go\
hosts.go\
ip.go\
ipsock.go\
net.go\

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@ -224,7 +224,7 @@ func isDomainName(s string) bool {
return ok
}
// LookupHost looks up the host name using the local DNS resolver.
// LookupHost looks for name using the local hosts file and DNS resolver.
// It returns the canonical name for the host and an array of that
// host's addresses.
func LookupHost(name string) (cname string, addrs []string, err os.Error) {
@ -236,7 +236,12 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
err = dnserr
return
}
// Use entries from /etc/hosts if they match.
addrs = lookupStaticHost(name)
if len(addrs) > 0 {
cname = name
return
}
// If name is rooted (trailing dot) or has enough dots,
// try it by itself first.
rooted := len(name) > 0 && name[len(name)-1] == '.'

78
src/pkg/net/hosts.go Normal file
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@ -0,0 +1,78 @@
// 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
data map[string][]string
time int64
path string
}
func readHosts() {
now, _, _ := os.Time()
hp := hostsPath
if len(hosts.data) == 0 || hosts.time+cacheMaxAge <= now || hosts.path != hp {
hs := make(map[string][]string)
var file *file
file, _ = open(hp)
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
}
h := f[1]
old, _ := hs[h]
hs[h] = appendHost(old, f[0])
}
// Update the data cache.
hosts.time, _, _ = os.Time()
hosts.path = hp
hosts.data = hs
file.close()
}
}
func appendHost(hosts []string, address string) []string {
n := len(hosts)
if n+1 > cap(hosts) { // reallocate
a := make([]string, n, 2*n+1)
copy(a, hosts)
hosts = a
}
hosts = hosts[0 : n+1]
hosts[n] = address
return hosts
}
// 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.data) != 0 {
if ips, ok := hosts.data[host]; ok {
return ips
}
}
return nil
}

48
src/pkg/net/hosts_test.go Normal file
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@ -0,0 +1,48 @@
// 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.
package net
import (
"testing"
)
type hostTest struct {
host string
ips []IP
}
var hosttests = []hostTest{
hostTest{"odin", []IP{
IPv4(127, 0, 0, 2),
IPv4(127, 0, 0, 3),
ParseIP("::2"),
}},
hostTest{"thor", []IP{
IPv4(127, 1, 1, 1),
}},
hostTest{"loki", []IP{}},
}
func TestLookupStaticHost(t *testing.T) {
p := hostsPath
hostsPath = "hosts_testdata"
for i := 0; i < len(hosttests); i++ {
tt := hosttests[i]
ips := lookupStaticHost(tt.host)
if len(ips) != len(tt.ips) {
t.Errorf("# of hosts = %v; want %v",
len(ips), len(tt.ips))
return
}
for k, v := range ips {
if tt.ips[k].String() != v {
t.Errorf("lookupStaticHost(%q) = %v; want %v",
tt.host, v, tt.ips[k])
}
}
}
hostsPath = p
}

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@ -0,0 +1,10 @@
255.255.255.255 broadcasthost
127.0.0.2 odin
127.0.0.3 odin # inline comment
::2 odin
127.1.1.1 thor
# Bogus entries that must be ignored.
123.123.123 loki
321.321.321.321
# TODO(yvesj): Should we be able to parse this? From a Darwin system.
fe80::1%lo0 localhost

View File

@ -278,6 +278,10 @@ func parseIPv4(s string) IP {
var p [IPv4len]byte
i := 0
for j := 0; j < IPv4len; j++ {
if i >= len(s) {
// Missing octets.
return nil
}
if j > 0 {
if s[i] != '.' {
return nil