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// 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.
// This file is a modified version of net/hosts.go from the golang repo
package hosts
import (
"bufio"
"bytes"
"io"
"net"
"os"
"strings"
"sync"
"time"
"github.com/coredns/coredns/plugin"
)
const cacheMaxAge = 5 * time.Second
func parseLiteralIP(addr string) net.IP {
if i := strings.Index(addr, "%"); i >= 0 {
// discard ipv6 zone
addr = addr[0:i]
}
return net.ParseIP(addr)
}
func absDomainName(b string) string {
return plugin.Name(b).Normalize()
}
// Hostsfile contains known host entries.
type Hostsfile struct {
sync.Mutex
// list of zones we are authoritive for
Origins []string
// Key for the list of literal IP addresses must be a host
// name. It would be part of DNS labels, a FQDN or an absolute
// FQDN.
// For now the key is converted to lower case for convenience.
byNameV4 map[string][]net.IP
byNameV6 map[string][]net.IP
// Key for the list of host names must be a literal IP address
// including IPv6 address with zone identifier.
// We don't support old-classful IP address notation.
byAddr map[string][]string
expire time.Time
path string
mtime time.Time
size int64
}
// ReadHosts determines if the cached data needs to be updated based on the size and modification time of the hostsfile.
func (h *Hostsfile) ReadHosts() {
now := time.Now()
if now.Before(h.expire) && len(h.byAddr) > 0 {
return
}
stat, err := os.Stat(h.path)
if err == nil && h.mtime.Equal(stat.ModTime()) && h.size == stat.Size() {
h.expire = now.Add(cacheMaxAge)
return
}
var file *os.File
if file, _ = os.Open(h.path); file == nil {
return
}
defer file.Close()
h.Parse(file)
// Update the data cache.
h.expire = now.Add(cacheMaxAge)
h.mtime = stat.ModTime()
h.size = stat.Size()
}
// Parse reads the hostsfile and populates the byName and byAddr maps.
func (h *Hostsfile) Parse(file io.Reader) {
hsv4 := make(map[string][]net.IP)
hsv6 := make(map[string][]net.IP)
is := make(map[string][]string)
scanner := bufio.NewScanner(file)
for scanner.Scan() {
line := scanner.Bytes()
if i := bytes.Index(line, []byte{'#'}); i >= 0 {
// Discard comments.
line = line[0:i]
}
f := bytes.Fields(line)
if len(f) < 2 {
continue
}
addr := parseLiteralIP(string(f[0]))
if addr == nil {
continue
}
ver := ipVersion(string(f[0]))
for i := 1; i < len(f); i++ {
name := absDomainName(string(f[i]))
if plugin.Zones(h.Origins).Matches(name) == "" {
// name is not in Origins
continue
}
switch ver {
case 4:
hsv4[name] = append(hsv4[name], addr)
case 6:
hsv6[name] = append(hsv6[name], addr)
default:
continue
}
is[addr.String()] = append(is[addr.String()], name)
}
}
h.byNameV4 = hsv4
h.byNameV6 = hsv6
h.byAddr = is
}
// ipVersion returns what IP version was used textually
func ipVersion(s string) int {
for i := 0; i < len(s); i++ {
switch s[i] {
case '.':
return 4
case ':':
return 6
}
}
return 0
}
// LookupStaticHostV4 looks up the IPv4 addresses for the given host from the hosts file.
func (h *Hostsfile) LookupStaticHostV4(host string) []net.IP {
h.Lock()
defer h.Unlock()
h.ReadHosts()
if len(h.byNameV4) != 0 {
if ips, ok := h.byNameV4[absDomainName(host)]; ok {
ipsCp := make([]net.IP, len(ips))
copy(ipsCp, ips)
return ipsCp
}
}
return nil
}
// LookupStaticHostV6 looks up the IPv6 addresses for the given host from the hosts file.
func (h *Hostsfile) LookupStaticHostV6(host string) []net.IP {
h.Lock()
defer h.Unlock()
h.ReadHosts()
if len(h.byNameV6) != 0 {
if ips, ok := h.byNameV6[absDomainName(host)]; ok {
ipsCp := make([]net.IP, len(ips))
copy(ipsCp, ips)
return ipsCp
}
}
return nil
}
// LookupStaticAddr looks up the hosts for the given address from the hosts file.
func (h *Hostsfile) LookupStaticAddr(addr string) []string {
h.Lock()
defer h.Unlock()
h.ReadHosts()
addr = parseLiteralIP(addr).String()
if addr == "" {
return nil
}
if len(h.byAddr) != 0 {
if hosts, ok := h.byAddr[addr]; ok {
hostsCp := make([]string, len(hosts))
copy(hostsCp, hosts)
return hostsCp
}
}
return nil
}
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