forked from coredns/coredns
/
hostsfile.go
228 lines (196 loc) · 5.23 KB
/
hostsfile.go
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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"
)
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()
}
type hostsMap struct {
// 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
}
func newHostsMap() *hostsMap {
return &hostsMap{
byNameV4: make(map[string][]net.IP),
byNameV6: make(map[string][]net.IP),
byAddr: make(map[string][]string),
}
}
// Hostsfile contains known host entries.
type Hostsfile struct {
sync.RWMutex
// list of zones we are authoritive for
Origins []string
// hosts maps for lookups
hmap *hostsMap
// inline saves the hosts file that is inlined in a Corefile.
// We need a copy here as we want to use it to initialize the maps for parse.
inline *hostsMap
// path to the hosts file
path string
// mtime and size are only read and modified by a single goroutine
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() {
file, err := os.Open(h.path)
if err != nil {
// We already log a warning if the file doesn't exist or can't be opened on setup. No need to return the error here.
return
}
defer file.Close()
stat, err := file.Stat()
if err == nil && h.mtime.Equal(stat.ModTime()) && h.size == stat.Size() {
return
}
h.Lock()
defer h.Unlock()
h.parseReader(file)
// Update the data cache.
h.mtime = stat.ModTime()
h.size = stat.Size()
}
func (h *Hostsfile) initInline(inline []string) {
if len(inline) == 0 {
return
}
hmap := newHostsMap()
h.inline = h.parse(strings.NewReader(strings.Join(inline, "\n")), hmap)
*h.hmap = *h.inline
}
func (h *Hostsfile) parseReader(r io.Reader) {
h.hmap = h.parse(r, h.inline)
}
// Parse reads the hostsfile and populates the byName and byAddr maps.
func (h *Hostsfile) parse(r io.Reader, override *hostsMap) *hostsMap {
hmap := newHostsMap()
scanner := bufio.NewScanner(r)
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:
hmap.byNameV4[name] = append(hmap.byNameV4[name], addr)
case 6:
hmap.byNameV6[name] = append(hmap.byNameV6[name], addr)
default:
continue
}
hmap.byAddr[addr.String()] = append(hmap.byAddr[addr.String()], name)
}
}
if override == nil {
return hmap
}
for name := range override.byNameV4 {
hmap.byNameV4[name] = append(hmap.byNameV4[name], override.byNameV4[name]...)
}
for name := range override.byNameV4 {
hmap.byNameV6[name] = append(hmap.byNameV6[name], override.byNameV6[name]...)
}
for addr := range override.byAddr {
hmap.byAddr[addr] = append(hmap.byAddr[addr], override.byAddr[addr]...)
}
return hmap
}
// 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.RLock()
defer h.RUnlock()
if len(h.hmap.byNameV4) != 0 {
if ips, ok := h.hmap.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.RLock()
defer h.RUnlock()
if len(h.hmap.byNameV6) != 0 {
if ips, ok := h.hmap.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.RLock()
defer h.RUnlock()
addr = parseLiteralIP(addr).String()
if addr == "" {
return nil
}
if len(h.hmap.byAddr) != 0 {
if hosts, ok := h.hmap.byAddr[addr]; ok {
hostsCp := make([]string, len(hosts))
copy(hostsCp, hosts)
return hostsCp
}
}
return nil
}