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sandbox_dns_unix.go
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sandbox_dns_unix.go
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// +build !windows
package libnetwork
import (
"fmt"
"io/ioutil"
"os"
"path"
"path/filepath"
"strconv"
"strings"
"github.com/docker/libnetwork/etchosts"
"github.com/docker/libnetwork/resolvconf"
"github.com/docker/libnetwork/resolvconf/dns"
"github.com/docker/libnetwork/types"
"github.com/sirupsen/logrus"
)
const (
defaultPrefix = "/var/lib/docker/network/files"
dirPerm = 0755
filePerm = 0644
)
func (sb *sandbox) startResolver(restore bool) {
sb.resolverOnce.Do(func() {
var err error
sb.resolver = NewResolver(resolverIPSandbox, true, sb.Key(), sb)
defer func() {
if err != nil {
sb.resolver = nil
}
}()
// In the case of live restore container is already running with
// right resolv.conf contents created before. Just update the
// external DNS servers from the restored sandbox for embedded
// server to use.
if !restore {
err = sb.rebuildDNS()
if err != nil {
logrus.Errorf("Updating resolv.conf failed for container %s, %q", sb.ContainerID(), err)
return
}
}
sb.resolver.SetExtServers(sb.extDNS)
if err = sb.osSbox.InvokeFunc(sb.resolver.SetupFunc(0)); err != nil {
logrus.Errorf("Resolver Setup function failed for container %s, %q", sb.ContainerID(), err)
return
}
if err = sb.resolver.Start(); err != nil {
logrus.Errorf("Resolver Start failed for container %s, %q", sb.ContainerID(), err)
}
})
}
func (sb *sandbox) setupResolutionFiles() error {
if err := sb.buildHostsFile(); err != nil {
return err
}
if err := sb.updateParentHosts(); err != nil {
return err
}
return sb.setupDNS()
}
func (sb *sandbox) buildHostsFile() error {
if sb.config.hostsPath == "" {
sb.config.hostsPath = defaultPrefix + "/" + sb.id + "/hosts"
}
dir, _ := filepath.Split(sb.config.hostsPath)
if err := createBasePath(dir); err != nil {
return err
}
// This is for the host mode networking
if sb.config.originHostsPath != "" {
if err := copyFile(sb.config.originHostsPath, sb.config.hostsPath); err != nil && !os.IsNotExist(err) {
return types.InternalErrorf("could not copy source hosts file %s to %s: %v", sb.config.originHostsPath, sb.config.hostsPath, err)
}
return nil
}
extraContent := make([]etchosts.Record, 0, len(sb.config.extraHosts))
for _, extraHost := range sb.config.extraHosts {
extraContent = append(extraContent, etchosts.Record{Hosts: extraHost.name, IP: extraHost.IP})
}
return etchosts.Build(sb.config.hostsPath, "", sb.config.hostName, sb.config.domainName, extraContent)
}
func (sb *sandbox) updateHostsFile(ifaceIP string) error {
if ifaceIP == "" {
return nil
}
if sb.config.originHostsPath != "" {
return nil
}
// User might have provided a FQDN in hostname or split it across hostname
// and domainname. We want the FQDN and the bare hostname.
fqdn := sb.config.hostName
mhost := sb.config.hostName
if sb.config.domainName != "" {
fqdn = fmt.Sprintf("%s.%s", fqdn, sb.config.domainName)
}
parts := strings.SplitN(fqdn, ".", 2)
if len(parts) == 2 {
mhost = fmt.Sprintf("%s %s", fqdn, parts[0])
}
extraContent := []etchosts.Record{{Hosts: mhost, IP: ifaceIP}}
sb.addHostsEntries(extraContent)
return nil
}
func (sb *sandbox) addHostsEntries(recs []etchosts.Record) {
if err := etchosts.Add(sb.config.hostsPath, recs); err != nil {
logrus.Warnf("Failed adding service host entries to the running container: %v", err)
}
}
func (sb *sandbox) deleteHostsEntries(recs []etchosts.Record) {
if err := etchosts.Delete(sb.config.hostsPath, recs); err != nil {
logrus.Warnf("Failed deleting service host entries to the running container: %v", err)
}
}
func (sb *sandbox) updateParentHosts() error {
var pSb Sandbox
for _, update := range sb.config.parentUpdates {
sb.controller.WalkSandboxes(SandboxContainerWalker(&pSb, update.cid))
if pSb == nil {
continue
}
if err := etchosts.Update(pSb.(*sandbox).config.hostsPath, update.ip, update.name); err != nil {
return err
}
}
return nil
}
func (sb *sandbox) restorePath() {
if sb.config.resolvConfPath == "" {
sb.config.resolvConfPath = defaultPrefix + "/" + sb.id + "/resolv.conf"
}
sb.config.resolvConfHashFile = sb.config.resolvConfPath + ".hash"
if sb.config.hostsPath == "" {
sb.config.hostsPath = defaultPrefix + "/" + sb.id + "/hosts"
}
}
func (sb *sandbox) setExternalResolvers(content []byte, addrType int, checkLoopback bool) {
servers := resolvconf.GetNameservers(content, addrType)
for _, ip := range servers {
hostLoopback := false
if checkLoopback {
hostLoopback = dns.IsIPv4Localhost(ip)
}
sb.extDNS = append(sb.extDNS, extDNSEntry{
IPStr: ip,
HostLoopback: hostLoopback,
})
}
}
func (sb *sandbox) setupDNS() error {
var newRC *resolvconf.File
if sb.config.resolvConfPath == "" {
sb.config.resolvConfPath = defaultPrefix + "/" + sb.id + "/resolv.conf"
}
sb.config.resolvConfHashFile = sb.config.resolvConfPath + ".hash"
dir, _ := filepath.Split(sb.config.resolvConfPath)
if err := createBasePath(dir); err != nil {
return err
}
// This is for the host mode networking
if sb.config.originResolvConfPath != "" {
if err := copyFile(sb.config.originResolvConfPath, sb.config.resolvConfPath); err != nil {
if !os.IsNotExist(err) {
return fmt.Errorf("could not copy source resolv.conf file %s to %s: %v", sb.config.originResolvConfPath, sb.config.resolvConfPath, err)
}
logrus.Infof("%s does not exist, we create an empty resolv.conf for container", sb.config.originResolvConfPath)
if err := createFile(sb.config.resolvConfPath); err != nil {
return err
}
}
return nil
}
currRC, err := resolvconf.Get()
if err != nil {
if !os.IsNotExist(err) {
return err
}
// it's ok to continue if /etc/resolv.conf doesn't exist, default resolvers (Google's Public DNS)
// will be used
currRC = &resolvconf.File{}
logrus.Infof("/etc/resolv.conf does not exist")
}
if len(sb.config.dnsList) > 0 || len(sb.config.dnsSearchList) > 0 || len(sb.config.dnsOptionsList) > 0 {
var (
err error
dnsList = resolvconf.GetNameservers(currRC.Content, types.IP)
dnsSearchList = resolvconf.GetSearchDomains(currRC.Content)
dnsOptionsList = resolvconf.GetOptions(currRC.Content)
)
if len(sb.config.dnsList) > 0 {
dnsList = sb.config.dnsList
}
if len(sb.config.dnsSearchList) > 0 {
dnsSearchList = sb.config.dnsSearchList
}
if len(sb.config.dnsOptionsList) > 0 {
dnsOptionsList = sb.config.dnsOptionsList
}
newRC, err = resolvconf.Build(sb.config.resolvConfPath, dnsList, dnsSearchList, dnsOptionsList)
if err != nil {
return err
}
// After building the resolv.conf from the user config save the
// external resolvers in the sandbox. Note that --dns 127.0.0.x
// config refers to the loopback in the container namespace
sb.setExternalResolvers(newRC.Content, types.IPv4, false)
} else {
// If the host resolv.conf file has 127.0.0.x container should
// use the host restolver for queries. This is supported by the
// docker embedded DNS server. Hence save the external resolvers
// before filtering it out.
sb.setExternalResolvers(currRC.Content, types.IPv4, true)
// Replace any localhost/127.* (at this point we have no info about ipv6, pass it as true)
if newRC, err = resolvconf.FilterResolvDNS(currRC.Content, true); err != nil {
return err
}
// No contention on container resolv.conf file at sandbox creation
if err := ioutil.WriteFile(sb.config.resolvConfPath, newRC.Content, filePerm); err != nil {
return types.InternalErrorf("failed to write unhaltered resolv.conf file content when setting up dns for sandbox %s: %v", sb.ID(), err)
}
}
// Write hash
if err := ioutil.WriteFile(sb.config.resolvConfHashFile, []byte(newRC.Hash), filePerm); err != nil {
return types.InternalErrorf("failed to write resolv.conf hash file when setting up dns for sandbox %s: %v", sb.ID(), err)
}
return nil
}
func (sb *sandbox) updateDNS(ipv6Enabled bool) error {
var (
currHash string
hashFile = sb.config.resolvConfHashFile
)
// This is for the host mode networking
if sb.config.originResolvConfPath != "" {
return nil
}
if len(sb.config.dnsList) > 0 || len(sb.config.dnsSearchList) > 0 || len(sb.config.dnsOptionsList) > 0 {
return nil
}
currRC, err := resolvconf.GetSpecific(sb.config.resolvConfPath)
if err != nil {
if !os.IsNotExist(err) {
return err
}
} else {
h, err := ioutil.ReadFile(hashFile)
if err != nil {
if !os.IsNotExist(err) {
return err
}
} else {
currHash = string(h)
}
}
if currHash != "" && currHash != currRC.Hash {
// Seems the user has changed the container resolv.conf since the last time
// we checked so return without doing anything.
//logrus.Infof("Skipping update of resolv.conf file with ipv6Enabled: %t because file was touched by user", ipv6Enabled)
return nil
}
// replace any localhost/127.* and remove IPv6 nameservers if IPv6 disabled.
newRC, err := resolvconf.FilterResolvDNS(currRC.Content, ipv6Enabled)
if err != nil {
return err
}
err = ioutil.WriteFile(sb.config.resolvConfPath, newRC.Content, 0644)
if err != nil {
return err
}
// write the new hash in a temp file and rename it to make the update atomic
dir := path.Dir(sb.config.resolvConfPath)
tmpHashFile, err := ioutil.TempFile(dir, "hash")
if err != nil {
return err
}
if err = tmpHashFile.Chmod(filePerm); err != nil {
tmpHashFile.Close()
return err
}
_, err = tmpHashFile.Write([]byte(newRC.Hash))
if err1 := tmpHashFile.Close(); err == nil {
err = err1
}
if err != nil {
return err
}
return os.Rename(tmpHashFile.Name(), hashFile)
}
// Embedded DNS server has to be enabled for this sandbox. Rebuild the container's
// resolv.conf by doing the following
// - Add only the embedded server's IP to container's resolv.conf
// - If the embedded server needs any resolv.conf options add it to the current list
func (sb *sandbox) rebuildDNS() error {
currRC, err := resolvconf.GetSpecific(sb.config.resolvConfPath)
if err != nil {
return err
}
if len(sb.extDNS) == 0 {
sb.setExternalResolvers(currRC.Content, types.IPv4, false)
}
var (
dnsList = []string{sb.resolver.NameServer()}
dnsOptionsList = resolvconf.GetOptions(currRC.Content)
dnsSearchList = resolvconf.GetSearchDomains(currRC.Content)
)
// external v6 DNS servers has to be listed in resolv.conf
dnsList = append(dnsList, resolvconf.GetNameservers(currRC.Content, types.IPv6)...)
// If the user config and embedded DNS server both have ndots option set,
// remember the user's config so that unqualified names not in the docker
// domain can be dropped.
resOptions := sb.resolver.ResolverOptions()
dnsOpt:
for _, resOpt := range resOptions {
if strings.Contains(resOpt, "ndots") {
for _, option := range dnsOptionsList {
if strings.Contains(option, "ndots") {
parts := strings.Split(option, ":")
if len(parts) != 2 {
return fmt.Errorf("invalid ndots option %v", option)
}
if num, err := strconv.Atoi(parts[1]); err != nil {
return fmt.Errorf("invalid number for ndots option %v", option)
} else if num > 0 {
// if the user sets ndots, use the user setting
sb.ndotsSet = true
break dnsOpt
}
}
}
}
}
if !sb.ndotsSet {
// if the user did not set the ndots, set it to 0 to prioritize the service name resolution
// Ref: https://linux.die.net/man/5/resolv.conf
dnsOptionsList = append(dnsOptionsList, resOptions...)
}
_, err = resolvconf.Build(sb.config.resolvConfPath, dnsList, dnsSearchList, dnsOptionsList)
return err
}
func createBasePath(dir string) error {
return os.MkdirAll(dir, dirPerm)
}
func createFile(path string) error {
var f *os.File
dir, _ := filepath.Split(path)
err := createBasePath(dir)
if err != nil {
return err
}
f, err = os.Create(path)
if err == nil {
f.Close()
}
return err
}
func copyFile(src, dst string) error {
sBytes, err := ioutil.ReadFile(src)
if err != nil {
return err
}
return ioutil.WriteFile(dst, sBytes, filePerm)
}