a8f7c5ee48
Some configuration in a container depends on whether it has support for IPv6 (including default entries for '::1' etc in '/etc/hosts'). Before this change, the container's support for IPv6 was determined by whether it was connected to any IPv6-enabled networks. But, that can change over time, it isn't a property of the container itself. So, instead, detect IPv6 support by looking for '::1' on the container's loopback interface. It will not be present if the kernel does not have IPv6 support, or the user has disabled it in new namespaces by other means. Once IPv6 support has been determined for the container, its '/etc/hosts' is re-generated accordingly. The daemon no longer disables IPv6 on all interfaces during initialisation. It now disables IPv6 only for interfaces that have not been assigned an IPv6 address. (But, even if IPv6 is disabled for the container using the sysctl 'net.ipv6.conf.all.disable_ipv6=1', interfaces connected to IPv6 networks still get IPv6 addresses that appear in the internal DNS. There's more to-do!) Signed-off-by: Rob Murray <rob.murray@docker.com>
487 lines
15 KiB
Go
487 lines
15 KiB
Go
//go:build !windows
|
|
|
|
package libnetwork
|
|
|
|
import (
|
|
"bytes"
|
|
"context"
|
|
"fmt"
|
|
"net"
|
|
"net/netip"
|
|
"os"
|
|
"path"
|
|
"path/filepath"
|
|
"strconv"
|
|
"strings"
|
|
|
|
"github.com/containerd/log"
|
|
"github.com/docker/docker/errdefs"
|
|
"github.com/docker/docker/libnetwork/etchosts"
|
|
"github.com/docker/docker/libnetwork/resolvconf"
|
|
"github.com/docker/docker/libnetwork/types"
|
|
)
|
|
|
|
const (
|
|
defaultPrefix = "/var/lib/docker/network/files"
|
|
dirPerm = 0o755
|
|
filePerm = 0o644
|
|
|
|
resolverIPSandbox = "127.0.0.11"
|
|
)
|
|
|
|
// finishInitDNS is to be called after the container namespace has been created,
|
|
// before it the user process is started. The container's support for IPv6 can be
|
|
// determined at this point.
|
|
func (sb *Sandbox) finishInitDNS() error {
|
|
if err := sb.buildHostsFile(); err != nil {
|
|
return errdefs.System(err)
|
|
}
|
|
for _, ep := range sb.Endpoints() {
|
|
if err := sb.updateHostsFile(ep.getEtcHostsAddrs()); err != nil {
|
|
return errdefs.System(err)
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
func (sb *Sandbox) startResolver(restore bool) {
|
|
sb.resolverOnce.Do(func() {
|
|
var err error
|
|
// The embedded resolver is always started with proxyDNS set as true, even when the sandbox is only attached to
|
|
// an internal network. This way, it's the driver responsibility to make sure `connect` syscall fails fast when
|
|
// no external connectivity is available (eg. by not setting a default gateway).
|
|
sb.resolver = NewResolver(resolverIPSandbox, true, 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 {
|
|
log.G(context.TODO()).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 {
|
|
log.G(context.TODO()).Errorf("Resolver Setup function failed for container %s, %q", sb.ContainerID(), err)
|
|
return
|
|
}
|
|
|
|
if err = sb.resolver.Start(); err != nil {
|
|
log.G(context.TODO()).Errorf("Resolver Start failed for container %s, %q", sb.ContainerID(), err)
|
|
}
|
|
})
|
|
}
|
|
|
|
func (sb *Sandbox) setupResolutionFiles() error {
|
|
// Create a hosts file that can be mounted during container setup. For most
|
|
// networking modes (not host networking) it will be re-created before the
|
|
// container start, once its support for IPv6 is known.
|
|
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
|
|
}
|
|
if err := sb.buildHostsFile(); err != nil {
|
|
return err
|
|
}
|
|
|
|
return sb.setupDNS()
|
|
}
|
|
|
|
func (sb *Sandbox) buildHostsFile() error {
|
|
// This is for the host mode networking
|
|
if sb.config.useDefaultSandBox && len(sb.config.extraHosts) == 0 {
|
|
// We are working under the assumption that the origin file option had been properly expressed by the upper layer
|
|
// if not here we are going to error out
|
|
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})
|
|
}
|
|
|
|
// Assume IPv6 support, unless it's definitely disabled.
|
|
buildf := etchosts.Build
|
|
if en, ok := sb.ipv6Enabled(); ok && !en {
|
|
buildf = etchosts.BuildNoIPv6
|
|
}
|
|
if err := buildf(sb.config.hostsPath, "", sb.config.hostName, sb.config.domainName, extraContent); err != nil {
|
|
return err
|
|
}
|
|
|
|
return sb.updateParentHosts()
|
|
}
|
|
|
|
func (sb *Sandbox) updateHostsFile(ifaceIPs []string) error {
|
|
if len(ifaceIPs) == 0 {
|
|
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
|
|
if sb.config.domainName != "" {
|
|
fqdn += "." + sb.config.domainName
|
|
}
|
|
hosts := fqdn
|
|
|
|
if hostName, _, ok := strings.Cut(fqdn, "."); ok {
|
|
hosts += " " + hostName
|
|
}
|
|
|
|
var extraContent []etchosts.Record
|
|
for _, ip := range ifaceIPs {
|
|
extraContent = append(extraContent, etchosts.Record{Hosts: hosts, IP: ip})
|
|
}
|
|
|
|
sb.addHostsEntries(extraContent)
|
|
return nil
|
|
}
|
|
|
|
func (sb *Sandbox) addHostsEntries(recs []etchosts.Record) {
|
|
// Assume IPv6 support, unless it's definitely disabled.
|
|
if en, ok := sb.ipv6Enabled(); ok && !en {
|
|
var filtered []etchosts.Record
|
|
for _, rec := range recs {
|
|
if addr, err := netip.ParseAddr(rec.IP); err == nil && !addr.Is6() {
|
|
filtered = append(filtered, rec)
|
|
}
|
|
}
|
|
recs = filtered
|
|
}
|
|
if err := etchosts.Add(sb.config.hostsPath, recs); err != nil {
|
|
log.G(context.TODO()).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 {
|
|
log.G(context.TODO()).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 {
|
|
// TODO(thaJeztah): was it intentional for this loop to re-use prior results of pSB? If not, we should make pSb local and always replace here.
|
|
if s, _ := sb.controller.GetSandbox(update.cid); s != nil {
|
|
pSb = s
|
|
}
|
|
if pSb == nil {
|
|
continue
|
|
}
|
|
// TODO(robmry) - filter out IPv6 addresses here if !sb.ipv6Enabled() but...
|
|
// - this is part of the implementation of '--link', which will be removed along
|
|
// with the rest of legacy networking.
|
|
// - IPv6 addresses shouldn't be allocated if IPv6 is not available in a container,
|
|
// and that change will come along later.
|
|
// - I think this may be dead code, it's not possible to start a parent container with
|
|
// '--link child' unless the child has already started ("Error response from daemon:
|
|
// Cannot link to a non running container"). So, when the child starts and this method
|
|
// is called with updates for parents, the parents aren't running and GetSandbox()
|
|
// returns nil.)
|
|
if err := etchosts.Update(pSb.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 && isIPv4Loopback(ip) {
|
|
hostLoopback = true
|
|
}
|
|
sb.extDNS = append(sb.extDNS, extDNSEntry{
|
|
IPStr: ip,
|
|
HostLoopback: hostLoopback,
|
|
})
|
|
}
|
|
}
|
|
|
|
// isIPv4Loopback checks if the given IP address is an IPv4 loopback address.
|
|
// It's based on the logic in Go's net.IP.IsLoopback(), but only the IPv4 part:
|
|
// https://github.com/golang/go/blob/go1.16.6/src/net/ip.go#L120-L126
|
|
func isIPv4Loopback(ipAddress string) bool {
|
|
if ip := net.ParseIP(ipAddress); ip != nil {
|
|
if ip4 := ip.To4(); ip4 != nil {
|
|
return ip4[0] == 127
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
func (sb *Sandbox) setupDNS() error {
|
|
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
|
|
}
|
|
|
|
// When the user specify a conainter in the host namespace and do no have any dns option specified
|
|
// we just copy the host resolv.conf from the host itself
|
|
if sb.config.useDefaultSandBox && len(sb.config.dnsList) == 0 && len(sb.config.dnsSearchList) == 0 && len(sb.config.dnsOptionsList) == 0 {
|
|
// We are working under the assumption that the origin file option had been properly expressed by the upper layer
|
|
// if not here we are going to error out
|
|
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)
|
|
}
|
|
log.G(context.TODO()).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
|
|
}
|
|
|
|
originResolvConfPath := sb.config.originResolvConfPath
|
|
if originResolvConfPath == "" {
|
|
// fallback if not specified
|
|
originResolvConfPath = resolvconf.Path()
|
|
}
|
|
currRC, err := os.ReadFile(originResolvConfPath)
|
|
if err != nil {
|
|
if !os.IsNotExist(err) {
|
|
return err
|
|
}
|
|
// No /etc/resolv.conf found: we'll use the default resolvers (Google's Public DNS).
|
|
log.G(context.TODO()).WithField("path", originResolvConfPath).Infof("no resolv.conf found, falling back to defaults")
|
|
}
|
|
|
|
var newRC *resolvconf.File
|
|
if len(sb.config.dnsList) > 0 || len(sb.config.dnsSearchList) > 0 || len(sb.config.dnsOptionsList) > 0 {
|
|
var (
|
|
dnsList = sb.config.dnsList
|
|
dnsSearchList = sb.config.dnsSearchList
|
|
dnsOptionsList = sb.config.dnsOptionsList
|
|
)
|
|
if len(sb.config.dnsList) == 0 {
|
|
dnsList = resolvconf.GetNameservers(currRC, resolvconf.IP)
|
|
}
|
|
if len(sb.config.dnsSearchList) == 0 {
|
|
dnsSearchList = resolvconf.GetSearchDomains(currRC)
|
|
}
|
|
if len(sb.config.dnsOptionsList) == 0 {
|
|
dnsOptionsList = resolvconf.GetOptions(currRC)
|
|
}
|
|
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, resolvconf.IPv4, len(sb.config.dnsList) == 0)
|
|
} else {
|
|
// If the host resolv.conf file has 127.0.0.x container should
|
|
// use the host resolver for queries. This is supported by the
|
|
// docker embedded DNS server. Hence save the external resolvers
|
|
// before filtering it out.
|
|
sb.setExternalResolvers(currRC, resolvconf.IPv4, true)
|
|
|
|
// Replace any localhost/127.* (at this point we have no info about ipv6, pass it as true)
|
|
newRC, err = resolvconf.FilterResolvDNS(currRC, true)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
// No contention on container resolv.conf file at sandbox creation
|
|
err = os.WriteFile(sb.config.resolvConfPath, newRC.Content, filePerm)
|
|
if 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
|
|
err = os.WriteFile(sb.config.resolvConfHashFile, newRC.Hash, filePerm)
|
|
if 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 {
|
|
// This is for the host mode networking
|
|
if sb.config.useDefaultSandBox {
|
|
return nil
|
|
}
|
|
|
|
if len(sb.config.dnsList) > 0 || len(sb.config.dnsSearchList) > 0 || len(sb.config.dnsOptionsList) > 0 {
|
|
return nil
|
|
}
|
|
|
|
var currHash []byte
|
|
currRC, err := resolvconf.GetSpecific(sb.config.resolvConfPath)
|
|
if err != nil {
|
|
if !os.IsNotExist(err) {
|
|
return err
|
|
}
|
|
} else {
|
|
currHash, err = os.ReadFile(sb.config.resolvConfHashFile)
|
|
if err != nil && !os.IsNotExist(err) {
|
|
return err
|
|
}
|
|
}
|
|
|
|
if len(currHash) > 0 && !bytes.Equal(currHash, currRC.Hash) {
|
|
// Seems the user has changed the container resolv.conf since the last time
|
|
// we checked so return without doing anything.
|
|
// log.G(ctx).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 = os.WriteFile(sb.config.resolvConfPath, newRC.Content, filePerm)
|
|
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 := os.CreateTemp(dir, "hash")
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if err = tmpHashFile.Chmod(filePerm); err != nil {
|
|
tmpHashFile.Close()
|
|
return err
|
|
}
|
|
_, err = tmpHashFile.Write(newRC.Hash)
|
|
if err1 := tmpHashFile.Close(); err == nil {
|
|
err = err1
|
|
}
|
|
if err != nil {
|
|
return err
|
|
}
|
|
return os.Rename(tmpHashFile.Name(), sb.config.resolvConfHashFile)
|
|
}
|
|
|
|
// 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 := os.ReadFile(sb.config.resolvConfPath)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
// 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()
|
|
dnsOptionsList := resolvconf.GetOptions(currRC)
|
|
|
|
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", parts[1])
|
|
} else if num >= 0 {
|
|
// if the user sets ndots, use the user setting
|
|
sb.ndotsSet = true
|
|
break dnsOpt
|
|
} else {
|
|
return fmt.Errorf("invalid number for ndots option: %v", num)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
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...)
|
|
}
|
|
if len(sb.extDNS) == 0 {
|
|
sb.setExternalResolvers(currRC, resolvconf.IPv4, false)
|
|
}
|
|
|
|
var (
|
|
// external v6 DNS servers have to be listed in resolv.conf
|
|
dnsList = append([]string{sb.resolver.NameServer()}, resolvconf.GetNameservers(currRC, resolvconf.IPv6)...)
|
|
dnsSearchList = resolvconf.GetSearchDomains(currRC)
|
|
)
|
|
|
|
_, 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 := os.ReadFile(src)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
return os.WriteFile(dst, sBytes, filePerm)
|
|
}
|