add hostname to /etc/hosts when running with host network

Some tools depend on the hostname being present in /etc/hosts. I would
argue they are broken but its not like we can do anything about that.

This adds the hostname with the local host ip when the host network is
used. For private networking we already add the hostname.

We also now correctly force host networking in chroot mode, it was
silently ignored before thus causing extra confusion here.

Fixes #4446

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

run_common.go

@@ -35,6 +35,7 @@ import (
 	"github.com/containers/common/libnetwork/network"
 	"github.com/containers/common/libnetwork/resolvconf"
 	netTypes "github.com/containers/common/libnetwork/types"
+	netUtil "github.com/containers/common/libnetwork/util"
 	"github.com/containers/common/pkg/config"
 	"github.com/containers/common/pkg/subscriptions"
 	imageTypes "github.com/containers/image/v5/types"
@@ -117,7 +118,7 @@ func (b *Builder) addResolvConf(rdir string, chownOpts *idtools.IDPair, dnsServe
 }
 
 // generateHosts creates a containers hosts file
-func (b *Builder) generateHosts(rdir string, chownOpts *idtools.IDPair, imageRoot string) (string, error) {
+func (b *Builder) generateHosts(rdir string, chownOpts *idtools.IDPair, imageRoot string, spec *spec.Spec) (string, error) {
 	conf, err := config.Default()
 	if err != nil {
 		return "", err
@@ -128,12 +129,34 @@ func (b *Builder) generateHosts(rdir string, chownOpts *idtools.IDPair, imageRoo
 		return "", err
 	}
 
+	var entries etchosts.HostEntries
+	isHost := true
+	if spec.Linux != nil {
+		for _, ns := range spec.Linux.Namespaces {
+			if ns.Type == specs.NetworkNamespace {
+				isHost = false
+				break
+			}
+		}
+	}
+	// add host entry for local ip when running in host network
+	if spec.Hostname != "" && isHost {
+		ip := netUtil.GetLocalIP()
+		if ip != "" {
+			entries = append(entries, etchosts.HostEntry{
+				Names: []string{spec.Hostname},
+				IP:    ip,
+			})
+		}
+	}
+
 	targetfile := filepath.Join(rdir, "hosts")
 	if err := etchosts.New(&etchosts.Params{
 		BaseFile:                 path,
 		ExtraHosts:               b.CommonBuildOpts.AddHost,
 		HostContainersInternalIP: etchosts.GetHostContainersInternalIP(conf, nil, nil),
 		TargetFile:               targetfile,
+		ContainerIPs:             entries,
 	}); err != nil {
 		return "", err
 	}
@@ -368,6 +391,9 @@ func checkAndOverrideIsolationOptions(isolation define.Isolation, options *RunOp
 		if (pidns != nil && pidns.Host) && (userns != nil && !userns.Host) {
 			return fmt.Errorf("not allowed to mix host PID namespace with container user namespace")
 		}
+	case IsolationChroot:
+		logrus.Info("network namespace isolation not supported with chroot isolation, forcing host network")
+		options.NamespaceOptions.AddOrReplace(define.NamespaceOption{Name: string(specs.NetworkNamespace), Host: true})
 	}
 	return nil
 }

run_freebsd.go

@@ -196,7 +196,7 @@ func (b *Builder) Run(command []string, options RunOptions) error {
 
 	hostFile := ""
 	if !options.NoHosts && !contains(volumes, config.DefaultHostsFile) && options.ConfigureNetwork != define.NetworkDisabled {
-		hostFile, err = b.generateHosts(path, rootIDPair, mountPoint)
+		hostFile, err = b.generateHosts(path, rootIDPair, mountPoint, spec)
 		if err != nil {
 			return err
 		}

run_linux.go

@@ -264,7 +264,7 @@ func (b *Builder) Run(command []string, options RunOptions) error {
 
 	hostFile := ""
 	if !options.NoHosts && !contains(volumes, config.DefaultHostsFile) && options.ConfigureNetwork != define.NetworkDisabled {
-		hostFile, err = b.generateHosts(path, rootIDPair, mountPoint)
+		hostFile, err = b.generateHosts(path, rootIDPair, mountPoint, spec)
 		if err != nil {
 			return err
 		}

tests/run.bats

@@ -682,14 +682,18 @@ function configure_and_check_user() {
 
 	run_buildah from --quiet --pull=false $WITH_POLICY_JSON debian
 	cid=$output
-	run_buildah run --network=host $cid cat /etc/hosts
+	run_buildah run --network=host --hostname $hostname $cid cat /etc/hosts
+	assert "$output" =~ "$ip[[:blank:]]$hostname"
 	hostOutput=$output
 	m=$(buildah mount $cid)
 	run cat $m/etc/hosts
 	[ "$status" -eq 0 ]
 	expect_output --substring ""
 	run_buildah run --network=host --no-hosts $cid cat /etc/hosts
 	[ "$output" != "$hostOutput" ]
+	# --isolation chroot implies host networking so check for the correct hosts entry
+	run_buildah run --isolation chroot --hostname $hostname $cid cat /etc/hosts
+	assert "$output" =~ "$ip[[:blank:]]$hostname"
 	run_buildah rm -a
 
 	run_buildah from --quiet --pull=false $WITH_POLICY_JSON debian