Properly share UTS namespaces in a pod

pkg/namespaces/namespaces.go

@@ -4,17 +4,30 @@ import (
 	"strings"
 )
 
+const (
+	bridgeType    = "bridge"
+	containerType = "container"
+	defaultType   = "default"
+	hostType      = "host"
+	noneType      = "none"
+	nsType        = "ns"
+	podType       = "pod"
+	privateType   = "private"
+	shareableType = "shareable"
+	slirpType     = "slirp4netns"
+)
+
 // CgroupMode represents cgroup mode in the container.
 type CgroupMode string
 
 // IsHost indicates whether the container uses the host's cgroup.
 func (n CgroupMode) IsHost() bool {
-	return n == "host"
+	return n == hostType
 }
 
 // IsNS indicates a cgroup namespace passed in by path (ns:<path>)
 func (n CgroupMode) IsNS() bool {
-	return strings.HasPrefix(string(n), "ns:")
+	return strings.HasPrefix(string(n), nsType)
 }
 
 // NS gets the path associated with a ns:<path> cgroup ns
@@ -29,29 +42,29 @@ func (n CgroupMode) NS() string {
 // IsContainer indicates whether the container uses a new cgroup namespace.
 func (n CgroupMode) IsContainer() bool {
 	parts := strings.SplitN(string(n), ":", 2)
-	return len(parts) > 1 && parts[0] == "container"
+	return len(parts) > 1 && parts[0] == containerType
 }
 
 // Container returns the name of the container whose cgroup namespace is going to be used.
 func (n CgroupMode) Container() string {
 	parts := strings.SplitN(string(n), ":", 2)
-	if len(parts) > 1 {
+	if len(parts) > 1 && parts[0] == containerType {
 		return parts[1]
 	}
 	return ""
 }
 
 // IsPrivate indicates whether the container uses the a private cgroup.
 func (n CgroupMode) IsPrivate() bool {
-	return n == "private"
+	return n == privateType
 }
 
 // Valid indicates whether the Cgroup namespace is valid.
 func (n CgroupMode) Valid() bool {
 	parts := strings.Split(string(n), ":")
 	switch mode := parts[0]; mode {
-	case "", "host", "private", "ns":
-	case "container":
+	case "", hostType, privateType, nsType:
+	case containerType:
 		if len(parts) != 2 || parts[1] == "" {
 			return false
 		}
@@ -66,7 +79,7 @@ type UsernsMode string
 
 // IsHost indicates whether the container uses the host's userns.
 func (n UsernsMode) IsHost() bool {
-	return n == "host"
+	return n == hostType
 }
 
 // IsKeepID indicates whether container uses a mapping where the (uid, gid) on the host is lept inside of the namespace.
@@ -83,8 +96,8 @@ func (n UsernsMode) IsPrivate() bool {
 func (n UsernsMode) Valid() bool {
 	parts := strings.Split(string(n), ":")
 	switch mode := parts[0]; mode {
-	case "", "host", "keep-id", "ns":
-	case "container":
+	case "", hostType, "keep-id", nsType:
+	case containerType:
 		if len(parts) != 2 || parts[1] == "" {
 			return false
 		}
@@ -111,13 +124,13 @@ func (n UsernsMode) NS() string {
 // IsContainer indicates whether container uses a container userns.
 func (n UsernsMode) IsContainer() bool {
 	parts := strings.SplitN(string(n), ":", 2)
-	return len(parts) > 1 && parts[0] == "container"
+	return len(parts) > 1 && parts[0] == containerType
 }
 
 // Container is the id of the container which network this container is connected to.
 func (n UsernsMode) Container() string {
 	parts := strings.SplitN(string(n), ":", 2)
-	if len(parts) > 1 {
+	if len(parts) > 1 && parts[0] == containerType {
 		return parts[1]
 	}
 	return ""
@@ -133,19 +146,19 @@ func (n UTSMode) IsPrivate() bool {
 
 // IsHost indicates whether the container uses the host's UTS namespace.
 func (n UTSMode) IsHost() bool {
-	return n == "host"
+	return n == hostType
 }
 
 // IsContainer indicates whether the container uses a container's UTS namespace.
 func (n UTSMode) IsContainer() bool {
 	parts := strings.SplitN(string(n), ":", 2)
-	return len(parts) > 1 && parts[0] == "container"
+	return len(parts) > 1 && parts[0] == containerType
 }
 
 // Container returns the name of the container whose uts namespace is going to be used.
 func (n UTSMode) Container() string {
 	parts := strings.SplitN(string(n), ":", 2)
-	if len(parts) > 1 {
+	if len(parts) > 1 && parts[0] == containerType {
 		return parts[1]
 	}
 	return ""
@@ -155,8 +168,8 @@ func (n UTSMode) Container() string {
 func (n UTSMode) Valid() bool {
 	parts := strings.Split(string(n), ":")
 	switch mode := parts[0]; mode {
-	case "", "host":
-	case "container":
+	case "", hostType:
+	case containerType:
 		if len(parts) != 2 || parts[1] == "" {
 			return false
 		}
@@ -171,28 +184,28 @@ type IpcMode string
 
 // IsPrivate indicates whether the container uses its own private ipc namespace which cannot be shared.
 func (n IpcMode) IsPrivate() bool {
-	return n == "private"
+	return n == privateType
 }
 
 // IsHost indicates whether the container shares the host's ipc namespace.
 func (n IpcMode) IsHost() bool {
-	return n == "host"
+	return n == hostType
 }
 
 // IsShareable indicates whether the container's ipc namespace can be shared with another container.
 func (n IpcMode) IsShareable() bool {
-	return n == "shareable"
+	return n == shareableType
 }
 
 // IsContainer indicates whether the container uses another container's ipc namespace.
 func (n IpcMode) IsContainer() bool {
 	parts := strings.SplitN(string(n), ":", 2)
-	return len(parts) > 1 && parts[0] == "container"
+	return len(parts) > 1 && parts[0] == containerType
 }
 
 // IsNone indicates whether container IpcMode is set to "none".
 func (n IpcMode) IsNone() bool {
-	return n == "none"
+	return n == noneType
 }
 
 // IsEmpty indicates whether container IpcMode is empty
@@ -208,7 +221,7 @@ func (n IpcMode) Valid() bool {
 // Container returns the name of the container ipc stack is going to be used.
 func (n IpcMode) Container() string {
 	parts := strings.SplitN(string(n), ":", 2)
-	if len(parts) > 1 && parts[0] == "container" {
+	if len(parts) > 1 && parts[0] == containerType {
 		return parts[1]
 	}
 	return ""
@@ -224,21 +237,21 @@ func (n PidMode) IsPrivate() bool {
 
 // IsHost indicates whether the container uses the host's pid namespace.
 func (n PidMode) IsHost() bool {
-	return n == "host"
+	return n == hostType
 }
 
 // IsContainer indicates whether the container uses a container's pid namespace.
 func (n PidMode) IsContainer() bool {
 	parts := strings.SplitN(string(n), ":", 2)
-	return len(parts) > 1 && parts[0] == "container"
+	return len(parts) > 1 && parts[0] == containerType
 }
 
 // Valid indicates whether the pid namespace is valid.
 func (n PidMode) Valid() bool {
 	parts := strings.Split(string(n), ":")
 	switch mode := parts[0]; mode {
-	case "", "host":
-	case "container":
+	case "", hostType:
+	case containerType:
 		if len(parts) != 2 || parts[1] == "" {
 			return false
 		}
@@ -251,7 +264,7 @@ func (n PidMode) Valid() bool {
 // Container returns the name of the container whose pid namespace is going to be used.
 func (n PidMode) Container() string {
 	parts := strings.SplitN(string(n), ":", 2)
-	if len(parts) > 1 {
+	if len(parts) > 1 && parts[0] == containerType {
 		return parts[1]
 	}
 	return ""
@@ -262,17 +275,17 @@ type NetworkMode string
 
 // IsNone indicates whether container isn't using a network stack.
 func (n NetworkMode) IsNone() bool {
-	return n == "none"
+	return n == noneType
 }
 
 // IsHost indicates whether the container uses the host's network stack.
 func (n NetworkMode) IsHost() bool {
-	return n == "host"
+	return n == hostType
 }
 
 // IsDefault indicates whether container uses the default network stack.
 func (n NetworkMode) IsDefault() bool {
-	return n == "default"
+	return n == defaultType
 }
 
 // IsPrivate indicates whether container uses its private network stack.
@@ -283,13 +296,13 @@ func (n NetworkMode) IsPrivate() bool {
 // IsContainer indicates whether container uses a container network stack.
 func (n NetworkMode) IsContainer() bool {
 	parts := strings.SplitN(string(n), ":", 2)
-	return len(parts) > 1 && parts[0] == "container"
+	return len(parts) > 1 && parts[0] == containerType
 }
 
 // Container is the id of the container which network this container is connected to.
 func (n NetworkMode) Container() string {
 	parts := strings.SplitN(string(n), ":", 2)
-	if len(parts) > 1 {
+	if len(parts) > 1 && parts[0] == containerType {
 		return parts[1]
 	}
 	return ""
@@ -305,17 +318,17 @@ func (n NetworkMode) UserDefined() string {
 
 // IsBridge indicates whether container uses the bridge network stack
 func (n NetworkMode) IsBridge() bool {
-	return n == "bridge"
+	return n == bridgeType
 }
 
 // IsSlirp4netns indicates if we are running a rootless network stack
 func (n NetworkMode) IsSlirp4netns() bool {
-	return n == "slirp4netns"
+	return n == slirpType
 }
 
 // IsNS indicates a network namespace passed in by path (ns:<path>)
 func (n NetworkMode) IsNS() bool {
-	return strings.HasPrefix(string(n), "ns:")
+	return strings.HasPrefix(string(n), nsType)
 }
 
 // NS gets the path associated with a ns:<path> network ns
@@ -329,7 +342,7 @@ func (n NetworkMode) NS() string {
 
 // IsPod returns whether the network refers to pod networking
 func (n NetworkMode) IsPod() bool {
-	return n == "pod"
+	return n == podType
 }
 
 // IsUserDefined indicates user-created network

pkg/spec/spec.go

@@ -174,10 +174,20 @@ func (config *CreateConfig) createConfigToOCISpec(runtime *libpod.Runtime, userM
 	}
 
 	hostname := config.Hostname
-	if hostname == "" && (config.NetMode.IsHost() || config.UtsMode.IsHost()) {
-		hostname, err = os.Hostname()
-		if err != nil {
-			return nil, errors.Wrap(err, "unable to retrieve hostname")
+	if hostname == "" {
+		if utsCtrID := config.UtsMode.Container(); utsCtrID != "" {
+			utsCtr, err := runtime.GetContainer(utsCtrID)
+			if err != nil {
+				return nil, errors.Wrapf(err, "unable to retrieve hostname from dependency container %s", utsCtrID)
+			}
+			hostname = utsCtr.Hostname()
+		} else if config.NetMode.IsHost() || config.UtsMode.IsHost() {
+			hostname, err = os.Hostname()
+			if err != nil {
+				return nil, errors.Wrap(err, "unable to retrieve hostname of the host")
+			}
+		} else {
+			logrus.Debug("No hostname set; container's hostname will default to runtime default")
 		}
 	}
 	g.RemoveHostname()
@@ -541,8 +551,8 @@ func addPidNS(config *CreateConfig, g *generate.Generator) error {
 	if pidMode.IsHost() {
 		return g.RemoveLinuxNamespace(string(spec.PIDNamespace))
 	}
-	if pidMode.IsContainer() {
-		logrus.Debug("using container pidmode")
+	if pidCtr := pidMode.Container(); pidCtr != "" {
+		logrus.Debugf("using container %s pidmode", pidCtr)
 	}
 	if IsPod(string(pidMode)) {
 		logrus.Debug("using pod pidmode")
@@ -579,8 +589,8 @@ func addNetNS(config *CreateConfig, g *generate.Generator) error {
 	} else if netMode.IsBridge() {
 		logrus.Debug("Using bridge netmode")
 		return nil
-	} else if netMode.IsContainer() {
-		logrus.Debug("Using container netmode")
+	} else if netCtr := netMode.Container(); netCtr != "" {
+		logrus.Debugf("using container %s netmode", netCtr)
 		return nil
 	} else if IsNS(string(netMode)) {
 		logrus.Debug("Using ns netmode")
@@ -606,6 +616,9 @@ func addUTSNS(config *CreateConfig, g *generate.Generator) error {
 	if utsMode.IsHost() {
 		return g.RemoveLinuxNamespace(string(spec.UTSNamespace))
 	}
+	if utsCtr := utsMode.Container(); utsCtr != "" {
+		logrus.Debugf("using container %s utsmode", utsCtr)
+	}
 	return nil
 }
 
@@ -617,8 +630,8 @@ func addIpcNS(config *CreateConfig, g *generate.Generator) error {
 	if ipcMode.IsHost() {
 		return g.RemoveLinuxNamespace(string(spec.IPCNamespace))
 	}
-	if ipcMode.IsContainer() {
-		logrus.Debug("Using container ipcmode")
+	if ipcCtr := ipcMode.Container(); ipcCtr != "" {
+		logrus.Debugf("Using container %s ipcmode", ipcCtr)
 	}
 
 	return nil
@@ -635,8 +648,8 @@ func addCgroupNS(config *CreateConfig, g *generate.Generator) error {
 	if cgroupMode.IsPrivate() {
 		return g.AddOrReplaceLinuxNamespace(string(spec.CgroupNamespace), "")
 	}
-	if cgroupMode.IsContainer() {
-		logrus.Debug("Using container cgroup mode")
+	if cgCtr := cgroupMode.Container(); cgCtr != "" {
+		logrus.Debugf("Using container %s cgroup mode", cgCtr)
 	}
 	return nil
 }

test/e2e/pod_infra_container_test.go

@@ -383,4 +383,24 @@ var _ = Describe("Podman pod create", func() {
 		session.WaitWithDefaultTimeout()
 		Expect(session.ExitCode()).To(Equal(0))
 	})
+
+	It("podman run hostname is shared", func() {
+		session := podmanTest.Podman([]string{"pod", "create"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		podID := session.OutputToString()
+
+		// verify we can add a host to the infra's /etc/hosts
+		session = podmanTest.Podman([]string{"run", "--pod", podID, ALPINE, "hostname"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		hostname := session.OutputToString()
+
+		infraName := podID[:12] + "-infra"
+		// verify we can see the other hosts of infra's /etc/hosts
+		session = podmanTest.Podman([]string{"inspect", infraName})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(session.OutputToString()).To(ContainSubstring(hostname))
+	})
 })