podman: fix --uts=host

Do not set any hostname value in the OCI configuration when --uts=host
is used and the user didn't specify any value.  This prevents an error
from the OCI runtime as it cannot set the hostname without a new UTS
namespace.

Differently, the HOSTNAME environment variable is always set.  When
--uts=host is used, HOSTNAME gets the value from the host.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

Closes: #1280
Approved by: baude

3 files changed, 36 insertions, 11 deletions

diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index 2aba1abde..ba02c9f5a 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -215,8 +215,14 @@ func (c *Container) generateSpec(ctx context.Context) (*spec.Spec, error) {
 	g.AddAnnotation(crioAnnotations.Created, c.config.CreatedTime.Format(time.RFC3339Nano))
 	g.AddAnnotation("org.opencontainers.image.stopSignal", fmt.Sprintf("%d", c.config.StopSignal))
 
-	g.SetHostname(c.Hostname())
-	g.AddProcessEnv("HOSTNAME", g.Config.Hostname)
+	for _, i := range c.config.Spec.Linux.Namespaces {
+		if string(i.Type) == spec.UTSNamespace {
+			hostname := c.Hostname()
+			g.SetHostname(hostname)
+			g.AddProcessEnv("HOSTNAME", hostname)
+			break
+		}
+	}
 
 	// Only add container environment variable if not already present
 	foundContainerEnv := false
diff --git a/pkg/spec/spec.go b/pkg/spec/spec.go
index 97305610a..dec3a05ef 100644
--- a/pkg/spec/spec.go
+++ b/pkg/spec/spec.go
@@ -74,18 +74,23 @@ func CreateConfigToOCISpec(config *CreateConfig) (*spec.Spec, error) { //nolint
 		g.AddAnnotation(key, val)
 	}
 	g.SetRootReadonly(config.ReadOnlyRootfs)
-	if config.Hostname == "" {
-		if config.NetMode.IsHost() {
-			config.Hostname, err = os.Hostname()
-			if err != nil {
-				return nil, errors.Wrap(err, "unable to retrieve hostname")
-			}
+
+	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")
 		}
 	}
-	g.SetHostname(config.Hostname)
-	if config.Hostname != "" {
-		g.AddProcessEnv("HOSTNAME", config.Hostname)
+	g.RemoveHostname()
+	if config.Hostname != "" || !config.UtsMode.IsHost() {
+		// Set the hostname in the OCI configuration only
+		// if specified by the user or if we are creating
+		// a new UTS namespace.
+		g.SetHostname(hostname)
 	}
+	g.AddProcessEnv("HOSTNAME", hostname)
+
 	for sysctlKey, sysctlVal := range config.Sysctl {
 		g.AddLinuxSysctl(sysctlKey, sysctlVal)
 	}
diff --git a/test/e2e/run_networking_test.go b/test/e2e/run_networking_test.go
index a4bdcdf89..021825d4b 100644
--- a/test/e2e/run_networking_test.go
+++ b/test/e2e/run_networking_test.go
@@ -114,6 +114,20 @@ var _ = Describe("Podman rmi", func() {
 		match, _ := session.GrepString(hostname)
 		Expect(match).Should(BeTrue())
 	})
+	It("podman run --net host --uts host hostname test", func() {
+		session := podmanTest.Podman([]string{"run", "--rm", "--net", "host", "--uts", "host", ALPINE, "printenv", "HOSTNAME"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		match, _ := session.GrepString(hostname)
+		Expect(match).Should(BeTrue())
+	})
+	It("podman run --uts host hostname test", func() {
+		session := podmanTest.Podman([]string{"run", "--rm", "--uts", "host", ALPINE, "printenv", "HOSTNAME"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		match, _ := session.GrepString(hostname)
+		Expect(match).Should(BeTrue())
+	})
 
 	It("podman run --net host --hostname ... hostname test", func() {
 		session := podmanTest.Podman([]string{"run", "--rm", "--net", "host", "--hostname", "foobar", ALPINE, "printenv", "HOSTNAME"})