Populate /etc/hosts file when run in a user namespace

We do not populate the hostname field with the IP Address
when running within a user namespace.

Fixes https://github.com/containers/podman/issues/7490

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

3 files changed, 36 insertions, 4 deletions

diff --git a/libpod/container_internal.go b/libpod/container_internal.go
index d64d3ab87..4ae571de6 100644
--- a/libpod/container_internal.go
+++ b/libpod/container_internal.go
@@ -976,6 +976,21 @@ func (c *Container) completeNetworkSetup() error {
 			}
 		}
 	}
+	// check if we have a bindmount for /etc/hosts
+	if hostsBindMount, ok := state.BindMounts["/etc/hosts"]; ok && len(c.cniHosts()) > 0 {
+		ctrHostPath := filepath.Join(c.state.RunDir, "hosts")
+		if hostsBindMount == ctrHostPath {
+			// read the existing hosts
+			b, err := ioutil.ReadFile(hostsBindMount)
+			if err != nil {
+				return err
+			}
+			if err := ioutil.WriteFile(hostsBindMount, append(b, []byte(c.cniHosts())...), 0644); err != nil {
+				return err
+			}
+		}
+	}
+
 	// check if we have a bindmount for resolv.conf
 	resolvBindMount := state.BindMounts["/etc/resolv.conf"]
 	if len(outResolvConf) < 1 || resolvBindMount == "" || len(c.config.NetNsCtr) > 0 {
@@ -997,6 +1012,15 @@ func (c *Container) completeNetworkSetup() error {
 	return ioutil.WriteFile(resolvBindMount, []byte(strings.Join(outResolvConf, "\n")), 0644)
 }
 
+func (c *Container) cniHosts() string {
+	var hosts string
+	if len(c.state.NetworkStatus) > 0 && len(c.state.NetworkStatus[0].IPs) > 0 {
+		ipAddress := strings.Split(c.state.NetworkStatus[0].IPs[0].Address.String(), "/")[0]
+		hosts += fmt.Sprintf("%s\t%s %s\n", ipAddress, c.Hostname(), c.Config().Name)
+	}
+	return hosts
+}
+
 // Initialize a container, creating it in the runtime
 func (c *Container) init(ctx context.Context, retainRetries bool) error {
 	span, _ := opentracing.StartSpanFromContext(ctx, "init")
diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index 894982973..41cc80789 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -1543,10 +1543,7 @@ func (c *Container) getHosts() string {
 		// When using slirp4netns, the interface gets a static IP
 		hosts += fmt.Sprintf("# used by slirp4netns\n%s\t%s %s\n", "10.0.2.100", c.Hostname(), c.Config().Name)
 	}
-	if len(c.state.NetworkStatus) > 0 && len(c.state.NetworkStatus[0].IPs) > 0 {
-		ipAddress := strings.Split(c.state.NetworkStatus[0].IPs[0].Address.String(), "/")[0]
-		hosts += fmt.Sprintf("%s\t%s %s\n", ipAddress, c.Hostname(), c.Config().Name)
-	}
+	hosts += c.cniHosts()
 	return hosts
 }
 
diff --git a/test/e2e/run_networking_test.go b/test/e2e/run_networking_test.go
index 044e56e6c..0f8b3e939 100644
--- a/test/e2e/run_networking_test.go
+++ b/test/e2e/run_networking_test.go
@@ -477,6 +477,17 @@ var _ = Describe("Podman run networking", func() {
 		Expect(session.ExitCode()).To(Equal(0))
 	})
 
+	It("podman run --uidmap /etc/hosts contains --hostname", func() {
+		SkipIfRootless("uidmap population of cninetworks not supported for rootless users")
+		session := podmanTest.Podman([]string{"run", "--uidmap", "0:100000:1000", "--rm", "--hostname", "foohostname", ALPINE, "grep", "foohostname", "/etc/hosts"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		session = podmanTest.Podman([]string{"run", "--uidmap", "0:100000:1000", "--rm", "--hostname", "foohostname", "-v", "/etc/hosts:/etc/hosts", ALPINE, "grep", "foohostname", "/etc/hosts"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(1))
+	})
+
 	It("podman run network in user created network namespace", func() {
 		SkipIfRootless("ip netns is not supported for rootless users")
 		if Containerized() {