Ensure that hostname is added to hosts with net=host

libpod/container_internal_linux.go

@@ -1541,11 +1541,31 @@ func (c *Container) getHosts() string {
 		}
 	}
 
-	if c.config.NetMode.IsSlirp4netns() {
-		// 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)
-	}
 	hosts += c.cniHosts()
+
+	// If not making a network namespace, add our own hostname.
+	if c.Hostname() != "" {
+		if c.config.NetMode.IsSlirp4netns() {
+			// 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)
+		} else {
+			hasNetNS := false
+			for _, ns := range c.config.Spec.Linux.Namespaces {
+				if ns.Type == spec.NetworkNamespace {
+					hasNetNS = true
+					break
+				}
+			}
+			if !hasNetNS {
+				// 127.0.1.1 and host's hostname to match Docker
+				osHostname, err := os.Hostname()
+				if err != nil {
+					osHostname = c.Hostname()
+				}
+				hosts += fmt.Sprintf("127.0.1.1 %s\n", osHostname)
+			}
+		}
+	}
 	return hosts
 }
 

pkg/specgen/generate/namespaces.go

@@ -342,7 +342,7 @@ func specConfigureNamespaces(s *specgen.SpecGenerator, g *generate.Generator, rt
 				return errors.Wrapf(err, "error looking up container to share uts namespace with")
 			}
 			hostname = utsCtr.Hostname()
-		case s.NetNS.NSMode == specgen.Host || s.UtsNS.NSMode == specgen.Host:
+		case (s.NetNS.NSMode == specgen.Host && hostname == "") || s.UtsNS.NSMode == specgen.Host:
 			tmpHostname, err := os.Hostname()
 			if err != nil {
 				return errors.Wrap(err, "unable to retrieve hostname of the host")

test/e2e/run_networking_test.go

@@ -571,4 +571,19 @@ var _ = Describe("Podman run networking", func() {
 		podrm.WaitWithDefaultTimeout()
 		Expect(podrm.ExitCode()).To(BeZero())
 	})
+
+	It("podman run net=host adds entry to /etc/hosts", func() {
+		run := podmanTest.Podman([]string{"run", "--net=host", ALPINE, "cat", "/etc/hosts"})
+		run.WaitWithDefaultTimeout()
+		Expect(run.ExitCode()).To(BeZero())
+		Expect(strings.Contains(run.OutputToString(), "127.0.1.1")).To(BeTrue())
+	})
+
+	It("podman run with --net=host and --hostname sets correct hostname", func() {
+		hostname := "testctr"
+		run := podmanTest.Podman([]string{"run", "--net=host", "--hostname", hostname, ALPINE, "hostname"})
+		run.WaitWithDefaultTimeout()
+		Expect(run.ExitCode()).To(BeZero())
+		Expect(strings.Contains(run.OutputToString(), "testctr")).To(BeTrue())
+	})
 })