e2e: add hostname interpolation test.

e2e/networking/inputs/docker_bridged_hostname_interpolation.nomad

@@ -0,0 +1,24 @@
+job "networking" {
+  datacenters = ["dc1", "dc2"]
+
+  constraint {
+    attribute = "${attr.kernel.name}"
+    value     = "linux"
+  }
+
+  group "bridged" {
+    network {
+      hostname = "mylittlepony-${NOMAD_ALLOC_INDEX}"
+      mode     = "bridge"
+    }
+
+    task "sleep" {
+      driver = "docker"
+      config {
+        image   = "busybox:1"
+        command = "/bin/sleep"
+        args    = ["300"]
+      }
+    }
+  }
+}

e2e/networking/networking.go

@@ -68,3 +68,27 @@ func (tc *NetworkingE2ETest) TestNetworking_DockerBridgedHostname(f *framework.F
 	f.NoError(err, "failed to run hostname exec command")
 	f.Contains(hostsOutput, "mylittlepony", "/etc/hosts doesn't contain hostname entry")
 }
+
+func (tc *NetworkingE2ETest) TestNetworking_DockerBridgedHostnameInterpolation(f *framework.F) {
+
+	jobID := "test-networking-" + uuid.Generate()[0:8]
+	f.NoError(e2eutil.Register(jobID, "networking/inputs/docker_bridged_hostname_interpolation.nomad"))
+	tc.jobIDs = append(tc.jobIDs, jobID)
+	f.NoError(e2eutil.WaitForAllocStatusExpected(jobID, "default", []string{"running"}),
+		"job should be running with 1 alloc")
+
+	// Grab the allocations for the job.
+	allocs, _, err := tc.Nomad().Jobs().Allocations(jobID, false, nil)
+	f.NoError(err, "failed to get allocs for job")
+	f.Len(allocs, 1, "job should have one alloc")
+
+	// Run the hostname command within the allocation.
+	hostnameOutput, err := e2eutil.AllocExec(allocs[0].ID, "sleep", "hostname", "default", nil)
+	f.NoError(err, "failed to run hostname exec command")
+	f.Equal("mylittlepony-0", strings.TrimSpace(hostnameOutput), "incorrect hostname set within container")
+
+	// Check the /etc/hosts file for the correct IP address and hostname entry.
+	hostsOutput, err := e2eutil.AllocExec(allocs[0].ID, "sleep", "cat /etc/hosts", "default", nil)
+	f.NoError(err, "failed to run hostname exec command")
+	f.Contains(hostsOutput, "mylittlepony-0", "/etc/hosts doesn't contain hostname entry")
+}