Merge pull request #1464 from mheon/optionally_disable_port_reservation

Add a way to disable port reservation

libpod.conf

@@ -80,3 +80,11 @@ pause_image = "k8s.gcr.io/pause:3.1"
 
 # Default command to run the pause container
 pause_command = "/pause"
+
+# Determines whether libpod will reserve ports on the host when they are
+# forwarded to containers. When enabled, when ports are forwarded to containers,
+# they are held open by conmon as long as the container is running, ensuring that
+# they cannot be reused by other programs on the host. However, this can cause
+# significant memory usage if a container has many ports forwarded to it.
+# Disabling this can save memory.
+#enable_port_reservation = true

libpod/oci.go

@@ -66,6 +66,7 @@ type OCIRuntime struct {
 	socketsDir    string
 	logSizeMax    int64
 	noPivot       bool
+	reservePorts  bool
 }
 
 // syncInfo is used to return data from monitor process to daemon
@@ -75,7 +76,7 @@ type syncInfo struct {
 }
 
 // Make a new OCI runtime with provided options
-func newOCIRuntime(name string, path string, conmonPath string, conmonEnv []string, cgroupManager string, tmpDir string, logSizeMax int64, noPivotRoot bool) (*OCIRuntime, error) {
+func newOCIRuntime(name string, path string, conmonPath string, conmonEnv []string, cgroupManager string, tmpDir string, logSizeMax int64, noPivotRoot bool, reservePorts bool) (*OCIRuntime, error) {
 	runtime := new(OCIRuntime)
 	runtime.name = name
 	runtime.path = path
@@ -85,6 +86,7 @@ func newOCIRuntime(name string, path string, conmonPath string, conmonEnv []stri
 	runtime.tmpDir = tmpDir
 	runtime.logSizeMax = logSizeMax
 	runtime.noPivot = noPivotRoot
+	runtime.reservePorts = reservePorts
 
 	runtime.exitsDir = filepath.Join(runtime.tmpDir, "exits")
 	runtime.socketsDir = filepath.Join(runtime.tmpDir, "socket")
@@ -311,15 +313,17 @@ func (r *OCIRuntime) createOCIContainer(ctr *Container, cgroupParent string) (er
 	cmd.Env = append(cmd.Env, fmt.Sprintf("_OCI_STARTPIPE=%d", 4))
 	cmd.Env = append(cmd.Env, fmt.Sprintf("XDG_RUNTIME_DIR=%s", runtimeDir))
 
-	ports, err := bindPorts(ctr.config.PortMappings)
-	if err != nil {
-		return err
-	}
+	if r.reservePorts {
+		ports, err := bindPorts(ctr.config.PortMappings)
+		if err != nil {
+			return err
+		}
 
-	// Leak the port we bound in the conmon process.  These fd's won't be used
-	// by the container and conmon will keep the ports busy so that another
-	// process cannot use them.
-	cmd.ExtraFiles = append(cmd.ExtraFiles, ports...)
+		// Leak the port we bound in the conmon process.  These fd's won't be used
+		// by the container and conmon will keep the ports busy so that another
+		// process cannot use them.
+		cmd.ExtraFiles = append(cmd.ExtraFiles, ports...)
+	}
 
 	if rootless.IsRootless() {
 		ctr.rootlessSlirpSyncR, ctr.rootlessSlirpSyncW, err = os.Pipe()

libpod/runtime.go

@@ -164,6 +164,14 @@ type RuntimeConfig struct {
 	InfraImage string `toml:"infra_image"`
 	// InfraCommand is the command run to start up a pod infra container
 	InfraCommand string `toml:"infra_command"`
+	// EnablePortReservation determines whether libpod will reserve ports on
+	// the host when they are forwarded to containers.
+	// When enabled, when ports are forwarded to containers, they are
+	// held open by conmon as long as the container is running, ensuring
+	// that they cannot be reused by other programs on the host.
+	// However, this can cause significant memory usage if a container has
+	// many ports forwarded to it. Disabling this can save memory.
+	EnablePortReservation bool `toml:"enable_port_reservation"`
 }
 
 var (
@@ -190,16 +198,17 @@ var (
 		ConmonEnvVars: []string{
 			"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
 		},
-		CgroupManager: SystemdCgroupsManager,
-		HooksDir:      hooks.DefaultDir,
-		StaticDir:     filepath.Join(storage.DefaultStoreOptions.GraphRoot, "libpod"),
-		TmpDir:        "",
-		MaxLogSize:    -1,
-		NoPivotRoot:   false,
-		CNIConfigDir:  "/etc/cni/net.d/",
-		CNIPluginDir:  []string{"/usr/libexec/cni", "/usr/lib/cni", "/opt/cni/bin"},
-		InfraCommand:  DefaultInfraCommand,
-		InfraImage:    DefaultInfraImage,
+		CgroupManager:         SystemdCgroupsManager,
+		HooksDir:              hooks.DefaultDir,
+		StaticDir:             filepath.Join(storage.DefaultStoreOptions.GraphRoot, "libpod"),
+		TmpDir:                "",
+		MaxLogSize:            -1,
+		NoPivotRoot:           false,
+		CNIConfigDir:          "/etc/cni/net.d/",
+		CNIPluginDir:          []string{"/usr/libexec/cni", "/usr/lib/cni", "/opt/cni/bin"},
+		InfraCommand:          DefaultInfraCommand,
+		InfraImage:            DefaultInfraImage,
+		EnablePortReservation: true,
 	}
 )
 
@@ -467,7 +476,8 @@ func makeRuntime(runtime *Runtime) (err error) {
 	ociRuntime, err := newOCIRuntime("runc", runtime.ociRuntimePath,
 		runtime.conmonPath, runtime.config.ConmonEnvVars,
 		runtime.config.CgroupManager, runtime.config.TmpDir,
-		runtime.config.MaxLogSize, runtime.config.NoPivotRoot)
+		runtime.config.MaxLogSize, runtime.config.NoPivotRoot,
+		runtime.config.EnablePortReservation)
 	if err != nil {
 		return err
 	}