Add UpdatePodSandbox to API

This API is called by the container runtime to update pod sandbox
resources when they change. This is for the In-place Pod Resize
KEP-1287.

pkg/api/api.proto

@@ -101,6 +101,11 @@ service Plugin {
   // can update any of the remaining containers in the runtime in response.
   rpc StopContainer(StopContainerRequest) returns (StopContainerResponse);
 
+  // UpdatePodSandbox relays the corresponding request to the plugin.
+  // TODO: Add comment on anything the plugin can do in response (if
+  // applicable).
+  rpc UpdatePodSandbox(UpdatePodSandboxRequest) returns (UpdatePodSandboxResponse);
+
   // StateChange relays any remaining pod or container lifecycle/state change
   // events the plugin has subscribed for. These can be used to trigger any
   // plugin-specific processing which needs to occur in connection with any of
@@ -206,6 +211,18 @@ message StopContainerResponse {
   repeated ContainerUpdate update = 1;
 }
 
+message UpdatePodSandboxRequest {
+  // Pod being updated.
+  PodSandbox pod = 1;
+  // Resources to update.
+  LinuxResources linux_resources = 2;
+}
+
+message UpdatePodSandboxResponse {
+  // Requested updates to pods.
+  repeated PodSandboxUpdate update = 1;
+}
+
 message StateChangeEvent {
   // Event type of notification.
   Event event = 1;
@@ -234,7 +251,10 @@ enum Event {
   POST_UPDATE_CONTAINER = 9;
   STOP_CONTAINER = 10;
   REMOVE_CONTAINER = 11;
+  // TODO: Should this be moved to the end (assuming it's not used anywhere)?
   LAST = 12;
+  UPDATE_POD_SANDBOX = 13;
+  POST_UPDATE_POD_SANDBOX = 14;
 }
 
 // Pod metadata that is considered relevant for a plugin.
@@ -445,6 +465,18 @@ message ContainerEviction {
   string reason = 2;
 }
 
+// Requested update to an already created pod sandbox.
+message PodSandboxUpdate {
+  string pod_sandbox_id = 1;
+  LinuxPodSandboxUpdate linux = 2;
+  bool ignore_failure = 3;
+}
+
+// Updates to (linux) resources.
+message LinuxPodSandboxUpdate {
+  LinuxResources resources = 1;
+}
+
 // KeyValue represents an environment variable.
 message KeyValue {
   string key = 1;