address comments

- fix comments
- expand README to reference existing going on work across communities
- don't manipuelate network devices on host network namespaced pods

Signed-off-by: Antonio Ojea <[email protected]>

plugins/network-device-injector/README.md

@@ -1,6 +1,23 @@
 ## Network Device Injector Plugin
 
 This sample plugin can inject existing network devices into containers using pod annotations.
+Network devices are network namespaced, this implies that in Kubernetes they are Pod scoped
+and no container scoped, all containers are able to access the network device inside the Pod.
+
+Traditionally in Kubernetes the CNI plugin is the responsable of configuring the default network
+interface for Pods, but there are use cases where the Pod may need to use additional network interfaces,
+a more detailed explanation of all the possible technologies to add interfaces to Pods was presented during
+[SIG Network meeting 14/03/2024](https://www.youtube.com/watch?v=67UzeMEaqnM&list=PL69nYSiGNLP2E8vmnqo5MwPOY25sDWIxb&index=1),
+[slides](Slides in https://docs.google.com/presentation/d/1pjDCtpdbCSWaqCbBYWgzTxAewOVbMf6rUS5SbjAJAe8/edit?usp=sharing).
+
+Kubernetes project is working on [provide a better API](https://docs.google.com/document/d/1VBBj8Fh0ks0_-dacpqx6kD2tlIvj0XfFxtMuSfOJ22w/edit)
+introducing network device claims that would naturally provide a built in means to inject.
+
+[Network Devices may be included in the OCI Runtime Specification](https://github.com/opencontainers/runtime-spec/issues/1239), this will allow
+implementations to be more declarative offloading the low level implementation details to the runtime implementation.
+
+Pods that run in the host network namespace can not inject any network device as those are already running on the same network namespace,
+and any modification can impact the existing system networking.
 
 ### Network Device Annotations
 
@@ -23,11 +40,11 @@ The parameters are based on the existing linux netdevice representation.
 https://man7.org/linux/man-pages/man7/netdevice.7.html
 
 `name` is mandatory and refers to the name of the network interface in the host,
-the rest of the parameters is optional.
+the rest of the parameters are optional.
 `new_name` is the name of the interface inside the Pod.
 
-The plugin only injects interfaces on the Pod, for more advanced networking configuration
-like routing, traffic redirection or dynamic address configuration new plugins can be created.
+The plugin only injects interfaces on the Pod network namespace for which the containers are attached when created,
+for more advanced networking configuration like routing, traffic redirection or dynamic address configuration new plugins can be created.
 
 ## Testing
 

plugins/network-device-injector/network-device-injector.go

@@ -302,12 +302,13 @@ type plugin struct {
 }
 
 func (p *plugin) RunPodSandbox(_ context.Context, pod *api.PodSandbox) error {
-	log.WithField("namespace", pod.GetNamespace()).WithField("name", pod.GetName).Info("Started pod...")
+	log.WithField("namespace", pod.GetNamespace()).WithField("name", pod.GetName).Debug("Started pod...")
 	if verbose {
 		dump("RunPodSandbox", "pod", pod)
 	}
 
-	// inject associated devices of the netdevice to the container
+	// inject associated netdevices (based on received pod annotations) into the pod
+	// network namespace that will be attached to the pod's containers
 	netdevices, err := parseNetdevices(pod.Annotations)
 	if err != nil {
 		return err
@@ -325,8 +326,10 @@ func (p *plugin) RunPodSandbox(_ context.Context, pod *api.PodSandbox) error {
 			break
 		}
 	}
-	// TODO check host network namespace
+
+	// Pods running on the host network namespace has this value empty
 	if ns == "" {
+		log.WithField("namespace", pod.GetNamespace()).WithField("name", pod.GetName).Info("Pod using host namespace, skipping ...")
 		return nil
 	}
 
@@ -341,7 +344,7 @@ func (p *plugin) RunPodSandbox(_ context.Context, pod *api.PodSandbox) error {
 }
 
 func (p *plugin) StopPodSandbox(_ context.Context, pod *api.PodSandbox) error {
-	log.WithField("namespace", pod.GetNamespace()).WithField("name", pod.GetName).Info("Stopped pod...")
+	log.WithField("namespace", pod.GetNamespace()).WithField("name", pod.GetName).Debug("Stopped pod...")
 	if verbose {
 		dump("StopPodSandbox", "pod", pod)
 	}