Implement port-forwarding logic on Podman

As explained in [1], this makes use of a helper sidecar container
(aptly named "odo-helper-port-forwarding") to be added to the Pod Spec created by odo.
In this scope, port-forwarding will be equivalent of executing a socat command in this
helper container, like so:

socat -d tcp-listen:20002,reuseaddr,fork tcp:localhost:5858

In the command above, this will open up port 20001 on the helper container,
and forwarding requests to localhost:5858
(which would be in the application container, part of the same Pod)

[1] redhat-developer#6510

pkg/portForward/podmanportforward/portForward.go

@@ -0,0 +1,131 @@
+package podmanportforward
+
+import (
+	"fmt"
+	"io"
+	"reflect"
+	"strings"
+	"sync"
+
+	"github.com/devfile/api/v2/pkg/apis/workspaces/v1alpha2"
+	"github.com/devfile/library/v2/pkg/devfile/parser"
+	"k8s.io/klog"
+
+	"github.com/redhat-developer/odo/pkg/api"
+	"github.com/redhat-developer/odo/pkg/exec"
+	"github.com/redhat-developer/odo/pkg/portForward"
+	"github.com/redhat-developer/odo/pkg/remotecmd"
+)
+
+const pfHelperContainer = "odo-helper-port-forwarding"
+
+type PFClient struct {
+	remoteProcessHandler remotecmd.RemoteProcessHandler
+
+	appliedPorts map[api.ForwardedPort]struct{}
+}
+
+var _ portForward.Client = (*PFClient)(nil)
+
+func NewPFClient(execClient exec.Client) *PFClient {
+	return &PFClient{
+		remoteProcessHandler: remotecmd.NewKubeExecProcessHandler(execClient),
+		appliedPorts:         make(map[api.ForwardedPort]struct{}),
+	}
+}
+
+func (o *PFClient) StartPortForwarding(
+	devFileObj parser.DevfileObj,
+	componentName string,
+	debug bool,
+	randomPorts bool,
+	out io.Writer,
+	errOut io.Writer,
+	definedPorts []api.ForwardedPort,
+) error {
+	var appliedPorts []api.ForwardedPort
+	for port, _ := range o.appliedPorts {
+		appliedPorts = append(appliedPorts, port)
+	}
+	if reflect.DeepEqual(appliedPorts, definedPorts) {
+		klog.V(3).Infof("Port forwarding should already be running for defined ports: %v", definedPorts)
+		return nil
+	}
+
+	o.StopPortForwarding(componentName)
+
+	outputHandler := func(fwPort api.ForwardedPort) remotecmd.CommandOutputHandler {
+		return func(status remotecmd.RemoteProcessStatus, stdout []string, stderr []string, err error) {
+			klog.V(4).Infof("Status for port-forwarding (from %s:%d -> %d): %s", fwPort.LocalAddress, fwPort.LocalPort, fwPort.ContainerPort, status)
+			klog.V(4).Info(strings.Join(stdout, "\n"))
+			klog.V(4).Info(strings.Join(stderr, "\n"))
+			switch status {
+			case remotecmd.Running:
+				o.appliedPorts[fwPort] = struct{}{}
+			case remotecmd.Stopped, remotecmd.Errored:
+				delete(o.appliedPorts, fwPort)
+				if status == remotecmd.Stopped {
+					fmt.Fprintf(out, "Stopped port-forwarding from %s:%d -> %d", fwPort.LocalAddress, fwPort.LocalPort, fwPort.ContainerPort)
+				}
+			}
+		}
+	}
+
+	for _, port := range definedPorts {
+		err := o.remoteProcessHandler.StartProcessForCommand(getCommandDefinition(port), getPodName(componentName), pfHelperContainer, outputHandler(port))
+		if err != nil {
+			klog.V(4).Infof("error while creating port-forwarding for container port %d: %v", port.ContainerPort, err)
+			continue
+		}
+		o.appliedPorts[port] = struct{}{}
+	}
+	return nil
+}
+
+func (o *PFClient) StopPortForwarding(componentName string) {
+	if len(o.appliedPorts) == 0 {
+		return
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(len(o.appliedPorts))
+	for port, _ := range o.appliedPorts {
+		port := port
+		go func() {
+			defer wg.Done()
+			err := o.remoteProcessHandler.StopProcessForCommand(getCommandDefinition(port), getPodName(componentName), pfHelperContainer)
+			if err != nil {
+				klog.V(4).Infof("error while stopping port-forwarding for container port %d: %v", port.ContainerPort, err)
+			}
+		}()
+	}
+	wg.Wait()
+
+	o.appliedPorts = nil
+}
+
+func (o *PFClient) GetForwardedPorts() map[string][]v1alpha2.Endpoint {
+	result := make(map[string][]v1alpha2.Endpoint)
+	for port, _ := range o.appliedPorts {
+		result[port.ContainerName] = append(result[port.ContainerName], v1alpha2.Endpoint{
+			Name:       port.PortName,
+			TargetPort: port.ContainerPort,
+			Exposure:   v1alpha2.EndpointExposure(port.Exposure),
+		})
+	}
+	return result
+}
+
+func getPodName(componentName string) string {
+	return fmt.Sprintf("%s-app", componentName)
+}
+
+func getCommandDefinition(port api.ForwardedPort) remotecmd.CommandDefinition {
+	return remotecmd.CommandDefinition{
+		Id: fmt.Sprintf("pf-%s", port.PortName),
+		// PidDirectory needs to be writable
+		PidDirectory: "/projects/",
+		//TODO(rm3l) Use the right L4 protocol: tcp or udp?
+		CmdLine: fmt.Sprintf("socat -d tcp-listen:%d,reuseaddr,fork tcp:localhost:%d", port.LocalPort, port.ContainerPort),
+	}
+}