Add version to shim protocol

Document environment variables and test shim start response parsing.

Signed-off-by: Derek McGowan <derek@mcg.dev>

runtime/v2/shim/shim.go

@@ -59,12 +59,12 @@ type StartOpts struct {
 
 // BootstrapParams is a JSON payload returned in stdout from shim.Start call.
 type BootstrapParams struct {
+	// Version is the version of shim parameters (expected 2 for shim v2)
+	Version int `json:"version"`
 	// Address is a address containerd should use to connect to shim.
 	Address string `json:"address"`
 	// Protocol is either TTRPC or GRPC.
 	Protocol string `json:"protocol"`
-	// Caps is a list of capabilities supported by shim implementation (reserved for future)
-	//Caps []string `json:"caps"`
 }
 
 type StopStatus struct {
@@ -147,6 +147,8 @@ var (
 
 const (
 	ttrpcAddressEnv = "TTRPC_ADDRESS"
+	grpcAddressEnv  = "GRPC_ADDRESS"
+	namespaceEnv    = "NAMESPACE"
 )
 
 func parseFlags() {

runtime/v2/shim/util.go

@@ -69,6 +69,8 @@ func Command(ctx context.Context, config *CommandConfig) (*exec.Cmd, error) {
 		os.Environ(),
 		"GOMAXPROCS=2",
 		fmt.Sprintf("%s=%s", ttrpcAddressEnv, config.TTRPCAddress),
+		fmt.Sprintf("%s=%s", grpcAddressEnv, config.Address),
+		fmt.Sprintf("%s=%s", namespaceEnv, ns),
 	)
 	if config.SchedCore {
 		cmd.Env = append(cmd.Env, "SCHED_CORE=1")