Add cimfs differ and snapshotter

Details about CimFs project are discussed in #8346

Signed-off-by: Amit Barve <ambarve@microsoft.com>

vendor/github.com/Microsoft/hcsshim/hcn/hcnerrors.go

@@ -6,11 +6,12 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/windows"
+
 	"github.com/Microsoft/hcsshim/internal/hcs"
 	"github.com/Microsoft/hcsshim/internal/hcserror"
 	"github.com/Microsoft/hcsshim/internal/interop"
-	"github.com/sirupsen/logrus"
-	"golang.org/x/sys/windows"
 )
 
 var (
@@ -63,8 +64,8 @@ func (e *HcnError) Error() string {
 }
 
 func CheckErrorWithCode(err error, code ErrorCode) bool {
-	hcnError, ok := err.(*HcnError)
-	if ok {
+	var hcnError *HcnError
+	if errors.As(err, &hcnError) {
 		return hcnError.code == code
 	}
 	return false
@@ -81,7 +82,7 @@ func IsPortAlreadyExistsError(err error) bool {
 func new(hr error, title string, rest string) error {
 	err := &HcnError{}
 	hcsError := hcserror.New(hr, title, rest)
-	err.HcsError = hcsError.(*hcserror.HcsError)
+	err.HcsError = hcsError.(*hcserror.HcsError) //nolint:errorlint
 	err.code = ErrorCode(hcserror.Win32FromError(hr))
 	return err
 }
@@ -97,6 +98,8 @@ type NetworkNotFoundError struct {
 	NetworkID   string
 }
 
+var _ error = NetworkNotFoundError{}
+
 func (e NetworkNotFoundError) Error() string {
 	if e.NetworkName != "" {
 		return fmt.Sprintf("Network name %q not found", e.NetworkName)
@@ -110,6 +113,8 @@ type EndpointNotFoundError struct {
 	EndpointID   string
 }
 
+var _ error = EndpointNotFoundError{}
+
 func (e EndpointNotFoundError) Error() string {
 	if e.EndpointName != "" {
 		return fmt.Sprintf("Endpoint name %q not found", e.EndpointName)
@@ -122,6 +127,8 @@ type NamespaceNotFoundError struct {
 	NamespaceID string
 }
 
+var _ error = NamespaceNotFoundError{}
+
 func (e NamespaceNotFoundError) Error() string {
 	return fmt.Sprintf("Namespace ID %q not found", e.NamespaceID)
 }
@@ -131,6 +138,8 @@ type LoadBalancerNotFoundError struct {
 	LoadBalancerId string
 }
 
+var _ error = LoadBalancerNotFoundError{}
+
 func (e LoadBalancerNotFoundError) Error() string {
 	return fmt.Sprintf("LoadBalancer %q not found", e.LoadBalancerId)
 }
@@ -140,6 +149,8 @@ type RouteNotFoundError struct {
 	RouteId string
 }
 
+var _ error = RouteNotFoundError{}
+
 func (e RouteNotFoundError) Error() string {
 	return fmt.Sprintf("SDN Route %q not found", e.RouteId)
 }
@@ -147,19 +158,31 @@ func (e RouteNotFoundError) Error() string {
 // IsNotFoundError returns a boolean indicating whether the error was caused by
 // a resource not being found.
 func IsNotFoundError(err error) bool {
-	switch pe := err.(type) {
-	case NetworkNotFoundError:
+	// Calling [errors.As] in a loop over `[]error{NetworkNotFoundError{}, ...}` will not work,
+	// since the loop variable will be an interface type (ie, `error`) and `errors.As(error, *error)` will
+	// always succeed.
+	// Unless golang adds loops over (or arrays of) types, we need to manually call `errors.As` for
+	// each potential error type.
+	//
+	// Also, for T = NetworkNotFoundError and co, the error implementation is for T, not *T
+	if e := (NetworkNotFoundError{}); errors.As(err, &e) {
 		return true
-	case EndpointNotFoundError:
-		return true
-	case NamespaceNotFoundError:
-		return true
-	case LoadBalancerNotFoundError:
-		return true
-	case RouteNotFoundError:
-		return true
-	case *hcserror.HcsError:
-		return pe.Err == hcs.ErrElementNotFound
 	}
+	if e := (EndpointNotFoundError{}); errors.As(err, &e) {
+		return true
+	}
+	if e := (NamespaceNotFoundError{}); errors.As(err, &e) {
+		return true
+	}
+	if e := (LoadBalancerNotFoundError{}); errors.As(err, &e) {
+		return true
+	}
+	if e := (RouteNotFoundError{}); errors.As(err, &e) {
+		return true
+	}
+	if e := (&hcserror.HcsError{}); errors.As(err, &e) {
+		return errors.Is(e.Err, hcs.ErrElementNotFound)
+	}
+
 	return false
 }

vendor/github.com/Microsoft/hcsshim/hcn/hcnnamespace.go

@@ -4,6 +4,7 @@ package hcn
 
 import (
 	"encoding/json"
+	"errors"
 	"os"
 	"syscall"
 
@@ -378,7 +379,8 @@ func (namespace *HostComputeNamespace) Sync() error {
 	shimPath := runhcs.VMPipePath(cfg.HostUniqueID)
 	if err := runhcs.IssueVMRequest(shimPath, &req); err != nil {
 		// The shim is likely gone. Simply ignore the sync as if it didn't exist.
-		if perr, ok := err.(*os.PathError); ok && perr.Err == syscall.ERROR_FILE_NOT_FOUND {
+		var perr *os.PathError
+		if errors.As(err, &perr) && errors.Is(perr.Err, syscall.ERROR_FILE_NOT_FOUND) {
 			// Remove the reg key there is no point to try again
 			_ = cfg.Remove()
 			return nil