Use unix and windows specific connection error checks

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

core/remotes/docker/resolver.go

@@ -28,7 +28,6 @@ import (
 	"os"
 	"path"
 	"strings"
-	"syscall"
 
 	"github.com/containerd/errdefs"
 	"github.com/containerd/log"
@@ -778,7 +777,7 @@ func isTLSError(err error) bool {
 }
 
 func isPortError(err error, host string) bool {
-	if errors.Is(err, syscall.ECONNREFUSED) || os.IsTimeout(err) {
+	if isConnError(err) || os.IsTimeout(err) {
 		if _, port, _ := net.SplitHostPort(host); port != "" {
 			// Port is specified, will not retry on different port with scheme change
 			return false

core/remotes/docker/resolver_unix.go

@@ -0,0 +1,28 @@
+//go:build !windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package docker
+
+import (
+	"errors"
+	"syscall"
+)
+
+func isConnError(err error) bool {
+	return errors.Is(err, syscall.ECONNREFUSED)
+}

core/remotes/docker/resolver_windows.go

@@ -0,0 +1,30 @@
+//go:build windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package docker
+
+import (
+	"errors"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+func isConnError(err error) bool {
+	return errors.Is(err, syscall.ECONNREFUSED) || errors.Is(err, windows.WSAECONNREFUSED)
+}