Vendor nftables library, add utils.SupportsIPTables and utils.SupportsNFTables

Signed-off-by: Dan Winship <danwinship@redhat.com>

vendor/sigs.k8s.io/knftables/exec.go

@@ -0,0 +1,48 @@
+/*
+Copyright 2023 The Kubernetes 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 knftables
+
+import (
+	"os/exec"
+)
+
+// execer is a mockable wrapper around os/exec.
+type execer interface {
+	// LookPath wraps exec.LookPath
+	LookPath(file string) (string, error)
+
+	// Run runs cmd as with cmd.Output(). If an error occurs, and the process outputs
+	// stderr, then that output will be returned in the error.
+	Run(cmd *exec.Cmd) (string, error)
+}
+
+// realExec implements execer by actually using os/exec
+type realExec struct{}
+
+// LookPath is part of execer
+func (realExec) LookPath(file string) (string, error) {
+	return exec.LookPath(file)
+}
+
+// Run is part of execer
+func (realExec) Run(cmd *exec.Cmd) (string, error) {
+	out, err := cmd.Output()
+	if err != nil {
+		err = wrapError(err)
+	}
+	return string(out), err
+}