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

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

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

@@ -0,0 +1,94 @@
+/*
+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 (
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+	"syscall"
+)
+
+type nftablesError struct {
+	wrapped error
+	msg     string
+	errno   syscall.Errno
+}
+
+// wrapError wraps an error resulting from running nft
+func wrapError(err error) error {
+	nerr := &nftablesError{wrapped: err, msg: err.Error()}
+	ee := &exec.ExitError{}
+	if errors.As(err, &ee) {
+		if len(ee.Stderr) > 0 {
+			nerr.msg = string(ee.Stderr)
+			eol := strings.Index(nerr.msg, "\n")
+			// The nft binary does not call setlocale() and so will return
+			// English error strings regardless of the locale.
+			enoent := strings.Index(nerr.msg, "No such file or directory")
+			eexist := strings.Index(nerr.msg, "File exists")
+			if enoent != -1 && (enoent < eol || eol == -1) {
+				nerr.errno = syscall.ENOENT
+			} else if eexist != -1 && (eexist < eol || eol == -1) {
+				nerr.errno = syscall.EEXIST
+			}
+		}
+	}
+	return nerr
+}
+
+// notFoundError returns an nftablesError with the given message for which IsNotFound will
+// return true.
+func notFoundError(format string, args ...interface{}) error {
+	return &nftablesError{msg: fmt.Sprintf(format, args...), errno: syscall.ENOENT}
+}
+
+// existsError returns an nftablesError with the given message for which IsAlreadyExists
+// will return true.
+func existsError(format string, args ...interface{}) error {
+	return &nftablesError{msg: fmt.Sprintf(format, args...), errno: syscall.EEXIST}
+}
+
+func (nerr *nftablesError) Error() string {
+	return nerr.msg
+}
+
+func (nerr *nftablesError) Unwrap() error {
+	return nerr.wrapped
+}
+
+// IsNotFound tests if err corresponds to an nftables "not found" error of any sort.
+// (e.g., in response to a "delete rule" command, this might indicate that the rule
+// doesn't exist, or the chain doesn't exist, or the table doesn't exist.)
+func IsNotFound(err error) bool {
+	var nerr *nftablesError
+	if errors.As(err, &nerr) {
+		return nerr.errno == syscall.ENOENT
+	}
+	return false
+}
+
+// IsAlreadyExists tests if err corresponds to an nftables "already exists" error (e.g.
+// when doing a "create" rather than an "add").
+func IsAlreadyExists(err error) bool {
+	var nerr *nftablesError
+	if errors.As(err, &nerr) {
+		return nerr.errno == syscall.EEXIST
+	}
+	return false
+}