feat(decl/fd): add memfd fd test resource

Signed-off-by: Leonardo Di Giovanna <leonardodigiovanna1@gmail.com>
Co-authored-by: Aldo Lacuku <aldo@lacuku.eu>

pkg/test/resource/fd/mem/doc.go

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (C) 2024 The Falco 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 mem provides the implementation of a memfd fd test resource. The resource exposes the mem fd (that can
+// be used for binding) in the 'fd' field.
+package mem

pkg/test/resource/fd/mem/mem.go

@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (C) 2024 The Falco 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 mem
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+
+	"github.com/go-logr/logr"
+	"golang.org/x/sys/unix"
+
+	"github.com/falcosecurity/event-generator/pkg/test/field"
+	"github.com/falcosecurity/event-generator/pkg/test/resource"
+)
+
+// memFD implements a mem FD resource.
+type memFD struct {
+	logger logr.Logger
+	// resourceName is the fd resource name.
+	resourceName string
+	// fileName is the file name associated with the mem FD.
+	fileName string
+	// fields defines the information exposed by memFD for binding.
+	fields struct {
+		FD int `field_type:"fd"`
+	}
+}
+
+// Verify that memFD implements resource.Resource interface.
+var _ resource.Resource = (*memFD)(nil)
+
+// New creates a new mem FD resource.
+func New(logger logr.Logger, resourceName, fileName string) resource.Resource {
+	m := &memFD{
+		logger:       logger,
+		resourceName: resourceName,
+		fileName:     fileName,
+	}
+	m.fields.FD = -1
+	return m
+}
+
+func (m *memFD) Name() string {
+	return m.resourceName
+}
+
+// Create creates a mem file descriptor and exposes it.
+func (m *memFD) Create(_ context.Context) error {
+	if m.fields.FD != -1 {
+		return fmt.Errorf("mem FD %q is already open", m.fileName)
+	}
+
+	fd, err := createMemFD(m.fileName)
+	if err != nil {
+		return fmt.Errorf("error creating mem FD %q: %w", m.fileName, err)
+	}
+
+	m.fields.FD = fd
+	return nil
+}
+
+// createMemFD creates a new mem file descriptor with the provided name and returns it.
+func createMemFD(name string) (int, error) {
+	fd, err := unix.MemfdCreate(name, 0)
+	if err != nil {
+		return 0, err
+	}
+
+	return fd, nil
+}
+
+// Destroy closes the exposed file descriptor.
+func (m *memFD) Destroy(_ context.Context) error {
+	if m.fields.FD == -1 {
+		return fmt.Errorf("mem FD %q is not open", m.fileName)
+	}
+
+	defer func() {
+		m.fields.FD = -1
+	}()
+
+	if err := unix.Close(m.fields.FD); err != nil {
+		m.logger.Error(err, "Error closing mem FD", "fileName", m.fileName)
+	}
+
+	return nil
+}
+
+func (m *memFD) Field(name string) (*field.Field, error) {
+	fieldContainer := reflect.ValueOf(m.fields)
+	return field.ByName(name, fieldContainer)
+}