ebpf: support native images on Windows

Allow loading eBPF programs packaged as signed Windows drivers.
Using native images significantly reduces which modifications can
be made before load time.

The .sys in testdata/windows were taken from the eBPF for
Windows project, available under the MIT license.

Signed-off-by: Lorenz Bauer <lmb@isovalent.com>

Author: lmb

collection.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"path/filepath"
 	"reflect"
 	"strings"
 
@@ -815,6 +816,13 @@ func resolveKconfig(m *MapSpec) error {
 // Omitting Collection.Close() during application shutdown is an error.
 // See the package documentation for details around Map and Program lifecycle.
 func LoadCollection(file string) (*Collection, error) {
+	if platform.IsWindows {
+		// This mirrors a check in efW.
+		if ext := filepath.Ext(file); ext == ".sys" {
+			return loadCollectionFromNativeImage(file)
+		}
+	}
+
 	spec, err := LoadCollectionSpec(file)
 	if err != nil {
 		return nil, err

collection_other.go

@@ -0,0 +1,9 @@
+//go:build !windows
+
+package ebpf
+
+import "github.com/cilium/ebpf/internal"
+
+func loadCollectionFromNativeImage(_ string) (*Collection, error) {
+	return nil, internal.ErrNotSupportedOnOS
+}

collection_windows.go

@@ -0,0 +1,136 @@
+package ebpf
+
+import (
+	"errors"
+	"fmt"
+	"unsafe"
+
+	"github.com/cilium/ebpf/internal/efw"
+	"github.com/cilium/ebpf/internal/sys"
+	"github.com/cilium/ebpf/internal/unix"
+)
+
+func loadCollectionFromNativeImage(file string) (_ *Collection, err error) {
+	mapFds := make([]efw.FD, 16)
+	programFds := make([]efw.FD, 16)
+	var maps map[string]*Map
+	var programs map[string]*Program
+
+	defer func() {
+		if err == nil {
+			return
+		}
+
+		for _, fd := range append(mapFds, programFds...) {
+			// efW never uses fd 0.
+			if fd != 0 {
+				_ = efw.EbpfCloseFd(int(fd))
+			}
+		}
+
+		for _, m := range maps {
+			_ = m.Close()
+		}
+
+		for _, p := range programs {
+			_ = p.Close()
+		}
+	}()
+
+	nMaps, nPrograms, err := efw.EbpfObjectLoadNativeFds(file, mapFds, programFds)
+	if errors.Is(err, efw.EBPF_NO_MEMORY) && (nMaps > len(mapFds) || nPrograms > len(programFds)) {
+		mapFds = make([]efw.FD, nMaps)
+		programFds = make([]efw.FD, nPrograms)
+
+		nMaps, nPrograms, err = efw.EbpfObjectLoadNativeFds(file, mapFds, programFds)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	mapFds = mapFds[:nMaps]
+	programFds = programFds[:nPrograms]
+
+	// The maximum length of a name is only 16 bytes on Linux, longer names
+	// are truncated. This is not a problem when loading from an ELF, since
+	// we get the full object name from the symbol table.
+	// When loading a native image we do not have this luxury. Use an efW native
+	// API to retrieve up to 64 bytes of the object name.
+
+	maps = make(map[string]*Map, len(mapFds))
+	for _, raw := range mapFds {
+		fd, err := sys.NewFD(int(raw))
+		if err != nil {
+			return nil, err
+		}
+
+		m, mapErr := newMapFromFD(fd)
+		if mapErr != nil {
+			_ = fd.Close()
+			return nil, mapErr
+		}
+
+		var efwMapInfo efw.BpfMapInfo
+		size := uint32(unsafe.Sizeof(efwMapInfo))
+		_, err = efw.EbpfObjectGetInfoByFd(m.FD(), unsafe.Pointer(&efwMapInfo), &size)
+		if err != nil {
+			_ = m.Close()
+			return nil, err
+		}
+
+		if size >= uint32(unsafe.Offsetof(efwMapInfo.Name)+unsafe.Sizeof(efwMapInfo.Name)) {
+			m.name = unix.ByteSliceToString(efwMapInfo.Name[:])
+		}
+
+		if m.name == "" {
+			_ = m.Close()
+			return nil, fmt.Errorf("unnamed map")
+		}
+
+		if _, ok := maps[m.name]; ok {
+			return nil, fmt.Errorf("duplicate map with the same name: %s", m.name)
+		}
+
+		maps[m.name] = m
+	}
+
+	programs = make(map[string]*Program, len(programFds))
+	for _, raw := range programFds {
+		fd, err := sys.NewFD(int(raw))
+		if err != nil {
+			return nil, err
+		}
+
+		program, err := newProgramFromFD(fd)
+		if err != nil {
+			_ = fd.Close()
+			return nil, err
+		}
+
+		var efwProgInfo efw.BpfProgInfo
+		size := uint32(unsafe.Sizeof(efwProgInfo))
+		_, err = efw.EbpfObjectGetInfoByFd(program.FD(), unsafe.Pointer(&efwProgInfo), &size)
+		if err != nil {
+			_ = program.Close()
+			return nil, err
+		}
+
+		if size >= uint32(unsafe.Offsetof(efwProgInfo.Name)+unsafe.Sizeof(efwProgInfo.Name)) {
+			program.name = unix.ByteSliceToString(efwProgInfo.Name[:])
+		}
+
+		if program.name == "" {
+			_ = program.Close()
+			return nil, fmt.Errorf("unnamed program")
+		}
+
+		if _, ok := programs[program.name]; ok {
+			_ = program.Close()
+			return nil, fmt.Errorf("duplicate program with the same name: %s", program.name)
+		}
+
+		programs[program.name] = program
+	}
+
+	return &Collection{programs, maps, nil}, nil
+}

collection_windows_test.go

@@ -0,0 +1,54 @@
+package ebpf
+
+import (
+	"path/filepath"
+	"sort"
+	"testing"
+
+	"github.com/go-quicktest/qt"
+)
+
+func TestLoadNativeImage(t *testing.T) {
+	for _, tc := range []struct {
+		file     string
+		maps     []string
+		programs []string
+	}{
+		{
+			"testdata/windows/cgroup_sock_addr.sys",
+			[]string{
+				"egress_connection_policy_map",
+				"ingress_connection_policy_map",
+				"socket_cookie_map",
+			},
+			[]string{
+				"authorize_connect4",
+				"authorize_connect6",
+				"authorize_recv_accept4",
+				"authorize_recv_accept6",
+			},
+		},
+	} {
+		t.Run(filepath.Base(tc.file), func(t *testing.T) {
+			coll, err := LoadCollection(tc.file)
+			qt.Assert(t, qt.IsNil(err))
+			defer coll.Close()
+
+			var mapNames []string
+			for name, obj := range coll.Maps {
+				qt.Assert(t, qt.Equals(obj.name, name))
+				mapNames = append(mapNames, name)
+			}
+			sort.Strings(mapNames)
+			qt.Assert(t, qt.DeepEquals(mapNames, tc.maps))
+
+			var programNames []string
+			for name, obj := range coll.Programs {
+				qt.Assert(t, qt.Equals(obj.name, name))
+				programNames = append(programNames, name)
+			}
+			sort.Strings(programNames)
+			qt.Assert(t, qt.DeepEquals(programNames, tc.programs))
+		})
+	}
+}

internal/efw/native.go

@@ -0,0 +1,44 @@
+//go:build windows
+
+package efw
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+/*
+ebpf_result_t ebpf_object_load_native_by_fds(
+
+	_In_z_ const char* file_name,
+	_Inout_ size_t* count_of_maps,
+	_Out_writes_opt_(count_of_maps) fd_t* map_fds,
+	_Inout_ size_t* count_of_programs,
+	_Out_writes_opt_(count_of_programs) fd_t* program_fds)
+*/
+var ebpfObjectLoadNativeByFdsProc = newProc("ebpf_object_load_native_by_fds")
+
+func EbpfObjectLoadNativeFds(fileName string, mapFds []FD, programFds []FD) (int, int, error) {
+	addr, err := ebpfObjectLoadNativeByFdsProc.Find()
+	if err != nil {
+		return 0, 0, err
+	}
+
+	fileBytes, err := windows.ByteSliceFromString(fileName)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	countOfMaps := Size(len(mapFds))
+	countOfPrograms := Size(len(programFds))
+	err = errorResult(syscall.SyscallN(addr,
+		uintptr(unsafe.Pointer(&fileBytes[0])),
+		uintptr(unsafe.Pointer(&countOfMaps)),
+		uintptr(unsafe.Pointer(&mapFds[0])),
+		uintptr(unsafe.Pointer(&countOfPrograms)),
+		uintptr(unsafe.Pointer(&programFds[0])),
+	))
+	return int(countOfMaps), int(countOfPrograms), err
+}

testdata/windows/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) eBPF for Windows contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.