package ebpf

import (
	"bytes"
	"encoding/binary"
	"errors"
	"fmt"
	"math"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"syscall"
	"testing"
	"time"

	qt "github.com/frankban/quicktest"

	"github.com/cilium/ebpf/asm"
	"github.com/cilium/ebpf/btf"
	"github.com/cilium/ebpf/internal"
	"github.com/cilium/ebpf/internal/sys"
	"github.com/cilium/ebpf/internal/testutils"
	"github.com/cilium/ebpf/internal/unix"
)

func TestProgramRun(t *testing.T) {
	testutils.SkipOnOldKernel(t, "4.8", "XDP program")

	pat := []byte{0xDE, 0xAD, 0xBE, 0xEF}
	buf := internal.EmptyBPFContext

	// r1  : ctx_start
	// r1+4: ctx_end
	ins := asm.Instructions{
		// r2 = *(r1+4)
		asm.LoadMem(asm.R2, asm.R1, 4, asm.Word),
		// r1 = *(r1+0)
		asm.LoadMem(asm.R1, asm.R1, 0, asm.Word),
		// r3 = r1
		asm.Mov.Reg(asm.R3, asm.R1),
		// r3 += len(buf)
		asm.Add.Imm(asm.R3, int32(len(buf))),
		// if r3 > r2 goto +len(pat)
		asm.JGT.Reg(asm.R3, asm.R2, "out"),
	}
	for i, b := range pat {
		ins = append(ins, asm.StoreImm(asm.R1, int16(i), int64(b), asm.Byte))
	}
	ins = append(ins,
		// return 42
		asm.LoadImm(asm.R0, 42, asm.DWord).WithSymbol("out"),
		asm.Return(),
	)

	t.Log(ins)

	prog, err := NewProgram(&ProgramSpec{
		Name:         "test",
		Type:         XDP,
		Instructions: ins,
		License:      "MIT",
	})
	if err != nil {
		t.Fatal(err)
	}
	defer prog.Close()

	p2, err := prog.Clone()
	if err != nil {
		t.Fatal("Can't clone program")
	}
	defer p2.Close()

	prog.Close()
	prog = p2

	ret, out, err := prog.Test(buf)
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal(err)
	}

	if ret != 42 {
		t.Error("Expected return value to be 42, got", ret)
	}

	if !bytes.Equal(out[:len(pat)], pat) {
		t.Errorf("Expected %v, got %v", pat, out)
	}
}

func TestProgramRunWithOptions(t *testing.T) {
	testutils.SkipOnOldKernel(t, "5.15", "XDP ctx_in/ctx_out")

	ins := asm.Instructions{
		// Return XDP_ABORTED
		asm.LoadImm(asm.R0, 0, asm.DWord),
		asm.Return(),
	}

	prog, err := NewProgram(&ProgramSpec{
		Name:         "test",
		Type:         XDP,
		Instructions: ins,
		License:      "MIT",
	})
	if err != nil {
		t.Fatal(err)
	}
	defer prog.Close()

	buf := internal.EmptyBPFContext
	xdp := sys.XdpMd{
		Data:    0,
		DataEnd: uint32(len(buf)),
	}
	xdpOut := sys.XdpMd{}
	opts := RunOptions{
		Data:       buf,
		Context:    xdp,
		ContextOut: &xdpOut,
	}
	ret, err := prog.Run(&opts)
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal(err)
	}

	if ret != 0 {
		t.Error("Expected return value to be 0, got", ret)
	}

	if xdp != xdpOut {
		t.Errorf("Expect xdp (%+v) == xdpOut (%+v)", xdp, xdpOut)
	}
}

func TestProgramRunEmptyData(t *testing.T) {
	testutils.SkipOnOldKernel(t, "5.13", "sk_lookup BPF_PROG_RUN")

	ins := asm.Instructions{
		// Return SK_DROP
		asm.LoadImm(asm.R0, 0, asm.DWord),
		asm.Return(),
	}

	prog, err := NewProgram(&ProgramSpec{
		Name:         "test",
		Type:         SkLookup,
		AttachType:   AttachSkLookup,
		Instructions: ins,
		License:      "MIT",
	})
	if err != nil {
		t.Fatal(err)
	}
	defer prog.Close()

	opts := RunOptions{
		Context: sys.SkLookup{
			Family: syscall.AF_INET,
		},
	}
	ret, err := prog.Run(&opts)
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal(err)
	}

	if ret != 0 {
		t.Error("Expected return value to be 0, got", ret)
	}
}

func TestProgramBenchmark(t *testing.T) {
	prog := mustSocketFilter(t)

	ret, duration, err := prog.Benchmark(internal.EmptyBPFContext, 1, nil)
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal("Error from Benchmark:", err)
	}

	if ret != 2 {
		t.Error("Expected return value 2, got", ret)
	}

	if duration == 0 {
		t.Error("Expected non-zero duration")
	}
}

func TestProgramTestRunInterrupt(t *testing.T) {
	testutils.SkipOnOldKernel(t, "5.0", "EINTR from BPF_PROG_TEST_RUN")

	prog := mustSocketFilter(t)

	var (
		tgid    = unix.Getpid()
		tidChan = make(chan int, 1)
		exit    = make(chan struct{})
		errs    = make(chan error, 1)
		timeout = time.After(5 * time.Second)
	)

	defer close(exit)

	go func() {
		runtime.LockOSThread()
		defer func() {
			// Wait for the test to allow us to unlock the OS thread, to
			// ensure that we don't send SIGUSR1 to the wrong thread.
			<-exit
			runtime.UnlockOSThread()
		}()

		tidChan <- unix.Gettid()

		// Block this thread in the BPF syscall, so that we can
		// trigger EINTR by sending a signal.
		opts := RunOptions{
			Data:   internal.EmptyBPFContext,
			Repeat: math.MaxInt32,
			Reset: func() {
				// We don't know how long finishing the
				// test run would take, so flag that we've seen
				// an interruption and abort the goroutine.
				close(errs)
				runtime.Goexit()
			},
		}
		_, _, err := prog.run(&opts)

		errs <- err
	}()

	tid := <-tidChan
	for {
		err := unix.Tgkill(tgid, tid, syscall.SIGUSR1)
		if err != nil {
			t.Fatal("Can't send signal to goroutine thread:", err)
		}

		select {
		case err, ok := <-errs:
			if !ok {
				return
			}

			testutils.SkipIfNotSupported(t, err)
			if err == nil {
				t.Fatal("testRun wasn't interrupted")
			}

			t.Fatal("testRun returned an error:", err)

		case <-timeout:
			t.Fatal("Timed out trying to interrupt the goroutine")

		default:
		}
	}
}

func TestProgramClose(t *testing.T) {
	prog := mustSocketFilter(t)

	if err := prog.Close(); err != nil {
		t.Fatal("Can't close program:", err)
	}
}

func TestProgramPin(t *testing.T) {
	prog := mustSocketFilter(t)
	c := qt.New(t)

	tmp := testutils.TempBPFFS(t)

	path := filepath.Join(tmp, "program")
	if err := prog.Pin(path); err != nil {
		t.Fatal(err)
	}

	pinned := prog.IsPinned()
	c.Assert(pinned, qt.IsTrue)

	prog.Close()

	prog, err := LoadPinnedProgram(path, nil)
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal(err)
	}
	defer prog.Close()

	if prog.Type() != SocketFilter {
		t.Error("Expected pinned program to have type SocketFilter, but got", prog.Type())
	}

	if haveObjName() == nil {
		if prog.name != "test" {
			t.Errorf("Expected program to have object name 'test', got '%s'", prog.name)
		}
	} else {
		if prog.name != "program" {
			t.Errorf("Expected program to have file name 'program', got '%s'", prog.name)
		}
	}

	if !prog.IsPinned() {
		t.Error("Expected IsPinned to be true")
	}
}

func TestProgramUnpin(t *testing.T) {
	prog := mustSocketFilter(t)
	c := qt.New(t)

	tmp := testutils.TempBPFFS(t)

	path := filepath.Join(tmp, "program")
	if err := prog.Pin(path); err != nil {
		t.Fatal(err)
	}

	pinned := prog.IsPinned()
	c.Assert(pinned, qt.IsTrue)

	if err := prog.Unpin(); err != nil {
		t.Fatal("Failed to unpin program:", err)
	}
	if _, err := os.Stat(path); err == nil {
		t.Fatal("Pinned program path still exists after unpinning:", err)
	}
}

func TestProgramLoadPinnedWithFlags(t *testing.T) {
	// Introduced in commit 6e71b04a8224.
	testutils.SkipOnOldKernel(t, "4.14", "file_flags in BPF_OBJ_GET")

	prog := mustSocketFilter(t)

	tmp := testutils.TempBPFFS(t)

	path := filepath.Join(tmp, "program")
	if err := prog.Pin(path); err != nil {
		t.Fatal(err)
	}

	prog.Close()

	_, err := LoadPinnedProgram(path, &LoadPinOptions{
		Flags: math.MaxUint32,
	})
	testutils.SkipIfNotSupported(t, err)
	if !errors.Is(err, unix.EINVAL) {
		t.Fatal("Invalid flags don't trigger an error:", err)
	}
}

func TestProgramVerifierOutputOnError(t *testing.T) {
	_, err := NewProgram(&ProgramSpec{
		Type: SocketFilter,
		Instructions: asm.Instructions{
			asm.Return(),
		},
		License: "MIT",
	})
	if err == nil {
		t.Fatal("Expected program to be invalid")
	}

	ve, ok := err.(*VerifierError)
	if !ok {
		t.Fatal("NewProgram does return an unwrapped VerifierError")
	}

	if !strings.Contains(ve.Error(), "R0 !read_ok") {
		t.Logf("%+v", ve)
		t.Error("Missing verifier log in error summary")
	}
}

func TestProgramKernelVersion(t *testing.T) {
	testutils.SkipOnOldKernel(t, "4.20", "KernelVersion")
	prog, err := NewProgram(&ProgramSpec{
		Type: Kprobe,
		Instructions: asm.Instructions{
			asm.LoadImm(asm.R0, 0, asm.DWord),
			asm.Return(),
		},
		KernelVersion: 42,
		License:       "MIT",
	})
	if err != nil {
		t.Fatal("Could not load Kprobe program")
	}
	defer prog.Close()
}

func TestProgramVerifierOutput(t *testing.T) {
	prog, err := NewProgramWithOptions(socketFilterSpec, ProgramOptions{
		LogLevel: LogLevelInstruction,
	})
	if err != nil {
		t.Fatal(err)
	}
	defer prog.Close()

	if prog.VerifierLog == "" {
		t.Error("Expected VerifierLog to be present")
	}

	// Issue 64
	_, err = NewProgramWithOptions(&ProgramSpec{
		Type: SocketFilter,
		Instructions: asm.Instructions{
			asm.Mov.Reg(asm.R0, asm.R1),
		},
		License: "MIT",
	}, ProgramOptions{
		LogLevel: LogLevelInstruction,
	})

	if err == nil {
		t.Fatal("Expected an error from invalid program")
	}

	var ve *internal.VerifierError
	if !errors.As(err, &ve) {
		t.Error("Error is not a VerifierError")
	}
}

// Test all scenarios where the VerifierError.Truncated flag is expected to be
// true, marked with an x. LL means ProgramOption.LogLevel.
//
// |      | Valid | Invalid |
// |------|-------|---------|
// | LL=0 |       |    x    |
// | LL>0 |   x   |    x    |
func TestProgramVerifierLogTruncated(t *testing.T) {
	// Make the buffer intentionally small to coerce ENOSPC.
	// 128 bytes is the smallest the kernel will accept.
	logSize := 128

	check := func(t *testing.T, err error) {
		if err == nil {
			t.Fatal("Expected an error")
		}
		var ve *internal.VerifierError
		if !errors.As(err, &ve) {
			t.Fatal("Error is not a VerifierError")
		}
		if !ve.Truncated {
			t.Errorf("VerifierError is not truncated: %+v", ve)
		}
	}

	// Generate a base program of sufficient size whose verifier log does not fit
	// a 128-byte buffer. This should always result in ENOSPC, setting the
	// VerifierError.Truncated flag.
	base := func() (out asm.Instructions) {
		for i := 0; i < 32; i++ {
			out = append(out, asm.Mov.Reg(asm.R0, asm.R1))
		}
		return
	}()

	invalid := func() (out asm.Instructions) {
		out = base
		// Touch R10 (read-only frame pointer) to reliably force a verifier error.
		out = append(out, asm.Mov.Reg(asm.R10, asm.R0))
		out = append(out, asm.Return())
		return
	}()

	valid := func() (out asm.Instructions) {
		out = base
		out = append(out, asm.Return())
		return
	}()

	// Start out with testing against the invalid program.
	spec := &ProgramSpec{
		Type:         SocketFilter,
		License:      "MIT",
		Instructions: invalid,
	}

	// Set an undersized log buffer without explicitly requesting a verifier log
	// for an invalid program.
	_, err := NewProgramWithOptions(spec, ProgramOptions{LogSize: logSize})
	check(t, err)

	// Explicitly request a verifier log for an invalid program.
	_, err = NewProgramWithOptions(spec, ProgramOptions{
		LogSize:  logSize,
		LogLevel: LogLevelInstruction,
	})
	check(t, err)

	// Run tests against a valid program from here on out.
	spec.Instructions = valid

	// Don't request a verifier log, only set LogSize. Expect the valid program to
	// be created without errors.
	prog, err := NewProgramWithOptions(spec, ProgramOptions{
		LogSize: logSize,
	})
	if err != nil {
		t.Fatal(err)
	}
	prog.Close()

	// Explicitly request verifier log for a valid program. If a log is requested
	// and the buffer is too small, ENOSPC occurs even for valid programs.
	_, err = NewProgramWithOptions(spec, ProgramOptions{
		LogSize:  logSize,
		LogLevel: LogLevelInstruction,
	})
	check(t, err)
}

func TestProgramWithUnsatisfiedMap(t *testing.T) {
	coll, err := LoadCollectionSpec("testdata/loader-el.elf")
	if err != nil {
		t.Fatal(err)
	}

	// The program will have at least one map reference.
	progSpec := coll.Programs["xdp_prog"]
	progSpec.ByteOrder = nil

	_, err = NewProgram(progSpec)
	testutils.SkipIfNotSupported(t, err)
	if !errors.Is(err, asm.ErrUnsatisfiedMapReference) {
		t.Fatal("Expected an error wrapping asm.ErrUnsatisfiedMapReference, got", err)
	}
	t.Log(err)
}

func TestProgramName(t *testing.T) {
	if err := haveObjName(); err != nil {
		t.Skip(err)
	}

	prog := mustSocketFilter(t)

	var info sys.ProgInfo
	if err := sys.ObjInfo(prog.fd, &info); err != nil {
		t.Fatal(err)
	}

	if name := unix.ByteSliceToString(info.Name[:]); name != "test" {
		t.Errorf("Name is not test, got '%s'", name)
	}
}

func TestSanitizeName(t *testing.T) {
	for input, want := range map[string]string{
		"test":     "test",
		"t-est":    "test",
		"t_est":    "t_est",
		"hörnchen": "hrnchen",
	} {
		if have := SanitizeName(input, -1); have != want {
			t.Errorf("Wanted '%s' got '%s'", want, have)
		}
	}
}

func TestProgramCloneNil(t *testing.T) {
	p, err := (*Program)(nil).Clone()
	if err != nil {
		t.Fatal(err)
	}

	if p != nil {
		t.Fatal("Cloning a nil Program doesn't return nil")
	}
}

func TestProgramMarshaling(t *testing.T) {
	const idx = uint32(0)

	arr := createProgramArray(t)
	defer arr.Close()

	prog := mustSocketFilter(t)

	if err := arr.Put(idx, prog); err != nil {
		t.Fatal("Can't put program:", err)
	}

	if err := arr.Lookup(idx, Program{}); err == nil {
		t.Fatal("Lookup accepts non-pointer Program")
	}

	var prog2 *Program
	defer prog2.Close()

	if err := arr.Lookup(idx, prog2); err == nil {
		t.Fatal("Get accepts *Program")
	}

	testutils.SkipOnOldKernel(t, "4.12", "lookup for ProgramArray")

	if err := arr.Lookup(idx, &prog2); err != nil {
		t.Fatal("Can't unmarshal program:", err)
	}
	defer prog2.Close()

	if prog2 == nil {
		t.Fatal("Unmarshalling set program to nil")
	}
}

func TestProgramFromFD(t *testing.T) {
	prog := mustSocketFilter(t)

	// If you're thinking about copying this, don't. Use
	// Clone() instead.
	prog2, err := NewProgramFromFD(dupFD(t, prog.FD()))
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal(err)
	}
	defer prog2.Close()

	// Name and type are supposed to be copied from program info.
	if haveObjName() == nil && prog2.name != "test" {
		t.Errorf("Expected program to have name test, got '%s'", prog2.name)
	}

	if prog2.typ != SocketFilter {
		t.Errorf("Expected program to have type SocketFilter, got '%s'", prog2.typ)
	}
}

func TestHaveProgTestRun(t *testing.T) {
	testutils.CheckFeatureTest(t, haveProgRun)
}

func TestProgramGetNextID(t *testing.T) {
	testutils.SkipOnOldKernel(t, "4.13", "bpf_prog_get_next_id")

	// Ensure there is at least one program loaded
	_ = mustSocketFilter(t)

	// As there can be multiple eBPF programs, we loop over all of them and
	// make sure, the IDs increase and the last call will return ErrNotExist
	last := ProgramID(0)
	for {
		next, err := ProgramGetNextID(last)
		if errors.Is(err, os.ErrNotExist) {
			if last == 0 {
				t.Fatal("Got ErrNotExist on the first iteration")
			}
			break
		}
		if err != nil {
			t.Fatal("Unexpected error:", err)
		}
		if next <= last {
			t.Fatalf("Expected next ID (%d) to be higher than the last ID (%d)", next, last)
		}
		last = next
	}
}

func TestNewProgramFromID(t *testing.T) {
	prog := mustSocketFilter(t)

	info, err := prog.Info()
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal("Could not get program info:", err)
	}

	id, ok := info.ID()
	if !ok {
		t.Skip("Program ID not supported")
	}

	prog2, err := NewProgramFromID(id)
	if err != nil {
		t.Fatalf("Can't get FD for program ID %d: %v", id, err)
	}
	prog2.Close()

	// As there can be multiple programs, we use max(uint32) as ProgramID to trigger an expected error.
	_, err = NewProgramFromID(ProgramID(math.MaxUint32))
	if !errors.Is(err, os.ErrNotExist) {
		t.Fatal("Expected ErrNotExist, got:", err)
	}
}

func TestProgramRejectIncorrectByteOrder(t *testing.T) {
	spec := socketFilterSpec.Copy()

	spec.ByteOrder = binary.BigEndian
	if internal.NativeEndian == binary.BigEndian {
		spec.ByteOrder = binary.LittleEndian
	}

	_, err := NewProgram(spec)
	if err == nil {
		t.Error("Incorrect ByteOrder should be rejected at load time")
	}
}

func TestProgramSpecTag(t *testing.T) {
	arr := createArray(t)
	defer arr.Close()

	spec := &ProgramSpec{
		Type: SocketFilter,
		Instructions: asm.Instructions{
			asm.LoadImm(asm.R0, -1, asm.DWord),
			asm.LoadMapPtr(asm.R1, arr.FD()),
			asm.Mov.Imm32(asm.R0, 0),
			asm.Return(),
		},
		License: "MIT",
	}

	prog, err := NewProgram(spec)
	if err != nil {
		t.Fatal(err)
	}
	defer prog.Close()

	info, err := prog.Info()
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal(err)
	}

	tag, err := spec.Tag()
	if err != nil {
		t.Fatal("Can't calculate tag:", err)
	}

	if tag != info.Tag {
		t.Errorf("Calculated tag %s doesn't match kernel tag %s", tag, info.Tag)
	}
}

func TestProgramAttachToKernel(t *testing.T) {
	// See https://github.com/torvalds/linux/commit/290248a5b7d829871b3ea3c62578613a580a1744
	testutils.SkipOnOldKernel(t, "5.5", "attach_btf_id")

	haveTestmod := haveTestmod(t)

	tests := []struct {
		attachTo    string
		programType ProgramType
		attachType  AttachType
		flags       uint32
	}{
		{
			attachTo:    "task_getpgid",
			programType: LSM,
			attachType:  AttachLSMMac,
		},
		{
			attachTo:    "inet_dgram_connect",
			programType: Tracing,
			attachType:  AttachTraceFEntry,
		},
		{
			attachTo:    "inet_dgram_connect",
			programType: Tracing,
			attachType:  AttachTraceFExit,
		},
		{
			attachTo:    "bpf_modify_return_test",
			programType: Tracing,
			attachType:  AttachModifyReturn,
		},
		{
			attachTo:    "kfree_skb",
			programType: Tracing,
			attachType:  AttachTraceRawTp,
		},
		{
			attachTo:    "bpf_testmod_test_read",
			programType: Tracing,
			attachType:  AttachTraceFEntry,
		},
		{
			attachTo:    "bpf_testmod_test_read",
			programType: Tracing,
			attachType:  AttachTraceFExit,
		},
		{
			attachTo:    "bpf_testmod_test_read",
			programType: Tracing,
			attachType:  AttachModifyReturn,
		},
		{
			attachTo:    "bpf_testmod_test_read",
			programType: Tracing,
			attachType:  AttachTraceRawTp,
		},
	}
	for _, test := range tests {
		name := fmt.Sprintf("%s:%s", test.attachType, test.attachTo)
		t.Run(name, func(t *testing.T) {
			if strings.HasPrefix(test.attachTo, "bpf_testmod_") && !haveTestmod {
				t.Skip("bpf_testmod not loaded")
			}

			prog, err := NewProgram(&ProgramSpec{
				AttachTo:   test.attachTo,
				AttachType: test.attachType,
				Instructions: asm.Instructions{
					asm.LoadImm(asm.R0, 0, asm.DWord),
					asm.Return(),
				},
				License: "GPL",
				Type:    test.programType,
				Flags:   test.flags,
			})
			if err != nil {
				t.Fatal("Can't load program:", err)
			}
			prog.Close()
		})
	}
}

func TestProgramKernelTypes(t *testing.T) {
	if _, err := os.Stat("/sys/kernel/btf/vmlinux"); os.IsNotExist(err) {
		t.Skip("/sys/kernel/btf/vmlinux not present")
	}

	btfSpec, err := btf.LoadSpec("/sys/kernel/btf/vmlinux")
	if err != nil {
		t.Fatal(err)
	}

	prog, err := NewProgramWithOptions(&ProgramSpec{
		Type:       Tracing,
		AttachType: AttachTraceIter,
		AttachTo:   "bpf_map",
		Instructions: asm.Instructions{
			asm.Mov.Imm(asm.R0, 0),
			asm.Return(),
		},
		License: "MIT",
	}, ProgramOptions{
		KernelTypes: btfSpec,
	})
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal("NewProgram with Target:", err)
	}
	prog.Close()
}

func TestProgramBindMap(t *testing.T) {
	testutils.SkipOnOldKernel(t, "5.10", "BPF_PROG_BIND_MAP")

	arr, err := NewMap(&MapSpec{
		Type:       Array,
		KeySize:    4,
		ValueSize:  4,
		MaxEntries: 1,
	})
	if err != nil {
		t.Errorf("Failed to load map: %v", err)
	}
	defer arr.Close()

	prog := mustSocketFilter(t)

	// The attached map does not contain BTF information. So
	// the metadata part of the program will be empty. This
	// test just makes sure that we can bind a map to a program.
	if err := prog.BindMap(arr); err != nil {
		t.Errorf("Failed to bind map to program: %v", err)
	}
}

func TestProgramInstructions(t *testing.T) {
	name := "test_prog"
	spec := &ProgramSpec{
		Type: SocketFilter,
		Name: name,
		Instructions: asm.Instructions{
			asm.LoadImm(asm.R0, -1, asm.DWord).WithSymbol(name),
			asm.Return(),
		},
		License: "MIT",
	}

	prog, err := NewProgram(spec)
	if err != nil {
		t.Fatal(err)
	}
	defer prog.Close()

	pi, err := prog.Info()
	testutils.SkipIfNotSupported(t, err)
	if err != nil {
		t.Fatal(err)
	}

	insns, err := pi.Instructions()
	if err != nil {
		t.Fatal(err)
	}

	tag, err := spec.Tag()
	if err != nil {
		t.Fatal(err)
	}

	tagXlated, err := insns.Tag(internal.NativeEndian)
	if err != nil {
		t.Fatal(err)
	}

	if tag != tagXlated {
		t.Fatalf("tag %s differs from xlated instructions tag %s", tag, tagXlated)
	}
}

func createProgramArray(t *testing.T) *Map {
	t.Helper()

	arr, err := NewMap(&MapSpec{
		Type:       ProgramArray,
		KeySize:    4,
		ValueSize:  4,
		MaxEntries: 1,
	})
	if err != nil {
		t.Fatal(err)
	}
	return arr
}

var socketFilterSpec = &ProgramSpec{
	Name: "test",
	Type: SocketFilter,
	Instructions: asm.Instructions{
		asm.LoadImm(asm.R0, 2, asm.DWord),
		asm.Return(),
	},
	License: "MIT",
}

func mustSocketFilter(tb testing.TB) *Program {
	tb.Helper()

	prog, err := NewProgram(socketFilterSpec)
	if err != nil {
		tb.Fatal(err)
	}
	tb.Cleanup(func() { prog.Close() })

	return prog
}

// Print the full verifier log when loading a program fails.
func ExampleVerifierError_retrieveFullLog() {
	_, err := NewProgram(&ProgramSpec{
		Type: SocketFilter,
		Instructions: asm.Instructions{
			asm.LoadImm(asm.R0, 0, asm.DWord),
			// Missing Return
		},
		License: "MIT",
	})

	var ve *VerifierError
	if errors.As(err, &ve) {
		// Using %+v will print the whole verifier error, not just the last
		// few lines.
		fmt.Printf("Verifier error: %+v\n", ve)
	}
}

// VerifierLog understands a variety of formatting flags.
func ExampleVerifierError() {
	err := internal.ErrorWithLog(
		"catastrophe",
		syscall.ENOSPC,
		[]byte("first\nsecond\nthird"),
		false,
	)

	fmt.Printf("With %%s: %s\n", err)
	err.Truncated = true
	fmt.Printf("With %%v and a truncated log: %v\n", err)
	fmt.Printf("All log lines: %+v\n", err)
	fmt.Printf("First line: %+1v\n", err)
	fmt.Printf("Last two lines: %-2v\n", err)

	// Output: With %s: catastrophe: no space left on device: third (2 line(s) omitted)
	// With %v and a truncated log: catastrophe: no space left on device: second: third (truncated, 1 line(s) omitted)
	// All log lines: catastrophe: no space left on device:
	// 	first
	// 	second
	// 	third
	// 	(truncated)
	// First line: catastrophe: no space left on device:
	// 	first
	// 	(2 line(s) omitted)
	// 	(truncated)
	// Last two lines: catastrophe: no space left on device:
	// 	(1 line(s) omitted)
	// 	second
	// 	third
	// 	(truncated)
}

// Use NewProgramWithOptions if you'd like to get the verifier output
// for a program, or if you want to change the buffer size used when
// generating error messages.
func ExampleProgram_retrieveVerifierLog() {
	spec := &ProgramSpec{
		Type: SocketFilter,
		Instructions: asm.Instructions{
			asm.LoadImm(asm.R0, 0, asm.DWord),
			asm.Return(),
		},
		License: "MIT",
	}

	prog, err := NewProgramWithOptions(spec, ProgramOptions{
		LogLevel: LogLevelInstruction,
		LogSize:  1024,
	})
	if err != nil {
		panic(err)
	}
	defer prog.Close()

	fmt.Println("The verifier output is:")
	fmt.Println(prog.VerifierLog)
}

// It's possible to read a program directly from a ProgramArray.
func ExampleProgram_unmarshalFromMap() {
	progArray, err := LoadPinnedMap("/path/to/map", nil)
	if err != nil {
		panic(err)
	}
	defer progArray.Close()

	// Load a single program
	var prog *Program
	if err := progArray.Lookup(uint32(0), &prog); err != nil {
		panic(err)
	}
	defer prog.Close()

	fmt.Println("first prog:", prog)

	// Iterate all programs
	var (
		key     uint32
		entries = progArray.Iterate()
	)

	for entries.Next(&key, &prog) {
		fmt.Println(key, "is", prog)
	}

	if err := entries.Err(); err != nil {
		panic(err)
	}
}

func ExampleProgramSpec_Tag() {
	spec := &ProgramSpec{
		Type: SocketFilter,
		Instructions: asm.Instructions{
			asm.LoadImm(asm.R0, 0, asm.DWord),
			asm.Return(),
		},
		License: "MIT",
	}

	prog, _ := NewProgram(spec)
	info, _ := prog.Info()
	tag, _ := spec.Tag()

	if info.Tag != tag {
		fmt.Printf("The tags don't match: %s != %s\n", info.Tag, tag)
	} else {
		fmt.Println("The programs are identical, tag is", tag)
	}
}

func dupFD(tb testing.TB, fd int) int {
	tb.Helper()

	dup, err := unix.FcntlInt(uintptr(fd), unix.F_DUPFD_CLOEXEC, 1)
	if err != nil {
		tb.Fatal("Can't dup fd:", err)
	}

	return dup
}