switch to go vendoring

vendor/github.com/cilium/ebpf/collection.go

@@ -0,0 +1,668 @@
+package ebpf
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"reflect"
+	"strings"
+
+	"github.com/cilium/ebpf/asm"
+	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/btf"
+)
+
+// CollectionOptions control loading a collection into the kernel.
+//
+// Maps and Programs are passed to NewMapWithOptions and NewProgramsWithOptions.
+type CollectionOptions struct {
+	Maps     MapOptions
+	Programs ProgramOptions
+}
+
+// CollectionSpec describes a collection.
+type CollectionSpec struct {
+	Maps     map[string]*MapSpec
+	Programs map[string]*ProgramSpec
+
+	// ByteOrder specifies whether the ELF was compiled for
+	// big-endian or little-endian architectures.
+	ByteOrder binary.ByteOrder
+}
+
+// Copy returns a recursive copy of the spec.
+func (cs *CollectionSpec) Copy() *CollectionSpec {
+	if cs == nil {
+		return nil
+	}
+
+	cpy := CollectionSpec{
+		Maps:      make(map[string]*MapSpec, len(cs.Maps)),
+		Programs:  make(map[string]*ProgramSpec, len(cs.Programs)),
+		ByteOrder: cs.ByteOrder,
+	}
+
+	for name, spec := range cs.Maps {
+		cpy.Maps[name] = spec.Copy()
+	}
+
+	for name, spec := range cs.Programs {
+		cpy.Programs[name] = spec.Copy()
+	}
+
+	return &cpy
+}
+
+// RewriteMaps replaces all references to specific maps.
+//
+// Use this function to use pre-existing maps instead of creating new ones
+// when calling NewCollection. Any named maps are removed from CollectionSpec.Maps.
+//
+// Returns an error if a named map isn't used in at least one program.
+func (cs *CollectionSpec) RewriteMaps(maps map[string]*Map) error {
+	for symbol, m := range maps {
+		// have we seen a program that uses this symbol / map
+		seen := false
+		fd := m.FD()
+		for progName, progSpec := range cs.Programs {
+			err := progSpec.Instructions.RewriteMapPtr(symbol, fd)
+
+			switch {
+			case err == nil:
+				seen = true
+
+			case asm.IsUnreferencedSymbol(err):
+				// Not all programs need to use the map
+
+			default:
+				return fmt.Errorf("program %s: %w", progName, err)
+			}
+		}
+
+		if !seen {
+			return fmt.Errorf("map %s not referenced by any programs", symbol)
+		}
+
+		// Prevent NewCollection from creating rewritten maps
+		delete(cs.Maps, symbol)
+	}
+
+	return nil
+}
+
+// RewriteConstants replaces the value of multiple constants.
+//
+// The constant must be defined like so in the C program:
+//
+//    volatile const type foobar;
+//    volatile const type foobar = default;
+//
+// Replacement values must be of the same length as the C sizeof(type).
+// If necessary, they are marshalled according to the same rules as
+// map values.
+//
+// From Linux 5.5 the verifier will use constants to eliminate dead code.
+//
+// Returns an error if a constant doesn't exist.
+func (cs *CollectionSpec) RewriteConstants(consts map[string]interface{}) error {
+	rodata := cs.Maps[".rodata"]
+	if rodata == nil {
+		return errors.New("missing .rodata section")
+	}
+
+	if rodata.BTF == nil {
+		return errors.New(".rodata section has no BTF")
+	}
+
+	if n := len(rodata.Contents); n != 1 {
+		return fmt.Errorf("expected one key in .rodata, found %d", n)
+	}
+
+	kv := rodata.Contents[0]
+	value, ok := kv.Value.([]byte)
+	if !ok {
+		return fmt.Errorf("first value in .rodata is %T not []byte", kv.Value)
+	}
+
+	buf := make([]byte, len(value))
+	copy(buf, value)
+
+	err := patchValue(buf, rodata.BTF.Value, consts)
+	if err != nil {
+		return err
+	}
+
+	rodata.Contents[0] = MapKV{kv.Key, buf}
+	return nil
+}
+
+// Assign the contents of a CollectionSpec to a struct.
+//
+// This function is a shortcut to manually checking the presence
+// of maps and programs in a CollectionSpec. Consider using bpf2go
+// if this sounds useful.
+//
+// 'to' must be a pointer to a struct. A field of the
+// struct is updated with values from Programs or Maps if it
+// has an `ebpf` tag and its type is *ProgramSpec or *MapSpec.
+// The tag's value specifies the name of the program or map as
+// found in the CollectionSpec.
+//
+//    struct {
+//        Foo     *ebpf.ProgramSpec `ebpf:"xdp_foo"`
+//        Bar     *ebpf.MapSpec     `ebpf:"bar_map"`
+//        Ignored int
+//    }
+//
+// Returns an error if any of the eBPF objects can't be found, or
+// if the same MapSpec or ProgramSpec is assigned multiple times.
+func (cs *CollectionSpec) Assign(to interface{}) error {
+	// Assign() only supports assigning ProgramSpecs and MapSpecs,
+	// so doesn't load any resources into the kernel.
+	getValue := func(typ reflect.Type, name string) (interface{}, error) {
+		switch typ {
+
+		case reflect.TypeOf((*ProgramSpec)(nil)):
+			if p := cs.Programs[name]; p != nil {
+				return p, nil
+			}
+			return nil, fmt.Errorf("missing program %q", name)
+
+		case reflect.TypeOf((*MapSpec)(nil)):
+			if m := cs.Maps[name]; m != nil {
+				return m, nil
+			}
+			return nil, fmt.Errorf("missing map %q", name)
+
+		default:
+			return nil, fmt.Errorf("unsupported type %s", typ)
+		}
+	}
+
+	return assignValues(to, getValue)
+}
+
+// LoadAndAssign loads Maps and Programs into the kernel and assigns them
+// to a struct.
+//
+// This function is a shortcut to manually checking the presence
+// of maps and programs in a CollectionSpec. Consider using bpf2go
+// if this sounds useful.
+//
+// 'to' must be a pointer to a struct. A field of the struct is updated with
+// a Program or Map if it has an `ebpf` tag and its type is *Program or *Map.
+// The tag's value specifies the name of the program or map as found in the
+// CollectionSpec. Before updating the struct, the requested objects and their
+// dependent resources are loaded into the kernel and populated with values if
+// specified.
+//
+//    struct {
+//        Foo     *ebpf.Program `ebpf:"xdp_foo"`
+//        Bar     *ebpf.Map     `ebpf:"bar_map"`
+//        Ignored int
+//    }
+//
+// opts may be nil.
+//
+// Returns an error if any of the fields can't be found, or
+// if the same Map or Program is assigned multiple times.
+func (cs *CollectionSpec) LoadAndAssign(to interface{}, opts *CollectionOptions) error {
+	loader := newCollectionLoader(cs, opts)
+	defer loader.cleanup()
+
+	// Support assigning Programs and Maps, lazy-loading the required objects.
+	assignedMaps := make(map[string]bool)
+	getValue := func(typ reflect.Type, name string) (interface{}, error) {
+		switch typ {
+
+		case reflect.TypeOf((*Program)(nil)):
+			return loader.loadProgram(name)
+
+		case reflect.TypeOf((*Map)(nil)):
+			assignedMaps[name] = true
+			return loader.loadMap(name)
+
+		default:
+			return nil, fmt.Errorf("unsupported type %s", typ)
+		}
+	}
+
+	// Load the Maps and Programs requested by the annotated struct.
+	if err := assignValues(to, getValue); err != nil {
+		return err
+	}
+
+	// Populate the requested maps. Has a chance of lazy-loading other dependent maps.
+	if err := loader.populateMaps(); err != nil {
+		return err
+	}
+
+	// Evaluate the loader's objects after all (lazy)loading has taken place.
+	for n, m := range loader.maps {
+		switch m.typ {
+		case ProgramArray:
+			// Require all lazy-loaded ProgramArrays to be assigned to the given object.
+			// Without any references, they will be closed on the first GC and all tail
+			// calls into them will miss.
+			if !assignedMaps[n] {
+				return fmt.Errorf("ProgramArray %s must be assigned to prevent missed tail calls", n)
+			}
+		}
+	}
+
+	loader.finalize()
+
+	return nil
+}
+
+// Collection is a collection of Programs and Maps associated
+// with their symbols
+type Collection struct {
+	Programs map[string]*Program
+	Maps     map[string]*Map
+}
+
+// NewCollection creates a Collection from a specification.
+func NewCollection(spec *CollectionSpec) (*Collection, error) {
+	return NewCollectionWithOptions(spec, CollectionOptions{})
+}
+
+// NewCollectionWithOptions creates a Collection from a specification.
+func NewCollectionWithOptions(spec *CollectionSpec, opts CollectionOptions) (*Collection, error) {
+	loader := newCollectionLoader(spec, &opts)
+	defer loader.cleanup()
+
+	// Create maps first, as their fds need to be linked into programs.
+	for mapName := range spec.Maps {
+		if _, err := loader.loadMap(mapName); err != nil {
+			return nil, err
+		}
+	}
+
+	for progName := range spec.Programs {
+		if _, err := loader.loadProgram(progName); err != nil {
+			return nil, err
+		}
+	}
+
+	// Maps can contain Program and Map stubs, so populate them after
+	// all Maps and Programs have been successfully loaded.
+	if err := loader.populateMaps(); err != nil {
+		return nil, err
+	}
+
+	maps, progs := loader.maps, loader.programs
+
+	loader.finalize()
+
+	return &Collection{
+		progs,
+		maps,
+	}, nil
+}
+
+type handleCache struct {
+	btfHandles map[*btf.Spec]*btf.Handle
+	btfSpecs   map[io.ReaderAt]*btf.Spec
+}
+
+func newHandleCache() *handleCache {
+	return &handleCache{
+		btfHandles: make(map[*btf.Spec]*btf.Handle),
+		btfSpecs:   make(map[io.ReaderAt]*btf.Spec),
+	}
+}
+
+func (hc handleCache) btfHandle(spec *btf.Spec) (*btf.Handle, error) {
+	if hc.btfHandles[spec] != nil {
+		return hc.btfHandles[spec], nil
+	}
+
+	handle, err := btf.NewHandle(spec)
+	if err != nil {
+		return nil, err
+	}
+
+	hc.btfHandles[spec] = handle
+	return handle, nil
+}
+
+func (hc handleCache) btfSpec(rd io.ReaderAt) (*btf.Spec, error) {
+	if hc.btfSpecs[rd] != nil {
+		return hc.btfSpecs[rd], nil
+	}
+
+	spec, err := btf.LoadSpecFromReader(rd)
+	if err != nil {
+		return nil, err
+	}
+
+	hc.btfSpecs[rd] = spec
+	return spec, nil
+}
+
+func (hc handleCache) close() {
+	for _, handle := range hc.btfHandles {
+		handle.Close()
+	}
+}
+
+type collectionLoader struct {
+	coll     *CollectionSpec
+	opts     *CollectionOptions
+	maps     map[string]*Map
+	programs map[string]*Program
+	handles  *handleCache
+}
+
+func newCollectionLoader(coll *CollectionSpec, opts *CollectionOptions) *collectionLoader {
+	if opts == nil {
+		opts = &CollectionOptions{}
+	}
+
+	return &collectionLoader{
+		coll,
+		opts,
+		make(map[string]*Map),
+		make(map[string]*Program),
+		newHandleCache(),
+	}
+}
+
+// finalize should be called when all the collectionLoader's resources
+// have been successfully loaded into the kernel and populated with values.
+func (cl *collectionLoader) finalize() {
+	cl.maps, cl.programs = nil, nil
+}
+
+// cleanup cleans up all resources left over in the collectionLoader.
+// Call finalize() when Map and Program creation/population is successful
+// to prevent them from getting closed.
+func (cl *collectionLoader) cleanup() {
+	cl.handles.close()
+	for _, m := range cl.maps {
+		m.Close()
+	}
+	for _, p := range cl.programs {
+		p.Close()
+	}
+}
+
+func (cl *collectionLoader) loadMap(mapName string) (*Map, error) {
+	if m := cl.maps[mapName]; m != nil {
+		return m, nil
+	}
+
+	mapSpec := cl.coll.Maps[mapName]
+	if mapSpec == nil {
+		return nil, fmt.Errorf("missing map %s", mapName)
+	}
+
+	m, err := newMapWithOptions(mapSpec, cl.opts.Maps, cl.handles)
+	if err != nil {
+		return nil, fmt.Errorf("map %s: %w", mapName, err)
+	}
+
+	cl.maps[mapName] = m
+	return m, nil
+}
+
+func (cl *collectionLoader) loadProgram(progName string) (*Program, error) {
+	if prog := cl.programs[progName]; prog != nil {
+		return prog, nil
+	}
+
+	progSpec := cl.coll.Programs[progName]
+	if progSpec == nil {
+		return nil, fmt.Errorf("unknown program %s", progName)
+	}
+
+	progSpec = progSpec.Copy()
+
+	// Rewrite any reference to a valid map.
+	for i := range progSpec.Instructions {
+		ins := &progSpec.Instructions[i]
+
+		if !ins.IsLoadFromMap() || ins.Reference == "" {
+			continue
+		}
+
+		if uint32(ins.Constant) != math.MaxUint32 {
+			// Don't overwrite maps already rewritten, users can
+			// rewrite programs in the spec themselves
+			continue
+		}
+
+		m, err := cl.loadMap(ins.Reference)
+		if err != nil {
+			return nil, fmt.Errorf("program %s: %w", progName, err)
+		}
+
+		fd := m.FD()
+		if fd < 0 {
+			return nil, fmt.Errorf("map %s: %w", ins.Reference, internal.ErrClosedFd)
+		}
+		if err := ins.RewriteMapPtr(m.FD()); err != nil {
+			return nil, fmt.Errorf("program %s: map %s: %w", progName, ins.Reference, err)
+		}
+	}
+
+	prog, err := newProgramWithOptions(progSpec, cl.opts.Programs, cl.handles)
+	if err != nil {
+		return nil, fmt.Errorf("program %s: %w", progName, err)
+	}
+
+	cl.programs[progName] = prog
+	return prog, nil
+}
+
+func (cl *collectionLoader) populateMaps() error {
+	for mapName, m := range cl.maps {
+		mapSpec, ok := cl.coll.Maps[mapName]
+		if !ok {
+			return fmt.Errorf("missing map spec %s", mapName)
+		}
+
+		mapSpec = mapSpec.Copy()
+
+		// Replace any object stubs with loaded objects.
+		for i, kv := range mapSpec.Contents {
+			switch v := kv.Value.(type) {
+			case programStub:
+				// loadProgram is idempotent and could return an existing Program.
+				prog, err := cl.loadProgram(string(v))
+				if err != nil {
+					return fmt.Errorf("loading program %s, for map %s: %w", v, mapName, err)
+				}
+				mapSpec.Contents[i] = MapKV{kv.Key, prog}
+
+			case mapStub:
+				// loadMap is idempotent and could return an existing Map.
+				innerMap, err := cl.loadMap(string(v))
+				if err != nil {
+					return fmt.Errorf("loading inner map %s, for map %s: %w", v, mapName, err)
+				}
+				mapSpec.Contents[i] = MapKV{kv.Key, innerMap}
+			}
+		}
+
+		// Populate and freeze the map if specified.
+		if err := m.finalize(mapSpec); err != nil {
+			return fmt.Errorf("populating map %s: %w", mapName, err)
+		}
+	}
+
+	return nil
+}
+
+// LoadCollection parses an object file and converts it to a collection.
+func LoadCollection(file string) (*Collection, error) {
+	spec, err := LoadCollectionSpec(file)
+	if err != nil {
+		return nil, err
+	}
+	return NewCollection(spec)
+}
+
+// Close frees all maps and programs associated with the collection.
+//
+// The collection mustn't be used afterwards.
+func (coll *Collection) Close() {
+	for _, prog := range coll.Programs {
+		prog.Close()
+	}
+	for _, m := range coll.Maps {
+		m.Close()
+	}
+}
+
+// DetachMap removes the named map from the Collection.
+//
+// This means that a later call to Close() will not affect this map.
+//
+// Returns nil if no map of that name exists.
+func (coll *Collection) DetachMap(name string) *Map {
+	m := coll.Maps[name]
+	delete(coll.Maps, name)
+	return m
+}
+
+// DetachProgram removes the named program from the Collection.
+//
+// This means that a later call to Close() will not affect this program.
+//
+// Returns nil if no program of that name exists.
+func (coll *Collection) DetachProgram(name string) *Program {
+	p := coll.Programs[name]
+	delete(coll.Programs, name)
+	return p
+}
+
+// structField represents a struct field containing the ebpf struct tag.
+type structField struct {
+	reflect.StructField
+	value reflect.Value
+}
+
+// ebpfFields extracts field names tagged with 'ebpf' from a struct type.
+// Keep track of visited types to avoid infinite recursion.
+func ebpfFields(structVal reflect.Value, visited map[reflect.Type]bool) ([]structField, error) {
+	if visited == nil {
+		visited = make(map[reflect.Type]bool)
+	}
+
+	structType := structVal.Type()
+	if structType.Kind() != reflect.Struct {
+		return nil, fmt.Errorf("%s is not a struct", structType)
+	}
+
+	if visited[structType] {
+		return nil, fmt.Errorf("recursion on type %s", structType)
+	}
+
+	fields := make([]structField, 0, structType.NumField())
+	for i := 0; i < structType.NumField(); i++ {
+		field := structField{structType.Field(i), structVal.Field(i)}
+
+		// If the field is tagged, gather it and move on.
+		name := field.Tag.Get("ebpf")
+		if name != "" {
+			fields = append(fields, field)
+			continue
+		}
+
+		// If the field does not have an ebpf tag, but is a struct or a pointer
+		// to a struct, attempt to gather its fields as well.
+		var v reflect.Value
+		switch field.Type.Kind() {
+		case reflect.Ptr:
+			if field.Type.Elem().Kind() != reflect.Struct {
+				continue
+			}
+
+			if field.value.IsNil() {
+				return nil, fmt.Errorf("nil pointer to %s", structType)
+			}
+
+			// Obtain the destination type of the pointer.
+			v = field.value.Elem()
+
+		case reflect.Struct:
+			// Reference the value's type directly.
+			v = field.value
+
+		default:
+			continue
+		}
+
+		inner, err := ebpfFields(v, visited)
+		if err != nil {
+			return nil, fmt.Errorf("field %s: %w", field.Name, err)
+		}
+
+		fields = append(fields, inner...)
+	}
+
+	return fields, nil
+}
+
+// assignValues attempts to populate all fields of 'to' tagged with 'ebpf'.
+//
+// getValue is called for every tagged field of 'to' and must return the value
+// to be assigned to the field with the given typ and name.
+func assignValues(to interface{},
+	getValue func(typ reflect.Type, name string) (interface{}, error)) error {
+
+	toValue := reflect.ValueOf(to)
+	if toValue.Type().Kind() != reflect.Ptr {
+		return fmt.Errorf("%T is not a pointer to struct", to)
+	}
+
+	if toValue.IsNil() {
+		return fmt.Errorf("nil pointer to %T", to)
+	}
+
+	fields, err := ebpfFields(toValue.Elem(), nil)
+	if err != nil {
+		return err
+	}
+
+	type elem struct {
+		// Either *Map or *Program
+		typ  reflect.Type
+		name string
+	}
+
+	assigned := make(map[elem]string)
+	for _, field := range fields {
+		// Get string value the field is tagged with.
+		tag := field.Tag.Get("ebpf")
+		if strings.Contains(tag, ",") {
+			return fmt.Errorf("field %s: ebpf tag contains a comma", field.Name)
+		}
+
+		// Check if the eBPF object with the requested
+		// type and tag was already assigned elsewhere.
+		e := elem{field.Type, tag}
+		if af := assigned[e]; af != "" {
+			return fmt.Errorf("field %s: object %q was already assigned to %s", field.Name, tag, af)
+		}
+
+		// Get the eBPF object referred to by the tag.
+		value, err := getValue(field.Type, tag)
+		if err != nil {
+			return fmt.Errorf("field %s: %w", field.Name, err)
+		}
+
+		if !field.value.CanSet() {
+			return fmt.Errorf("field %s: can't set value", field.Name)
+		}
+		field.value.Set(reflect.ValueOf(value))
+
+		assigned[e] = field.Name
+	}
+
+	return nil
+}