mirror of
https://github.com/superseriousbusiness/gotosocial
synced 2024-12-08 22:46:19 +01:00
215 lines
4.7 KiB
Go
215 lines
4.7 KiB
Go
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package link
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import (
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"fmt"
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"unsafe"
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"github.com/cilium/ebpf"
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"github.com/cilium/ebpf/internal"
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)
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var ErrNotSupported = internal.ErrNotSupported
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// Link represents a Program attached to a BPF hook.
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type Link interface {
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// Replace the current program with a new program.
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//
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// Passing a nil program is an error. May return an error wrapping ErrNotSupported.
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Update(*ebpf.Program) error
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// Persist a link by pinning it into a bpffs.
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//
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// May return an error wrapping ErrNotSupported.
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Pin(string) error
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// Close frees resources.
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//
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// The link will be broken unless it has been pinned. A link
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// may continue past the lifetime of the process if Close is
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// not called.
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Close() error
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// Prevent external users from implementing this interface.
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isLink()
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}
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// ID uniquely identifies a BPF link.
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type ID uint32
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// RawLinkOptions control the creation of a raw link.
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type RawLinkOptions struct {
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// File descriptor to attach to. This differs for each attach type.
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Target int
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// Program to attach.
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Program *ebpf.Program
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// Attach must match the attach type of Program.
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Attach ebpf.AttachType
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}
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// RawLinkInfo contains metadata on a link.
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type RawLinkInfo struct {
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Type Type
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ID ID
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Program ebpf.ProgramID
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}
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// RawLink is the low-level API to bpf_link.
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//
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// You should consider using the higher level interfaces in this
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// package instead.
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type RawLink struct {
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fd *internal.FD
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}
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// AttachRawLink creates a raw link.
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func AttachRawLink(opts RawLinkOptions) (*RawLink, error) {
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if err := haveBPFLink(); err != nil {
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return nil, err
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}
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if opts.Target < 0 {
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return nil, fmt.Errorf("invalid target: %s", internal.ErrClosedFd)
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}
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progFd := opts.Program.FD()
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if progFd < 0 {
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return nil, fmt.Errorf("invalid program: %s", internal.ErrClosedFd)
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}
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attr := bpfLinkCreateAttr{
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targetFd: uint32(opts.Target),
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progFd: uint32(progFd),
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attachType: opts.Attach,
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}
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fd, err := bpfLinkCreate(&attr)
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if err != nil {
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return nil, fmt.Errorf("can't create link: %s", err)
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}
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return &RawLink{fd}, nil
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}
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// LoadPinnedRawLink loads a persisted link from a bpffs.
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func LoadPinnedRawLink(fileName string) (*RawLink, error) {
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return loadPinnedRawLink(fileName, UnspecifiedType)
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}
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func loadPinnedRawLink(fileName string, typ Type) (*RawLink, error) {
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fd, err := internal.BPFObjGet(fileName)
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if err != nil {
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return nil, fmt.Errorf("load pinned link: %s", err)
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}
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link := &RawLink{fd}
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if typ == UnspecifiedType {
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return link, nil
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}
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info, err := link.Info()
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if err != nil {
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link.Close()
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return nil, fmt.Errorf("get pinned link info: %s", err)
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}
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if info.Type != typ {
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link.Close()
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return nil, fmt.Errorf("link type %v doesn't match %v", info.Type, typ)
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}
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return link, nil
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}
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func (l *RawLink) isLink() {}
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// FD returns the raw file descriptor.
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func (l *RawLink) FD() int {
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fd, err := l.fd.Value()
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if err != nil {
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return -1
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}
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return int(fd)
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}
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// Close breaks the link.
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//
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// Use Pin if you want to make the link persistent.
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func (l *RawLink) Close() error {
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return l.fd.Close()
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}
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// Pin persists a link past the lifetime of the process.
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//
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// Calling Close on a pinned Link will not break the link
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// until the pin is removed.
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func (l *RawLink) Pin(fileName string) error {
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if err := internal.BPFObjPin(fileName, l.fd); err != nil {
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return fmt.Errorf("can't pin link: %s", err)
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}
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return nil
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}
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// Update implements Link.
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func (l *RawLink) Update(new *ebpf.Program) error {
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return l.UpdateArgs(RawLinkUpdateOptions{
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New: new,
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})
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}
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// RawLinkUpdateOptions control the behaviour of RawLink.UpdateArgs.
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type RawLinkUpdateOptions struct {
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New *ebpf.Program
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Old *ebpf.Program
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Flags uint32
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}
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// UpdateArgs updates a link based on args.
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func (l *RawLink) UpdateArgs(opts RawLinkUpdateOptions) error {
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newFd := opts.New.FD()
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if newFd < 0 {
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return fmt.Errorf("invalid program: %s", internal.ErrClosedFd)
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}
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var oldFd int
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if opts.Old != nil {
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oldFd = opts.Old.FD()
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if oldFd < 0 {
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return fmt.Errorf("invalid replacement program: %s", internal.ErrClosedFd)
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}
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}
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linkFd, err := l.fd.Value()
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if err != nil {
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return fmt.Errorf("can't update link: %s", err)
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}
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attr := bpfLinkUpdateAttr{
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linkFd: linkFd,
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newProgFd: uint32(newFd),
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oldProgFd: uint32(oldFd),
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flags: opts.Flags,
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}
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return bpfLinkUpdate(&attr)
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}
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// struct bpf_link_info
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type bpfLinkInfo struct {
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typ uint32
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id uint32
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prog_id uint32
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}
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// Info returns metadata about the link.
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func (l *RawLink) Info() (*RawLinkInfo, error) {
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var info bpfLinkInfo
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err := internal.BPFObjGetInfoByFD(l.fd, unsafe.Pointer(&info), unsafe.Sizeof(info))
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if err != nil {
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return nil, fmt.Errorf("link info: %s", err)
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}
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return &RawLinkInfo{
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Type(info.typ),
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ID(info.id),
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ebpf.ProgramID(info.prog_id),
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}, nil
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}
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