link: add Detach()

Signed-off-by: Florian Lehner <[email protected]>

Author: florianl

internal/cmd/gentypes/main.go

@@ -609,6 +609,10 @@ import (
 				rename("relative_fd", "relative_fd_or_id"),
 			},
 		},
+		{
+			"LinkDetach", retError, "link_detach", "BPF_LINK_DETACH",
+			nil,
+		},
 		{
 			"LinkUpdate", retError, "link_update", "BPF_LINK_UPDATE",
 			nil,

internal/sys/types.go

@@ -1064,6 +1064,16 @@ func LinkCreateUprobeMulti(attr *LinkCreateUprobeMultiAttr) (*FD, error) {
 	return NewFD(int(fd))
 }
 
+type LinkDetachAttr struct {
+	_      structs.HostLayout
+	LinkFd uint32
+}
+
+func LinkDetach(attr *LinkDetachAttr) error {
+	_, err := BPF(BPF_LINK_DETACH, unsafe.Pointer(attr), unsafe.Sizeof(*attr))
+	return err
+}
+
 type LinkGetFdByIdAttr struct {
 	_  structs.HostLayout
 	Id LinkID

link/cgroup.go

@@ -167,6 +167,10 @@ func (cg *progAttachCgroup) Unpin() error {
 	return fmt.Errorf("can't unpin cgroup: %w", ErrNotSupported)
 }
 
+func (cg *progAttachCgroup) Detach() error {
+	return fmt.Errorf("can't detach cgroup: %w", ErrNotSupported)
+}
+
 func (cg *progAttachCgroup) Info() (*Info, error) {
 	return nil, fmt.Errorf("can't get cgroup info: %w", ErrNotSupported)
 }

link/link.go

@@ -9,6 +9,7 @@ import (
 	"github.com/cilium/ebpf/btf"
 	"github.com/cilium/ebpf/internal"
 	"github.com/cilium/ebpf/internal/sys"
+	"github.com/cilium/ebpf/internal/unix"
 )
 
 // Type is the kind of link.
@@ -40,6 +41,11 @@ type Link interface {
 	// not called.
 	Close() error
 
+	// Detach the link from its corresponding attachment point.
+	//
+	// May return an error wrapping ErrNotSupported.
+	Detach() error
+
 	// Info returns metadata on a link.
 	//
 	// May return an error wrapping ErrNotSupported.
@@ -225,6 +231,24 @@ func (l *RawLink) UpdateArgs(opts RawLinkUpdateOptions) error {
 	return nil
 }
 
+// Detach the link from its corresponding attachment point.
+func (l *RawLink) Detach() error {
+	attr := sys.LinkDetachAttr{
+		LinkFd: l.fd.Uint(),
+	}
+
+	err := sys.LinkDetach(&attr)
+
+	switch {
+	case errors.Is(err, unix.EOPNOTSUPP):
+		return internal.ErrNotSupported
+	case err != nil:
+		return fmt.Errorf("detach link: %w", err)
+	default:
+		return nil
+	}
+}
+
 // Info returns metadata about the link.
 //
 // Linktype specific metadata is not included and can be retrieved

link/link_other_test.go

@@ -141,3 +141,15 @@ func mustLoadProgram(tb testing.TB, typ ebpf.ProgramType, attachType ebpf.Attach
 
 	return prog
 }
+
+func TestDetachLinkFail(t *testing.T) {
+	prog := mustLoadProgram(t, ebpf.Kprobe, 0, "")
+	defer prog.Close()
+
+	uprobeLink, err := bashEx.Uprobe(bashSym, prog, nil)
+	qt.Assert(t, qt.IsNil(err))
+	defer uprobeLink.Close()
+
+	err = uprobeLink.Detach()
+	qt.Assert(t, qt.ErrorIs(err, ErrNotSupported), qt.Commentf("got error: %s", err))
+}

link/link_test.go

@@ -56,6 +56,14 @@ func TestUnpinRawLink(t *testing.T) {
 	qt.Assert(t, qt.IsFalse(link.IsPinned()))
 }
 
+func TestDetachRawLink(t *testing.T) {
+	link, _ := newRawLink(t)
+
+	if err := link.Detach(); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestRawLinkLoadPinnedWithOptions(t *testing.T) {
 	link, path := newPinnedRawLink(t)
 	defer link.Close()

link/perf_event.go

@@ -199,6 +199,10 @@ func (pi *perfEventIoctl) Unpin() error {
 	return fmt.Errorf("perf event ioctl unpin: %w", ErrNotSupported)
 }
 
+func (pi *perfEventIoctl) Detach() error {
+	return fmt.Errorf("perf event ioctl detach: %w", ErrNotSupported)
+}
+
 func (pi *perfEventIoctl) Info() (*Info, error) {
 	return nil, fmt.Errorf("perf event ioctl info: %w", ErrNotSupported)
 }

link/raw_tracepoint.go

@@ -74,6 +74,10 @@ func (frt *simpleRawTracepoint) Unpin() error {
 	return fmt.Errorf("unpin raw_tracepoint: %w", ErrNotSupported)
 }
 
+func (frt *simpleRawTracepoint) Detach() error {
+	return fmt.Errorf("detach raw_tracepoint: %w", ErrNotSupported)
+}
+
 func (frt *simpleRawTracepoint) Info() (*Info, error) {
 	return nil, fmt.Errorf("can't get raw_tracepoint info: %w", ErrNotSupported)
 }