link: add Replace, Before, After WIP

- Is this a good idea? Signed-off-by: Lorenz Bauer <[email protected]>
cilium · Oct 10, 2023 · 660b2b3 · 660b2b3
1 parent 7dd5e97
commit 660b2b3
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Showing 5 changed files with 42 additions and 16 deletions.
diff --git a/link/anchor.go b/link/anchor.go
@@ -7,7 +7,11 @@ import (
 	"github.com/cilium/ebpf/internal/sys"
 )
 
-const anchorTypeFlags = sys.BPF_F_LINK_MPROG | sys.BPF_F_ID
+const anchorFlags = sys.BPF_F_REPLACE |
+	sys.BPF_F_BEFORE |
+	sys.BPF_F_AFTER |
+	sys.BPF_F_ID |
+	sys.BPF_F_LINK_MPROG
 
 type AttachAnchor interface {
 	target() (fdOrID uint32, flags uint32, _ error)
@@ -72,3 +76,26 @@ type anchorProgramID struct {
 func (apid *anchorProgramID) target() (uint32, uint32, error) {
 	return uint32(apid.Program), sys.BPF_F_ID, nil
 }
+
+func Before(anchor AttachAnchor) AttachAnchor {
+	return anchorPosition{anchor, sys.BPF_F_BEFORE}
+}
+
+func After(anchor AttachAnchor) AttachAnchor {
+	return anchorPosition{anchor, sys.BPF_F_AFTER}
+}
+
+func Replace(anchor AttachAnchor) AttachAnchor {
+	return anchorPosition{anchor, sys.BPF_F_REPLACE}
+}
+
+type anchorPosition struct {
+	anchor AttachAnchor
+	flag   uint32
+}
+
+func (ap anchorPosition) target() (uint32, uint32, error) {
+	fdOrId, flags, err := ap.anchor.target()
+	flags |= ap.flag
+	return fdOrId, flags, err
+}
diff --git a/link/program.go b/link/program.go
@@ -28,8 +28,8 @@ type RawAttachProgramOptions struct {
 // You should use one of the higher level abstractions available in this
 // package if possible.
 func RawAttachProgram(opts RawAttachProgramOptions) error {
-	if opts.Flags&anchorTypeFlags != 0 {
-		return fmt.Errorf("don't specify attach target type in flags")
+	if opts.Flags&anchorFlags != 0 {
+		return fmt.Errorf("disallowed flags: use Anchor to specify attach target")
 	}
 
 	attr := sys.ProgAttachAttr{
@@ -80,6 +80,10 @@ type RawDetachProgramOptions struct {
 // You should use one of the higher level abstractions available in this
 // package if possible.
 func RawDetachProgram(opts RawDetachProgramOptions) error {
+	if opts.Flags&anchorFlags != 0 {
+		return fmt.Errorf("disallowed flags: use Anchor to specify attach target")
+	}
+
 	attr := sys.ProgDetachAttr{
 		TargetFdOrIfindex: uint32(opts.Target),
 		AttachBpfFd:       uint32(opts.Program.FD()),

diff --git a/link/program_test.go b/link/program_test.go
@@ -6,7 +6,6 @@ import (
 	"testing"
 
 	"github.com/cilium/ebpf"
-	"github.com/cilium/ebpf/internal/sys"
 	"github.com/cilium/ebpf/internal/testutils"
 
 	qt "github.com/frankban/quicktest"
@@ -95,17 +94,15 @@ func TestRawAttachProgramAnchor(t *testing.T) {
 				Target:  iface.Index,
 				Program: b,
 				Attach:  ebpf.AttachTCXIngress,
-				Anchor:  anchor,
-				Flags:   sys.BPF_F_AFTER,
+				Anchor:  After(anchor),
 			})
 			qt.Assert(t, err, qt.IsNil)
 
 			err = RawDetachProgram(RawDetachProgramOptions{
 				Target:  iface.Index,
 				Program: b,
 				Attach:  ebpf.AttachTCXIngress,
-				Anchor:  anchor,
-				Flags:   sys.BPF_F_AFTER,
+				Anchor:  After(anchor),
 			})
 			qt.Assert(t, err, qt.IsNil)
 		})
@@ -116,8 +113,7 @@ func TestRawAttachProgramAnchor(t *testing.T) {
 		Target:  iface.Index,
 		Program: b,
 		Attach:  ebpf.AttachTCXIngress,
-		Anchor:  AnchorProgram(a),
-		Flags:   sys.BPF_F_REPLACE,
+		Anchor:  Replace(AnchorProgram(a)),
 	})
 	qt.Assert(t, err, qt.IsNil)
 

diff --git a/link/tcx.go b/link/tcx.go
@@ -27,8 +27,8 @@ func AttachTCX(opts TCXOptions) (Link, error) {
 		return nil, fmt.Errorf("interface %d is out of bounds", opts.Interface)
 	}
 
-	if opts.Flags&anchorTypeFlags != 0 {
-		return nil, fmt.Errorf("don't specify attach target type in flags")
+	if opts.Flags&anchorFlags != 0 {
+		return nil, fmt.Errorf("disallowed flags: use Anchor to specify attach target")
 	}
 
 	attr := sys.LinkCreateTcxAttr{

diff --git a/link/tcx_test.go b/link/tcx_test.go
@@ -6,11 +6,11 @@ import (
 	"net"
 	"testing"
 
+	qt "github.com/frankban/quicktest"
+
 	"github.com/cilium/ebpf"
-	"github.com/cilium/ebpf/internal/sys"
 	"github.com/cilium/ebpf/internal/testutils"
 	"github.com/cilium/ebpf/internal/unix"
-	qt "github.com/frankban/quicktest"
 )
 
 func TestTCX(t *testing.T) {
@@ -49,8 +49,7 @@ func TestTCXAnchor(t *testing.T) {
 				Program:   b,
 				Attach:    ebpf.AttachTCXEgress,
 				Interface: iface,
-				Anchor:    anchor,
-				Flags:     sys.BPF_F_AFTER,
+				Anchor:    After(anchor),
 			})
 			qt.Assert(t, err, qt.IsNil)
 			qt.Assert(t, linkB.Close(), qt.IsNil)