link: add Cookie to Tracing and LSM opts

Signed-off-by: Mattia Meleleo <[email protected]>

link/tracing.go

@@ -96,16 +96,22 @@ type TracingOptions struct {
 	// If empty (AttachNone), the legacy attach method via raw tracepoint
 	// open will be used.
 	AttachType ebpf.AttachType
+	// Arbitrary value that can be fetched from an eBPF program
+	// via `bpf_get_attach_cookie()`.
+	Cookie uint64
 }
 
 type LSMOptions struct {
 	// Program must be of type LSM with attach type
 	// AttachLSMMac.
 	Program *ebpf.Program
+	// Arbitrary value that can be fetched from an eBPF program
+	// via `bpf_get_attach_cookie()`.
+	Cookie uint64
 }
 
 // attachBTFID links all BPF program types (Tracing/LSM) that they attach to a btf_id.
-func attachBTFID(program *ebpf.Program, at ebpf.AttachType) (Link, error) {
+func attachBTFID(program *ebpf.Program, at ebpf.AttachType, cookie uint64) (Link, error) {
 	if program.FD() < 0 {
 		return nil, fmt.Errorf("invalid program %w", sys.ErrClosedFd)
 	}
@@ -121,6 +127,7 @@ func attachBTFID(program *ebpf.Program, at ebpf.AttachType) (Link, error) {
 		fd, err = sys.LinkCreateTracing(&sys.LinkCreateTracingAttr{
 			ProgFd:     uint32(program.FD()),
 			AttachType: sys.AttachType(at),
+			Cookie:     cookie,
 		})
 		if err == nil {
 			break
@@ -131,6 +138,10 @@ func attachBTFID(program *ebpf.Program, at ebpf.AttachType) (Link, error) {
 		fallthrough
 	case ebpf.AttachNone:
 		// Attach via RawTracepointOpen
+		if cookie > 0 {
+			return nil, fmt.Errorf("create raw tracepoint with cookie: %w", ErrNotSupported)
+		}
+
 		fd, err = sys.RawTracepointOpen(&sys.RawTracepointOpenAttr{
 			ProgFd: uint32(program.FD()),
 		})
@@ -168,7 +179,7 @@ func AttachTracing(opts TracingOptions) (Link, error) {
 		return nil, fmt.Errorf("invalid program type %s, expected Tracing", t)
 	}
 
-	return attachBTFID(opts.Program, opts.AttachType)
+	return attachBTFID(opts.Program, opts.AttachType, opts.Cookie)
 }
 
 // AttachLSM links a Linux security module (LSM) BPF Program to a BPF
@@ -178,5 +189,5 @@ func AttachLSM(opts LSMOptions) (Link, error) {
 		return nil, fmt.Errorf("invalid program type %s, expected LSM", t)
 	}
 
-	return attachBTFID(opts.Program, ebpf.AttachLSMMac)
+	return attachBTFID(opts.Program, ebpf.AttachLSMMac, opts.Cookie)
 }

link/tracing_test.go

@@ -1,7 +1,6 @@
 package link
 
 import (
-	"fmt"
 	"testing"
 
 	"github.com/cilium/ebpf"
@@ -85,30 +84,27 @@ func TestTracing(t *testing.T) {
 
 	test := func(
 		t *testing.T,
-		method string,
-		pt ebpf.ProgramType,
-		at ebpf.AttachType,
-		ato string,
-		atOpt ebpf.AttachType) {
-		prog := mustLoadProgram(t, pt, at, ato)
-		link, err := AttachTracing(TracingOptions{Program: prog, AttachType: atOpt})
-		err2 := fmt.Errorf("%s: %w", method, err)
-		testutils.SkipIfNotSupported(t, err2)
+		programType ebpf.ProgramType,
+		attachType ebpf.AttachType,
+		attachTo string,
+		attachTypeOpt ebpf.AttachType) {
+		prog := mustLoadProgram(t, programType, attachType, attachTo)
+
+		link, err := AttachTracing(TracingOptions{Program: prog, AttachType: attachTypeOpt})
+		testutils.SkipIfNotSupported(t, err)
 		if err != nil {
-			t.Fatal(err2)
-		}
-		testLink(t, link, prog)
-		if err = link.Close(); err != nil {
 			t.Fatal(err)
 		}
+		testLink(t, link, prog)
+		link.Close()
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			// exercise attach via BPF link
-			test(t, "bpf_link", tt.programType, tt.attachType, tt.attachTo, tt.attachType)
+			test(t, tt.programType, tt.attachType, tt.attachTo, tt.attachType)
 			// exercise legacy attach via RawTracepointOpen
-			test(t, "raw_tracepoint_open", tt.programType, tt.attachType, tt.attachTo, ebpf.AttachNone)
+			test(t, tt.programType, tt.attachType, tt.attachTo, ebpf.AttachNone)
 		})
 	}
 }