feat: export netkit and tcx probes

Export the two feature probes for users. These are quite useful and in
particular the one for netkit is needed for Cilium to throw an error
earlier.

Signed-off-by: Daniel Borkmann <[email protected]>
Link: cilium/cilium#33878

link/syscalls.go

@@ -129,6 +129,15 @@ var haveProgQuery = internal.NewFeatureTest("BPF_PROG_QUERY", func() error {
 	return errors.New("syscall succeeded unexpectedly")
 }, "4.15")
 
+// HaveTCX probes the running kernel for the availability of the tcx layer.
+//
+// Upstream commit e420bed0250 ("bpf: Add fd-based tcx multi-prog infra with link support")
+//
+// See the package documentation for the meaning of the error return value.
+func HaveTCX() error {
+	return haveTCX()
+}
+
 var haveTCX = internal.NewFeatureTest("tcx", func() error {
 	prog, err := ebpf.NewProgram(&ebpf.ProgramSpec{
 		Type:    ebpf.SchedCLS,
@@ -164,6 +173,15 @@ var haveTCX = internal.NewFeatureTest("tcx", func() error {
 	return errors.New("syscall succeeded unexpectedly")
 }, "6.6")
 
+// HaveNetkit probes the running kernel for the availability of netkit devices.
+//
+// Upstream commit 35dfaad7188c ("netkit, bpf: Add bpf programmable net device")
+//
+// See the package documentation for the meaning of the error return value.
+func HaveNetkit() error {
+	return haveNetkit()
+}
+
 var haveNetkit = internal.NewFeatureTest("netkit", func() error {
 	prog, err := ebpf.NewProgram(&ebpf.ProgramSpec{
 		Type:    ebpf.SchedCLS,