syscalls: omit AttachType field in haveProgAttach

Discovered while running the test suite on kernel 4.14.

With the addition BPF_PROG_ATTACH tests in package link, the haveProgAttach
feature test was added, gated on 4.10. This helper uses the AttachType field,
which sets the bpf_attr expected_attach_type field, which is only available
as of 4.17. As probing CGroupSKB is sufficient, omit setting AttachType.

This patch fixes the tests on kernels between 4.10 and 4.17.

Signed-off-by: Timo Beckers <timo@isovalent.com>

link/syscalls.go

@@ -27,9 +27,8 @@ const (
 
 var haveProgAttach = internal.FeatureTest("BPF_PROG_ATTACH", "4.10", func() error {
 	prog, err := ebpf.NewProgram(&ebpf.ProgramSpec{
-		Type:       ebpf.CGroupSKB,
-		AttachType: ebpf.AttachCGroupInetIngress,
-		License:    "MIT",
+		Type:    ebpf.CGroupSKB,
+		License: "MIT",
 		Instructions: asm.Instructions{
 			asm.Mov.Imm(asm.R0, 0),
 			asm.Return(),

prog.go

@@ -58,7 +58,12 @@ type ProgramSpec struct {
 	Name string
 
 	// Type determines at which hook in the kernel a program will run.
-	Type       ProgramType
+	Type ProgramType
+
+	// AttachType of the program, needed to differentiate allowed context
+	// accesses in some newer program types like CGroupSockAddr.
+	//
+	// Available on kernels 4.17 and later.
 	AttachType AttachType
 
 	// Name of a kernel data structure or function to attach to. Its