tests: Run end to end tests in subtests, replace XDPAction

Currently the end to end tests support checking both the CBPF to C to
EBPF and CBPF to EBPF backends.

Run these in separate subtests so that we can easily check the result of
either, including if both fail.
This introduces a "backend" abstraction to allow us to delay compiling /
doing anything until we are in the subtest.

Have the backend return a result type expressing if the packet matched
the filter, as the XDPDrop == packet matched is an arbitrary construct
that doesn't map well to other potential backends, such as a native cBPF
one.

Author: arthurfabre

c_test.go

@@ -32,11 +32,8 @@ func TestFunctionName(t *testing.T) {
 
 const entryPoint = "xdp_filter"
 
-// loadC compiles classic BPF to C, which is compiled with clang
-// XDPDrop on match, XDPPass otherwise
-func loadC(tb testing.TB, insns []bpf.Instruction) *ebpf.ProgramSpec {
-	tb.Helper()
-
+// cBackend compiles classic BPF to C, which is compiled with clang
+func cBackend(tb testing.TB, insns []bpf.Instruction, in []byte) result {
 	elf, err := buildC(insns, entryPoint)
 	if err != nil {
 		tb.Fatal(err)
@@ -48,5 +45,5 @@ func loadC(tb testing.TB, insns []bpf.Instruction) *ebpf.ProgramSpec {
 		tb.Fatal(err)
 	}
 
-	return spec.Programs[entryPoint]
+	return testProg(tb, spec.Programs[entryPoint], in)
 }

ebpf_test.go

@@ -7,22 +7,19 @@ import (
 	"golang.org/x/net/bpf"
 )
 
-// loadEBPF compiles classic BPF to eBPF
-// XDPDrop on match, XDPPass otherwise
-func loadEBPF(tb testing.TB, insns []bpf.Instruction) *ebpf.ProgramSpec {
-	tb.Helper()
-
+// ebpfBacked is backend that compiles classic BPF to eBPF
+func ebpfBackend(tb testing.TB, insns []bpf.Instruction, in []byte) result {
 	prog, err := buildEBPF(insns)
 	if err != nil {
 		tb.Fatal(err)
 	}
 
 	tb.Logf("\n%v", prog)
 
-	return &ebpf.ProgramSpec{
+	return testProg(tb, &ebpf.ProgramSpec{
 		Name:         "ebpf_filter",
 		Type:         ebpf.XDP,
 		Instructions: prog,
 		License:      "BSD",
-	}
+	}, in)
 }