selftests/bpf: Test wire_len/gso_segs in BPF_PROG_TEST_RUN

Make sure we can pass arbitrary data in wire_len/gso_segs.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191213223028.161282-2-sdf@google.com

tools/testing/selftests/bpf/prog_tests/skb_ctx.c

@@ -11,6 +11,8 @@ void test_skb_ctx(void)
 		.cb[4] = 5,
 		.priority = 6,
 		.tstamp = 7,
+		.wire_len = 100,
+		.gso_segs = 8,
 	};
 	struct bpf_prog_test_run_attr tattr = {
 		.data_in = &pkt_v4,

tools/testing/selftests/bpf/progs/test_skb_ctx.c

@@ -18,5 +18,10 @@ int process(struct __sk_buff *skb)
 	skb->priority++;
 	skb->tstamp++;
 
+	if (skb->wire_len != 100)
+		return 1;
+	if (skb->gso_segs != 8)
+		return 1;
+
 	return 0;
 }