bpf/flow_dissector: don't adjust nhoff by ETH_HLEN in BPF_PROG_TEST_RUN

Now that we use skb-less flow dissector let's return true nhoff and
thoff. We used to adjust them by ETH_HLEN because that's how it was
done in the skb case. For VLAN tests that looks confusing: nhoff is
pointing to vlan parts :-\

Warning, this is an API change for BPF_PROG_TEST_RUN! Feel free to drop
if you think that it's too late at this point to fix it.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

net/bpf/test_run.c

@@ -418,9 +418,6 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
 		retval = bpf_flow_dissect(prog, &ctx, eth->h_proto, ETH_HLEN,
 					  size);
 
-		flow_keys.nhoff -= ETH_HLEN;
-		flow_keys.thoff -= ETH_HLEN;
-
 		if (signal_pending(current)) {
 			preempt_enable();
 			rcu_read_unlock();

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

@@ -82,8 +82,8 @@ struct test tests[] = {
 			.tcp.doff = 5,
 		},
 		.keys = {
-			.nhoff = 0,
-			.thoff = sizeof(struct iphdr),
+			.nhoff = ETH_HLEN,
+			.thoff = ETH_HLEN + sizeof(struct iphdr),
 			.addr_proto = ETH_P_IP,
 			.ip_proto = IPPROTO_TCP,
 			.n_proto = __bpf_constant_htons(ETH_P_IP),
@@ -98,8 +98,8 @@ struct test tests[] = {
 			.tcp.doff = 5,
 		},
 		.keys = {
-			.nhoff = 0,
-			.thoff = sizeof(struct ipv6hdr),
+			.nhoff = ETH_HLEN,
+			.thoff = ETH_HLEN + sizeof(struct ipv6hdr),
 			.addr_proto = ETH_P_IPV6,
 			.ip_proto = IPPROTO_TCP,
 			.n_proto = __bpf_constant_htons(ETH_P_IPV6),
@@ -116,8 +116,8 @@ struct test tests[] = {
 			.tcp.doff = 5,
 		},
 		.keys = {
-			.nhoff = VLAN_HLEN,
-			.thoff = VLAN_HLEN + sizeof(struct iphdr),
+			.nhoff = ETH_HLEN + VLAN_HLEN,
+			.thoff = ETH_HLEN + VLAN_HLEN + sizeof(struct iphdr),
 			.addr_proto = ETH_P_IP,
 			.ip_proto = IPPROTO_TCP,
 			.n_proto = __bpf_constant_htons(ETH_P_IP),
@@ -134,8 +134,9 @@ struct test tests[] = {
 			.tcp.doff = 5,
 		},
 		.keys = {
-			.nhoff = VLAN_HLEN * 2,
-			.thoff = VLAN_HLEN * 2 + sizeof(struct ipv6hdr),
+			.nhoff = ETH_HLEN + VLAN_HLEN * 2,
+			.thoff = ETH_HLEN + VLAN_HLEN * 2 +
+				sizeof(struct ipv6hdr),
 			.addr_proto = ETH_P_IPV6,
 			.ip_proto = IPPROTO_TCP,
 			.n_proto = __bpf_constant_htons(ETH_P_IPV6),
@@ -238,9 +239,6 @@ void test_flow_dissector(void)
 	 * We use a known path in the net/tun driver that calls
 	 * eth_get_headlen and we manually export bpf_flow_keys
 	 * via BPF map in this case.
-	 *
-	 * Note, that since eth_get_headlen operates on a L2 level,
-	 * we adjust exported nhoff/thoff by ETH_HLEN.
 	 */
 
 	err = bpf_prog_attach(prog_fd, 0, BPF_FLOW_DISSECTOR, 0);
@@ -262,9 +260,6 @@ void test_flow_dissector(void)
 		err = bpf_map_lookup_elem(keys_fd, &key, &flow_keys);
 		CHECK_ATTR(err, tests[i].name, "bpf_map_lookup_elem %d\n", err);
 
-		flow_keys.nhoff -= ETH_HLEN;
-		flow_keys.thoff -= ETH_HLEN;
-
 		CHECK_ATTR(err, tests[i].name, "skb-less err %d\n", err);
 		CHECK_FLOW_KEYS(tests[i].name, flow_keys, tests[i].keys);
 	}