selftests/bpf: Add netkit test for pkt_type

Add a test case to assert that the skb->pkt_type which was set from the BPF
program is retained from the netkit xmit side to the peer's device at tcx
ingress location.

  # ./vmtest.sh -- ./test_progs -t netkit
  [...]
  ./test_progs -t netkit
  [    1.140780] bpf_testmod: loading out-of-tree module taints kernel.
  [    1.141127] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
  [    1.284601] tsc: Refined TSC clocksource calibration: 3408.006 MHz
  [    1.286672] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x311fd9b189d, max_idle_ns: 440795225691 ns
  [    1.290384] clocksource: Switched to clocksource tsc
  torvalds#345     tc_netkit_basic:OK
  torvalds#346     tc_netkit_device:OK
  torvalds#347     tc_netkit_multi_links:OK
  torvalds#348     tc_netkit_multi_opts:OK
  torvalds#349     tc_netkit_neigh_links:OK
  torvalds#350     tc_netkit_pkt_type:OK
  Summary: 6/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20240524163619.26001-4-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -99,6 +99,16 @@ static int create_netkit(int mode, int policy, int peer_policy, int *ifindex,
 	return err;
 }
 
+static void move_netkit(void)
+{
+	ASSERT_OK(system("ip link set " netkit_peer " netns foo"),
+			 "move peer");
+	ASSERT_OK(system("ip netns exec foo ip link set dev "
+			 netkit_peer " up"), "up peer");
+	ASSERT_OK(system("ip netns exec foo ip addr add dev "
+			 netkit_peer " 10.0.0.2/24"), "addr peer");
+}
+
 static void destroy_netkit(void)
 {
 	ASSERT_OK(system("ip link del dev " netkit_name), "del primary");
@@ -695,3 +705,77 @@ void serial_test_tc_netkit_neigh_links(void)
 	serial_test_tc_netkit_neigh_links_target(NETKIT_L2, BPF_NETKIT_PRIMARY);
 	serial_test_tc_netkit_neigh_links_target(NETKIT_L3, BPF_NETKIT_PRIMARY);
 }
+
+static void serial_test_tc_netkit_pkt_type_mode(int mode)
+{
+	LIBBPF_OPTS(bpf_netkit_opts, optl_nk);
+	LIBBPF_OPTS(bpf_tcx_opts, optl_tcx);
+	int err, ifindex, ifindex2;
+	struct test_tc_link *skel;
+	struct bpf_link *link;
+
+	err = create_netkit(mode, NETKIT_PASS, NETKIT_PASS,
+			    &ifindex, true);
+	if (err)
+		return;
+
+	ifindex2 = if_nametoindex(netkit_peer);
+	ASSERT_NEQ(ifindex, ifindex2, "ifindex_1_2");
+
+	skel = test_tc_link__open();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		goto cleanup;
+
+	ASSERT_EQ(bpf_program__set_expected_attach_type(skel->progs.tc1,
+		  BPF_NETKIT_PRIMARY), 0, "tc1_attach_type");
+	ASSERT_EQ(bpf_program__set_expected_attach_type(skel->progs.tc7,
+		  BPF_TCX_INGRESS), 0, "tc7_attach_type");
+
+	err = test_tc_link__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
+	assert_mprog_count_ifindex(ifindex,  BPF_NETKIT_PRIMARY, 0);
+	assert_mprog_count_ifindex(ifindex2, BPF_TCX_INGRESS, 0);
+
+	link = bpf_program__attach_netkit(skel->progs.tc1, ifindex, &optl_nk);
+	if (!ASSERT_OK_PTR(link, "link_attach"))
+		goto cleanup;
+
+	skel->links.tc1 = link;
+
+	assert_mprog_count_ifindex(ifindex,  BPF_NETKIT_PRIMARY, 1);
+	assert_mprog_count_ifindex(ifindex2, BPF_TCX_INGRESS, 0);
+
+	link = bpf_program__attach_tcx(skel->progs.tc7, ifindex2, &optl_tcx);
+	if (!ASSERT_OK_PTR(link, "link_attach"))
+		goto cleanup;
+
+	skel->links.tc7 = link;
+
+	assert_mprog_count_ifindex(ifindex,  BPF_NETKIT_PRIMARY, 1);
+	assert_mprog_count_ifindex(ifindex2, BPF_TCX_INGRESS, 1);
+
+	move_netkit();
+
+	tc_skel_reset_all_seen(skel);
+	skel->bss->set_type = true;
+	ASSERT_EQ(send_icmp(), 0, "icmp_pkt");
+
+	ASSERT_EQ(skel->bss->seen_tc1, true, "seen_tc1");
+	ASSERT_EQ(skel->bss->seen_tc7, true, "seen_tc7");
+
+	ASSERT_EQ(skel->bss->seen_host,  true, "seen_host");
+	ASSERT_EQ(skel->bss->seen_mcast, true, "seen_mcast");
+cleanup:
+	test_tc_link__destroy(skel);
+
+	assert_mprog_count_ifindex(ifindex,  BPF_NETKIT_PRIMARY, 0);
+	destroy_netkit();
+}
+
+void serial_test_tc_netkit_pkt_type(void)
+{
+	serial_test_tc_netkit_pkt_type_mode(NETKIT_L2);
+	serial_test_tc_netkit_pkt_type_mode(NETKIT_L3);
+}

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

@@ -4,7 +4,8 @@
 
 #include <linux/bpf.h>
 #include <linux/if_ether.h>
-
+#include <linux/stddef.h>
+#include <linux/if_packet.h>
 #include <bpf/bpf_endian.h>
 #include <bpf/bpf_helpers.h>
 
@@ -16,7 +17,13 @@ bool seen_tc3;
 bool seen_tc4;
 bool seen_tc5;
 bool seen_tc6;
+bool seen_tc7;
+
+bool set_type;
+
 bool seen_eth;
+bool seen_host;
+bool seen_mcast;
 
 SEC("tc/ingress")
 int tc1(struct __sk_buff *skb)
@@ -28,8 +35,16 @@ int tc1(struct __sk_buff *skb)
 	if (bpf_skb_load_bytes(skb, 0, &eth, sizeof(eth)))
 		goto out;
 	seen_eth = eth.h_proto == bpf_htons(ETH_P_IP);
+	seen_host = skb->pkt_type == PACKET_HOST;
+	if (seen_host && set_type) {
+		eth.h_dest[0] = 4;
+		if (bpf_skb_store_bytes(skb, 0, &eth, sizeof(eth), 0))
+			goto fail;
+		bpf_skb_change_type(skb, PACKET_MULTICAST);
+	}
 out:
 	seen_tc1 = true;
+fail:
 	return TCX_NEXT;
 }
 
@@ -67,3 +82,21 @@ int tc6(struct __sk_buff *skb)
 	seen_tc6 = true;
 	return TCX_PASS;
 }
+
+SEC("tc/ingress")
+int tc7(struct __sk_buff *skb)
+{
+	struct ethhdr eth = {};
+
+	if (skb->protocol != __bpf_constant_htons(ETH_P_IP))
+		goto out;
+	if (bpf_skb_load_bytes(skb, 0, &eth, sizeof(eth)))
+		goto out;
+	if (eth.h_dest[0] == 4 && set_type) {
+		seen_mcast = skb->pkt_type == PACKET_MULTICAST;
+		bpf_skb_change_type(skb, PACKET_HOST);
+	}
+out:
+	seen_tc7 = true;
+	return TCX_PASS;
+}