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
  #345     tc_netkit_basic:OK
  #346     tc_netkit_device:OK
  #347     tc_netkit_multi_links:OK
  #348     tc_netkit_multi_opts:OK
  #349     tc_netkit_neigh_links:OK
  #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>

1 files changed, 34 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_tc_link.c b/tools/testing/selftests/bpf/progs/test_tc_link.c
index 992400acb957..ab3eae3d6af8 100644
--- a/tools/testing/selftests/bpf/progs/test_tc_link.c
+++ b/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;
+}