selftests/bpf: Add bpf_fib_lookup test

This patch tests the bpf_fib_lookup helper when looking up
a neigh in NUD_FAILED and NUD_STALE state. It also adds test
for the new BPF_FIB_LOOKUP_SKIP_NEIGH flag.
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230217205515.3583372-2-martin.lau@linux.dev

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+
+#include <sys/types.h>
+#include <net/if.h>
+
+#include "test_progs.h"
+#include "network_helpers.h"
+#include "fib_lookup.skel.h"
+
+#define SYS(fmt, ...)						\
+	({							\
+		char cmd[1024];					\
+		snprintf(cmd, sizeof(cmd), fmt, ##__VA_ARGS__);	\
+		if (!ASSERT_OK(system(cmd), cmd))		\
+			goto fail;				\
+	})
+
+#define NS_TEST			"fib_lookup_ns"
+#define IPV6_IFACE_ADDR		"face::face"
+#define IPV6_NUD_FAILED_ADDR	"face::1"
+#define IPV6_NUD_STALE_ADDR	"face::2"
+#define IPV4_IFACE_ADDR		"10.0.0.254"
+#define IPV4_NUD_FAILED_ADDR	"10.0.0.1"
+#define IPV4_NUD_STALE_ADDR	"10.0.0.2"
+#define DMAC			"11:11:11:11:11:11"
+#define DMAC_INIT { 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, }
+
+struct fib_lookup_test {
+	const char *desc;
+	const char *daddr;
+	int expected_ret;
+	int lookup_flags;
+	__u8 dmac[6];
+};
+
+static const struct fib_lookup_test tests[] = {
+	{ .desc = "IPv6 failed neigh",
+	  .daddr = IPV6_NUD_FAILED_ADDR, .expected_ret = BPF_FIB_LKUP_RET_NO_NEIGH, },
+	{ .desc = "IPv6 stale neigh",
+	  .daddr = IPV6_NUD_STALE_ADDR, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .dmac = DMAC_INIT, },
+	{ .desc = "IPv6 skip neigh",
+	  .daddr = IPV6_NUD_FAILED_ADDR, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH, },
+	{ .desc = "IPv4 failed neigh",
+	  .daddr = IPV4_NUD_FAILED_ADDR, .expected_ret = BPF_FIB_LKUP_RET_NO_NEIGH, },
+	{ .desc = "IPv4 stale neigh",
+	  .daddr = IPV4_NUD_STALE_ADDR, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .dmac = DMAC_INIT, },
+	{ .desc = "IPv4 skip neigh",
+	  .daddr = IPV4_NUD_FAILED_ADDR, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH, },
+};
+
+static int ifindex;
+
+static int setup_netns(void)
+{
+	int err;
+
+	SYS("ip link add veth1 type veth peer name veth2");
+	SYS("ip link set dev veth1 up");
+
+	SYS("ip addr add %s/64 dev veth1 nodad", IPV6_IFACE_ADDR);
+	SYS("ip neigh add %s dev veth1 nud failed", IPV6_NUD_FAILED_ADDR);
+	SYS("ip neigh add %s dev veth1 lladdr %s nud stale", IPV6_NUD_STALE_ADDR, DMAC);
+
+	SYS("ip addr add %s/24 dev veth1 nodad", IPV4_IFACE_ADDR);
+	SYS("ip neigh add %s dev veth1 nud failed", IPV4_NUD_FAILED_ADDR);
+	SYS("ip neigh add %s dev veth1 lladdr %s nud stale", IPV4_NUD_STALE_ADDR, DMAC);
+
+	err = write_sysctl("/proc/sys/net/ipv4/conf/veth1/forwarding", "1");
+	if (!ASSERT_OK(err, "write_sysctl(net.ipv4.conf.veth1.forwarding)"))
+		goto fail;
+
+	err = write_sysctl("/proc/sys/net/ipv6/conf/veth1/forwarding", "1");
+	if (!ASSERT_OK(err, "write_sysctl(net.ipv6.conf.veth1.forwarding)"))
+		goto fail;
+
+	return 0;
+fail:
+	return -1;
+}
+
+static int set_lookup_params(struct bpf_fib_lookup *params, const char *daddr)
+{
+	int ret;
+
+	memset(params, 0, sizeof(*params));
+
+	params->l4_protocol = IPPROTO_TCP;
+	params->ifindex = ifindex;
+
+	if (inet_pton(AF_INET6, daddr, params->ipv6_dst) == 1) {
+		params->family = AF_INET6;
+		ret = inet_pton(AF_INET6, IPV6_IFACE_ADDR, params->ipv6_src);
+		if (!ASSERT_EQ(ret, 1, "inet_pton(IPV6_IFACE_ADDR)"))
+			return -1;
+		return 0;
+	}
+
+	ret = inet_pton(AF_INET, daddr, &params->ipv4_dst);
+	if (!ASSERT_EQ(ret, 1, "convert IP[46] address"))
+		return -1;
+	params->family = AF_INET;
+	ret = inet_pton(AF_INET, IPV4_IFACE_ADDR, &params->ipv4_src);
+	if (!ASSERT_EQ(ret, 1, "inet_pton(IPV4_IFACE_ADDR)"))
+		return -1;
+
+	return 0;
+}
+
+static void mac_str(char *b, const __u8 *mac)
+{
+	sprintf(b, "%02X:%02X:%02X:%02X:%02X:%02X",
+		mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
+}
+
+void test_fib_lookup(void)
+{
+	struct bpf_fib_lookup *fib_params;
+	struct nstoken *nstoken = NULL;
+	struct __sk_buff skb = { };
+	struct fib_lookup *skel;
+	int prog_fd, err, ret, i;
+
+	/* The test does not use the skb->data, so
+	 * use pkt_v6 for both v6 and v4 test.
+	 */
+	LIBBPF_OPTS(bpf_test_run_opts, run_opts,
+		    .data_in = &pkt_v6,
+		    .data_size_in = sizeof(pkt_v6),
+		    .ctx_in = &skb,
+		    .ctx_size_in = sizeof(skb),
+	);
+
+	skel = fib_lookup__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel open_and_load"))
+		return;
+	prog_fd = bpf_program__fd(skel->progs.fib_lookup);
+
+	SYS("ip netns add %s", NS_TEST);
+
+	nstoken = open_netns(NS_TEST);
+	if (!ASSERT_OK_PTR(nstoken, "open_netns"))
+		goto fail;
+
+	if (setup_netns())
+		goto fail;
+
+	ifindex = if_nametoindex("veth1");
+	skb.ifindex = ifindex;
+	fib_params = &skel->bss->fib_params;
+
+	for (i = 0; i < ARRAY_SIZE(tests); i++) {
+		printf("Testing %s\n", tests[i].desc);
+
+		if (set_lookup_params(fib_params, tests[i].daddr))
+			continue;
+		skel->bss->fib_lookup_ret = -1;
+		skel->bss->lookup_flags = BPF_FIB_LOOKUP_OUTPUT |
+			tests[i].lookup_flags;
+
+		err = bpf_prog_test_run_opts(prog_fd, &run_opts);
+		if (!ASSERT_OK(err, "bpf_prog_test_run_opts"))
+			continue;
+
+		ASSERT_EQ(tests[i].expected_ret, skel->bss->fib_lookup_ret,
+			  "fib_lookup_ret");
+
+		ret = memcmp(tests[i].dmac, fib_params->dmac, sizeof(tests[i].dmac));
+		if (!ASSERT_EQ(ret, 0, "dmac not match")) {
+			char expected[18], actual[18];
+
+			mac_str(expected, tests[i].dmac);
+			mac_str(actual, fib_params->dmac);
+			printf("dmac expected %s actual %s\n", expected, actual);
+		}
+	}
+
+fail:
+	if (nstoken)
+		close_netns(nstoken);
+	system("ip netns del " NS_TEST " &> /dev/null");
+	fib_lookup__destroy(skel);
+}

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+
+#include <linux/types.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_tracing_net.h"
+
+struct bpf_fib_lookup fib_params = {};
+int fib_lookup_ret = 0;
+int lookup_flags = 0;
+
+SEC("tc")
+int fib_lookup(struct __sk_buff *skb)
+{
+	fib_lookup_ret = bpf_fib_lookup(skb, &fib_params, sizeof(fib_params),
+					lookup_flags);
+
+	return TC_ACT_SHOT;
+}
+
+char _license[] SEC("license") = "GPL";