bpf, selftests: Add redirect_neigh selftest

Add a small test that exercises the new redirect_neigh() helper for the
IPv4 and IPv6 case.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/0fc7d9c5f9a6cc1c65b0d3be83b44b1ec9889f43.1601477936.git.daniel@iogearbox.net

1 files changed, 144 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_tc_neigh.c b/tools/testing/selftests/bpf/progs/test_tc_neigh.c
new file mode 100644
index 000000000000..889a72c3024f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_tc_neigh.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <linux/bpf.h>
+#include <linux/stddef.h>
+#include <linux/pkt_cls.h>
+#include <linux/if_ether.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+#ifndef barrier_data
+# define barrier_data(ptr)	asm volatile("": :"r"(ptr) :"memory")
+#endif
+
+#ifndef ctx_ptr
+# define ctx_ptr(field)		(void *)(long)(field)
+#endif
+
+#define dst_to_src_tmp		0xeeddddeeU
+#define src_to_dst_tmp		0xeeffffeeU
+
+#define ip4_src			0xac100164 /* 172.16.1.100 */
+#define ip4_dst			0xac100264 /* 172.16.2.100 */
+
+#define ip6_src			{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
+				  0x00, 0x01, 0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe }
+#define ip6_dst			{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
+				  0x00, 0x02, 0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe }
+
+#ifndef v6_equal
+# define v6_equal(a, b)		(a.s6_addr32[0] == b.s6_addr32[0] && \
+				 a.s6_addr32[1] == b.s6_addr32[1] && \
+				 a.s6_addr32[2] == b.s6_addr32[2] && \
+				 a.s6_addr32[3] == b.s6_addr32[3])
+#endif
+
+static __always_inline bool is_remote_ep_v4(struct __sk_buff *skb,
+					    __be32 addr)
+{
+	void *data_end = ctx_ptr(skb->data_end);
+	void *data = ctx_ptr(skb->data);
+	struct iphdr *ip4h;
+
+	if (data + sizeof(struct ethhdr) > data_end)
+		return false;
+
+	ip4h = (struct iphdr *)(data + sizeof(struct ethhdr));
+	if ((void *)(ip4h + 1) > data_end)
+		return false;
+
+	return ip4h->daddr == addr;
+}
+
+static __always_inline bool is_remote_ep_v6(struct __sk_buff *skb,
+					    struct in6_addr addr)
+{
+	void *data_end = ctx_ptr(skb->data_end);
+	void *data = ctx_ptr(skb->data);
+	struct ipv6hdr *ip6h;
+
+	if (data + sizeof(struct ethhdr) > data_end)
+		return false;
+
+	ip6h = (struct ipv6hdr *)(data + sizeof(struct ethhdr));
+	if ((void *)(ip6h + 1) > data_end)
+		return false;
+
+	return v6_equal(ip6h->daddr, addr);
+}
+
+SEC("chk_neigh") int tc_chk(struct __sk_buff *skb)
+{
+	void *data_end = ctx_ptr(skb->data_end);
+	void *data = ctx_ptr(skb->data);
+	__u32 *raw = data;
+
+	if (data + sizeof(struct ethhdr) > data_end)
+		return TC_ACT_SHOT;
+
+	return !raw[0] && !raw[1] && !raw[2] ? TC_ACT_SHOT : TC_ACT_OK;
+}
+
+SEC("dst_ingress") int tc_dst(struct __sk_buff *skb)
+{
+	int idx = dst_to_src_tmp;
+	__u8 zero[ETH_ALEN * 2];
+	bool redirect = false;
+
+	switch (skb->protocol) {
+	case __bpf_constant_htons(ETH_P_IP):
+		redirect = is_remote_ep_v4(skb, __bpf_constant_htonl(ip4_src));
+		break;
+	case __bpf_constant_htons(ETH_P_IPV6):
+		redirect = is_remote_ep_v6(skb, (struct in6_addr)ip6_src);
+		break;
+	}
+
+	if (!redirect)
+		return TC_ACT_OK;
+
+	barrier_data(&idx);
+	idx = bpf_ntohl(idx);
+
+	__builtin_memset(&zero, 0, sizeof(zero));
+	if (bpf_skb_store_bytes(skb, 0, &zero, sizeof(zero), 0) < 0)
+		return TC_ACT_SHOT;
+
+	return bpf_redirect_neigh(idx, 0);
+}
+
+SEC("src_ingress") int tc_src(struct __sk_buff *skb)
+{
+	int idx = src_to_dst_tmp;
+	__u8 zero[ETH_ALEN * 2];
+	bool redirect = false;
+
+	switch (skb->protocol) {
+	case __bpf_constant_htons(ETH_P_IP):
+		redirect = is_remote_ep_v4(skb, __bpf_constant_htonl(ip4_dst));
+		break;
+	case __bpf_constant_htons(ETH_P_IPV6):
+		redirect = is_remote_ep_v6(skb, (struct in6_addr)ip6_dst);
+		break;
+	}
+
+	if (!redirect)
+		return TC_ACT_OK;
+
+	barrier_data(&idx);
+	idx = bpf_ntohl(idx);
+
+	__builtin_memset(&zero, 0, sizeof(zero));
+	if (bpf_skb_store_bytes(skb, 0, &zero, sizeof(zero), 0) < 0)
+		return TC_ACT_SHOT;
+
+	return bpf_redirect_neigh(idx, 0);
+}
+
+char __license[] SEC("license") = "GPL";