bpf, selftests: Make redirect_neigh test more extensible

Rename into test_tc_redirect.sh and move setup and test code into separate
functions so they can be reused for newly added tests in here. Also remove
the crude hack to override ifindex inside the object file via xxd and sed
and just use a simple map instead. Map given iproute2 does not support BTF
fully and therefore neither global data at this point.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20201010234006.7075-6-daniel@iogearbox.net

Author: borkmann

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

@@ -13,17 +13,10 @@
 #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 */
 
@@ -39,6 +32,18 @@
 				 a.s6_addr32[3] == b.s6_addr32[3])
 #endif
 
+enum {
+	dev_src,
+	dev_dst,
+};
+
+struct bpf_map_def SEC("maps") ifindex_map = {
+	.type		= BPF_MAP_TYPE_ARRAY,
+	.key_size	= sizeof(int),
+	.value_size	= sizeof(int),
+	.max_entries	= 2,
+};
+
 static __always_inline bool is_remote_ep_v4(struct __sk_buff *skb,
 					    __be32 addr)
 {
@@ -73,7 +78,14 @@ static __always_inline bool is_remote_ep_v6(struct __sk_buff *skb,
 	return v6_equal(ip6h->daddr, addr);
 }
 
-SEC("chk_neigh") int tc_chk(struct __sk_buff *skb)
+static __always_inline int get_dev_ifindex(int which)
+{
+	int *ifindex = bpf_map_lookup_elem(&ifindex_map, &which);
+
+	return ifindex ? *ifindex : 0;
+}
+
+SEC("chk_egress") int tc_chk(struct __sk_buff *skb)
 {
 	void *data_end = ctx_ptr(skb->data_end);
 	void *data = ctx_ptr(skb->data);
@@ -87,7 +99,6 @@ SEC("chk_neigh") int tc_chk(struct __sk_buff *skb)
 
 SEC("dst_ingress") int tc_dst(struct __sk_buff *skb)
 {
-	int idx = dst_to_src_tmp;
 	__u8 zero[ETH_ALEN * 2];
 	bool redirect = false;
 
@@ -103,19 +114,15 @@ SEC("dst_ingress") int tc_dst(struct __sk_buff *skb)
 	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);
+	return bpf_redirect_neigh(get_dev_ifindex(dev_src), 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;
 
@@ -131,14 +138,11 @@ SEC("src_ingress") int tc_src(struct __sk_buff *skb)
 	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);
+	return bpf_redirect_neigh(get_dev_ifindex(dev_dst), 0);
 }
 
 char __license[] SEC("license") = "GPL";