selftests/bpf: Introduce verdict programs for sockmap_redir

Instead of piggybacking on test_sockmap_listen, introduce
test_sockmap_redir especially for sockmap redirection tests.

Suggested-by: Jiayuan Chen <[e-mail]>
Signed-off-by: Michal Luczaj <[e-mail]>
Signed-off-by: Martin KaFai Lau <[e-mail]>
Acked-by: John Fastabend <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

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

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+SEC(".maps") struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u64);
+} nop_map, sock_map;
+
+SEC(".maps") struct {
+	__uint(type, BPF_MAP_TYPE_SOCKHASH);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u64);
+} nop_hash, sock_hash;
+
+SEC(".maps") struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 2);
+	__type(key, int);
+	__type(value, unsigned int);
+} verdict_map;
+
+/* Set by user space */
+int redirect_type;
+int redirect_flags;
+
+#define redirect_map(__data)                                                   \
+	_Generic((__data),                                                     \
+		 struct __sk_buff * : bpf_sk_redirect_map,                     \
+		 struct sk_msg_md * : bpf_msg_redirect_map                     \
+	)((__data), &sock_map, (__u32){0}, redirect_flags)
+
+#define redirect_hash(__data)                                                  \
+	_Generic((__data),                                                     \
+		 struct __sk_buff * : bpf_sk_redirect_hash,                    \
+		 struct sk_msg_md * : bpf_msg_redirect_hash                    \
+	)((__data), &sock_hash, &(__u32){0}, redirect_flags)
+
+#define DEFINE_PROG(__type, __param)                                           \
+SEC("sk_" XSTR(__type))                                                        \
+int prog_ ## __type ## _verdict(__param data)                                  \
+{                                                                              \
+	unsigned int *count;                                                   \
+	int verdict;                                                           \
+									       \
+	if (redirect_type == BPF_MAP_TYPE_SOCKMAP)                             \
+		verdict = redirect_map(data);                                  \
+	else if (redirect_type == BPF_MAP_TYPE_SOCKHASH)                       \
+		verdict = redirect_hash(data);                                 \
+	else                                                                   \
+		verdict = redirect_type - __MAX_BPF_MAP_TYPE;                  \
+									       \
+	count = bpf_map_lookup_elem(&verdict_map, &verdict);                   \
+	if (count)                                                             \
+		(*count)++;                                                    \
+									       \
+	return verdict;                                                        \
+}
+
+DEFINE_PROG(skb, struct __sk_buff *);
+DEFINE_PROG(msg, struct sk_msg_md *);
+
+char _license[] SEC("license") = "GPL";