bpf: Fix build error without CONFIG_INET

If CONFIG_INET is not set, building fails:

kernel/bpf/verifier.o: In function `check_mem_access':
verifier.c: undefined reference to `bpf_xdp_sock_is_valid_access'
kernel/bpf/verifier.o: In function `convert_ctx_accesses':
verifier.c: undefined reference to `bpf_xdp_sock_convert_ctx_access'

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: fada7fd ("bpf: Allow bpf_map_lookup_elem() on an xskmap")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/linux/bpf.h

@@ -728,13 +728,6 @@ void __cpu_map_insert_ctx(struct bpf_map *map, u32 index);
 void __cpu_map_flush(struct bpf_map *map);
 int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
 		    struct net_device *dev_rx);
-bool bpf_xdp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
-				  struct bpf_insn_access_aux *info);
-u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
-				    const struct bpf_insn *si,
-				    struct bpf_insn *insn_buf,
-				    struct bpf_prog *prog,
-				    u32 *target_size);
 
 /* Return map's numa specified by userspace */
 static inline int bpf_map_attr_numa_node(const union bpf_attr *attr)
@@ -1110,6 +1103,15 @@ u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
 				    struct bpf_insn *insn_buf,
 				    struct bpf_prog *prog,
 				    u32 *target_size);
+
+bool bpf_xdp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
+				  struct bpf_insn_access_aux *info);
+
+u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
+				    const struct bpf_insn *si,
+				    struct bpf_insn *insn_buf,
+				    struct bpf_prog *prog,
+				    u32 *target_size);
 #else
 static inline bool bpf_tcp_sock_is_valid_access(int off, int size,
 						enum bpf_access_type type,
@@ -1126,6 +1128,21 @@ static inline u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
 {
 	return 0;
 }
+static inline bool bpf_xdp_sock_is_valid_access(int off, int size,
+						enum bpf_access_type type,
+						struct bpf_insn_access_aux *info)
+{
+	return false;
+}
+
+static inline u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
+						  const struct bpf_insn *si,
+						  struct bpf_insn *insn_buf,
+						  struct bpf_prog *prog,
+						  u32 *target_size)
+{
+	return 0;
+}
 #endif /* CONFIG_INET */
 
 #endif /* _LINUX_BPF_H */