bpf: Only add BTF IDs for socket security hooks when CONFIG_SECURITY_NETWORK is on

When CONFIG_SECURITY_NETWORK is disabled, there will be build warnings
from resolve_btfids:

  WARN: resolve_btfids: unresolved symbol bpf_lsm_socket_socketpair
  ......
  WARN: resolve_btfids: unresolved symbol bpf_lsm_inet_conn_established

Fixing it by wrapping these BTF ID definitions by CONFIG_SECURITY_NETWORK.

Fixes: 69fd337a ("bpf: per-cgroup lsm flavor")
Fixes: 9113d7e4 ("bpf: expose bpf_{g,s}etsockopt to lsm cgroup")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20220901065126.3856297-1-houtao@huaweicloud.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

kernel/bpf/bpf_lsm.c

@@ -41,17 +41,21 @@ BTF_SET_END(bpf_lsm_hooks)
  */
 BTF_SET_START(bpf_lsm_current_hooks)
 /* operate on freshly allocated sk without any cgroup association */
+#ifdef CONFIG_SECURITY_NETWORK
 BTF_ID(func, bpf_lsm_sk_alloc_security)
 BTF_ID(func, bpf_lsm_sk_free_security)
+#endif
 BTF_SET_END(bpf_lsm_current_hooks)
 
 /* List of LSM hooks that trigger while the socket is properly locked.
  */
 BTF_SET_START(bpf_lsm_locked_sockopt_hooks)
+#ifdef CONFIG_SECURITY_NETWORK
 BTF_ID(func, bpf_lsm_socket_sock_rcv_skb)
 BTF_ID(func, bpf_lsm_sock_graft)
 BTF_ID(func, bpf_lsm_inet_csk_clone)
 BTF_ID(func, bpf_lsm_inet_conn_established)
+#endif
 BTF_SET_END(bpf_lsm_locked_sockopt_hooks)
 
 /* List of LSM hooks that trigger while the socket is _not_ locked,
@@ -59,8 +63,10 @@ BTF_SET_END(bpf_lsm_locked_sockopt_hooks)
  * in the early init phase.
  */
 BTF_SET_START(bpf_lsm_unlocked_sockopt_hooks)
+#ifdef CONFIG_SECURITY_NETWORK
 BTF_ID(func, bpf_lsm_socket_post_create)
 BTF_ID(func, bpf_lsm_socket_socketpair)
+#endif
 BTF_SET_END(bpf_lsm_unlocked_sockopt_hooks)
 
 #ifdef CONFIG_CGROUP_BPF