bpf: get rid of cgroup helper related ifdefs

As recently discussed during the task_under_cgroup_hierarchy() addition,
we should get rid of the ifdefs surrounding the bpf_skb_under_cgroup()
helper. If related functionality is not built-in, the helper cannot be
used anyway, which is also in line with what we do for all other helpers.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -1114,6 +1114,16 @@ static inline bool sk_stream_is_writeable(const struct sock *sk)
 	       sk_stream_memory_free(sk);
 }
 
+static inline int sk_under_cgroup_hierarchy(struct sock *sk,
+					    struct cgroup *ancestor)
+{
+#ifdef CONFIG_SOCK_CGROUP_DATA
+	return cgroup_is_descendant(sock_cgroup_ptr(&sk->sk_cgrp_data),
+				    ancestor);
+#else
+	return -ENOTSUPP;
+#endif
+}
 
 static inline bool sk_has_memory_pressure(const struct sock *sk)
 {

net/core/filter.c

@@ -2374,7 +2374,6 @@ bpf_get_skb_set_tunnel_proto(enum bpf_func_id which)
 	}
 }
 
-#ifdef CONFIG_SOCK_CGROUP_DATA
 static u64 bpf_skb_under_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 {
 	struct sk_buff *skb = (struct sk_buff *)(long)r1;
@@ -2395,7 +2394,7 @@ static u64 bpf_skb_under_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 	if (unlikely(!cgrp))
 		return -EAGAIN;
 
-	return cgroup_is_descendant(sock_cgroup_ptr(&sk->sk_cgrp_data), cgrp);
+	return sk_under_cgroup_hierarchy(sk, cgrp);
 }
 
 static const struct bpf_func_proto bpf_skb_under_cgroup_proto = {
@@ -2406,7 +2405,6 @@ static const struct bpf_func_proto bpf_skb_under_cgroup_proto = {
 	.arg2_type	= ARG_CONST_MAP_PTR,
 	.arg3_type	= ARG_ANYTHING,
 };
-#endif
 
 static unsigned long bpf_xdp_copy(void *dst_buff, const void *src_buff,
 				  unsigned long off, unsigned long len)
@@ -2515,10 +2513,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 		return &bpf_skb_event_output_proto;
 	case BPF_FUNC_get_smp_processor_id:
 		return &bpf_get_smp_processor_id_proto;
-#ifdef CONFIG_SOCK_CGROUP_DATA
 	case BPF_FUNC_skb_under_cgroup:
 		return &bpf_skb_under_cgroup_proto;
-#endif
 	default:
 		return sk_filter_func_proto(func_id);
 	}