net: bpfilter: fix iptables failure if bpfilter_umh is disabled

When iptables command is executed, ip_{set/get}sockopt() try to upload
bpfilter.ko if bpfilter is enabled. if it couldn't find bpfilter.ko,
command is failed.
bpfilter.ko is generated if CONFIG_BPFILTER_UMH is enabled.
ip_{set/get}sockopt() only checks CONFIG_BPFILTER.
So that if CONFIG_BPFILTER is enabled and CONFIG_BPFILTER_UMH is disabled,
iptables command is always failed.

test config:
   CONFIG_BPFILTER=y
   # CONFIG_BPFILTER_UMH is not set

test command:
   %iptables -L
   iptables: No chain/target/match by that name.

Fixes: d2ba09c17a06 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_sockglue.c

@@ -1246,7 +1246,7 @@ int ip_setsockopt(struct sock *sk, int level,
 		return -ENOPROTOOPT;
 
 	err = do_ip_setsockopt(sk, level, optname, optval, optlen);
-#ifdef CONFIG_BPFILTER
+#if IS_ENABLED(CONFIG_BPFILTER_UMH)
 	if (optname >= BPFILTER_IPT_SO_SET_REPLACE &&
 	    optname < BPFILTER_IPT_SET_MAX)
 		err = bpfilter_ip_set_sockopt(sk, optname, optval, optlen);
@@ -1559,7 +1559,7 @@ int ip_getsockopt(struct sock *sk, int level,
 	int err;
 
 	err = do_ip_getsockopt(sk, level, optname, optval, optlen, 0);
-#ifdef CONFIG_BPFILTER
+#if IS_ENABLED(CONFIG_BPFILTER_UMH)
 	if (optname >= BPFILTER_IPT_SO_GET_INFO &&
 	    optname < BPFILTER_IPT_GET_MAX)
 		err = bpfilter_ip_get_sockopt(sk, optname, optval, optlen);
@@ -1596,7 +1596,7 @@ int compat_ip_getsockopt(struct sock *sk, int level, int optname,
 	err = do_ip_getsockopt(sk, level, optname, optval, optlen,
 		MSG_CMSG_COMPAT);
 
-#ifdef CONFIG_BPFILTER
+#if IS_ENABLED(CONFIG_BPFILTER_UMH)
 	if (optname >= BPFILTER_IPT_SO_GET_INFO &&
 	    optname < BPFILTER_IPT_GET_MAX)
 		err = bpfilter_ip_get_sockopt(sk, optname, optval, optlen);