netfilter: provide udp*_lib_lookup for nf_tproxy

It is now possible to enable the libified nf_tproxy modules without
also enabling NETFILTER_XT_TARGET_TPROXY, which throws off the
ifdef logic in the udp core code:

net/ipv6/netfilter/nf_tproxy_ipv6.o: In function `nf_tproxy_get_sock_v6':
nf_tproxy_ipv6.c:(.text+0x1a8): undefined reference to `udp6_lib_lookup'
net/ipv4/netfilter/nf_tproxy_ipv4.o: In function `nf_tproxy_get_sock_v4':
nf_tproxy_ipv4.c:(.text+0x3d0): undefined reference to `udp4_lib_lookup'

We can actually simplify the conditions now to provide the two functions
exactly when they are needed.

Fixes: 45ca4e0cf2 ("netfilter: Libify xt_TPROXY")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Máté Eckl <ecklm94@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/udp.c

@@ -544,9 +544,7 @@ EXPORT_SYMBOL_GPL(udp4_lib_lookup_skb);
 /* Must be called under rcu_read_lock().
  * Does increment socket refcount.
  */
-#if IS_ENABLED(CONFIG_NETFILTER_XT_MATCH_SOCKET) || \
-    IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TPROXY) || \
-    IS_ENABLED(CONFIG_NF_SOCKET_IPV4)
+#if IS_ENABLED(CONFIG_NF_TPROXY_IPV4) || IS_ENABLED(CONFIG_NF_SOCKET_IPV4)
 struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
 			     __be32 daddr, __be16 dport, int dif)
 {

net/ipv6/udp.c

@@ -285,9 +285,7 @@ EXPORT_SYMBOL_GPL(udp6_lib_lookup_skb);
 /* Must be called under rcu_read_lock().
  * Does increment socket refcount.
  */
-#if IS_ENABLED(CONFIG_NETFILTER_XT_MATCH_SOCKET) || \
-    IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TPROXY) || \
-    IS_ENABLED(CONFIG_NF_SOCKET_IPV6)
+#if IS_ENABLED(CONFIG_NF_TPROXY_IPV6) || IS_ENABLED(CONFIG_NF_SOCKET_IPV6)
 struct sock *udp6_lib_lookup(struct net *net, const struct in6_addr *saddr, __be16 sport,
 			     const struct in6_addr *daddr, __be16 dport, int dif)
 {