netfilter: flowtable infrastructure depends on NETFILTER_INGRESS

config NF_FLOW_TABLE depends on NETFILTER_INGRESS. If users forget to
enable this toggle, flowtable registration fails with EOPNOTSUPP.

Moreover, turn 'select NF_FLOW_TABLE' in every flowtable family flavour
into dependency instead, otherwise this new dependency on
NETFILTER_INGRESS causes a warning. This also allows us to remove the
explicit dependency between family flowtables <-> NF_TABLES and
NF_CONNTRACK, given they depend on the NF_FLOW_TABLE core that already
expresses the general dependencies for this new infrastructure.

Moreover, NF_FLOW_TABLE_INET depends on NF_FLOW_TABLE_IPV4 and
NF_FLOWTABLE_IPV6, which already depends on NF_FLOW_TABLE. So we can get
rid of direct dependency with NF_FLOW_TABLE.

In general, let's avoid 'select', it just makes things more complicated.
Reported-by: John Crispin <john@phrozen.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv4/netfilter/Kconfig

@@ -80,8 +80,7 @@ endif # NF_TABLES
 
 config NF_FLOW_TABLE_IPV4
 	tristate "Netfilter flow table IPv4 module"
-	depends on NF_CONNTRACK && NF_TABLES
-	select NF_FLOW_TABLE
+	depends on NF_FLOW_TABLE
 	help
 	  This option adds the flow table IPv4 support.
 

net/ipv6/netfilter/Kconfig

@@ -73,8 +73,7 @@ endif # NF_TABLES
 
 config NF_FLOW_TABLE_IPV6
 	tristate "Netfilter flow table IPv6 module"
-	depends on NF_CONNTRACK && NF_TABLES
-	select NF_FLOW_TABLE
+	depends on NF_FLOW_TABLE
 	help
 	  This option adds the flow table IPv6 support.
 

net/netfilter/Kconfig

@@ -666,8 +666,8 @@ endif # NF_TABLES
 
 config NF_FLOW_TABLE_INET
 	tristate "Netfilter flow table mixed IPv4/IPv6 module"
-	depends on NF_FLOW_TABLE_IPV4 && NF_FLOW_TABLE_IPV6
-	select NF_FLOW_TABLE
+	depends on NF_FLOW_TABLE_IPV4
+	depends on NF_FLOW_TABLE_IPV6
 	help
           This option adds the flow table mixed IPv4/IPv6 support.
 
@@ -675,7 +675,9 @@ config NF_FLOW_TABLE_INET
 
 config NF_FLOW_TABLE
 	tristate "Netfilter flow table module"
-	depends on NF_CONNTRACK && NF_TABLES
+	depends on NETFILTER_INGRESS
+	depends on NF_CONNTRACK
+	depends on NF_TABLES
 	help
 	  This option adds the flow table core infrastructure.