netfilter: add kmod-nfnetlink-ct{helper,timeout}

Add kmod-nfnetlink-ct{helper,timeout} to allow handling firewall rules
in userspace (together with conntrackd). The timeout module allows
specifying custom expiration rules.

Signed-off-by: Joel Low <[email protected]>
Link: openwrt/openwrt#17267
(cherry picked from commit 0e2dcfc)
Link: openwrt/openwrt#17358
Signed-off-by: Hauke Mehrtens <[email protected]>

config/Config-kernel.in

@@ -1239,6 +1239,13 @@ config KERNEL_MPTCP_IPV6
 	default KERNEL_MPTCP
 endif
 
+config KERNEL_NF_CONNTRACK_TIMEOUT
+	bool "Per-connection connection tracking timeout"
+	default y if !SMALL_FLASH
+	help
+	   Select this option to enable support for per-connection conntrack timeouts.
+	   Increases the (uncompressed) size of nf_conntrack.ko by ~8kB.
+
 #
 # NFS related symbols
 #

package/kernel/linux/modules/netfilter.mk

@@ -1048,6 +1048,40 @@ endef
 $(eval $(call KernelPackage,nfnetlink-queue))
 
 
+define KernelPackage/nfnetlink-cthelper
+  TITLE:=Netfilter User space conntrack helpers
+  FILES:=$(LINUX_DIR)/net/netfilter/nfnetlink_cthelper.ko
+  KCONFIG:=CONFIG_NF_CT_NETLINK_HELPER
+  AUTOLOAD:=$(call AutoProbe,nfnetlink_cthelper)
+  $(call AddDepends/nfnetlink,+kmod-nfnetlink-queue +kmod-nf-conntrack-netlink)
+endef
+
+define KernelPackage/nfnetlink-cthelper/description
+ Kernel modules support for a netlink-based connection tracking
+ userspace helpers interface
+endef
+
+$(eval $(call KernelPackage,nfnetlink-cthelper))
+
+
+define KernelPackage/nfnetlink-cttimeout
+  TITLE:=Netfilter conntrack expectation timeout
+  FILES:=$(LINUX_DIR)/net/netfilter/nfnetlink_cttimeout.ko
+  KCONFIG:=CONFIG_NF_CT_NETLINK_TIMEOUT
+  AUTOLOAD:=$(call AutoProbe,nfnetlink_cttimeout)
+  $(call AddDepends/nfnetlink,+kmod-nf-conntrack +kmod-nf-conntrack-timeout @KERNEL_NF_CONNTRACK_TIMEOUT)
+endef
+
+define KernelPackage/nfnetlink-cttimeout/description
+ Kernel modules support for a netlink-based connection tracking
+ userspace timeout interface
+
+ Requires CONFIG_NF_CONNTRACK_TIMEOUT (only enabled for non-small flash devices)
+endef
+
+$(eval $(call KernelPackage,nfnetlink-cttimeout))
+
+
 define KernelPackage/nf-conntrack-netlink
   TITLE:=Connection tracking netlink interface
   FILES:=$(LINUX_DIR)/net/netfilter/nf_conntrack_netlink.ko