netfilter: add iptables-mod-rpfilter package

Unlike /proc/sys/net/ipv4/conf/INTF/rp_filter flag, rule iptables -t raw
-I PREROUTING -m rpfilter --invert -j DROP prevents conntrack table to
become full when a packet flood with randomly selected source IP addresses
is received from the lan side.

Signed-off-by: Alin Nastac <alin.nastac@gmail.com>

include/netfilter.mk

@@ -106,6 +106,8 @@ $(eval $(call nf_add,IPT_FILTER,CONFIG_NETFILTER_XT_MATCH_STRING, $(P_XT)xt_stri
 $(eval $(call nf_add,IPT_IPOPT,CONFIG_NETFILTER_XT_MATCH_DSCP, $(P_XT)xt_dscp))
 $(eval $(call nf_add,IPT_IPOPT,CONFIG_NETFILTER_XT_TARGET_DSCP, $(P_XT)xt_DSCP))
 $(eval $(call nf_add,IPT_HASHLIMIT,CONFIG_NETFILTER_XT_MATCH_HASHLIMIT, $(P_XT)xt_hashlimit))
+$(eval $(call nf_add,IPT_RPFILTER,CONFIG_IP_NF_MATCH_RPFILTER, $(P_V4)ipt_rpfilter))
+$(eval $(call nf_add,IPT_RPFILTER,CONFIG_IP6_NF_MATCH_RPFILTER, $(P_V6)ip6t_rpfilter))
 $(eval $(call nf_add,IPT_IPOPT,CONFIG_NETFILTER_XT_MATCH_LENGTH, $(P_XT)xt_length))
 $(eval $(call nf_add,IPT_IPOPT,CONFIG_NETFILTER_XT_MATCH_STATISTIC, $(P_XT)xt_statistic))
 $(eval $(call nf_add,IPT_IPOPT,CONFIG_NETFILTER_XT_MATCH_TCPMSS, $(P_XT)xt_tcpmss))

package/kernel/linux/modules/netfilter.mk

@@ -836,6 +836,24 @@ endef
 
 $(eval $(call KernelPackage,ipt-hashlimit))
 
+define KernelPackage/ipt-rpfilter
+  SUBMENU:=$(NF_MENU)
+  TITLE:=Netfilter rpfilter match
+  DEPENDS:=+kmod-ipt-core
+  KCONFIG:=$(KCONFIG_IPT_RPFILTER)
+  FILES:=$(realpath \
+	$(LINUX_DIR)/net/ipv4/netfilter/ipt_rpfilter.ko \
+	$(LINUX_DIR)/net/ipv6/netfilter/ip6t_rpfilter.ko)
+  AUTOLOAD:=$(call AutoProbe,ipt_rpfilter ip6t_rpfilter)
+  $(call KernelPackage/ipt)
+endef
+
+define KernelPackage/ipt-rpfilter/description
+ Kernel modules support for the Netfilter rpfilter match
+endef
+
+$(eval $(call KernelPackage,ipt-rpfilter))
+
 
 define KernelPackage/nft-core
   SUBMENU:=$(NF_MENU)

package/network/utils/iptables/Makefile

@@ -242,6 +242,19 @@ iptables extensions for hashlimit matching
 
 endef
 
+define Package/iptables-mod-rpfilter
+$(call Package/iptables/Module, +kmod-ipt-rpfilter)
+  TITLE:=rpfilter iptables extension
+endef
+
+define Package/iptables-mod-rpfilter/description
+iptables extensions for reverse path filter test on a packet
+
+ Matches:
+  - rpfilter
+
+endef
+
 define Package/iptables-mod-iprange
 $(call Package/iptables/Module, +kmod-ipt-iprange)
   TITLE:=IP range extension
@@ -565,6 +578,7 @@ $(eval $(call BuildPlugin,iptables-mod-cluster,$(IPT_CLUSTER-m)))
 $(eval $(call BuildPlugin,iptables-mod-clusterip,$(IPT_CLUSTERIP-m)))
 $(eval $(call BuildPlugin,iptables-mod-ulog,$(IPT_ULOG-m)))
 $(eval $(call BuildPlugin,iptables-mod-hashlimit,$(IPT_HASHLIMIT-m)))
+$(eval $(call BuildPlugin,iptables-mod-rpfilter,$(IPT_RPFILTER-m)))
 $(eval $(call BuildPlugin,iptables-mod-led,$(IPT_LED-m)))
 $(eval $(call BuildPlugin,iptables-mod-tproxy,$(IPT_TPROXY-m)))
 $(eval $(call BuildPlugin,iptables-mod-tee,$(IPT_TEE-m)))