Add support for showing ipv6 NAT table in Luci

When kmod-nf-nat6 and kmod-ipt-nat6 are installed, the firewall has also
the 'nat' table for ipv6, and packages like 'adblock' utilize that table.

Currently that table is not shown on the Luci firewall status page,
although it is visible by 'ip6tables -L -v -t nat' from console.

Detect 'nat' table's presence from /proc/net/ip6_tables_names

Show 'nat' table in Status->Firewall->IPv6 if that table is present.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
(cherry picked from commit a77ff30057)

modules/luci-base/luasrc/sys/iptparser.lua

@@ -19,6 +19,8 @@ luci.util   = require "luci.util"
 luci.sys    = require "luci.sys"
 luci.ip     = require "luci.ip"
 
+local pcall = pcall
+local io = require "io"
 local tonumber, ipairs, table = tonumber, ipairs, table
 
 module("luci.sys.iptparser")
@@ -37,6 +39,15 @@ function IptParser.__init__( self, family )
 	else
 		self._nulladdr = "::/0"
 		self._tables   = { "filter", "mangle", "raw" }
+		local ok, lines = pcall(io.lines, "/proc/net/ip6_tables_names")
+		if ok and lines then
+			local line
+			for line in lines do
+				if line == "nat" then
+					self._tables = { "filter", "nat", "mangle", "raw" }
+				end
+			end
+		end
 		self._command  = "ip6tables -t %s --line-numbers -nxvL"
 	end
 

modules/luci-mod-admin-full/luasrc/view/admin_status/iptables.htm

@@ -9,6 +9,7 @@
 	require "luci.sys.iptparser"
 	local wba = require "luci.tools.webadmin"
 	local fs = require "nixio.fs"
+	local io = require "io"
 
 	local has_ip6tables = fs.access("/usr/sbin/ip6tables")
 	local mode = 4
@@ -47,6 +48,15 @@
 	local tables = { "Filter", "NAT", "Mangle", "Raw" }
 	if mode == 6 then
 		tables = { "Filter", "Mangle", "Raw" }
+		local ok, lines = pcall(io.lines, "/proc/net/ip6_tables_names")
+		if ok and lines then
+			local line
+			for line in lines do
+				if line == "nat" then
+					tables = { "Filter", "NAT", "Mangle", "Raw" }
+				end
+			end
+		end
 	end
 -%>