luci-base: implement further ubus calls

Implement new ubus rpcd backend calls for later use in the frontend:

 - netdevs: dump information about Linux network devices present
 - boardjson: dump /etc/board.json if present
 - offload_support: query whether netfilter offloading is supported

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-base/root/usr/libexec/rpcd/luci

@@ -196,6 +196,83 @@ local methods = {
 				}
 			end
 		end
+	},
+
+	netdevs = {
+		call = function(args)
+			local dir = fs.dir("/sys/class/net")
+			local result = { }
+			if dir then
+				local dev
+				for dev in dir do
+					if not result[dev] then
+						result[dev] = { name = dev }
+					end
+
+					if fs.access("/sys/class/net/"..dev.."/master") then
+						local brname = fs.basename(fs.readlink("/sys/class/net/"..dev.."/master"))
+						if not result[brname] then
+							result[brname] = { name = brname }
+						end
+
+						if not result[brname].ports then
+							result[brname].ports = { }
+						end
+
+						result[brname].ports[#result[brname].ports+1] = dev
+					elseif fs.access("/sys/class/net/"..dev.."/bridge") then
+						if not result[dev].ports then
+							result[dev].ports = { }
+						end
+
+						result[dev].id = readfile("/sys/class/net/"..dev.."/bridge/bridge_id")
+						result[dev].stp = (readfile("/sys/class/net/"..dev.."/bridge/stp_state") ~= "0")
+						result[dev].bridge = true
+					end
+
+					local opr = readfile("/sys/class/net/"..dev.."/operstate")
+
+					result[dev].up = (opr == "up" or opr == "unknown")
+					result[dev].type = tonumber(readfile("/sys/class/net/"..dev.."/type"))
+					result[dev].name = dev
+
+					local mtu = tonumber(readfile("/sys/class/net/"..dev.."/mtu"))
+					if mtu and mtu > 0 then
+						result[dev].mtu = mtu
+					end
+
+					local qlen = tonumber(readfile("/sys/class/net/"..dev.."/tx_queue_len"))
+					if qlen and qlen > 0 then
+						result[dev].qlen = qlen
+					end
+
+					local master = fs.readlink("/sys/class/net/"..dev.."/master")
+					if master then
+						result[dev].master = fs.basename(master)
+					end
+
+					local mac = readfile("/sys/class/net/"..dev.."/address")
+					if mac and #mac == 17 then
+						result[dev].mac = mac
+					end
+				end
+			end
+			return result
+		end
+	},
+
+	boardjson = {
+		call = function(args)
+			local jsc = require "luci.jsonc"
+			return jsc.parse(fs.readfile("/etc/board.json") or "")
+		end
+	},
+
+	offload_support = {
+		call = function()
+			local fs = require "nixio.fs"
+			return { offload_support = not not fs.access("/sys/module/xt_FLOWOFFLOAD/refcnt") }
+		end
 	}
 }
 
@@ -256,6 +333,6 @@ elseif arg[1] == "call" then
 	local args = parseInput()
 	local method = validateArgs(arg[2], args)
 	local result, code = method.call(args)
-	print(json.stringify(result))
+	print((json.stringify(result):gsub("^%[%]$", "{}")))
 	os.exit(code or 0)
 end