gluon-state-check: implement state checker (#2245)

package/gluon-state-check/Makefile

+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=gluon-state-check
+PKG_VERSION:=1
+
+include ../gluon.mk
+
+define Package/gluon-state-check
+  TITLE:=Provides info about the routers state
+  DEPENDS:=+gluon-core +micrond
+endef
+
+define Package/gluon-state-check/description
+  gluon-state-check executes checks in `/lib/gluon/state/check.d/` and provides
+  a flag file for each check in `/var/gluon/state` depending on the return code
+  of the check. A flag file is created (or "touched") if the corresponding check
+  exits cleanly and gets removed otherwise. If the flags are "touched", they
+  are only accessed, but not modified. In this way, the atime of a flag file
+  reflects when the last check was performed and the mtime reflects when
+  when the state was last changed.
+
+  This package provides the following checks:
+  - `has_default_gw6` - check whether the router has a default IPv6-route on br-client.
+
+  The checks are executed once every minute (by micron.d).
+endef
+
+$(eval $(call BuildPackageGluon,gluon-state-check))

package/gluon-state-check/files/lib/gluon/state/check.d/has_default_gw6

+#!/bin/sh
+out=$(ip -6 route show default dev br-client 2>/dev/null) && [ -n "$out" ]

package/gluon-state-check/files/usr/lib/micron.d/gluon-state-check

+* * * * * /usr/sbin/gluon-state-check

package/gluon-state-check/luasrc/usr/sbin/gluon-state-check

+#!/usr/bin/lua
+
+local util = require 'gluon.util'
+local unistd = require 'posix.unistd'
+
+local state_dir = "/var/gluon/state/"
+local check_dir = "/lib/gluon/state/check.d/"
+
+
+local function set_flag(stateflag, state)
+	if state then
+		-- this does not modify atime
+		local flaghandle = io.open(stateflag, "w")
+		flaghandle:close()
+	else
+		os.remove(stateflag)
+	end
+end
+
+local function exec_check(checkpath)
+	local checkname = string.sub(checkpath, #check_dir+1)
+	local ret = os.execute(checkpath)
+	local flagfile = state_dir..checkname
+	set_flag(flagfile, 0==ret)
+end
+
+local function run_executable_checks()
+	for _, v in ipairs(util.glob(check_dir..'*')) do
+		if unistd.access(v, 'x') then
+			exec_check(v)
+		end
+	end
+end
+
+
+-- ensure state path exists
+if not unistd.access(state_dir) then
+	os.execute("mkdir -p "..state_dir)
+end
+
+run_executable_checks()