daemon: optional FFI to support e500

daemon/lua/kres.lua

 -- LuaJIT ffi bindings for libkres, a DNS resolver library.
 -- @note Since it's statically compiled, it expects to find the symbols in the C namespace.
 
-local ffi = require('ffi')
+local ffi_ok, ffi = pcall(require, 'ffi')
+if not ffi_ok then
+	local M = { error = 'FFI not available, resolver bindings disabled.' }
+	setmetatable(M, {__index = function(t,k,v) error(rawget(M, 'error')) end })
+	return M
+end
 local bit = require('bit')
 local bor = bit.bor
 local band = bit.band

daemon/lua/sandbox.lua

@@ -12,7 +12,9 @@ day = 24 * hour
 kres = require('kres')
 trust_anchors = require('trust_anchors')
 resolve = worker.resolve
-todname = kres.str2dname
+if rawget(kres, 'str2dname') ~= nil then
+	todname = kres.str2dname
+end
 
 -- Function aliases
 -- `env.VAR returns os.getenv(VAR)`

daemon/lua/trust_anchors.lua

+local ffi_ok, ffi = pcall(require, 'ffi')
+if not ffi_ok then
+	return { error = 'FFI not available, trust_anchors disabled.' }
+end
 local kres = require('kres')
-local C = require('ffi').C
+local C = ffi.C
 
 -- RFC5011 state table
 local key_state = {