output-lua: initial packet support

Add key for storing packet pointer in the lua stack and a utility
function to retrieve it from lua callbacks.

src/output-lua-common.c

@@ -89,6 +89,15 @@ void LuaPrintStack(lua_State *state) {
 }
 
 extern const char lualog_ext_key_tx;
+extern const char lualog_ext_key_p;
+
+Packet *LuaStateGetPacket(lua_State *luastate)
+{
+    lua_pushlightuserdata(luastate, (void *)&lualog_ext_key_p);
+    lua_gettable(luastate, LUA_REGISTRYINDEX);
+    void *p = lua_touserdata(luastate, -1);
+    return (Packet *)p;
+}
 
 void *LuaStateGetTX(lua_State *luastate)
 {

src/output-lua-common.h

@@ -28,6 +28,7 @@
 
 void LuaPrintStack(lua_State *state);
 
+Packet *LuaStateGetPacket(lua_State *luastate);
 void *LuaStateGetTX(lua_State *luastate);
 int LuaCallbackError(lua_State *luastate, const char *msg);
 int LuaReturnStringBuffer(lua_State *luastate, const uint8_t *input, size_t input_len);

src/output-lua.c

@@ -69,6 +69,8 @@ typedef struct LogLuaThreadCtx_ {
 } LogLuaThreadCtx;
 
 const char lualog_ext_key_tx[] = "suricata:lualog:tx:ptr";
+/* key for p (packet) pointer */
+const char lualog_ext_key_p[] = "suricata:lualog:pkt:ptr";
 
 static int LuaTxLogger(ThreadVars *tv, void *thread_data, const Packet *p, Flow *f, void *alstate, void *txptr, uint64_t tx_id)
 {