简化dns的解析逻辑

apps/sdlan/src/dns_proxy/dns_handler.erl

@@ -9,18 +9,11 @@
 -module(dns_handler).
 -author("anlicheng").
 
--behaviour(gen_server).
-
 -include_lib("dns_erlang/include/dns.hrl").
 -include_lib("pkt/include/pkt.hrl").
 -include("dns_proxy.hrl").
 
-%% API
+-export([handle/4]).
--export([start_link/0]).
-
-%% gen_server callbacks
--export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
--export([handle_ip_packet/5]).
 
 -define(SERVER, ?MODULE).
 -define(RESOLVER_POOL, dns_resolver_pool).
@@ -35,44 +28,7 @@
 %%% API
 %%%===================================================================
 
-start_link() ->
+handle(Sock, SrcIp, SrcPort, IpPacket) ->
-    gen_server:start_link(?MODULE, [], []).
-
-handle_ip_packet(Pid, Sock, SrcIp, SrcPort, Packet) when is_pid(Pid) ->
-    gen_server:cast(Pid, {handle_ip_packet, Sock, SrcIp, SrcPort, Packet}).
-
-%%%===================================================================
-%%% gen_server callbacks
-%%%===================================================================
-
-%% @private
-%% @doc Initializes the server
--spec(init(Args :: term()) ->
-    {ok, State :: #state{}} | {ok, State :: #state{}, timeout() | hibernate} |
-    {stop, Reason :: term()} | ignore).
-init([]) ->
-    {ok, #state{}}.
-
-%% @private
-%% @doc Handling call messages
--spec(handle_call(Request :: term(), From :: {pid(), Tag :: term()},
-    State :: #state{}) ->
-    {reply, Reply :: term(), NewState :: #state{}} |
-    {reply, Reply :: term(), NewState :: #state{}, timeout() | hibernate} |
-    {noreply, NewState :: #state{}} |
-    {noreply, NewState :: #state{}, timeout() | hibernate} |
-    {stop, Reason :: term(), Reply :: term(), NewState :: #state{}} |
-    {stop, Reason :: term(), NewState :: #state{}}).
-handle_call(_Request, _From, State = #state{}) ->
-    {reply, ok, State}.
-
-%% @private
-%% @doc Handling cast messages
--spec(handle_cast(Request :: term(), State :: #state{}) ->
-    {noreply, NewState :: #state{}} |
-    {noreply, NewState :: #state{}, timeout() | hibernate} |
-    {stop, Reason :: term(), NewState :: #state{}}).
-handle_cast({handle_ip_packet, Sock, SrcIp, SrcPort, IpPacket}, State) ->
     {#ipv4{saddr = ReqSAddr, daddr = ReqDAddr, p = Protocol}, ReqIpPayload} = pkt:ipv4(IpPacket),
     case Protocol =:= ?UDP_PROTOCOL of
         true ->
@@ -86,35 +42,7 @@ handle_cast({handle_ip_packet, Sock, SrcIp, SrcPort, IpPacket}, State) ->
             end;
         false ->
             logger:notice("[dns_handler] resolver invalid protocol: ~p", [Protocol])
-    end,
+    end.
-    {stop, normal, State}.
-
-%% @private
-%% @doc Handling all non call/cast messages
--spec(handle_info(Info :: timeout() | term(), State :: #state{}) ->
-    {noreply, NewState :: #state{}} |
-    {noreply, NewState :: #state{}, timeout() | hibernate} |
-    {stop, Reason :: term(), NewState :: #state{}}).
-handle_info(_Info, State) ->
-    {noreply, State}.
-
-%% @private
-%% @doc This function is called by a gen_server when it is about to
-%% terminate. It should be the opposite of Module:init/1 and do any
-%% necessary cleaning up. When it returns, the gen_server terminates
-%% with Reason. The return value is ignored.
--spec(terminate(Reason :: (normal | shutdown | {shutdown, term()} | term()),
-    State :: #state{}) -> term()).
-terminate(_Reason, _State = #state{}) ->
-    ok.
-
-%% @private
-%% @doc Convert process state when code is changed
--spec(code_change(OldVsn :: term() | {down, term()}, State :: #state{},
-    Extra :: term()) ->
-    {ok, NewState :: #state{}} | {error, Reason :: term()}).
-code_change(_OldVsn, State = #state{}, _Extra) ->
-    {ok, State}.
 
 %%%===================================================================
 %%% Internal functions
@@ -162,11 +90,8 @@ resolver0(Packet, QueryMsg = #dns_message{qc = 1, questions = [Question = #dns_q
                             RespMsg = build_response(QueryMsg, Cache),
                             {ok, dns:encode_message(RespMsg)};
                         miss ->
-                            Ref = make_ref(),
+                            case forward_to_upstream(Packet, QueryMsg) of
-                            forward_to_upstream(Ref, Packet, QueryMsg),
+                                {ok, Resp} ->
-                            logger:debug("[dns_handler] cache is miss, forward_to_upstream"),
-                            receive
-                                {dns_resolver_reply, Ref, Resp} ->
                                     case dns:decode_message(Resp) of
                                         RespMsg = #dns_message{answers = Answers} ->
                                             logger:debug("[dns_handler] get a response answers: ~p", [Answers]),
@@ -175,10 +100,10 @@ resolver0(Packet, QueryMsg = #dns_message{qc = 1, questions = [Question = #dns_q
                                         Error ->
                                             logger:debug("[dns_handler] parse reply get error: ~p", [Error]),
                                             {ok, EmptyDnsResp}
-                                    end
+                                    end;
-                            after 5000 ->
+                                {error, Reason} ->
-                                logger:debug("[dns_handler] forward_to_upstream timeout"),
+                                    logger:debug("[dns_handler] parse reply get error: ~p", [Reason]),
-                                {ok, EmptyDnsResp}
+                                    {ok, EmptyDnsResp}
                             end
                     end
             end
@@ -187,11 +112,6 @@ resolver0(_, Error) ->
     logger:warning("[dns_handler] decode dns_query get error: ~p", [Error]),
     {error, Error}.
 
--spec forward_to_upstream(Ref :: reference(), Request :: binary(), QueryMsg :: #dns_message{}) -> no_return().
-forward_to_upstream(Ref, Request, QueryMsg) ->
-    ReceiverPid = self(),
-    poolboy:transaction(?RESOLVER_POOL, fun(Pid) -> dns_resolver:forward(Pid, ReceiverPid, Ref, Request, QueryMsg) end).
-
 -spec build_response(QueryMsg :: #dns_message{}, Dns_cache :: #dns_cache{}) -> RespMsg :: #dns_message{}.
 build_response(QueryMsg, #dns_cache{expire_at = ExpireAt, answers = Answers, authority = Authority, additional = Additional, rc = RCode, flags = #{aa := AA}}) ->
     Now = os:system_time(second),
@@ -260,4 +180,24 @@ build_ip_packet(SAddr, DAddr, SPort, DPort, UdpPayload) when is_integer(SPort),
     IpCheckSum = dns_utils:ip_checksum(IpPacket0),
     IpHeader = pkt:ipv4(IpPacket0#ipv4{sum = IpCheckSum}),
 
-    <<IpHeader/binary, IpPayload/binary>>.
+    <<IpHeader/binary, IpPayload/binary>>.
+
+-spec forward_to_upstream(Request :: binary(), QueryMsg :: #dns_message{}) -> no_return().
+forward_to_upstream(Request, #dns_message{id = TxId, questions = [#dns_query{name = QName, type = QType, class = QClass}|_]}) ->
+    {ok, {DnsIp, DnsPort}} = application:get_env(sdlan, public_dns_server),
+    {ok, Socket} = gen_udp:open(0, [binary, {active, true}]),
+    ok = gen_udp:send(Socket, DnsIp, DnsPort, Request),
+    logger:debug("[dns_resolver] send to: ~p, packet: ~p", [{DnsIp, DnsPort}, Request]),
+    receive
+        {udp, Socket, DnsIp, DnsPort, Resp} ->
+            try dns:decode_message(Resp) of
+                #dns_message{id = TxId, questions = [#dns_query{name = QName, type = QType, class = QClass}|_]} ->
+                    {ok, Resp};
+                _ ->
+                    {error, invalid_dns_response}
+            catch error:Err ->
+                {error, Err}
+            end
+    after 2000 ->
+        {error, timeout}
+    end.

apps/sdlan/src/dns_proxy/dns_server.erl

@@ -14,11 +14,6 @@ loop(Sock) ->
     receive
         {udp, Sock, Ip, Port, Packet} ->
             logger:debug("[dns_server] ip: ~p, get a packet: ~p", [{Ip, Port}, Packet]),
-            case dns_handler_sup:start_handler() of
+            spawn(fun() -> dns_handler:handle(Sock, Ip, Port, Packet) end),
-                {ok, HandlerPid} ->
-                    dns_handler:handle_ip_packet(HandlerPid, Sock, Ip, Port, Packet);
-                Error ->
-                    logger:debug("[dns_server] start handler get error: ~p", [Error])
-            end,
             loop(Sock)
     end.