From d33fe7e5403038ed67a60e62e6cbca21a3ab1dc0 Mon Sep 17 00:00:00 2001
From: anlicheng <244108715@qq.com>
Date: Fri, 5 Dec 2025 18:32:06 +0800
Subject: [PATCH] =?UTF-8?q?=E5=86=85=E9=83=A8=E8=A7=A3=E6=9E=90ip=E5=9C=B0?=
 =?UTF-8?q?=E5=9D=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 apps/dns_proxy/src/dns_handler.erl | 82 +++++++++++++++++++++---------
 apps/dns_proxy/src/dns_utils.erl   | 28 ++++++++++
 2 files changed, 87 insertions(+), 23 deletions(-)
 create mode 100644 apps/dns_proxy/src/dns_utils.erl

diff --git a/apps/dns_proxy/src/dns_handler.erl b/apps/dns_proxy/src/dns_handler.erl
index 90ca8e2..8c24d30 100644
--- a/apps/dns_proxy/src/dns_handler.erl
+++ b/apps/dns_proxy/src/dns_handler.erl
@@ -74,30 +74,57 @@ handle_call(_Request, _From, State = #state{}) ->
     {stop, Reason :: term(), NewState :: #state{}}).
 handle_cast(handle, State = #state{socket = Sock, src_ip = SrcIp, src_port = SrcPort, packet = Packet}) ->
     case dns:decode_message(Packet) of
-        QueryMsg = #dns_message{qc = 1, questions = [Question|_]} ->
-            case dns_cache:lookup(Question) of
-                {hit, Cache} ->
-                    lager:debug("[dns_handler] question: ~p, hit cache: ~p", [Question, Cache]),
-                    RespMsg = build_response(QueryMsg, Cache),
+        QueryMsg = #dns_message{qc = 1, questions = [Question = #dns_query{name = QName, type = QType, class = QClass}|_]} ->
+            %% 查找是否是内置的域名
+            case search_inbuilt_domain(QName) of
+                {ok, Ip} ->
+                    Answer = #dns_rr {
+                        name = QName,
+                        type = QType,
+                        class = QClass,
+                        ttl = 300,
+                        data = #dns_rrdata_a {
+                            ip = Ip
+                        }
+                    },
+                    RespMsg = QueryMsg#dns_message{
+                        qr = true,
+                        ra = true,
+                        anc = 1,
+                        auc = 0,
+                        adc = 0,
+                        answers = [Answer],
+                        authority = [],
+                        additional = []
+                    },
                     gen_udp:send(Sock, SrcIp, SrcPort, dns:encode_message(RespMsg)),
+
                     {stop, normal, State};
-                miss ->
-                    lager:debug("[dns_handler] cache is miss"),
-                    Ref = make_ref(),
-                    forward_to_upstream(Ref, Packet, QueryMsg),
-                    receive
-                        {dns_resolver_reply, Ref, Resp} ->
-                            case dns:decode_message(Resp) of
-                                RespMsg = #dns_message{answers = Answers} ->
-                                    lager:debug("[dns_handler] get a response answers: ~p", [Answers]),
-                                    dns_cache:insert(Question, RespMsg),
-                                    gen_udp:send(Sock, SrcIp, SrcPort, Resp);
-                                Other ->
-                                    lager:debug("[dns_handler] parse reply get error: ~p", [Other])
-                            end,
-                            {stop, normal, State}
-                    after 5000 ->
-                        {stop, normal, State}
+                error ->
+                    case dns_cache:lookup(Question) of
+                        {hit, Cache} ->
+                            lager:debug("[dns_handler] question: ~p, hit cache answers: ~p", [Question, Cache#dns_cache.answers]),
+                            RespMsg = build_response(QueryMsg, Cache),
+                            gen_udp:send(Sock, SrcIp, SrcPort, dns:encode_message(RespMsg)),
+                            {stop, normal, State};
+                        miss ->
+                            lager:debug("[dns_handler] cache is miss"),
+                            Ref = make_ref(),
+                            forward_to_upstream(Ref, Packet, QueryMsg),
+                            receive
+                                {dns_resolver_reply, Ref, Resp} ->
+                                    case dns:decode_message(Resp) of
+                                        RespMsg = #dns_message{answers = Answers} ->
+                                            lager:debug("[dns_handler] get a response answers: ~p", [Answers]),
+                                            dns_cache:insert(Question, RespMsg),
+                                            gen_udp:send(Sock, SrcIp, SrcPort, Resp);
+                                        Other ->
+                                            lager:debug("[dns_handler] parse reply get error: ~p", [Other])
+                                    end,
+                                    {stop, normal, State}
+                            after 5000 ->
+                                {stop, normal, State}
+                            end
                     end
             end;
         Other ->
@@ -167,4 +194,13 @@ build_response(QueryMsg, #dns_cache{expire_at = ExpireAt, answers = Answers, aut
 adjust_ttl(RR = #dns_rr{}, RemainingTTL) ->
     RR#dns_rr{ttl = max(0, RemainingTTL)};
 adjust_ttl(RR, _RemainingTTL) ->
-    RR.
\ No newline at end of file
+    RR.
+
+search_inbuilt_domain(QName) when is_binary(QName) ->
+    Suffix = <<".iot.cn">>,
+    case dns_utils:ends_with(QName, Suffix) of
+        true ->
+            {ok, {192, 168, 1, 101}};
+        false ->
+            error
+    end.
\ No newline at end of file
diff --git a/apps/dns_proxy/src/dns_utils.erl b/apps/dns_proxy/src/dns_utils.erl
new file mode 100644
index 0000000..7cef0ef
--- /dev/null
+++ b/apps/dns_proxy/src/dns_utils.erl
@@ -0,0 +1,28 @@
+%%%-------------------------------------------------------------------
+%%% @author anlicheng
+%%% @copyright (C) 2025, <COMPANY>
+%%% @doc
+%%%
+%%% @end
+%%% Created : 05. 12月 2025 18:06
+%%%-------------------------------------------------------------------
+-module(dns_utils).
+-author("anlicheng").
+
+%% API
+-export([ends_with/2, parse_address/1]).
+
+-spec ends_with(Bin :: binary(), Suffix :: binary()) -> boolean().
+ends_with(Bin, Suffix) when is_binary(Bin), is_binary(Suffix) ->
+    case binary:match(Bin, Suffix) of
+        {Pos, Len} ->
+            Pos + Len =:= byte_size(Bin);
+        nomatch ->
+            false
+    end.
+
+-spec parse_address(Ip :: any()) -> {ok, IpAddress :: inet:ip4_address()} | {error, Reason :: any()}.
+parse_address(Ip = {Ip0, Ip1, Ip2, Ip3}) when is_integer(Ip0), is_integer(Ip1), is_integer(Ip2), is_integer(Ip3) ->
+    {ok, Ip};
+parse_address(Bin) when is_binary(Bin) ->
+    inet:parse_address(binary_to_list(Bin)).