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File 3351-inet_res-add-option-to-include-the-DNS-reply-in-nxdo.patch of Package erlang (Revision fab5cf9be99874816e9cecc0e0f8d85e)

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From f03b859396c5b0b53bc012f0c31be599ab2648e4 Mon Sep 17 00:00:00 2001
From: Andreas Schultz <andreas.schultz@travelping.com>
Date: Tue, 2 Mar 2021 13:05:51 +0100
Subject: [PATCH 1/2] inet_res: add option to include the DNS reply in nxdomain
 errors

A nxdomain error from a name server does contain the SOA record if
the domain exists at all. This record is usefull to determine a TTL
for negative caching of the failed entry.
---
 lib/kernel/doc/src/inet_res.xml    |  6 +++++
 lib/kernel/src/inet_res.erl        | 36 +++++++++++++++++++++---------
 lib/kernel/test/inet_res_SUITE.erl | 21 ++++++++++++++++-
 3 files changed, 51 insertions(+), 12 deletions(-)

diff --git a/lib/kernel/doc/src/inet_res.xml b/lib/kernel/doc/src/inet_res.xml
index 690d1c61d1..0d654bbc0e 100644
--- a/lib/kernel/doc/src/inet_res.xml
+++ b/lib/kernel/doc/src/inet_res.xml
@@ -299,6 +299,12 @@ inet_dns:record_type(_) -> undefined.</pre>
           <seemfa marker="stdlib:io#format/3"><c>io:format/2</c></seemfa>
           of queries, replies retransmissions, and so on, similar
           to from utilities, such as <c>dig</c> and <c>nslookup</c>.</p>
+        <p>Option <c>nxdomain_reply</c> (or rather <c>{nxdomain_reply,true}</c>)
+	  causes nxdomain errors from DNS servers to be returned as
+	  <c>{error, {nxdomain, dns_msg()}}</c>.
+	  <c>dns_msg()</c> contains the additional sections that where included
+	  by the answering server. This is mainly useful to inspect the SOA record
+	  to get the TTL for negative caching.</p>
         <p>If <c><anno>Opt</anno></c> is any atom, it is interpreted
           as <c>{<anno>Opt</anno>,true}</c> unless the atom string starts with
           <c>"no"</c>, making the
diff --git a/lib/kernel/src/inet_res.erl b/lib/kernel/src/inet_res.erl
index 4208e30c08..536b5abccc 100644
--- a/lib/kernel/src/inet_res.erl
+++ b/lib/kernel/src/inet_res.erl
@@ -61,7 +61,8 @@
       | {retry, integer()}
       | {timeout, integer()}
       | {udp_payload_size, integer()}
-      | {usevc, boolean()}.
+      | {usevc, boolean()}
+      | {nxdomain_reply, boolean()}.
 
 -type nameserver() :: {inet:ip_address(), Port :: 1..65535}.
 
@@ -262,7 +263,7 @@ do_nslookup(Name, Class, Type, Opts, Timeout) ->
 %% options record
 %%
 -record(options, { % These must be sorted!
-	  alt_nameservers,edns,inet6,nameservers,recurse,
+	  alt_nameservers,edns,inet6,nameservers,nxdomain_reply,recurse,
 	  retry,servfail_retry_timeout,timeout,udp_payload_size,usevc,
 	  verbose}). % this is a local option, not in inet_db
 %%
@@ -304,6 +305,12 @@ make_options([{verbose,Val}|Opts]=Opts0, [verbose|Names]=Names0) ->
        true ->
 	    erlang:error(badarg, [Opts0,Names0])
     end;
+make_options([{nxdomain_reply,Val}|Opts]=Opts0, [nxdomain|Names]=Names0) ->
+    if is_boolean(Val) ->
+	    [Val|make_options(Opts, Names)];
+       true ->
+	    erlang:error(badarg, [Opts0,Names0])
+    end;
 make_options([{Opt,Val}|Opts]=Opts0, [Opt|Names]=Names0) ->
     case inet_db:res_check_option(Opt, Val) of
 	true ->
@@ -313,6 +320,8 @@ make_options([{Opt,Val}|Opts]=Opts0, [Opt|Names]=Names0) ->
     end;
 make_options(Opts, [verbose|Names]) ->
     [false|make_options(Opts, Names)];
+make_options(Opts, [nxdomain_reply|Names]) ->
+    [false|make_options(Opts, Names)];
 make_options(Opts, [Name|Names]) ->
     [inet_db:res_option(Name)|make_options(Opts, Names)].
 
@@ -778,10 +787,10 @@ do_query(#q{options=#options{retry=Retry}}=Q, NSs, Timer) ->
 
 %% Loop until out of retries or name servers
 %%
-query_retries(_Q, _NSs, _Timer, Retry, I, S, Reason) when Retry =:= I ->
-    query_retries_error(S, Reason);
-query_retries(_Q, [], _Timer, _Retry, _I, S, Reason) ->
-    query_retries_error(S, Reason);
+query_retries(Q, _NSs, _Timer, Retry, I, S, Reason) when Retry =:= I ->
+    query_retries_error(Q, S, Reason);
+query_retries(Q, [], _Timer, _Retry, _I, S, Reason) ->
+    query_retries_error(Q, S, Reason);
 query_retries(Q, NSs, Timer, Retry, I, S, Reason) ->
     query_nss(Q, NSs, Timer, Retry, I, S, Reason, []).
 
@@ -878,9 +887,9 @@ query_nss_result(Q, NSs, Timer, Retry, I, S, Reason, RetryNSs, NS, Result) ->
             _ = udp_close(S),
             Result;
 	timeout -> % Out of total time timeout
-            query_retries_error(S, Reason); % The best reason we have
-	{error,{nxdomain=E,_}} ->
-            query_retries_error(S, E); % Definite answer
+            query_retries_error(Q, S, Reason); % The best reason we have
+	{error,{nxdomain,_} = E} ->
+            query_retries_error(Q, S, E); % Definite answer
 	{error,{E,_}=NewReason}
           when E =:= qfmterror;
                E =:= notimp;
@@ -924,9 +933,14 @@ query_nss_result(Q, NSs, Timer, Retry, I, S, Reason, RetryNSs, NS, Result) ->
 	    query_nss(Q, NSs, Timer, Retry, I, S, NewReason, [NS|RetryNSs])
     end.
 
-query_retries_error(S, Reason) ->
+query_retries_error(#q{options=#options{nxdomain_reply=NxReply}}, S, Reason) ->
     _ = udp_close(S),
-    {error, Reason}.
+    case Reason of
+        {nxdomain, _} when not NxReply ->
+            {error, nxdomain};
+        _ ->
+            {error, Reason}
+    end.
 
 
 query_ns(S0, Id, Buffer, IP, Port, Timer, Retry, I,
diff --git a/lib/kernel/test/inet_res_SUITE.erl b/lib/kernel/test/inet_res_SUITE.erl
index 9e25411f74..24e0e40e77 100644
--- a/lib/kernel/test/inet_res_SUITE.erl
+++ b/lib/kernel/test/inet_res_SUITE.erl
@@ -32,7 +32,7 @@
 	 init_per_testcase/2, end_per_testcase/2
         ]).
 -export([basic/1, resolve/1, edns0/1, txt_record/1, files_monitor/1,
-	 last_ms_answer/1, intermediate_error/1,
+	 nxdomain_reply/1, last_ms_answer/1, intermediate_error/1,
          servfail_retry_timeout_default/1, servfail_retry_timeout_1000/1,
          label_compression_limit/1
         ]).
@@ -127,6 +127,7 @@ zone_dir(TC) ->
 	resolve            -> otptest;
 	edns0              -> otptest;
 	files_monitor      -> otptest;
+	nxdomain_reply     -> otptest;
 	last_ms_answer     -> otptest;
         intermediate_error ->
             {internal,
@@ -933,6 +934,24 @@ do_files_monitor(Config) ->
 	inet:gethostbyname("resolve.otptest"),
     ok.
 
+%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Get full DNS answer on nxdomain (when option set)
+%% Check that we get the error code from the first server.
+
+nxdomain_reply(Config) when is_list(Config) ->
+    NS        = ns(Config),
+    Name      = "nxdomain.otptest",
+    Class     = in,
+    Type      = a,
+    Opts      = [{nameservers,[NS]}, {servfail_retry_timeout, 1000}, verbose],
+    ?P("try resolve"),
+    {error, nxdomain} = inet_res:resolve(Name, Class, Type, Opts),
+    {error, {nxdomain, Rec}} = inet_res:resolve(Name, Class, Type, [nxdomain_reply|Opts]),
+    ?P("resolved: "
+       "~n      ~p", [Rec]),
+    ok.
+
+
 %% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 %% Answer just when timeout is triggered (OTP-9221).
-- 
2.26.2

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File 3351-inet_res-add-option-to-include-the-DNS-reply-in-nxdo.patch of Package erlang (Revision fab5cf9be99874816e9cecc0e0f8d85e)

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