File 3547-Revise-handling-of-IPv4-compatible-IPv6-address-look.patch of Package erlang

From f52792b570a9d27f724fa0a107519b8f449c3de2 Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Fri, 2 Jul 2021 12:09:27 +0200
Subject: [PATCH 7/8] Revise handling of IPv4-compatible IPv6 address lookup

---
 lib/kernel/src/inet_db.erl  | 43 +++++++++++++++++--------------------
 lib/kernel/src/inet_res.erl | 16 +++++++++++++-
 2 files changed, 35 insertions(+), 24 deletions(-)

diff --git a/lib/kernel/src/inet_db.erl b/lib/kernel/src/inet_db.erl
index 4644bea344..f95d8c0eec 100644
--- a/lib/kernel/src/inet_db.erl
+++ b/lib/kernel/src/inet_db.erl
@@ -773,11 +773,11 @@ gethostbyaddr(Domain, IP) ->
 %% res_gethostbyaddr (newly resolved version)
 %% match data field directly and cache RRs.
 %%
-res_gethostbyaddr(Name, IP, Rec) ->
+res_gethostbyaddr(Domain, IP, Rec) ->
     RRs = res_filter_rrs(?S_PTR, Rec#dns_rec.anlist),
     ?dbg("res_gethostbyaddr: ~p - ~p~n", [IP, RRs]),
     LookupFun = res_lookup_fun(RRs),
-    case resolve_cnames(Name, ?S_PTR, LookupFun) of
+    case resolve_cnames(Domain, ?S_PTR, LookupFun) of
         {error, _} = Error ->
             Error;
         {_D, Domains, _Aliases} ->
@@ -791,31 +791,28 @@ res_gethostbyaddr(Name, IP, Rec) ->
     end.
 
 ent_gethostbyaddr([Domain], IP) ->
-    {IP_1, AddrType, Length} = norm_ip(IP),
-    H =
-        #hostent{
-           h_name = Domain,
-           h_aliases = [],
-           h_addr_list = [IP_1],
-           h_addrtype = AddrType,
-           h_length = Length },
-    {ok, H};
+    HEnt =
+        if
+            tuple_size(IP) =:= 4 ->
+                #hostent{
+                   h_name = Domain,
+                   h_aliases = [],
+                   h_addr_list = [IP],
+                   h_addrtype = inet,
+                   h_length = 4};
+            tuple_size(IP) =:= 8 ->
+                #hostent{
+                   h_name = Domain,
+                   h_aliases = [],
+                   h_addr_list = [IP],
+                   h_addrtype = inet6,
+                   h_length = 16}
+        end,
+    {ok, HEnt};
 ent_gethostbyaddr([_ | _] = _Domains, _IP) ->
     ?dbg("gethostbyaddr duplicate domains=~p~n", [_Domains]),
     {error, nxdomain}.
 
-%% Normalize an IPv4-compatible IPv6 address
-%% into a plain IPv4 address
-%%
-norm_ip(IP) when tuple_size(IP) =:= 4 ->
-    {IP, inet, 4};
-norm_ip({0,0,0,0,0,16#ffff,G,H}) ->
-    A = G bsr 8, B = G band 16#ff, C = H bsr 8, D = H band 16#ff,
-    {{A,B,C,D}, inet, 4};
-norm_ip(IP) when tuple_size(IP) =:= 8 ->
-    {IP, inet6, 16}.
-
-
 
 %%
 %% Register socket Modules
diff --git a/lib/kernel/src/inet_res.erl b/lib/kernel/src/inet_res.erl
index f5ab7e6a23..fda656831e 100644
--- a/lib/kernel/src/inet_res.erl
+++ b/lib/kernel/src/inet_res.erl
@@ -363,7 +363,12 @@ gethostbyaddr_tm(Addr, Timer) when is_list(Addr) ->
 	_Error -> {error, formerr}
     end;
 gethostbyaddr_tm(IP, Timer) ->
-    case dn_ip(IP) of
+    %% The call to norm_ip/1 here translates a lookup of
+    %% ::ffff:A.B.C.D (AAAA in ...ip6.arpa) into a plain
+    %% A.B.C.D (A in ...in-addr.arpa) lookup, and pretends
+    %% the result as if it was from the original IPv6 lookup
+    %%
+    case dn_ip(norm_ip(IP)) of
         {error, _} = Error ->
             Error;
         Name ->
@@ -1203,6 +1208,15 @@ dn_hex(N, Tail) when is_integer(N) ->
             [(N - 10) + $a, $. | Tail]
 end.
 
+%% Normalize an IPv4-compatible IPv6 address
+%% into a plain IPv4 address
+%%
+norm_ip({0,0,0,0,0,16#ffff,G,H}) ->
+    A = G bsr 8, B = G band 16#ff, C = H bsr 8, D = H band 16#ff,
+    {A,B,C,D};
+norm_ip(IP) ->
+    IP.
+
 
 
 dns_msg([]) -> [];
-- 
2.31.1