Merge branch 'raimo/stop-encouraging-v4-mapped/ERL-503/OTP-13716'

* raimo/stop-encouraging-v4-mapped/ERL-503/OTP-13716:
  Stop translating V4MAPPED addresses
  Stop returning V4MAPPED addresses
  Implement function for IPv4-mapped IPv6 addresses

6 files changed, 55 insertions, 45 deletions

diff --git a/lib/kernel/doc/src/inet.xml b/lib/kernel/doc/src/inet.xml
index abb045b744..9552332948 100644
--- a/lib/kernel/doc/src/inet.xml
+++ b/lib/kernel/doc/src/inet.xml
@@ -4,7 +4,7 @@
 <erlref>
   <header>
     <copyright>
-      <year>1997</year><year>2017</year>
+      <year>1997</year><year>2018</year>
       <holder>Ericsson AB. All Rights Reserved.</holder>
     </copyright>
     <legalnotice>
@@ -277,9 +277,7 @@ fe80::204:acff:fe17:bf38
         <p>Returns a <c>hostent</c> record for the host with the specified
           hostname.</p>
         <p>If resolver option <c>inet6</c> is <c>true</c>,
-          an IPv6 address is looked up. If that fails,
-          the IPv4 address is looked up and returned on
-          IPv6-mapped IPv4 format.</p>
+          an IPv6 address is looked up.</p>
       </desc>
     </func>
 
@@ -582,6 +580,19 @@ get_tcpi_sacked(Sock) ->
     </func>
 
     <func>
+      <name name="ipv4_mapped_ipv6_address" arity="1" />
+      <fsummary>Convert to and from IPv4-mapped IPv6 address.</fsummary>
+      <desc>
+	<p>
+	  Convert an IPv4 address to an IPv4-mapped IPv6 address
+	  or the reverse.  When converting from an IPv6 address
+	  all but the 2 low words are ignored so this function also
+	  works on some other types of addresses than IPv4-mapped.
+	</p>
+      </desc>
+    </func>
+
+    <func>
       <name name="parse_strict_address" arity="1" />
       <fsummary>Parse an IPv4 or IPv6 address strict.</fsummary>
       <desc>
diff --git a/lib/kernel/doc/src/inet_res.xml b/lib/kernel/doc/src/inet_res.xml
index 3454e3c6f9..351d86a93a 100644
--- a/lib/kernel/doc/src/inet_res.xml
+++ b/lib/kernel/doc/src/inet_res.xml
@@ -4,7 +4,7 @@
 <erlref>
   <header>
     <copyright>
-      <year>2009</year><year>2015</year>
+      <year>2009</year><year>2018</year>
       <holder>Ericsson AB. All Rights Reserved.</holder>
     </copyright>
     <legalnotice>
@@ -230,9 +230,7 @@ inet_dns:record_type(_) -> undefined.</pre>
           <seealso marker="#getbyname/2"><c>getbyname/2,3</c></seealso>.
         </p>
         <p>If resolver option <c>inet6</c> is <c>true</c>,
-          an IPv6 address is looked up. If that fails,
-          the IPv4 address is looked up and returned on
-          IPv6-mapped IPv4 format.</p>
+          an IPv6 address is looked up.</p>
       </desc>
     </func>
 
diff --git a/lib/kernel/src/inet.erl b/lib/kernel/src/inet.erl
index fe91b0d33e..4bad523dff 100644
--- a/lib/kernel/src/inet.erl
+++ b/lib/kernel/src/inet.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1997-2017. All Rights Reserved.
+%% Copyright Ericsson AB 1997-2018. All Rights Reserved.
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -34,7 +34,8 @@
 	 ip/1, stats/0, options/0, 
 	 pushf/3, popf/1, close/1, gethostname/0, gethostname/1, 
 	 parse_ipv4_address/1, parse_ipv6_address/1, parse_ipv4strict_address/1,
-	 parse_ipv6strict_address/1, parse_address/1, parse_strict_address/1, ntoa/1]).
+	 parse_ipv6strict_address/1, parse_address/1, parse_strict_address/1,
+         ntoa/1, ipv4_mapped_ipv6_address/1]).
 
 -export([connect_options/2, listen_options/2, udp_options/2, sctp_options/2]).
 -export([udp_module/1, tcp_module/1, tcp_module/2, sctp_module/1]).
@@ -675,6 +676,14 @@ parse_address(Addr) ->
 parse_strict_address(Addr) ->
     inet_parse:strict_address(Addr).
 
+-spec ipv4_mapped_ipv6_address(ip_address()) -> ip_address().
+ipv4_mapped_ipv6_address({D1,D2,D3,D4})
+  when (D1 bor D2 bor D3 bor D4) < 256 ->
+    {0,0,0,0,0,16#ffff,(D1 bsl 8) bor D2,(D3 bsl 8) bor D4};
+ipv4_mapped_ipv6_address({D1,D2,D3,D4,D5,D6,D7,D8})
+  when (D1 bor D2 bor D3 bor D4 bor D5 bor D6 bor D7 bor D8) < 65536 ->
+    {D7 bsr 8,D7 band 255,D8 bsr 8,D8 band 255}.
+
 %% Return a list of available options
 options() ->
     [
@@ -1244,9 +1253,7 @@ gethostbyname_string(Name, Type)
 	    inet ->
 		inet_parse:ipv4_address(Name);
 	    inet6 ->
-		%% XXX should we really translate IPv4 addresses here
-		%% even if we do not know if this host can do IPv6?
-		inet_parse:ipv6_address(Name)
+		inet_parse:ipv6strict_address(Name)
 	end of
 	{ok,IP} ->
 	    {ok,make_hostent(Name, [IP], [], Type)};
diff --git a/lib/kernel/src/inet_hosts.erl b/lib/kernel/src/inet_hosts.erl
index 0bdf00ac30..fc653bf0d3 100644
--- a/lib/kernel/src/inet_hosts.erl
+++ b/lib/kernel/src/inet_hosts.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %% 
-%% Copyright Ericsson AB 1997-2016. All Rights Reserved.
+%% Copyright Ericsson AB 1997-2018. All Rights Reserved.
 %% 
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -72,9 +72,6 @@ gethostbyname(Name, Type, Byname, Byaddr) ->
 
 gethostbyaddr({A,B,C,D}=IP) when ?ip(A,B,C,D) ->
     gethostbyaddr(IP, inet);
-%% ipv4  only ipv6 address
-gethostbyaddr({0,0,0,0,0,16#ffff=F,G,H}) when ?ip6(0,0,0,0,0,F,G,H) ->
-    gethostbyaddr({G bsr 8, G band 255, H bsr 8, H band 255});
 gethostbyaddr({A,B,C,D,E,F,G,H}=IP) when ?ip6(A,B,C,D,E,F,G,H) ->
     gethostbyaddr(IP, inet6);
 gethostbyaddr(Addr) when is_list(Addr) ->
diff --git a/lib/kernel/src/inet_res.erl b/lib/kernel/src/inet_res.erl
index 49aa5f8bda..6454802b04 100644
--- a/lib/kernel/src/inet_res.erl
+++ b/lib/kernel/src/inet_res.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1997-2016. All Rights Reserved.
+%% Copyright Ericsson AB 1997-2018. All Rights Reserved.
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -349,9 +349,6 @@ gethostbyaddr_tm({A,B,C,D} = IP, Timer) when ?ip(A,B,C,D) ->
 	{ok, HEnt} -> {ok, HEnt};
 	_ -> res_gethostbyaddr(dn_in_addr_arpa(A,B,C,D), IP, Timer)
     end;
-%% ipv4  only ipv6 address
-gethostbyaddr_tm({0,0,0,0,0,16#ffff,G,H},Timer) when is_integer(G+H) ->
-    gethostbyaddr_tm({G div 256, G rem 256, H div 256, H rem 256},Timer);
 gethostbyaddr_tm({A,B,C,D,E,F,G,H} = IP, Timer) when ?ip6(A,B,C,D,E,F,G,H) ->
     inet_db:res_update_conf(),
     case inet_db:gethostbyaddr(IP) of
@@ -431,28 +428,7 @@ gethostbyname(Name,Family,Timeout) ->
 gethostbyname_tm(Name,inet,Timer) ->
     getbyname_tm(Name,?S_A,Timer);
 gethostbyname_tm(Name,inet6,Timer) ->
-    case getbyname_tm(Name,?S_AAAA,Timer) of
-	{ok,HEnt} -> {ok,HEnt};
-	{error,nxdomain} ->
-	    case getbyname_tm(Name, ?S_A,Timer) of
-		{ok, HEnt} ->
-		    %% rewrite to a ipv4 only ipv6 address
-		    {ok,
-		     HEnt#hostent {
-		       h_addrtype = inet6,
-		       h_length = 16,
-		       h_addr_list = 
-		       lists:map(
-			 fun({A,B,C,D}) ->
-				 {0,0,0,0,0,16#ffff,A*256+B,C*256+D}
-			 end, HEnt#hostent.h_addr_list)
-		      }};
-		Error ->
-		    Error
-	    end;
-	Error ->
-	    Error
-    end;
+    getbyname_tm(Name,?S_AAAA,Timer);
 gethostbyname_tm(_Name, _Family, _Timer) ->
     {error, einval}.
 	    
diff --git a/lib/kernel/test/inet_SUITE.erl b/lib/kernel/test/inet_SUITE.erl
index ba0d075ef2..2e5f8c7d2c 100644
--- a/lib/kernel/test/inet_SUITE.erl
+++ b/lib/kernel/test/inet_SUITE.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1997-2017. All Rights Reserved.
+%% Copyright Ericsson AB 1997-2018. All Rights Reserved.
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -40,7 +40,8 @@
 	 lookup_bad_search_option/1,
 	 getif/1,
 	 getif_ifr_name_overflow/1,getservbyname_overflow/1, getifaddrs/1,
-	 parse_strict_address/1, simple_netns/1, simple_netns_open/1,
+	 parse_strict_address/1, ipv4_mapped_ipv6_address/1,
+         simple_netns/1, simple_netns_open/1,
          simple_bind_to_device/1, simple_bind_to_device_open/1]).
 
 -export([get_hosts/1, get_ipv6_hosts/1, parse_hosts/1, parse_address/1,
@@ -667,6 +668,26 @@ parse_strict_address(Config) when is_list(Config) ->
     {ok, {3089,3106,23603,50240,0,0,119,136}} =
 	inet:parse_strict_address("c11:0c22:5c33:c440::077:0088").
 
+ipv4_mapped_ipv6_address(Config) when is_list(Config) ->
+    {D1,D2,D3,D4} = IPv4Address =
+        {rand:uniform(256) - 1,
+         rand:uniform(256) - 1,
+         rand:uniform(256) - 1,
+         rand:uniform(256) - 1},
+    E7 = (D1 bsl 8) bor D2,
+    E8 = (D3 bsl 8) bor D4,
+    io:format("IPv4Address: ~p.~n", [IPv4Address]),
+    {0,0,0,0,0,65535,E7,E8} = inet:ipv4_mapped_ipv6_address(IPv4Address),
+    IPv6Address =
+        {rand:uniform(65536) - 1,
+         rand:uniform(65536) - 1,
+         rand:uniform(65536) - 1,
+         rand:uniform(65536) - 1,
+         rand:uniform(65536) - 1,
+         rand:uniform(65536) - 1, E7, E8},
+    IPv4Address = inet:ipv4_mapped_ipv6_address(IPv6Address),
+    ok.
+
 t_gethostnative(Config) when is_list(Config) ->
     %% this will result in 26 bytes sent which causes problem in Windows
     %% if the port-program has not assured stdin to be read in BINARY mode