File 0366-Rewrite-cname-lookups.patch of Package erlang

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File 0366-Rewrite-cname-lookups.patch of Package erlang (Revision 76356621c41f37937556526d87dbca4f)

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From 8dd980a138c201e7ee2b099c3bbda7f470c2986a Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Fri, 18 Jun 2021 18:35:03 +0200
Subject: [PATCH 6/8] Rewrite cname lookups

---
 lib/kernel/src/inet_db.erl  | 284 +++++++++++++++---------------------
 lib/kernel/src/inet_res.erl | 167 ++++++++++++---------
 2 files changed, 211 insertions(+), 240 deletions(-)

diff --git a/lib/kernel/src/inet_db.erl b/lib/kernel/src/inet_db.erl
index 0a749030ef..4644bea344 100644
--- a/lib/kernel/src/inet_db.erl
+++ b/lib/kernel/src/inet_db.erl
@@ -67,8 +67,8 @@
 -export([res_option/1, res_option/2, res_check_option/2]).
 -export([socks_option/1]).
 -export([getbyname/2, get_searchlist/0]).
--export([gethostbyaddr/1]).
--export([res_gethostbyaddr/2,res_hostent_by_domain/3]).
+-export([gethostbyaddr/2]).
+-export([res_gethostbyaddr/3,res_hostent_by_domain/3]).
 -export([res_update_conf/0, res_update_hosts/0]).
 %% inet help functions
 -export([tolower/1, eq_domains/2]).
@@ -651,6 +651,34 @@ get_searchlist() ->
     end.
 
 
+%%
+%% hostent_by_domain (cache version)
+%%
+hostent_by_domain(Domain, Type) ->
+    ?dbg("hostent_by_domain: ~p~n", [Domain]),
+    case resolve_cnames(stripdot(Domain), Type, fun lookup_cache_data/2) of
+        {error, _} = Error ->
+            Error;
+        {D, Addrs, Aliases} ->
+            {ok, make_hostent(D, Addrs, Aliases, Type)}
+    end.
+
+%%
+%% hostent_by_domain (newly resolved version)
+%% match data field directly and cache RRs.
+%%
+res_hostent_by_domain(Domain, Type, Rec) ->
+    RRs = res_filter_rrs(Type, Rec#dns_rec.anlist),
+    ?dbg("res_hostent_by_domain: ~p - ~p~n", [Domain, RRs]),
+    LookupFun = res_lookup_fun(RRs),
+    case resolve_cnames(stripdot(Domain), Type, LookupFun) of
+        {error, _} = Error ->
+            Error;
+        {D, Addrs, Aliases} ->
+            res_cache_answer(RRs),
+            {ok, make_hostent(D, Addrs, Aliases, Type)}
+    end.
+
 make_hostent(Name, Addrs, Aliases, ?S_A) ->
     #hostent {
 	      h_name = Name,
@@ -677,181 +705,117 @@ make_hostent(Name, Datas, Aliases, Type) ->
 	      h_aliases = Aliases
 	     }.
 
-hostent_by_domain(Domain, Type) ->
-    ?dbg("hostent_by_domain: ~p~n", [Domain]),
-    hostent_by_domain(stripdot(Domain), [], [], Type).
-
-hostent_by_domain(Domain, Aliases, LAliases, Type) ->
-    case lookup_type(Domain, Type) of
-	[] ->
-	    case lookup_cname(Domain) of
-		[] ->  
-		    {error, nxdomain};
-		[CName | _] ->
-		    LDomain = tolower(Domain),
-		    case lists:member(CName, [LDomain | LAliases]) of
-                        true -> 
-			    {error, nxdomain};
-                        false ->
-			    hostent_by_domain(CName, [Domain | Aliases],
-					      [LDomain | LAliases], Type)
-		    end
-	    end;
-	Addrs ->
-	    {ok, make_hostent(Domain, Addrs, Aliases, Type)}
-    end.
 
-%% lookup canonical name
-lookup_cname(Domain) ->
-    lookup_type(Domain, ?S_CNAME).
 
-%% lookup address record
-lookup_type(Domain, Type) ->
-    [R#dns_rr.data || R <- lookup_rr(Domain, in, Type) ].
-
-%% lookup resource record
-lookup_rr(Domain, Class, Type) ->
-    match_rr(dns_rr_match(tolower(Domain), Class, Type)).
-
-%%
-%% hostent_by_domain (newly resolved version)
-%% match data field directly and cache RRs.
-%%
-res_hostent_by_domain(Domain, Type, Rec) ->
-    RRs =
-        [RR#dns_rr{bm = tolower(N)} ||
-            #dns_rr{
-               domain = N,
-               class = in,
-               type = T} = RR <- Rec#dns_rec.anlist,
-            T =:= Type orelse T =:= ?S_CNAME],
-    res_cache_answer(RRs),
-    ?dbg("res_hostent_by_domain: ~p - ~p~n", [Domain, RRs]),
-    Domain_1 = stripdot(Domain),
-    res_hostent_by_domain(Domain_1, tolower(Domain_1), [], [], Type, RRs).
-
-res_hostent_by_domain(Domain, LcDomain, Aliases, LcAliases, Type, RRs) ->
-    case res_lookup_type(LcDomain, Type, RRs) of
-	[] ->
-	    case res_lookup_type(LcDomain, ?S_CNAME, RRs) of
-		[] ->  
-		    {error, nxdomain};
-		[CName | _] ->
-                    LcCName = tolower(CName),
-		    case lists:member(LcCName, [LcDomain | LcAliases]) of
-			true ->
-                            %% CNAME loop
-			    {error, nxdomain};
-			false ->
-			    res_hostent_by_domain(
-                              CName, LcCName,
-                              [Domain | Aliases], [LcDomain | LcAliases],
-                              Type, RRs)
-		    end
-	    end;
-	Addrs ->
-	    {ok, make_hostent(Domain, Addrs, Aliases, Type)}
+res_filter_rrs(Type, RRs) ->
+    [RR#dns_rr{bm = tolower(N)} ||
+        #dns_rr{
+           domain = N,
+           class = in,
+           type = T} = RR <- RRs,
+        T =:= Type orelse T =:= ?S_CNAME].
+
+res_lookup_fun(RRs) ->
+    fun (LcDomain, Type) ->
+            [Data
+             || #dns_rr{bm = LcD, type = T, data = Data}
+                    <- RRs,
+                LcD =:= LcDomain,
+                T   =:= Type]
     end.
 
-%% newly resolved lookup address record
-res_lookup_type(LcDomain, Type, RRs) ->
-    [R#dns_rr.data || R <- RRs,
-		      R#dns_rr.bm   =:= LcDomain,
-		      R#dns_rr.type =:= Type].
 
-%%
-%% gethostbyaddr (cache version)
-%% match data field directly
-%%
-gethostbyaddr(IP) ->
-    case dnip(IP) of
-	{ok, {IP1, HType, HLen, DnIP}} ->
-            gethostbyaddr(IP1, HType, HLen, DnIP, []);
-	Error -> Error
-    end.
+resolve_cnames(Domain, Type, LookupFun) ->
+    resolve_cnames(Domain, Type, LookupFun, tolower(Domain), [], []).
 
-gethostbyaddr(IP, HType, HLen, DnIP, DnIPs) ->
-    MatchPtrRR = dns_rr_match(DnIP, in, ptr),
-    case match_rr(MatchPtrRR) of
+resolve_cnames(Domain, Type, LookupFun, LcDomain, Aliases, LcAliases) ->
+    case LookupFun(LcDomain, Type) of
         [] ->
-            case lookup_cname(DnIP) of
-                [#dns_rr{data = DnIP_1} | _] ->
-                    DnIPs_1 = [DnIP | DnIPs],
-                    %% CNAME loop protection
-                    case lists:member(DnIP_1, DnIPs_1) of
+            case LookupFun(LcDomain, ?S_CNAME) of
+                [] ->
+                    %% Did not find neither Type nor CNAME record
+                    {error, nxdomain};
+                [CName] ->
+                    LcCname = tolower(CName),
+                    case lists:member(LcCname, [LcDomain | LcAliases]) of
                         true ->
+                            %% CNAME loop
                             {error, nxdomain};
                         false ->
-                            gethostbyaddr(IP, HType, HLen, DnIP_1, DnIPs_1)
+                            %% Repeat with the (more) canonical domain name
+                            resolve_cnames(
+                              CName, Type, LookupFun, LcCname,
+                              [Domain | Aliases], [LcDomain, LcAliases])
                     end;
-                CNames when is_list(CNames) ->
+                [_ | _] = _CNames ->
+                    ?dbg("resolve_cnames duplicate cnames=~p~n", [_CNames]),
                     {error, nxdomain}
             end;
-        RRs when is_list(RRs) ->
-            ent_gethostbyaddr(RRs, IP, HType, HLen)
+        [_ | _] = Results ->
+            {Domain, Results, Aliases}
+    end.
+
+
+%%
+%% gethostbyaddr (cache version)
+%% match data field directly
+%%
+gethostbyaddr(Domain, IP) ->
+    ?dbg("gethostbyaddr: ~p~n", [IP]),
+    case resolve_cnames(Domain, ?S_PTR, fun lookup_cache_data/2) of
+        {error, _} = Error ->
+            Error;
+        {_D, Domains, _Aliases} ->
+            ent_gethostbyaddr(Domains, IP)
     end.
 
 %%
 %% res_gethostbyaddr (newly resolved version)
 %% match data field directly and cache RRs.
 %%
-res_gethostbyaddr(IP, Rec) ->
-    {ok, {IP1, HType, HLen}} = dnt(IP),
-    RRs =
-        [RR#dns_rr{bm = tolower(N)} ||
-            #dns_rr{
-               domain = N,
-               class = in,
-               type = T} = RR <- Rec#dns_rec.anlist,
-            T =:= ?S_PTR orelse T =:= ?S_CNAME],
-    res_cache_answer(RRs),
-    case [RR || #dns_rr{type = ?S_PTR} = RR <- RRs] of
-        [] ->
-            {error, nxdomain};
-        PtrRRs ->
-            ent_gethostbyaddr(PtrRRs, IP1, HType, HLen)
+res_gethostbyaddr(Name, 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
+        {error, _} = Error ->
+            Error;
+        {_D, Domains, _Aliases} ->
+            case ent_gethostbyaddr(Domains, IP) of
+                {ok, _HEnt} = Result ->
+                    res_cache_answer(RRs),
+                    Result;
+                {error, _} = Error ->
+                    Error
+            end
     end.
 
-ent_gethostbyaddr([RR|RRs], IP, AddrType, Length) ->
-    %% debug
-    if RRs =/= [] ->
-            ?dbg("gethostbyaddr found extra=~p~n", [RRs]);
-       true -> ok
-    end,
-    Domain = RR#dns_rr.data,
+ent_gethostbyaddr([Domain], IP) ->
+    {IP_1, AddrType, Length} = norm_ip(IP),
     H =
         #hostent{
            h_name = Domain,
-           %% Since a PTR record should point to
-           %% the canonical name, this Domain should
-           %% have no CNAME record, so is this really reasonable?
-           h_aliases = lookup_cname(Domain),
-           h_addr_list = [IP],
+           h_aliases = [],
+           h_addr_list = [IP_1],
            h_addrtype = AddrType,
            h_length = Length },
-    {ok, H}.
+    {ok, H};
+ent_gethostbyaddr([_ | _] = _Domains, _IP) ->
+    ?dbg("gethostbyaddr duplicate domains=~p~n", [_Domains]),
+    {error, nxdomain}.
 
-
-dnip(IP) ->
-    case dnt(IP) of
-	{ok,{IP1 = {A,B,C,D}, inet, HLen}} ->
-	    {ok,{IP1, inet, HLen, dn_in_addr_arpa(A,B,C,D)}};
-	{ok,{IP1 = {A,B,C,D,E,F,G,H}, inet6, HLen}} ->
-	    {ok,{IP1, inet6, HLen, dn_ip6_int(A,B,C,D,E,F,G,H)}};
-	_ ->
-	    {error, formerr}
-    end.
+%% 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}.
 
 
-dnt(IP = {A,B,C,D}) when ?ip(A,B,C,D) ->
-    {ok, {IP, inet, 4}};
-dnt({0,0,0,0,0,16#ffff,G,H}) when is_integer(G+H) ->
-    A = G div 256, B = G rem 256, C = H div 256, D = H rem 256,
-    {ok, {{A,B,C,D}, inet, 4}};
-dnt(IP = {A,B,C,D,E,F,G,H}) when ?ip6(A,B,C,D,E,F,G,H) ->
-    {ok, {IP, inet6, 16}};
-dnt(_) ->
-    {error, formerr}.
 
 %%
 %% Register socket Modules
@@ -1758,6 +1722,11 @@ dns_rr_match(LcDomain, Class, Type, Data) ->
        cnt = '_', tm = '_', ttl = '_', bm = LcDomain, func = '_'}.
 
 
+lookup_cache_data(LcDomain, Type) ->
+    [Data
+     || #dns_rr{data = Data}
+            <- match_rr(dns_rr_match(LcDomain, in, Type))].
+
 %% We are simultaneously updating the table from all clients
 %% and the server, so we might get duplicate recource records
 %% in the table, i.e identical domain, class, type and data.
@@ -1892,25 +1861,6 @@ eq_domains(As, Bs) when is_list(As), is_list(Bs) ->
     false.
 
 
-dn_ip6_int(A,B,C,D,E,F,G,H) ->
-    dnib(H) ++ dnib(G) ++ dnib(F) ++ dnib(E) ++ 
-	dnib(D) ++ dnib(C) ++ dnib(B) ++ dnib(A) ++ "ip6.int".
-
-dn_in_addr_arpa(A,B,C,D) ->
-    integer_to_list(D) ++ "." ++
-	integer_to_list(C) ++ "." ++
-	integer_to_list(B) ++ "." ++
-	integer_to_list(A) ++ ".in-addr.arpa".
-
-dnib(X) ->
-    [hex(X), $., hex(X bsr 4), $., hex(X bsr 8), $., hex(X bsr 12), $.].
-
-hex(X) ->
-    X4 = (X band 16#f),
-    if X4 < 10 -> X4 + $0;
-       true -> (X4-10) + $a
-    end.
-
 %% Strip trailing dot, do not produce garbage unless necessary.
 %%
 stripdot(Name) ->
diff --git a/lib/kernel/src/inet_res.erl b/lib/kernel/src/inet_res.erl
index e238cfd2a1..f5ab7e6a23 100644
--- a/lib/kernel/src/inet_res.erl
+++ b/lib/kernel/src/inet_res.erl
@@ -355,40 +355,37 @@ gethostbyaddr(IP,Timeout) ->
     _ = inet:stop_timer(Timer),
     Res.    
 
-gethostbyaddr_tm({A,B,C,D} = IP, Timer) when ?ip(A,B,C,D) ->
-    inet_db:res_update_conf(),
-    case inet_db:gethostbyaddr(IP) of
-	{ok, HEnt} -> {ok, HEnt};
-	_ -> res_gethostbyaddr(dn_in_addr_arpa(A,B,C,D), IP, Timer)
-    end;
-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
-	{ok, HEnt} -> {ok, HEnt};
-	_ -> res_gethostbyaddr(dn_ip6_int(A,B,C,D,E,F,G,H), IP, Timer)
-    end;
-gethostbyaddr_tm(Addr,Timer) when is_list(Addr) ->
+gethostbyaddr_tm(Addr, Timer) when is_atom(Addr) ->
+    gethostbyaddr_tm(atom_to_list(Addr), Timer);
+gethostbyaddr_tm(Addr, Timer) when is_list(Addr) ->
     case inet_parse:address(Addr) of
-	{ok, IP} -> gethostbyaddr_tm(IP,Timer);
+	{ok, IP} -> gethostbyaddr_tm(IP, Timer);
 	_Error -> {error, formerr}
     end;
-gethostbyaddr_tm(Addr,Timer) when is_atom(Addr) ->
-    gethostbyaddr_tm(atom_to_list(Addr),Timer);
-gethostbyaddr_tm(_,_) -> {error, formerr}.
-
-%%
-%%  Send the gethostbyaddr query to:
-%%  1. the list of normal names servers
-%%  2. the list of alternative name servers
-%%
-res_gethostbyaddr(Addr, IP, Timer) ->
-    case res_query(Addr, in, ?S_PTR, [], Timer) of
-	{ok, Rec} ->
-	    inet_db:res_gethostbyaddr(IP, Rec);
-	{error,{qfmterror,_}} -> {error,einval};
-	{error,{Reason,_}} -> {error,Reason};
-	Error ->
-	    Error
+gethostbyaddr_tm(IP, Timer) ->
+    case dn_ip(IP) of
+        {error, _} = Error ->
+            Error;
+        Name ->
+            %% Try cached first
+            inet_db:res_update_conf(),
+            case inet_db:gethostbyaddr(Name, IP) of
+                {ok, _HEnt} = Result ->
+                    Result;
+                {error, nxdomain} ->
+                    %% Do a resolver lookup
+                    case res_query(Name, in, ?S_PTR, [], Timer) of
+                        {ok, Rec} ->
+                            %% Process and cache DNS Record
+                            inet_db:res_gethostbyaddr(Name, IP, Rec);
+                        {error,{qfmterror,_}} ->
+                            {error,einval};
+                        {error,{Reason,_}} ->
+                            {error,Reason};
+                        Error ->
+                            Error
+                    end
+            end
     end.
 
 %% --------------------------------------------------------------------------
@@ -479,12 +476,17 @@ getbyname_tm(Name, Type, Timer) when is_list(Name) ->
     case type_p(Type) of
 	true ->
 	    case inet_parse:visible_string(Name) of
-		false -> {error, formerr};
+		false ->
+                    {error, formerr};
 		true ->
+                    %% Try cached first
 		    inet_db:res_update_conf(),
 		    case inet_db:getbyname(Name, Type) of
-			{ok, HEnt} -> {ok, HEnt};
-			_ -> res_getbyname(Name, Type, Timer)
+			{ok, HEnt} ->
+                            {ok, HEnt};
+			_ ->
+                            %% Do a resolver lookup
+                            res_getbyname(Name, Type, Timer)
 		    end
 	    end;
 	false ->
@@ -577,6 +579,7 @@ res_getby_search(_Name, [], Reason,_,_) ->
 res_getby_query(Name, Type, Timer) ->
     case res_query(Name, in, Type, [], Timer) of
 	{ok, Rec} ->
+            %% Process and cache DNS Record
 	    inet_db:res_hostent_by_domain(Name, Type, Rec);
 	{error,{qfmterror,_}} -> {error,einval};
 	{error,{Reason,_}} -> {error,Reason};
@@ -586,6 +589,7 @@ res_getby_query(Name, Type, Timer) ->
 res_getby_query(Name, Type, Timer, NSs) ->
     case res_query(Name, in, Type, [], Timer, NSs) of
 	{ok, Rec} ->
+            %% Process and cache DNS Record
 	    inet_db:res_hostent_by_domain(Name, Type, Rec);
 	{error,{qfmterror,_}} -> {error,einval};
 	{error,{Reason,_}} -> {error,Reason};
@@ -1128,59 +1132,76 @@ decode_answer_noerror(
 %% 1.  "a.b.c"    => 
 %%       "a.b.c"
 %% 2.  "1.2.3.4"  =>  
-%%       "4.3.2.1.IN-ADDR.ARPA"
+%%       "4.3.2.1.in-addr.arpa"
 %% 3.  "4321:0:1:2:3:4:567:89ab" =>
-%%      "b.a.9.8.7.6.5.0.4.0.0.0.3.0.0.0.2.0.0.0.1.0.0.0.0.0.0.1.2.3.4.IP6.ARPA"
+%%      "b.a.9.8.7.6.5.0.4.0.0.0.3.0.0.0.2.0.0.0.1.0.0.0.0.0.0.1.2.3.4.ip6.arpa"
 %% 4.  {1,2,3,4} => as 2.
 %% 5.  {1,2,3,4,5,6,7,8} => as 3.
+%% 6.  Atom -> Recurse(String(Atom))
+%% 7.  Term => {error, formerr}
 %%
-nsdname({A,B,C,D}) -> 
-    {ok, dn_in_addr_arpa(A,B,C,D)};
-nsdname({A,B,C,D,E,F,G,H}) -> 
-    {ok, dn_ip6_int(A,B,C,D,E,F,G,H)};
+nsdname(Name) when is_atom(Name) ->
+    nsdname(atom_to_list(Name));
 nsdname(Name) when is_list(Name) ->
     case inet_parse:visible_string(Name) of
 	true ->
 	    case inet_parse:address(Name) of
-		{ok, Addr} -> 
-		    nsdname(Addr);
+		{ok, IP} ->
+                    dn_ip(IP);
 		_ ->
 		    {ok, Name}
 	    end;
 	_ -> {error, formerr}
     end;
-nsdname(Name) when is_atom(Name) ->
-    nsdname(atom_to_list(Name));
-nsdname(_) -> {error, formerr}.
-
-dn_in_addr_arpa(A,B,C,D) ->
-    integer_to_list(D) ++
-	("." ++	integer_to_list(C) ++ 
-	 ("." ++ integer_to_list(B) ++
-	  ("." ++ integer_to_list(A) ++ ".IN-ADDR.ARPA"))).
-
-dn_ip6_int(A,B,C,D,E,F,G,H) ->
-    dnib(H) ++ 
-	(dnib(G) ++ 
-	 (dnib(F) ++ 
-	  (dnib(E) ++ 
-	   (dnib(D) ++ 
-	    (dnib(C) ++ 
-	     (dnib(B) ++ 
-	      (dnib(A) ++ "IP6.ARPA"))))))).
-
-
-
--compile({inline, [dnib/1, dnib/3]}).
-dnib(X) ->
-    L = erlang:integer_to_list(X, 16),
-    dnib(4-length(L), L, []).
+nsdname(IP) ->
+    dn_ip(IP).
+
+%% Return the domain name for a PTR lookup of
+%% the argument IP address
 %%
-dnib(0, [], Acc) -> Acc;
-dnib(0, [C|Cs], Acc) ->
-    dnib(0, Cs, [C,$.|Acc]);
-dnib(N, Cs, Acc) ->
-    dnib(N-1, Cs, [$0,$.|Acc]).
+dn_ip({A,B,C,D}) when ?ip(A,B,C,D) ->
+    dn_ipv4([A,B,C,D], "in-addr.arpa");
+dn_ip({A,B,C,D,E,F,G,H}) when ?ip6(A,B,C,D,E,F,G,H) ->
+    dn_ipv6([A,B,C,D,E,F,G,H], "ip6.arpa");
+dn_ip(_) ->
+    {error, formerr}.
+
+dn_ipv4([], Dn) ->
+    Dn;
+dn_ipv4([A | As], Dn_0) when is_integer(A), A =< 255 ->
+    Dn = [$. | Dn_0],
+    if
+        A < 10 ->
+            dn_ipv4(As, dn_dec(A, Dn));
+        A < 100 ->
+            dn_ipv4(As, dn_dec(A div 10, dn_dec(A rem 10, Dn)));
+        true ->
+            B = A rem 100,
+            dn_ipv4(
+              As,
+              dn_dec(A div 100, dn_dec(B div 10, dn_dec(B rem 10, Dn))))
+    end.
+
+dn_ipv6([], Dn) ->
+    Dn;
+dn_ipv6([W | Ws], Dn) when is_integer(W), W =< 16#ffff ->
+    D = W band 16#f,   W_1 = W bsr 4,
+    C = W_1 band 16#f, W_2 = W_1 bsr 4,
+    B = W_2 band 16#f,
+    A = W_2 bsr 4,
+    dn_ipv6(Ws, dn_hex(D, dn_hex(C, dn_hex(B, dn_hex(A, Dn))))).
+
+-compile({inline, [dn_dec/2, dn_hex/2]}).
+dn_dec(N, Tail) when is_integer(N) ->
+    [N + $0 | Tail].
+
+dn_hex(N, Tail) when is_integer(N) ->
+    if
+        N < 10 ->
+            [N + $0, $. | Tail];
+        true ->
+            [(N - 10) + $a, $. | Tail]
+end.
 
 
 
-- 
2.31.1

Places

File 0366-Rewrite-cname-lookups.patch of Package erlang (Revision 76356621c41f37937556526d87dbca4f)

Places