add possibility to use a custom function for dns lookup

new config: `dns_lookup_hook`

README.md

@@ -274,7 +274,9 @@ Example of full configuration with keys which can use in `eradius`:
     %% Size of RADIUS receive buffer
     {recbuf, 8192},
     %% The minimum size of the send buffer to use for the RADIUS
-    {sndbuf, 131072}
+    {sndbuf, 131072},
+    %% Define a custom DNS-lookup function to replace `inet:gethostbyname/1`
+    {dns_lookup_hook, fun inet:gethostbyname/1}
 ]}].
 ```
 

src/eradius_client.erl

@@ -11,7 +11,7 @@
 %%   parameter. Changing it currently requires a restart. It can be given as a string or ip address tuple,
 %%   or the atom ``undefined'' (the default), which uses whatever address the OS selects.
 -module(eradius_client).
--export([start_link/0, send_request/2, send_request/3, send_remote_request/3, send_remote_request/4]).
+-export([start_link/0, send_request/2, send_request/3, send_remote_request/3, send_remote_request/4, get_ip/1]).
 %% internal
 -export([reconfigure/0, send_remote_request_loop/8, find_suitable_peer/1,
          restore_upstream_server/1, store_radius_server_from_pool/3,
@@ -655,7 +655,8 @@ find_suitable_peer([{IP, Port, Secret, _Opts} | Pool]) ->
     find_suitable_peer([{IP, Port, Secret} | Pool]).
 
 get_ip(Host) ->
-    case inet:gethostbyname(Host) of
+    DnsLookup = application:get_env(eradius, dns_lookup_hook, fun inet:gethostbyname/1 ),
+    case DnsLookup(Host) of
         {ok, #hostent{h_addrtype = inet, h_addr_list = [IP]}} ->
             IP;
         {ok, #hostent{h_addrtype = inet, h_addr_list = [_ | _] = IPs}} ->

test/eradius_client_SUITE.erl

@@ -47,6 +47,7 @@
 
 all() -> [
     send_request,
+    dns_lookup_hook,
     wanna_send,
     reconf_address,
     wanna_send,
@@ -72,6 +73,10 @@ init_per_testcase(send_request, Config) ->
     application:stop(eradius),
     eradius_test_handler:start(),
     Config;
+init_per_testcase(dns_lookup_hook, Config) ->
+    application:stop(eradius),
+    eradius_test_handler:start(),
+    Config;
 init_per_testcase(send_request_failover, Config) ->
     application:stop(eradius),
     eradius_test_handler:start(),
@@ -86,6 +91,9 @@ init_per_testcase(_Test, Config) ->
 end_per_testcase(send_request, Config) ->
     eradius_test_handler:stop(),
     Config;
+end_per_testcase(dns_lookup_hook, Config) ->
+    eradius_test_handler:stop(),
+    Config;
 end_per_testcase(send_request_failover, Config) ->
     eradius_test_handler:stop(),
     Config;
@@ -207,6 +215,22 @@ send_request(_Config) ->
     ?equal(accept, eradius_test_handler:send_request(eradius_test_handler:localhost(binary))),
     ok.
 
+dns_lookup_hook(_Config) ->
+    application:set_env(eradius, dns_lookup_hook, fun dns_lookup_callback/1),
+    ?equal(accept, eradius_test_handler:send_request(eradius_test_handler:localhost(binary))),
+
+    %% Test against 127.0.0.2 => timeout
+    application:set_env(eradius, dns_lookup_hook, fun dns_lookup_fail_callback/1),
+    try
+        eradius_test_handler:send_request(eradius_test_handler:localhost(binary), [{timeout, 100}]),
+        error(badmatch)
+    catch
+        error:{badmatch, {error, timeout}} ->
+            ok
+    end,
+    application:unset_env(eradius, dns_lookup_hook).
+
+
 send(FUN, Ports, Address) ->
     meckStart(),
     {ok, OldState} = gen_server:call(eradius_client, debug),
@@ -252,3 +276,9 @@ send_request_failover(_Config) ->
 check_upstream_servers(_Config) ->
     ?equal(?RADIUS_SERVERS, ets:tab2list(eradius_client)),
     ok.
+
+dns_lookup_callback(_) ->
+    {ok,{hostent,"localhost",[],inet,4,[{127,0,0,1}]}}.
+
+dns_lookup_fail_callback(_) ->
+    {ok,{hostent,"localhost",[],inet,4,[{127,0,0,2}]}}.

test/eradius_test_handler.erl

@@ -2,7 +2,7 @@
 
 -behaviour(eradius_server).
 
--export([start/0, stop/0, send_request/1, send_request_failover/1, radius_request/3]).
+-export([start/0, stop/0, send_request/1, send_request/2, send_request_failover/1, radius_request/3]).
 -export([localhost/1]).
 
 -include("include/eradius_lib.hrl").
@@ -30,7 +30,9 @@ stop() ->
     application:start(eradius).
 
 send_request(IP) ->
-    {ok, R, A} = eradius_client:send_request({IP, 1812, "secret"}, #radius_request{cmd = request}, []),
+    send_request(IP, []).
+send_request(IP, Options) ->
+    {ok, R, A} = eradius_client:send_request({IP, 1812, "secret"}, #radius_request{cmd = request}, Options),
     #radius_request{cmd = Cmd} = eradius_lib:decode_request(R, <<"secret">>, A),
     Cmd.