feat(eqmx_misc): add an api to ensure ipv6_probe socket option

src/emqx_misc.erl

@@ -43,6 +43,7 @@
         , now_to_secs/1
         , now_to_ms/1
         , index_of/2
+        , ipv6_probe/1
         ]).
 
 -export([ bin2hexstr_A_F/1
@@ -50,6 +51,22 @@
         , hexstr2bin/1
         ]).
 
+%% @doc Add `ipv6_probe' socket option if it's supported.
+ipv6_probe(Opts) ->
+    case persistent_term:get({?MODULE, ipv6_probe_supported}, unknown) of
+        unknown ->
+            %% e.g. 23.2.7.1-emqx-2-x86_64-unknown-linux-gnu-64
+            OtpVsn = emqx_vm:get_otp_version(),
+            Bool = (match =:= re:run(OtpVsn, "emqx", [{capture, none}])),
+            _ = persistent_term:put({?MODULE, ipv6_probe_supported}, Bool),
+            ipv6_probe(Bool, Opts);
+        Bool ->
+            ipv6_probe(Bool, Opts)
+    end.
+
+ipv6_probe(false, Opts) -> Opts;
+ipv6_probe(true, Opts) -> [ipv6_probe | Opts].
+
 %% @doc Merge options
 -spec(merge_opts(Opts, Opts) -> Opts when Opts :: proplists:proplist()).
 merge_opts(Defaults, Options) ->
@@ -258,3 +275,10 @@ hexchar2int(I) when I >= $0 andalso I =< $9 -> I - $0;
 hexchar2int(I) when I >= $A andalso I =< $F -> I - $A + 10;
 hexchar2int(I) when I >= $a andalso I =< $f -> I - $a + 10.
 
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+
+ipv6_probe_test() ->
+    ?assertEqual([ipv6_probe], ipv6_probe([])).
+
+-endif.

src/emqx_vm.erl

@@ -382,7 +382,7 @@ read_otp_version() ->
         {error, enoent} ->
             %% running tests etc.
             OtpMajor = erlang:system_info(otp_release),
-            OtpVsnFile = file:read_file(filename:join([ReleasesDir, OtpMajor, "OTP_VERSION"])),
+            OtpVsnFile = filename:join([ReleasesDir, OtpMajor, "OTP_VERSION"]),
             {ok, Vsn} = file:read_file(OtpVsnFile),
             Vsn
     end.