Merge pull request #258 from nickva/add-request-is-closed-function

Add mochiweb_request:is_closed/1 function

src/mochiweb_request.erl

@@ -59,6 +59,8 @@
 -export([accepted_content_types/2,
 	 accepts_content_type/2]).
 
+-export([is_closed/1]).
+
 -define(SAVE_QS, mochiweb_request_qs).
 
 -define(SAVE_PATH, mochiweb_request_path).
@@ -1140,3 +1142,13 @@ accept_header({?MODULE,
       undefined -> "*/*";
       Value -> Value
     end.
+
+%% @spec is_closed(request()) -> true | false | undefined
+%% @doc Check if a request connection is closing or already closed. This may be
+%% useful when processing long running request callbacks, when the client
+%% disconnects after a short timeout. This function works on Linux, NetBSD,
+%% OpenBSD, FreeBSD and MacOS. On other operating systems, like Windows for
+%% instance, it will return undefined.
+is_closed({?MODULE,
+        [Socket, _Opts, _Method, _RawPath, _Version, _Headers]}) ->
+    mochiweb_socket:is_closed(Socket).

src/mochiweb_socket.erl

@@ -7,7 +7,8 @@
 -export([listen/4,
          accept/1, transport_accept/1, finish_accept/1,
          recv/3, send/2, close/1, port/1, peername/1,
-         setopts/2, getopts/2, type/1, exit_if_closed/1]).
+         setopts/2, getopts/2, type/1, exit_if_closed/1,
+         is_closed/1]).
 
 -define(ACCEPT_TIMEOUT, 2000).
 -define(SSL_TIMEOUT, 10000).
@@ -180,3 +181,110 @@ exit_if_closed({error, einval = Error}) ->
     exit({shutdown, Error});
 exit_if_closed(Res) ->
     Res.
+
+%% @doc Check if the socket is closing or already closed. This function works
+%% with passive mode sockets on Linux, OpenBSD, NetBSD, FreeBSD and MacOS. On
+%% unsupported OS-es, like Windows, it returns undefined.
+is_closed(Socket) ->
+    OsType = os:type(),
+    case tcp_info_opt(OsType) of
+        {raw, _, _, _} = InfoOpt ->
+            case getopts(Socket, [InfoOpt]) of
+                {ok, [{raw, _, _, <<State:8/native, _/binary>>}]} ->
+                    tcp_is_closed(State, OsType);
+                {ok, []} ->
+                    undefined;
+                {error, einval} ->
+                    % Already cleaned up
+                    true;
+                {error, _} ->
+                    undefined
+            end;
+        undefined ->
+            undefined
+    end.
+
+% All OS-es have the tcpi_state (uint8) as first member of tcp_info struct
+
+tcp_info_opt({unix, linux}) ->
+    %% netinet/in.h
+    %%   IPPROTO_TCP = 6
+    %%
+    %% netinet/tcp.h
+    %%   #define TCP_INFO 11
+    %%
+    {raw, 6, 11, 1};
+tcp_info_opt({unix, darwin}) ->
+    %% netinet/in.h
+    %%   #define IPPROTO_TCP   6
+    %%
+    %% netinet/tcp.h
+    %%   #define TCP_CONNECTION_INFO  0x106
+    %%
+    {raw, 6, 16#106, 1};
+tcp_info_opt({unix, freebsd}) ->
+    %% sys/netinet/in.h
+    %%   #define  IPPROTO_TCP  6
+    %%
+    %% sys/netinet/tcp.h
+    %%   #define  TCP_INFO    32
+    %%
+    {raw, 6, 32, 1};
+tcp_info_opt({unix, netbsd}) ->
+    %% sys/netinet/in.h
+    %%   #define  IPPROTO_TCP 6
+    %%
+    %% sys/netinet/tcp.h
+    %%   #define  TCP_INFO 9
+    {raw, 6, 9, 1};
+tcp_info_opt({unix, openbsd}) ->
+    %% sys/netinet/in.h
+    %%   #define  IPPROTO_TCP 6
+    %%
+    %% sys/netinet/tcp.h
+    %%   #define  TCP_INFO 0x09
+    {raw, 6, 16#09, 1};
+tcp_info_opt({_, _}) ->
+    undefined.
+
+tcp_is_closed(State, {unix, linux}) ->
+    %% netinet/tcp.h
+    %%   enum
+    %%   {
+    %%     TCP_ESTABLISHED = 1,
+    %%     TCP_SYN_SENT,
+    %%     TCP_SYN_RECV,
+    %%     TCP_FIN_WAIT1,
+    %%     TCP_FIN_WAIT2,
+    %%     TCP_TIME_WAIT,
+    %%     TCP_CLOSE,
+    %%     TCP_CLOSE_WAIT,
+    %%     TCP_LAST_ACK,
+    %%     TCP_LISTEN,
+    %%     TCP_CLOSING
+    %%   }
+    %%
+    lists:member(State, [4, 5, 6, 7, 8, 9, 11]);
+tcp_is_closed(State, {unix, Type})
+  when
+      Type =:= darwin;
+      Type =:= freebsd;
+      Type =:= netbsd;
+      Type =:= openbsd
+  ->
+    %% tcp_fsm.h states are the same on macos, freebsd, netbsd and openbsd
+    %%
+    %% netinet/tcp_fsm.h
+    %%   #define TCPS_CLOSED             0       /* closed */
+    %%   #define TCPS_LISTEN             1       /* listening for connection */
+    %%   #define TCPS_SYN_SENT           2       /* active, have sent syn */
+    %%   #define TCPS_SYN_RECEIVED       3       /* have send and received syn */
+    %%   #define TCPS_ESTABLISHED        4       /* established */
+    %%   #define TCPS_CLOSE_WAIT         5       /* rcvd fin, waiting for close */
+    %%   #define TCPS_FIN_WAIT_1         6       /* have closed, sent fin */
+    %%   #define TCPS_CLOSING            7       /* closed xchd FIN; await FIN ACK */
+    %%   #define TCPS_LAST_ACK           8       /* had fin and close; await FIN ACK */
+    %%   #define TCPS_FIN_WAIT_2         9       /* have closed, fin is acked */
+    %%   #define TCPS_TIME_WAIT          10      /* in 2*msl quiet wait after close */
+    %%
+    lists:member(State, [0, 5, 6, 7, 8, 9, 10]).

test/mochiweb_request_tests.erl

@@ -235,4 +235,27 @@ should_close_test() ->
 		 (F({1, 0}, [{"Connection", "Keep-Alive"}]))),
     ok.
 
+is_closed_test() ->
+    Headers = mochiweb_headers:make([{"Accept", "text/html"}]),
+    {ok, Socket} = gen_tcp:listen(0, [{active, false}]),
+    Req = mochiweb_request:new(Socket, 'GET', "/foo", {1, 1}, Headers),
+    case is_closed_supported() of
+        true ->
+            ?assertNot(mochiweb_request:is_closed(Req)),
+            gen_tcp:close(Socket),
+            ?assert(mochiweb_request:is_closed(Req));
+        false ->
+            ?assertEqual(undefined, mochiweb_request:is_closed(Req)),
+            gen_tcp:close(Socket),
+            ?assertEqual(undefined, mochiweb_request:is_closed(Req))
+    end.
+
+is_closed_supported() ->
+    case os:type() of
+        {unix, OsName} ->
+            lists:member(OsName, [linux, openbsd, netbsd, freebsd, darwin]);
+        {_, _} ->
+            false
+    end.
+
 -endif.