erts/kernel: sendfile no longer uses async threads

This has been done because a slow client attack is possible if the
async thread pool is used. The scenario is:

Client does a request for a file and then slowly receives the file one
byte at a time. This will eventually fill the async thread pool with blocking
sendfile operations and thus starving the vm of all file operations.

If you still want to use the async threads pool for sendfile an option to
enable it has been introduced.

1 files changed, 54 insertions, 16 deletions

diff --git a/lib/kernel/test/sendfile_SUITE.erl b/lib/kernel/test/sendfile_SUITE.erl
index 4cf4c6489d..1d26702c64 100644
--- a/lib/kernel/test/sendfile_SUITE.erl
+++ b/lib/kernel/test/sendfile_SUITE.erl
@@ -24,7 +24,14 @@
 
 -compile(export_all).
 
-all() ->
+all() -> [{group,async_threads},
+	  {group,no_async_threads}].
+
+groups() ->
+    [{async_threads,[],tcs()},
+     {no_async_threads,[],tcs()}].
+
+tcs() ->
     [t_sendfile_small
      ,t_sendfile_big_all
      ,t_sendfile_big_size
@@ -63,6 +70,14 @@ init_per_suite(Config) ->
 end_per_suite(Config) ->
     file:delete(proplists:get_value(big_file, Config)).
 
+init_per_group(async_threads,Config) ->
+    [{sendfile_opts,[{use_threads,true}]}|Config];
+init_per_group(no_async_threads,Config) ->
+    [{sendfile_opts,[{use_threads,false}]}|Config].
+
+end_per_group(_,_Config) ->
+    ok.
+
 init_per_testcase(TC,Config) when TC == t_sendfile_recvduring;
 				  TC == t_sendfile_sendduring ->
     Filename = proplists:get_value(small_file, Config),
@@ -71,7 +86,7 @@ init_per_testcase(TC,Config) when TC == t_sendfile_recvduring;
 		   {_Size, Data} = sendfile_file_info(Filename),
 		   {ok,D} = file:open(Filename, [raw,binary,read]),
 		   prim_file:sendfile(D, Sock, 0, 0, 0,
-				      [],[],false,false,false),
+				      [],[],[]),
 		   Data
 	   end,
 
@@ -92,6 +107,7 @@ t_sendfile_small(Config) when is_list(Config) ->
 
     Send = fun(Sock) ->
 		   {Size, Data} = sendfile_file_info(Filename),
+		   %% Here we make sure to test the sendfile/2 api
 		   {ok, Size} = file:sendfile(Filename, Sock),
 		   Data
 	   end,
@@ -101,6 +117,7 @@ t_sendfile_small(Config) when is_list(Config) ->
 t_sendfile_many_small(Config) when is_list(Config) ->
     Filename = proplists:get_value(small_file, Config),
     FileOpts = proplists:get_value(file_opts, Config, []),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     error_logger:add_report_handler(?MODULE,[self()]),
 
@@ -109,7 +126,7 @@ t_sendfile_many_small(Config) when is_list(Config) ->
 		   N = 10000,
 		   {ok,D} = file:open(Filename,[read|FileOpts]),
 		   [begin
-			{ok,Size} = file:sendfile(D,Sock,0,0,[])
+			{ok,Size} = file:sendfile(D,Sock,0,0,SendfileOpts)
 		    end || _I <- lists:seq(1,N)],
 		   file:close(D),
 		   Size*N
@@ -127,11 +144,12 @@ t_sendfile_many_small(Config) when is_list(Config) ->
 
 t_sendfile_big_all(Config) when is_list(Config) ->
     Filename = proplists:get_value(big_file, Config),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     Send = fun(Sock) ->
 		   {ok, #file_info{size = Size}} =
 		       file:read_file_info(Filename),
-		   {ok, Size} = file:sendfile(Filename, Sock),
+		   {ok, Size} = sendfile(Filename, Sock, SendfileOpts),
 		   Size
 	   end,
 
@@ -140,12 +158,13 @@ t_sendfile_big_all(Config) when is_list(Config) ->
 t_sendfile_big_size(Config) ->
     Filename = proplists:get_value(big_file, Config),
     FileOpts = proplists:get_value(file_opts, Config, []),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     SendAll = fun(Sock) ->
 		      {ok, #file_info{size = Size}} =
 			  file:read_file_info(Filename),
 		      {ok,D} = file:open(Filename,[read|FileOpts]),
-		      {ok, Size} = file:sendfile(D, Sock,0,Size,[]),
+		      {ok, Size} = file:sendfile(D, Sock,0,Size,SendfileOpts),
 		      Size
 	      end,
 
@@ -154,12 +173,13 @@ t_sendfile_big_size(Config) ->
 t_sendfile_partial(Config) ->
     Filename = proplists:get_value(small_file, Config),
     FileOpts = proplists:get_value(file_opts, Config, []),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     SendSingle = fun(Sock) ->
 			 {_Size, <<Data:5/binary,_/binary>>} =
 			     sendfile_file_info(Filename),
 			 {ok,D} = file:open(Filename,[read|FileOpts]),
-			 {ok,5} = file:sendfile(D,Sock,0,5,[]),
+			 {ok,5} = file:sendfile(D,Sock,0,5,SendfileOpts),
 			 file:close(D),
 			 Data
 		 end,
@@ -170,14 +190,14 @@ t_sendfile_partial(Config) ->
     {ok,D} = file:open(Filename,[read|FileOpts]),
     {ok, <<FData/binary>>} = file:read(D,5),
     FSend = fun(Sock) ->
-		    {ok,5} = file:sendfile(D,Sock,0,5,[]),
+		    {ok,5} = file:sendfile(D,Sock,0,5,SendfileOpts),
 		    FData
 	    end,
 
     ok = sendfile_send(FSend),
 
     SSend = fun(Sock) ->
-		    {ok,3} = file:sendfile(D,Sock,5,3,[]),
+		    {ok,3} = file:sendfile(D,Sock,5,3,SendfileOpts),
 		    SData
 	    end,
 
@@ -190,12 +210,13 @@ t_sendfile_partial(Config) ->
 t_sendfile_offset(Config) ->
     Filename = proplists:get_value(small_file, Config),
     FileOpts = proplists:get_value(file_opts, Config, []),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     Send = fun(Sock) ->
 		   {_Size, <<_:5/binary,Data:3/binary,_/binary>> = AllData} =
 		       sendfile_file_info(Filename),
 		   {ok,D} = file:open(Filename,[read|FileOpts]),
-		   {ok,3} = file:sendfile(D,Sock,5,3,[]),
+		   {ok,3} = file:sendfile(D,Sock,5,3,SendfileOpts),
 		   {ok, AllData} = file:read(D,100),
 		   file:close(D),
 		   Data
@@ -205,10 +226,11 @@ t_sendfile_offset(Config) ->
 
 t_sendfile_sendafter(Config) ->
     Filename = proplists:get_value(small_file, Config),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     Send = fun(Sock) ->
 		   {Size, Data} = sendfile_file_info(Filename),
-		   {ok, Size} = file:sendfile(Filename, Sock),
+		   {ok, Size} = sendfile(Filename, Sock, SendfileOpts),
 		   ok = gen_tcp:send(Sock, <<2>>),
 		   <<Data/binary,2>>
 	   end,
@@ -217,10 +239,11 @@ t_sendfile_sendafter(Config) ->
 
 t_sendfile_recvafter(Config) ->
     Filename = proplists:get_value(small_file, Config),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     Send = fun(Sock) ->
 		   {Size, Data} = sendfile_file_info(Filename),
-		   {ok, Size} = file:sendfile(Filename, Sock),
+		   {ok, Size} = sendfile(Filename, Sock, SendfileOpts),
 		   ok = gen_tcp:send(Sock, <<1>>),
 		   {ok,<<1>>} = gen_tcp:recv(Sock, 1),
 		   <<Data/binary,1>>
@@ -230,6 +253,7 @@ t_sendfile_recvafter(Config) ->
 
 t_sendfile_sendduring(Config) ->
     Filename = proplists:get_value(big_file, Config),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     Send = fun(Sock) ->
 		   {ok, #file_info{size = Size}} =
@@ -238,7 +262,7 @@ t_sendfile_sendduring(Config) ->
 				      timer:sleep(50),
 				      ok = gen_tcp:send(Sock, <<2>>)
 			      end),
-		   {ok, Size} = file:sendfile(Filename, Sock),
+		   {ok, Size} = sendfile(Filename, Sock, SendfileOpts),
 		   Size+1
 	   end,
 
@@ -246,6 +270,7 @@ t_sendfile_sendduring(Config) ->
 
 t_sendfile_recvduring(Config) ->
     Filename = proplists:get_value(big_file, Config),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     Send = fun(Sock) ->
 		   {ok, #file_info{size = Size}} =
@@ -255,7 +280,7 @@ t_sendfile_recvduring(Config) ->
 				      ok = gen_tcp:send(Sock, <<1>>),
 				      {ok,<<1>>} = gen_tcp:recv(Sock, 1)
 			      end),
-		   {ok, Size} = file:sendfile(Filename, Sock),
+		   {ok, Size} = sendfile(Filename, Sock, SendfileOpts),
 		   timer:sleep(1000),
 		   Size+1
 	   end,
@@ -264,6 +289,7 @@ t_sendfile_recvduring(Config) ->
 
 t_sendfile_closeduring(Config) ->
     Filename = proplists:get_value(big_file, Config),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     Send = fun(Sock,SFServPid) ->
 		   spawn_link(fun() ->
@@ -272,13 +298,14 @@ t_sendfile_closeduring(Config) ->
 			      end),
 		   case erlang:system_info(thread_pool_size) of
 		       0 ->
-			   {error, closed} = file:sendfile(Filename, Sock);
+			   {error, closed} = sendfile(Filename, Sock,
+						      SendfileOpts);
 		       _Else ->
 			   %% This can return how much has been sent or
 			   %% {error,closed} depending on OS.
 			   %% How much is sent impossible to know as
 			   %%  the socket was closed mid sendfile
-			   case file:sendfile(Filename, Sock) of
+			   case sendfile(Filename, Sock, SendfileOpts) of
 			       {error, closed} ->
 				   ok;
 			       {ok, Size}  when is_integer(Size) ->
@@ -292,6 +319,7 @@ t_sendfile_closeduring(Config) ->
 
 t_sendfile_crashduring(Config) ->
     Filename = proplists:get_value(big_file, Config),
+    SendfileOpts = proplists:get_value(sendfile_opts, Config),
 
     error_logger:add_report_handler(?MODULE,[self()]),
 
@@ -300,7 +328,7 @@ t_sendfile_crashduring(Config) ->
 				      timer:sleep(50),
 				      exit(die)
 			      end),
-		   {error, closed} = file:sendfile(Filename, Sock),
+		   {error, closed} = sendfile(Filename, Sock, SendfileOpts),
 		   -1
 	   end,
     process_flag(trap_exit,true),
@@ -395,6 +423,16 @@ sendfile_file_info(File) ->
     {ok, Data} = file:read_file(File),
     {Size, Data}.
 
+sendfile(Filename,Sock,Opts) ->
+    case file:open(Filename, [read, raw, binary]) of
+	{error, Reason} ->
+	    {error, Reason};
+	{ok, Fd} ->
+	    Res = file:sendfile(Fd, Sock, 0, 0, Opts),
+	    _ = file:close(Fd),
+	    Res
+    end.
+
 
 %% Error handler