tftp: support transfer of files > 65535 blocks

The block count is an unsigned 2 byte integer. The common behaviour of
tftp clients and servers is to overflow the block count and wrap the
counter to 0 in order to support files larger than 32M. Modify the tftp
implementation to do the same rollover.

Interoperability was tested by transferring a 1.4G file using the HPA
tftp client.

2 files changed, 43 insertions, 30 deletions

diff --git a/lib/inets/src/tftp/tftp_engine.erl b/lib/inets/src/tftp/tftp_engine.erl
index 8d282a1e9d..493a29a68f 100644
--- a/lib/inets/src/tftp/tftp_engine.erl
+++ b/lib/inets/src/tftp/tftp_engine.erl
@@ -656,22 +656,11 @@ common_read(Config, Callback, Req, _LocalAccess, ExpectedBlockNo, ActualBlockNo,
 
 do_common_read(Config, Callback, Req, LocalAccess, BlockNo, Data, Prepared)
   when is_binary(Data), is_record(Prepared, prepared) ->
-    NextBlockNo = BlockNo + 1,
-    case NextBlockNo =< 65535 of
-        true ->
-            Reply = #tftp_msg_data{block_no = NextBlockNo, data = Data},
-            {Config2, Callback2, TransferRes} =
-                transfer(Config, Callback, Req, Reply, LocalAccess, NextBlockNo, Prepared),
-            ?MODULE:common_loop(Config2, Callback2, Req, TransferRes, LocalAccess, NextBlockNo);
-        false ->
-            Code = badblk,
-            Text = "Too big transfer ID = " ++ 
-                integer_to_list(NextBlockNo) ++ " > 65535", 
-            {undefined, Error} =
-                callback({abort, {Code, Text}}, Config, Callback, Req),
-            send_msg(Config, Req, Error),
-            terminate(Config, Req, ?ERROR(read, Code, Text, Req#tftp_msg_req.filename))
-    end.
+    NextBlockNo = (BlockNo + 1) rem 65536,
+    Reply = #tftp_msg_data{block_no = NextBlockNo, data = Data},
+    {Config2, Callback2, TransferRes} =
+        transfer(Config, Callback, Req, Reply, LocalAccess, NextBlockNo, Prepared),
+    ?MODULE:common_loop(Config2, Callback2, Req, TransferRes, LocalAccess, NextBlockNo).
 
 -spec common_write(#config{}, #callback{}, _, 'write', integer(), integer(), _, #prepared{}) -> no_return().
 
@@ -715,21 +704,10 @@ common_write(Config, Callback, Req, _, ExpectedBlockNo, ActualBlockNo, Data, Pre
 common_ack(Config, Callback, Req, LocalAccess, BlockNo, Prepared) 
   when is_record(Prepared, prepared) ->
     Reply = #tftp_msg_ack{block_no = BlockNo},
-    NextBlockNo = BlockNo + 1,
+    NextBlockNo = (BlockNo + 1) rem 65536,
     {Config2, Callback2, TransferRes} = 
         transfer(Config, Callback, Req, Reply, LocalAccess, NextBlockNo, Prepared),
-    case NextBlockNo =< 65535 of
-        true ->   
-            ?MODULE:common_loop(Config2, Callback2, Req, TransferRes, LocalAccess, NextBlockNo);
-        false ->
-            Code = badblk,
-            Text = "Too big transfer ID = " ++ 
-                integer_to_list(NextBlockNo) ++ " > 65535", 
-            {undefined, Error} =
-                callback({abort, {Code, Text}}, Config, Callback2, Req),
-            send_msg(Config, Req, Error),
-            terminate(Config, Req, ?ERROR(read, Code, Text, Req#tftp_msg_req.filename))
-    end.
+    ?MODULE:common_loop(Config2, Callback2, Req, TransferRes, LocalAccess, NextBlockNo).
 
 pre_terminate(Config, Req, Result) ->
     if
diff --git a/lib/inets/test/tftp_SUITE.erl b/lib/inets/test/tftp_SUITE.erl
index d29d210d7d..497a50e654 100644
--- a/lib/inets/test/tftp_SUITE.erl
+++ b/lib/inets/test/tftp_SUITE.erl
@@ -76,7 +76,7 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
 
 all() -> 
     [simple, extra, reuse_connection, resend_client,
-     resend_server].
+     resend_server, large_file].
 
 groups() -> 
     [].
@@ -902,6 +902,41 @@ reuse_connection(Config) when is_list(Config) ->
     ok.
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Large file: transfer > 65535 blocks
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+large_file(doc) ->
+    ["Start the daemon and test transfer of files greater than 32M."];
+large_file(suite) ->
+    [];
+large_file(Config) when is_list(Config) ->
+    ?VERIFY(ok, application:start(inets)),
+
+    {Port, DaemonPid} = ?IGNORE(?START_DAEMON(0, [{debug, brief}])),
+
+    %% Read fail
+    RemoteFilename = "tftp_temporary_large_file_remote_test_file.txt",
+    LocalFilename = "tftp_temporary_large_file_local_test_file.txt",
+
+    {ok, FH} = file:open(LocalFilename, [write,exclusive]),
+    {ok, Size} = file:position(FH, {eof, 2*512*65535}),
+    ok = file:truncate(FH),
+    ?IGNORE(file:close(FH)),
+
+    %% Write and read
+    ?VERIFY({ok, Size}, tftp:write_file(RemoteFilename, LocalFilename, [{port, Port}])),
+    ?IGNORE(file:delete(LocalFilename)),
+    ?VERIFY({ok, Size}, tftp:read_file(RemoteFilename, LocalFilename, [{port, Port}])),
+
+    %% Cleanup
+    unlink(DaemonPid),
+    exit(DaemonPid, kill),
+    ?VERIFY(ok, file:delete(LocalFilename)),
+    ?VERIFY(ok, file:delete(RemoteFilename)),
+    ?VERIFY(ok, application:stop(inets)),
+    ok.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %% Goodies
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%