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[2009-06-19 16:37 UTC] karachi at mail dot ru
Description:
------------
I tried to upload a file to ftp server using ftp wrapper functions. Sequence of steps are: fopen, fwrite, fclose. Sometimes file uploaded successfully and sometimes several last bytes of file didn't save. Server reports in log file that transmission was aborted, but fwrite() returns "true".
I found that fwrite() doesn't check ftp reply code before exiting. That's why ftp server can receive QUIT command before it processes data stored and close data connection as described in RFC 959: "The server may abort data transfer if the control connections
are closed without command." If I insert sleep(1) between fwrite() and fclose() everything works as expected.
Ftp server used: ProFTPD 1.3.2
Reproduce code:
---------------
<?php
$host = 'localhost';
$user = 'ftp';
$passwd = 'anonymous';
$f = fopen("/home/user/test/test_file", 'r') or
die ("Unable to open file");
$context = stream_context_create(
array(
"ftp" => array(
"overwrite" => true
)
)
);
$f1 = fopen("ftp://$host/test", 'wb', false, $context) or
die("Unable to open the file on ftp");
while ($str = fread($f, 1000))
{
fwrite($f1, $str) or die("Unable to write");
}
fclose($f1);
fclose($f);
?>
Expected result:
----------------
File is successfully stored on ftp server
Actual result:
--------------
Sometimes end of the file isn't stored. It doesn't depend on the size of the file.
PatchesPull RequestsHistoryAllCommentsChangesGit/SVN commits
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Last updated: Thu Nov 21 11:01:29 2024 UTC |
The solution may be something like this, although this may break things when the current transaction is not about to send a 226 Transfer complete. Index: ext/standard/ftp_fopen_wrapper.c =================================================================== --- ext/standard/ftp_fopen_wrapper.c (revision 287652) +++ ext/standard/ftp_fopen_wrapper.c (working copy) @@ -97,7 +97,16 @@ */ static int php_stream_ftp_stream_close(php_stream_wrapper *wrapper, php_stream *stream TSRMLS_DC) { + int result; + char tmp_line[512]; + php_stream *controlstream = (php_stream *)stream->wrapperdata; + + result = GET_FTP_RESULT(controlstream); + if (result != 226 && result != 250) { + // Maybe throw a warning? + return 1; + } if (controlstream) { php_stream_write_string(controlstream, "QUIT\r\n");Just stumbled across this (still in 5.3.1) a few days ago, trying to transmit data to three different FTP servers. One of the servers _never_ got a file, one got files, but in 9 out of 10 runs the last part of the files was cut off, only the last one got the files intact in about 8 of 10 runs (with the others also corrupted). I didn't find this bug report at first and so I opened up the PHP source for the first time in my life and was rather shocked: There's really no way that write operations using the ftp stream wrapper ever could've worked. If it works, it's out of pure luck. Was this never tested? The problem is, that FTP (see RFC959) uses the tear down of the _data_stream_ as its EOF marker. What this code does on the other hand, is just send a QUIT on the control stream and then tear down that one. So from the perspective of the FTP server it looks like an abort (transmission still in progress, but control channel lost). Now it just depends on the implementation of the server and sometimes some random timing issues (which TCP close is handled first) what the outcome is: Some FTP servers just annihilate everything that was transmitted so far (realizing it was a client abort during transmission or a network glitch - and the file probably corrupted anyway), others keep what they got so far. Only sometimes (out of luck) they maybe get the close on the data stream first and are still able to send the okay on the control stream (which is not handled by the current code, but what sjoerd added in his first idea of a patch). Now, I'm not really familiar with the PHP stream wrapper API at all, but below is my imagination of how this code could be made to work (I actually run it on a 30+ vhosts cluster): If we were only reading from the stream, it's probably okay to not care about a clean shutdown (especially because in this code part nothing really tells us reliably what exact state the FTP session is in). But if we have written to the FTP server, we MUST close the data stream first, then wait for a confirmation from the server - and only then both of us know, the data was sent completely: --- php-5.3.1/ext/standard/ftp_fopen_wrapper.c 2008-12-31 11:15:49.000000000 +0000 +++ php-5.3.1-ftp_fopen_wrapper_patch/ext/standard/ftp_fopen_wrapper.c 2009-12-16 18:41:07.000000000 +0000 @@ -97,14 +97,33 @@ */ static int php_stream_ftp_stream_close(php_stream_wrapper *wrapper, php_stream *stream TSRMLS_DC) { + int ret = 0, result = 0; + char tmp_line[512]; php_stream *controlstream = (php_stream *)stream->wrapperdata; - + + /* For write modes close data stream first to signal EOF to server */ + if (strpbrk(stream->mode, "wa+")) { + if (stream && controlstream) { + php_stream_close(stream); + stream = NULL; + + result = GET_FTP_RESULT(controlstream); + if (result != 226 && result != 250) { + php_error_docref(NULL TSRMLS_CC, E_WARNING, "FTP server reports %s", tmp_line); + ret = EOF; + } + } else { + php_error_docref(NULL TSRMLS_CC, E_WARNING, "Broken streams to FTP server"); + ret = EOF; + } + } + if (controlstream) { php_stream_write_string(controlstream, "QUIT\r\n"); php_stream_close(controlstream); - stream->wrapperdata = NULL; + controlstream = NULL; } - return 0; + return ret; } /* }}} */ @@ -563,8 +582,9 @@ goto errexit; } - /* remember control stream */ + /* remember control stream and mode */ datastream->wrapperdata = (zval *)stream; + strcpy(datastream->mode, mode); php_url_free(resource); return datastream; Now, I'd be very happy if somebody more familiar with the PHP API's could have a glance at this patch, maybe do some fine-tuning and then apply it and hopefully close this bug. I especially scratched my head regarding access to the mode of the stream and regarding error handling: Mode seems to be handled locally only in php_stream_url_wrap_ftp() and then to be discarded. I didn't see a cleaner and quicker way than to overwrite the mode in the stream from php_stream_xport_create() which seems to always be "r+", hoping to not break something elsewhere. Where would the clean way be to keep such things or get them from in this API? Is there some usable internals documentation? Or should I add some struct's to abstract/wrapperdata? But this quickly looked like changing _a_lot_ throughout this whole code... Then the error handling: From what I see in the code, php_stream_wrapper_log_error() would probably be the correct way? But I couldn't make it work (and would need access to the "context", that's handed over to the other functions, but not to close). I could also not get PHP's fclose() to return a failure. From some glances through the rest of the code, on all the higher levels, success/failure is just discarded? Despite the manual that says "Returns TRUE on success or FALSE on failure.". Is it really just not possible to get a FALSE value out of fclose within this API if I couldn't close my streams? So am I just plain stupid if I check the return values of PHP functions in my PHP code, because they're really just hardcoded to TRUE? I'm really sorry about being so ranty and would love to help, but it just looks like quite a few things are broken around here -- I should probably add some more bug reports. Currently I just used php_error_docref() to at least get a warning through to the top-level and hope that somebody familiar with this API can add a real solution. While my patch fixes the primary issue and catches errors, the PHP code still thinks it successfully wrote its data...Sorry, just realized that I went a little bit too far when cleaning up my mess for the diff/patch. :) --- php-5.3.1/ext/standard/ftp_fopen_wrapper.c 2008-12-31 11:15:49.000000000 +0000 +++ php-5.3.1-ftp_fopen_wrapper_patch/ext/standard/ftp_fopen_wrapper.c 2009-12-17 21:32:53.000000000 +0000 @@ -97,14 +97,34 @@ */ static int php_stream_ftp_stream_close(php_stream_wrapper *wrapper, php_stream *stream TSRMLS_DC) { + int ret = 0, result = 0; + char tmp_line[512]; php_stream *controlstream = (php_stream *)stream->wrapperdata; - + + /* For write modes close data stream first to signal EOF to server */ + if (strpbrk(stream->mode, "wa+")) { + if (stream && controlstream) { + php_stream_close(stream); + stream = NULL; + + result = GET_FTP_RESULT(controlstream); + if (result != 226 && result != 250) { + php_error_docref(NULL TSRMLS_CC, E_WARNING, "FTP server reports %s", tmp_line); + ret = EOF; + } + } else { + php_error_docref(NULL TSRMLS_CC, E_WARNING, "Broken streams to FTP server"); + ret = EOF; + } + } + if (controlstream) { php_stream_write_string(controlstream, "QUIT\r\n"); php_stream_close(controlstream); - stream->wrapperdata = NULL; + if (stream) + stream->wrapperdata = NULL; } - return 0; + return ret; } Also make sure that I or somebody else afterwards really does not call something on/in the streams after closing and probably freeing them (didn't really check out the internals of _php_stream_free() et al. -- and the control stream sort of being embedded within the data stream here, but me having to close them the other way round due to the FTP protocol, didn't really help in understanding what might go wrong somewhere deep in your API). But as I said, for me the patch works.