Bug #79222 [Com]: unread_bytes do not work

Edit report at https://bugs.php.net/bug.php?id=79222&edit=1 ID: 79222 Comment by: RobertBetts22 dot 94 at gmail dot com Reported by: skullnobrains at gmail dot com Summary: unread_bytes do not work Status: Open Type: Bug Package: Sockets related Operating System: linux PHP Version: 7.2.27 Block user comment: N Private report: N New Comment: not sure it is a bug. it is quite painful not to be able to determine the number of bytes that can be read before reading them any more other than with PEEK. (https://www.mythdhr.biz/)github.com Previous Comments: ------------------------------------------------------------------------ [2020-02-05 11:13:36] skullnobrains at gmail dot com hello again i confirm that if i disable the read buffer, the behavior becomes somehow consistent : PEEKING and then READING returns the same character(s). but the number of unread bytes is now always zero -- from what i gather, it is fairly likely PEEKING always worked previously either because i used to PEEK as soon as the select call returned while in this case, i read multiple packets so php has a chance to move data from one buffer to the next before i PEEK or because there was no buffering. example of a piece of working code that allows both ssl and plain connections. those are integrated in a select loop. if(!stream_get_meta_data($_r)["crypto"] and 22===ord(stream_socket_recvfrom($_r, 1, STREAM_PEEK))){ dbg('wants ssl'); $stats['ssl_wanted']++; $states[$_r]=10000; continue; } ... if($states[$_r]===10000){ $stats['ssl_ec_calls']++; if(true===$crypto=stream_socket_enable_crypto($_r,true,STREAM_CRYPTO_METHOD_ANY_SERVER)){ $states[$_r]=0; $stats['ssl_ok']++; dbg('SSL HANDSHAKE COMPLETED'); } elseif($crypto===false) answ("480 crypto requested but handshake cannot complete"); elseif($crypto!==0) answ("580 crypto requested but unexpected answer from enable_crypto()"); sdbg('ssl handshake status %s',$crypto); continue; } since unread_bytes used to be more or less reliable and definitely not always zero ( i have not written code that actually relies on that much in a while so that may have been back in the php5 days ) i would assume first case. may i suggest that using recv_from on a buffered socket raise at least a warning since the behavior is quite erratic and based on a race condition between the script and whatever php routine flushes the network buffers or be modified so it does take the php buffer into account which would be consistent rather than reading random later transmitted bytes or blocking ? also note the documentation of the PEEK flag of stream_socket_recv_from() is wrong as it clearly states the same bytes will be read again by a subsequent call to fread(). as far as i am concerned, i will stick to disabling php's internal buffering, forget about unread_bytes, and probably play a lot with blocking->non-blocking->blocking transitions so i can peek the number of bytes without blocking my scripts. if the buffering stays that way, i see little reason why unread bytes could not be made reliable. since select does not know about php's buffering, i believe the best course of action would be to integrate the buffer into recv_from() transparently and have unread bytes return the sum of the bytes in php's buffer and tcp's. we have low level socket functions for other cases. best regards anyway and thanks again for your time ------------------------------------------------------------------------ [2020-02-04 14:59:30] skullnobrains at gmail dot com i was actually performing a bunch of tests along those lines -> fgetc and other such functions do work as expected in that case the first char was ascii code 75 ( letter K ) so nothing very specific -> reading a single byte with stream_socket_recv_from fails w/o PEEK if i set the socket to non-blocking mode, both funcs return a single character without issue but not the same one !? regarding PEEK, there are a number of possible reasons to use it such as leaving incomplete data in system buffers rather than allocating and managing new ones. in my specific case, the beginning of each packet contains it's size and i want to read a single packet at a time without accidentally reading the beginning of a different packet. i have used recv_from in the past and this is the first time i see it fail while there are supposedly unread bytes or other such weird behaviors. again maybe i have been very lucky for a long time. i'm digging into stream_set_read_buffer since i suspect something changed by default ------------------------------------------------------------------------ [2020-02-04 14:33:00] nikic@php.net stream_socket_recvfrom() is a raw socket operation, it will perform a direct read from the stream and bypass PHP's internal read buffer. I would expect that if unread_bytes=255 and you did an fread() rather than stream_socket_recvfrom(), then that would return something. Could you test whether it does? > not sure it is a bug. it is quite painful not to be able to determine the number of bytes that > can be read before reading them any more other than with PEEK. That's not how you would typically do it (first time I hear about PEEK...) Normally you set the stream into non-blocking mode and then use stream_select() to determine whether it can be read. In non-blocking mode, fread() will return as much as can be read (which might be an empty string), but will not block the connection. ------------------------------------------------------------------------ [2020-02-04 14:18:30] skullnobrains at gmail dot com ok, duly noted. it did work reliably at some point though ( and strangely still does in some cases ) this explains why the number of unread bytes would be zero when data just freshly arrived into the network buffer. but that does not really explain why the internal buffer would contain 255 characters when it is actually empty ... ? not sure it is a bug. it is quite painful not to be able to determine the number of bytes that can be read before reading them any more other than with PEEK. thanks for your time best regards ------------------------------------------------------------------------ [2020-02-04 13:39:01] nikic@php.net unread_bytes is the number of bytes stored in PHP's internal read buffer. It does not indicate whether data is available to read or not. That's what stream_select() is for. The documentation has this peculiar note for this value: > Note: You shouldn't use this value in a script. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=79222 -- Edit this bug report at https://bugs.php.net/bug.php?id=79222&edit=1