#47289 [Com]: socket_read falls into endless loop if remote host disconnects

[patryk dot szczyglowski at gmail dot com]

 ID:               47289
 Comment by:       patryk dot szczyglowski at gmail dot com
 Reported By:      patryk dot szczyglowski at gmail dot com
 Status:           Feedback
 Bug Type:         Sockets related
 Operating System: Linux 2.6
 PHP Version:      5.2.8
 New Comment:

In php documentation:
"socket_read() returns the data as a string on success, or FALSE on
error (including if the remote host has closed the connection)."

So I used:

while (($res = socket_read(...)) !== false) {
  // .. do something
}

To correct it without changes in PHP source code this loop should
look:

while ($res != false) {
  // .. do something
}

but that's incorrect, because e.g. string '0' will match the condition
and it is perfectly valid content.

Low level recv() function returns 0 only on disconnect, and while
connected in blocking mode 0 is never returned to the application.
Current PHP implementation is not compatible with recv(2) and PHP
documentation.

So either you commit my patch or correct the documentation.

Thanks.


Previous Comments:
------------------------------------------------------------------------

[2009-02-03 19:09:26] il...@php.net

There is no loop in the code, how would it get stuck unless you are 
doing while(socket_read()) ?

------------------------------------------------------------------------

[2009-02-03 15:44:28] patryk dot szczyglowski at gmail dot com

Description:
------------
When PHP wants to read from a blocking socket when the remote host
disconnects, PHP ignores 0 return code from recv() system function and
drops into endless loop.

Reproduce code:
---------------
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_connect($socket, $ip, $port);
// disconnect remote host here
$rcv = socket_read($this->socket, 65536, PHP_BINARY_READ); // this line
never returns

Expected result:
----------------
socket_read returns with FALSE

--- php-5.2.8/ext/sockets/sockets.c.orig        2008-10-23 22:21:30.000000000
+0200
+++ php-5.2.8/ext/sockets/sockets.c     2009-01-29 17:32:53.000000000
+0100
@@ -903,6 +903,14 @@
                RETURN_FALSE;
        }
 
+       if (retval == 0) {
+               php_sock->error = errno;
+               SOCKETS_G(last_error) = errno;
+
+               efree(tmpbuf);
+               RETURN_FALSE;
+       }
+
        tmpbuf = erealloc(tmpbuf, retval + 1);
        tmpbuf[retval] = '\0' ;
  

Actual result:
--------------
socket_read never returns, it gets looped in ext/sockets/sockets.c:885


------------------------------------------------------------------------


-- 
Edit this bug report at http://bugs.php.net/?id=47289&edit=1