Looking for correct PHP socket error constants - php

Question

I have an odd problem that's likely due to my inexperience with socket programming.
I'm currently using the raw error code numbers I'm getting from socket_last_error() as I see I need to handle them. This is getting unwieldy.
I'd like to use predefined constants (either my own or builtin) to refer to the different types of socket errors/conditions I need to deal with.
The error tables I've found all use conflicting values.
At http://php.net/manual/en/sockets.constants.php (in a comment that lists the raw numbers), I see things like (excerpted):
SOCKET_EINPROGRESS 10036
SOCKET_EALREADY 10037
SOCKET_ENETUNREACH 10051
The one comment at http://php.net/socket_last_error contains a list of what are apparently the "standard C defines" for socket errors (?):
define('EINPROGRESS', 115); /* Operation now in progress */
define('EALREADY', 114); /* Operation already in progress */
define('ENETUNREACH', 101); /* Network is unreachable */
The errno.h file on my own system (hiding in /usr/include/asm-generic/) seems to support this:
#define EINPROGRESS 115 /* Operation now in progress */
#define EALREADY 114 /* Operation already in progress */
#define ENETUNREACH 101 /* Network is unreachable */
However those "standard definitions" seem to be subject to change depending on what OS you're on: BSD4.4's errno.h has things like
#define EINPROGRESS 36 /* Operation now in progress */
#define EALREADY 37 /* Operation already in progress */
#define ENETUNREACH 51 /* Network is unreachable */
Now we know what the socket_* functions were inspired by though!
Finally, I find what seems to be a hint of an explanation hiding in the VirtualBox source code:
#ifndef EALREADY
# if defined(RT_ERRNO_OS_BSD)
# define EALREADY (37)
# elif defined(RT_OS_LINUX)
# define EALREADY (114)
# else
# define EALREADY (149)
# endif
#endif
With all of this taken into account...
socket_last_error() returns an errno of 101 when Network is unreachable, as opposed to 51 or 10051. So this function appears to be in apparent violation of the socket library's officially-supplied constants, and seems to be using Linux's error codes instead.
([EDIT after adding my answer]: The 101 stated above was obtained on Linux.)
So now that I seem to be in Undocumented and/or Seemingly Undefined Behavior land... what do I do now? I'm on Linux right now; do these values ever change?
Is there some way I can use the offical SOCKET_* constants? I certainly wouldn't mind doing so.

Answer 1

Sounds like you've been researching this hard -- and also that the platform-specific stuff might be a nuisance. Let me suggest this code which will ostensibly fetch all defined constants grouped together as "sockets" constants:
$consts = get_defined_constants(TRUE);
$socket_constants = $consts["sockets"];
foreach($socket_constants as $key => $value){
echo $key . '=' . $value . "\n";
}
From that, I was able to construct this function which you may find useful on any platform for finding the names of socket constants which might match
function get_socket_constant_names($to_check) {
$consts = get_defined_constants(TRUE);
$socket_constants = $consts["sockets"];
$matches = array();
foreach($socket_constants as $key => $value){
if ($value == $to_check) {
$matches[] = $key;
}
}
return $matches;
}
This:
var_dump(get_socket_constant_names(101));
Yields this:
array(1) {
[0] =>
string(18) "SOCKET_ENETUNREACH"
}

Answer 2

I just did some digging.
WARNING. PHP returns OS-specific socket error codes.
I do not know how to retrieve error codes compatible with the socket_* constants, so you have to detect the OS :'(
See proof after source code.
The following are heavily elided to aid focus.
From https://github.com/php/php-src/blob/master/ext/sockets/sockets.c:
PHP_FUNCTION(socket_connect) {
// will set errno
retval = connect(php_sock->bsd_socket, (struct sockaddr *)&sin, sizeof(struct sockaddr_in));
if (retval != 0) {
// call macro defined in php_sockets.h with errno value
PHP_SOCKET_ERROR(php_sock, "unable to connect", errno);
RETURN_FALSE;
}
RETURN_TRUE;
}
PHP_FUNCTION(socket_last_error) {
// check for argument
if (arg1) {
if ((php_sock = (php_socket *)zend_fetch_resource(Z_RES_P(arg1), le_socket_name, le_socket)) == NULL) {
RETURN_FALSE;
}
// return errno from passed socket resource
RETVAL_LONG(php_sock->error);
} else {
// return errno from last globally set value
RETVAL_LONG(SOCKETS_G(last_error));
}
}
From https://github.com/php/php-src/blob/master/ext/sockets/php_sockets.h:
#define PHP_SOCKET_ERROR(socket, msg, errn) \
// store the value for this socket resource
(socket)->error = _err; \
// store the value globally
SOCKETS_G(last_error) = _err
Proof:
<?php
$s = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_set_nonblock($s);
socket_connect($s, "google.com", "80");
var_dump(socket_last_error());
var_dump(socket_strerror(socket_last_error()));
Observe the difference in socket_last_error():
linux$ php asdf.php
int(115)
string(25) "Operation now in progress"
freebsd$ php asdf.php
int(36)
string(25) "Operation now in progress"
TL;DR: There's no defined list of constants inside PHP (that I can see how to use). You must supply your own OS-correct list of constants.