ext/pdo_dblib: Added dblib_handle_check_liveness handler (php#21681)

Closes php#21681

In case of persistent connection it was not checked if the
connection was still alive always assuming it was.
If the connection was broken this caused PHP to reuse the
broken connection over and over.
dbdead function is supported by all dblib implementation
(MS, Sybase, FreeTDS).
Change tested manually, see
FreeTDS/freetds#711 (comment)

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>

Author: freddy77

NEWS

@@ -99,6 +99,9 @@ PHP                                                                        NEWS
   . Added TLS session resumption support for streams with new context options
     and Openssl\Session class. (Jakub Zelenka)
 
+- PDO_DBLIB;
+  . Added dblib_handle_check_liveness handler. (freddy77)
+
 - PDO_PGSQL:
   . Clear session-local state disconnect-equivalent processing.
     (KentarouTakeda)

UPGRADING

@@ -204,6 +204,10 @@ PHP 8.6 UPGRADE NOTES
   . Output of openssl_x509_parse() contains criticalExtensions listing all
     critical certificate extensions.
 
+- PDO_DBLIB:
+  . When using persistent connections, there is now a liveness check in the
+  constructor.
+
 - Phar:
   . Phar::mungServer() now supports reference values.
 

ext/pdo_dblib/dblib_driver.c

@@ -420,6 +420,17 @@ static int dblib_get_attribute(pdo_dbh_t *dbh, zend_long attr, zval *return_valu
 	return 1;
 }
 
+static zend_result dblib_handle_check_liveness(pdo_dbh_t *dbh)
+{
+	pdo_dblib_db_handle *H = (pdo_dblib_db_handle *)dbh->driver_data;
+
+	if (dbdead(H->link)) {
+		return FAILURE;
+	}
+
+	return SUCCESS;
+}
+
 static const struct pdo_dbh_methods dblib_methods = {
 	dblib_handle_closer,
 	dblib_handle_preparer,
@@ -432,7 +443,7 @@ static const struct pdo_dbh_methods dblib_methods = {
 	dblib_handle_last_id, /* last insert id */
 	dblib_fetch_error, /* fetch error */
 	dblib_get_attribute, /* get attr */
-	NULL, /* check liveness */
+	dblib_handle_check_liveness, /* check_liveness */
 	NULL, /* get driver methods */
 	NULL, /* request shutdown */
 	NULL, /* in transaction, use PDO's internal tracking mechanism */