Fix GH-9347: Current ODBC liveness checks may be inadequate

We implement SQL_ATTR_CONNECTION_DEAD for ODBC and PDO_ODBC.

This is semantically appropriate and should be used whenever the
driver supports it. In the event that it fails or says the connection
isn't dead (which may be inaccurate in some cases), try the old
heuristic.

Closes GH-9353.

Author: NattyNarwhal

NEWS

@@ -21,6 +21,10 @@ PHP                                                                        NEWS
   . Fixed bug GH-9431 (DateTime::getLastErrors() not returning false when no
     errors/warnings). (Derick)
 
+- ODBC:
+  . Fixed bug GH-9347 (Current ODBC liveness checks may be inadequate). (Calvin
+    Buckley)
+
 - Opcache:
   . Fixed bug GH-9371 (Crash with JIT on mac arm64)
     (jdp1024/David Carlier)
@@ -32,6 +36,10 @@ PHP                                                                        NEWS
     AEAD). (Jakub Zelenka)
   . Added openssl_cipher_key_length function. (Jakub Zelenka)
 
+- PDO_ODBC:
+  . Fixed bug GH-9347 (Current ODBC liveness checks may be inadequate). (Calvin
+    Buckley)
+
 - Random:
   . Fixed bug GH-9415 (Randomizer::getInt(0, 2**32 - 1) with Mt19937
     always returns 1). (timwolla)

ext/odbc/php_odbc.c

@@ -2246,7 +2246,20 @@ void odbc_do_connect(INTERNAL_FUNCTION_PARAMETERS, int persistent)
 				RETCODE ret;
 				UCHAR d_name[32];
 				SQLSMALLINT len;
+				SQLUINTEGER dead = SQL_CD_FALSE;
 
+				ret = SQLGetConnectAttr(db_conn->hdbc,
+					SQL_ATTR_CONNECTION_DEAD,
+					&dead, 0, NULL);
+				if (ret == SQL_SUCCESS && dead == SQL_CD_TRUE) {
+					/* Bail early here, since we know it's gone */
+					zend_hash_str_del(&EG(persistent_list), hashed_details, hashed_len);
+					goto try_and_get_another_connection;
+				}
+				/* If the driver doesn't support it, or returns
+				 * false (could be a false positive), fall back
+				 * to the old heuristic.
+				 */
 				ret = SQLGetInfo(db_conn->hdbc,
 					SQL_DATA_SOURCE_READ_ONLY,
 					d_name, sizeof(d_name), &len);

ext/pdo_odbc/odbc_driver.c

@@ -396,11 +396,19 @@ static zend_result odbc_handle_check_liveness(pdo_dbh_t *dbh)
 	RETCODE ret;
 	UCHAR d_name[32];
 	SQLSMALLINT len;
+	SQLUINTEGER dead = SQL_CD_FALSE;
 	pdo_odbc_db_handle *H = (pdo_odbc_db_handle *)dbh->driver_data;
 
+	ret = SQLGetConnectAttr(H->dbc, SQL_ATTR_CONNECTION_DEAD, &dead, 0, NULL);
+	if (ret == SQL_SUCCESS && dead == SQL_CD_TRUE) {
+		/* Bail early here, since we know it's gone */
+		return FAILURE;
+	}
 	/*
-	 * SQL_ATTR_CONNECTION_DEAD is tempting, but only in ODBC 3.5,
-	 * and not all drivers implement it properly
+	 * If the driver doesn't support SQL_ATTR_CONNECTION_DEAD, or if
+	 * it returns false (which could be a false positive), fall back
+	 * to using SQL_DATA_SOURCE_READ_ONLY, which isn't semantically
+	 * correct, but works with many drivers.
 	 */
 	ret = SQLGetInfo(H->dbc, SQL_DATA_SOURCE_READ_ONLY, d_name,
 		sizeof(d_name), &len);