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Subject: [PHP-DEV] [pdo_dblib] Correct TDS protocol version
Message-ID: <F8149564-633C-4F44-BB5E-E30BD8ADFD6C@sakiot.com>
Date: Sat, 2 Mar 2024 23:19:53 +0900
To: php internals <internals@lists.php.net>
From: saki@sakiot.com (Saki Takamachi)

Hi internals,

There seems to be an error in the handling of pdo_dblib's TDS protocol =
version, so I'm thinking of fixing these. Through this email, I would =
like to discuss the appropriate time and method for correction.

=E2=80=94 For your reference =E2=80=94
There are several derivatives of "SQL Server", with Microsoft SQL Server =
being the most popular. These communicate using the TDS protocol. =
However, the TDS protocol standards are not strictly unified, and the =
Sybase protocol and Microsoft SQL Server have different standards, so =
each is defined as a different "version" of the TDS protocol.
Therefore, pdo_dblib allows the user to specify a "version" for dsn and =
select which protocol version to use.
=E2=80=94 End =E2=80=94

The related issue:
https://github.com/php/php-src/issues/13475

The types and details of protocol versions are explained in the FreeTDS =
user guide:
https://www.freetds.org/userguide/ChoosingTdsProtocol.html

Summarize the explanation.

4.2: Available for older Sybase and Microsoft SQL Servers
5.0: Available for new Sybase
7.0 - 7.4: Available for new Microsoft SQL Server

Notes:
- There's actually a version too called 4.6, which appears to be for =
Open SQL Server. However, I plan to explore this in a little more =
detail.
- It seems that there are two types of 5.0, so I will investigate this =
as well.

Now take a look at the pdo_dblib implementation in php-src:
=
https://github.com/php/php-src/blob/ffc6f192a8f475dfdff942bb22f509d1eefd08=
47/ext/pdo_dblib/dblib_driver.c#L447

Excerpt the incorrect part:
```
{"5.0",DBVERSION_70} /* FIXME: This does not work with Sybase, but =
environ will */
{"6.0",DBVERSION_70}
{"8.0",DBVERSION_72}
{"10.0",DBVERSION_100}
```

`DBVERSION_70` (meaning 7.0) is specified for 5.0 and 6.0. And as far as =
I can tell, there is no version called 6.0. (`DBVERSION_60` is also not =
defined.)

There is also no version 8.0, but according to the FreeTDS user guide, =
it appears that versions of FreeTDS older than 1.3 can specify this, as =
7.1 was originally planned to be released as 8.0. However, PHP treats =
8.0 as an alias for 7.2 rather than 7.1, which is incorrect anyway.

`DBVERSION_50`, which would be used for 5.0, is also not defined, but =
according to the following page, `DBVERSION_100` means 5.0.
=
https://infocenter.sybase.com/help/index.jsp?topic=3D/com.sybase.dc20155_1=
251/html/newfesd/BABHHDEI.htm

Excerpt:

> DBVERSION_100 =E2=80=94 DB-Library is running with TDS version 5.0 =
protocol

So remove 6.0, 8.0 and 10.0 and 5.0 should look like this:
```
{"5.0",DBVERSION_100}
```

These changes are definitely a BC break. Therefore, I would appreciate =
any feedback you may have, including which versions should I make =
changes to?

Regards.

Saki