Guest session ID is too long for IPv6 users [2.0]

[MegaBrutal]

One of my users reported that they can't reset their password because they get a database error.

I finally reproduced the problem, it turns out it only affects users visiting through IPv6.
The following message appears in Error log:

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Database error: Data too long for column 'session' at row 1
File: /Sources/Subs.php
Line: 2780

On the referred line, SMF attempts the following SQL query:

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                $smcFunc['db_insert']($do_delete ? 'ignore' : 'replace',
                        '{db_prefix}log_online',
                        array('session' => 'string', 'id_member' => 'int', 'id_spider' => 'int', 'log_time' => 'int', 'ip' => 'raw', 'url' => 'string'),
                        array($session_id, $user_info['id'], empty($_SESSION['id_robot']) ? 0 : $_SESSION['id_robot'], time(), 'IFNULL(INET_ATON(\'' . $user_info['ip'] . '\'), 0)', $serialized),
                        array('session')
                );

Because the error message says that the value is too long for the `session` column, I checked `smf_log_online` and found that `session` is a VARCHAR(32):

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MariaDB [test]> DESCRIBE `smf_log_online`;
+-----------+-----------------------+------+-----+---------+-------+
| Field     | Type                  | Null | Key | Default | Extra |
+-----------+-----------------------+------+-----+---------+-------+
| session   | varchar(32)           | NO   | PRI |         |       |
| log_time  | int(10)               | NO   | MUL | 0       |       |
| id_member | mediumint(8) unsigned | NO   | MUL | 0       |       |
| id_spider | smallint(5) unsigned  | NO   |     | 0       |       |
| ip        | int(10) unsigned      | NO   |     | 0       |       |
| url       | text                  | NO   |     | NULL    |       |
+-----------+-----------------------+------+-----+---------+-------+

The session ID is constructed here:

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        // Guests use 0, members use their session ID.
        $session_id = $user_info['is_guest'] ? 'ip' . $user_info['ip'] : session_id();

With an IPv6 address, this value may easily exceed 32 characters.

I'm using the IPv6 Support mod. I tried to remove it because I assumed built-in IPv6 support of SMF has fleshed out by now and I don't really need this mod, but turns out I do – when I remove it, SMF stops showing, and probably even logging IPv6 addresses. Now that the mod is marked as outdate, I don't know what should I use to enable full IPv6 support. I hope if I upgrade to SMF 2.1 one time in the future, I won't need any mod for IPv6; but for now, I have to live with this. Still, it would be great if guest session IDs would be generated by other way, or the `session` field would be extended.

SMF: 2.0.19
DB: MariaDB 10.5.18-MariaDB-0+deb11u1 Debian 11
PHP: 7.4.33-1+deb11u1
Webserver: 2.4.54-1~deb11u1

[Diego Andrés]

Doubt it will be fixed.
But you can just update the size of the column, SMF 2.1 uses 128.