Avoid send close in ssl connections #5096
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Summary of Changes
Hello @Gonlo2, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request resolves an issue where ProxySQL's custom connection closing mechanism would send unencrypted QUIT messages to MySQL backends configured with SSL. This behavior caused MySQL to abruptly terminate connections, leading to an increase in aborted_clients metrics and obscuring actual network problems. The changes introduce a conditional check to prevent these unencrypted messages from being sent when SSL is in use, thereby improving the accuracy of monitoring metrics and preventing unnecessary connection resets.
Highlights
- Issue Resolution: Prevents sending unencrypted close messages to SSL-enabled MySQL backends, which previously caused abrupt connection terminations.
- Metric Accuracy: Addresses the problem of
aborted_clientsmetrics being inflated due to these erroneous connection closures, improving the clarity of monitoring data. - Conditional Logic: Modifies connection closing functions in
MySQL_Monitor.cppandmysql_connection.cppto conditionally send theQUITcommand only when SSL is not in use.
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Code Review
This pull request correctly prevents sending an unencrypted COM_QUIT packet over an SSL connection by adding a check for !my->options.use_ssl in close_mysql functions. This avoids abrupt connection closures from the MySQL backend. My review suggests a small improvement to also check for connection compression. This would make the fix more complete, especially in lib/mysql_connection.cpp where a FIXME comment explicitly mentions that both encryption and compression are not supported by the custom close_mysql logic.
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| static void close_mysql(MYSQL *my) { | ||
| if (my->net.pvio) { | ||
| if (my->net.pvio && !my->options.use_ssl) { |
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This change correctly avoids sending an unencrypted COM_QUIT packet over an SSL connection. To make this more robust, you could also check if compression is enabled, as sending an uncompressed packet on a compressed connection would also be incorrect. This would be consistent with a similar FIXME comment in lib/mysql_connection.cpp.
if (my->net.pvio && !my->options.use_ssl && !my->options.compress) {There was a problem hiding this comment.
According to the comment that it does not work with compression this change would be fine but, since I have not tested it, I did not want to introduce it. If you can check it and it solves this issue, I see no problem in extending the patch.
| // FIXME: currently doesn't support encryption and compression | ||
| void MySQL_Connection::close_mysql() { | ||
| if ((send_quit) && (mysql->net.pvio) && ret_mysql) { | ||
| if ((send_quit) && (mysql->net.pvio) && ret_mysql && !mysql->options.use_ssl) { |
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This change correctly avoids sending an unencrypted COM_QUIT packet over an SSL connection, which addresses part of the FIXME on line 2959. To further address the FIXME, you could also add a check to prevent sending an uncompressed packet when compression is enabled.
if ((send_quit) && (mysql->net.pvio) && ret_mysql && !mysql->options.use_ssl && !mysql->options.compress) {There was a problem hiding this comment.
According to the comment that it does not work with compression this change would be fine but, since I have not tested it, I did not want to introduce it. If you can check it and it solves this issue, I see no problem in extending the patch.
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Can one of the admins verify this patch? |
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@renecannao please review |
3 participants
This PR avoid sending an unencrypted message to a server that uses SSL, as this will cause the backend to abruptly close the connection.
A clear description of the issue
It seems that since the standard MySQL function is blocking, this logic has been recoded in ProxySQL to use a non blocking aproach, at least partially because it doesn't allow SSL or compression. This causes the MySQL backend to receive an incorrect message (or rather, an invalid message since it is not encrypted) and MySQL abruptly cuts the connection. This is not a serious problem since the desired result is achieved in the end, but it makes it difficult to detect real network problems since the MySQL metrics constantly show that there are problems.
Not sending anything can be worse than sending something, but it works for us, and I don't know if it works for you too.
ProxySQL version
v3.0.2
The steps to reproduce the issue
Anything that attempts to close a backend connection if SSL is used can be seen in the MySQL errors defining
log_error_verbosity=3or with the global status metricaborted_clients.