MQTT Integration with custom TLS stack

[ashwiniprabhug]

I have a custom TLS client implementation in C built directly on OpenSSL.
It fully manages:

• DNS + TCP connection
• SSL_CTX / SSL objects
• TLS handshake
• Certificate verification
• SSL_read / SSL_write

I am trying to understand whether this TLS stack can be safely integrated
with an MQTT client in Python (paho-mqtt), or whether the correct design
is to use an MQTT C client instead.

From my understanding:

• paho-mqtt (Python) assumes ownership of the socket and TLS lifecycle
  via Python ssl.SSLContext
• There is no supported way to inject an external OpenSSL SSL* or
  custom TLS read/write layer into paho-mqtt
• Mixing a custom TLS stack with paho-mqtt would break reconnect,
  keepalive, and socket lifecycle guarantees

Is this understanding correct?

If custom TLS behavior is required (custom OpenSSL build, cipher control,
handshake logic), is the recommended approach to:

1. Use an MQTT C client (Paho C / libmosquitto) with the custom TLS stack
2. Or restrict Python usage to ssl.SSLContext only?

Looking for confirmation from maintainers or guidance on supported designs.