Non-PSRAM boards allocated 512-byte MQTT buffers for non-JWT slots, so the
desired buffer size was a per-slot variable while the allocated size was fixed
at `esp_mqtt_client_init()`: IDF 4.4 does not resize those buffers in
`esp_mqtt_set_config()`, and the wrapper's own reassembly buffer is allocated
once for the client's lifetime. A slot reconfigured from non-JWT to JWT
therefore kept 512-byte buffers, and a valid JWT CONNECT (frame plus a 768-byte
token) could not fit — with no error naming the cause. Stopping and starting the
same handle could not change the capacity either.
Give every client 896 bytes on every board. The cost is 384 bytes per client on
a non-PSRAM board, which caps at 2 active slots, against a TLS handshake that
needs 16 KB of contiguous internal DRAM. In exchange the capacity transition
stops existing, so the reconfigure path never needs to recreate a client to grow
its buffers.
agessaman
0d391cea82