agessaman 383339eccc fix(mqtt): size the status buffer for real field maxima ...

The worst-case test added with the connection-health fields did not model
production maxima -- it used a 28-byte model and a 24-byte firmware string,
while MQTTBridge permits _origin[32], _device_id[65], _board_model[64],
_firmware_version[64] and derives a 63-byte client version. isValidName()
rejects [ ] / \ : , ? * but permits '"', so a 31-character node name of
quotes is legal and every quote escapes to two bytes.

Measured at those real maxima:

  without connection-health fields   762 bytes
  with connection-health fields      851 bytes
  buffer                             768 bytes

So the 768-byte buffer already had only six bytes of headroom before this
work, and the four new fields overflow it. Overflow is silent:
serializeComplete() returns 0 and clears the buffer, and the bridge
publishes only a positive length, so a device would simply stop publishing
status with no error anywhere -- the same blindness the connection-health
fields exist to remove.

Raises STATUS_JSON_BUFFER_SIZE to 1024 and corrects the test to use the
actual maxima. Status serializes into the shared 2048-byte publish scratch
buffer, so this costs no extra RAM; only the PSRAM-allocation-failed stack
fallback grows by 256 bytes. A static_assert keeps the status ceiling within
the shared buffer.

Found by adversarial review of the preceding commit.

2026-09-26 11:09:21 -07:00

..

test_mqtt_payload_builder.cpp

fix(mqtt): size the status buffer for real field maxima

2026-09-26 11:09:21 -07:00