Ported from meshcore-dev/MeshCore#2140 (Quency-D <hj_zzns@163.com>).
The upstream v1.16.0 merge changed the Heltec FEM LNA to disabled by
default (upstream commit 696aae6e). This patch restores the enabled
default for repeater via the new "radio.fem.rxgain" preference
(defaulted to 1), while also making the setting user-configurable
and persisted across reboots.
When "flood_max_unscoped" and "flood_max_advert" were inserted at offsets
291-292 in a previous commit, they displaced "fan_mode" and "fan_timeout_secs"
from their established positions. On upgrade, devices with existing saved
prefs would load the old "fan_mode" byte (0, 1, or 2) into "flood_max_unscoped"
and the low byte of "fan_timeout_secs" into "flood_max_advert", both yielding
values of 0 or 1. A "flood_max_unscoped" or "flood_max_advert" of 0 or 1
effectively silences the repeater, causing it to drop nearly all unscoped
flood and advert packets. Additionally, "rx_boosted_gain" was displaced to
offset 291 in the new layout, causing it to read 0 (gain disabled) on devices
whose prefs were saved before the layout change.
Restore a correct, upgrade-safe layout:
290: reserved_290 (placeholder; preserves the byte that held
rx_boosted_gain in the layout before this series)
291: rx_boosted_gain
292: fan_mode
293-294: fan_timeout_secs (uint16_t)
295: flood_max_unscoped
296: flood_max_advert
"flood_max_unscoped" and "flood_max_advert" are moved to the end so that
existing saved prefs with "fan_mode"/"fan_timeout_secs" at 291-294 are
read correctly on upgrade, and the repeater resumes normal flood forwarding
behaviour.
Also fix a copy-paste bug in loadPrefsInt where the availability
checks for "flood_max_unscoped" and "flood_max_advert" both used
sizeof(rx_boosted_gain) instead of their own field sizes.
When RADIOLIB_STATIC_ONLY=1 is set, RadioLib's SPItransferStream()
allocates two fixed-size stack buffers (buffOut and buffIn) of
RADIOLIB_STATIC_ARRAY_SIZE bytes each, instead of heap-allocating
exactly the right size.
The default value of RADIOLIB_STATIC_ARRAY_SIZE is 256. When receiving
a maximum-size LoRa packet (255 bytes, equal to MAX_TRANS_UNIT),
SX126x::readBuffer() passes a 3-byte SPI command header
(CMD_READ_BUFFER + offset + NOP) plus 255 bytes of payload to
SPItransferStream(), for a total buffLen of 258 bytes. This overflows
the 256-byte stack buffers by 2 bytes, corrupting adjacent locals and
occasionally the stack canary, triggering __stack_chk_fail.
The same overflow occurs on the transmit path: SX126x::writeBuffer()
passes a 2-byte command header plus 255 bytes of payload (buffLen=257),
also overflowing the 256-byte buffer.
The overflow is small (2 bytes on the read path, 1 byte on the write
path), so it only intermittently reaches the stack canary depending on
compiler-generated stack frame layout.
Set RADIOLIB_STATIC_ARRAY_SIZE=260 to eliminate the overflow on both
paths, with 2 bytes of margin on the read path (258 < 260) and 3 bytes
on the write path (257 < 260). The value is placed in [arduino_base] so
it applies to all target platforms.
