Add some lora parameter clamping logic to coalesce to defaults and enforce some bounds (#9808)

src/mesh/Default.h

@@ -66,9 +66,22 @@ class Default
         if (numOnlineNodes <= 40) {
             return 1.0;
         } else {
-            // Get bandwidth in kHz - convert from code if not using preset
-            float bwKHz =
-                config.lora.use_preset ? modemPresetToBwKHz(config.lora.modem_preset, false) : bwCodeToKHz(config.lora.bandwidth);
+            // Resolve SF and BW from preset or manual config
+            // When use_preset is true, config.lora.spread_factor and bandwidth may be 0
+            // because applyModemConfig() sets them on RadioInterface, not on config.lora
+            float bwKHz;
+            uint8_t sf;
+            uint8_t cr;
+            if (config.lora.use_preset) {
+                modemPresetToParams(config.lora.modem_preset, false, bwKHz, sf, cr);
+            } else {
+                sf = config.lora.spread_factor;
+                bwKHz = bwCodeToKHz(config.lora.bandwidth);
+            }
+
+            // Guard against invalid values
+            sf = clampSpreadFactor(sf);
+            bwKHz = clampBandwidthKHz(bwKHz);
 
             // throttlingFactor = 2^SF / (BW_in_kHz * scaling_divisor)
             // With scaling_divisor=100:
@@ -76,11 +89,11 @@ class Default
             // In SF10 and BW=250khz (mediumslow), this gives 0.04096 rather than the original 0.04
             // In SF9 and BW=250khz (mediumfast), this gives 0.02048 rather than the original 0.02
             // In SF7 and BW=250khz (shortfast), this gives 0.00512 rather than the original 0.01
-            float throttlingFactor = static_cast<float>(pow_of_2(config.lora.spread_factor)) / (bwKHz * 100.0f);
+            float throttlingFactor = static_cast<float>(pow_of_2(sf)) / (bwKHz * 100.0f);
 
 #if USERPREFS_EVENT_MODE
             // If we are in event mode, scale down the throttling factor by 4
-            throttlingFactor = static_cast<float>(pow_of_2(config.lora.spread_factor)) / (bwKHz * 25.0f);
+            throttlingFactor = static_cast<float>(pow_of_2(sf)) / (bwKHz * 25.0f);
 #endif
 
             // Scaling up traffic based on number of nodes over 40

src/mesh/MeshRadio.h

@@ -24,6 +24,45 @@ extern const RegionInfo *myRegion;
 
 extern void initRegion();
 
+// Valid LoRa spread factor range and defaults
+constexpr uint8_t LORA_SF_MIN = 7;
+constexpr uint8_t LORA_SF_MAX = 12;
+constexpr uint8_t LORA_SF_DEFAULT = 11; // LONG_FAST default
+
+// Valid LoRa coding rate range and default
+constexpr uint8_t LORA_CR_MIN = 4;
+constexpr uint8_t LORA_CR_MAX = 8;
+constexpr uint8_t LORA_CR_DEFAULT = 5; // LONG_FAST default
+
+// Default bandwidth in kHz (LONG_FAST)
+constexpr float LORA_BW_DEFAULT_KHZ = 250.0f;
+
+/// Clamp spread factor to the valid LoRa range [7, 12].
+/// Out-of-range values (including 0 from unset preset mode) return LORA_SF_DEFAULT.
+static inline uint8_t clampSpreadFactor(uint8_t sf)
+{
+    if (sf < LORA_SF_MIN || sf > LORA_SF_MAX)
+        return LORA_SF_DEFAULT;
+    return sf;
+}
+
+/// Clamp coding rate to the valid LoRa range [4, 8].
+/// Out-of-range values return LORA_CR_DEFAULT.
+static inline uint8_t clampCodingRate(uint8_t cr)
+{
+    if (cr < LORA_CR_MIN || cr > LORA_CR_MAX)
+        return LORA_CR_DEFAULT;
+    return cr;
+}
+
+/// Ensure bandwidth is positive. Non-positive values return LORA_BW_DEFAULT_KHZ.
+static inline float clampBandwidthKHz(float bwKHz)
+{
+    if (bwKHz <= 0.0f)
+        return LORA_BW_DEFAULT_KHZ;
+    return bwKHz;
+}
+
 static inline float bwCodeToKHz(uint16_t bwCode)
 {
     if (bwCode == 31)

src/modules/AdminModule.cpp

@@ -23,6 +23,7 @@
 #endif
 
 #include "Default.h"
+#include "MeshRadio.h"
 #include "TypeConversions.h"
 
 #if !MESHTASTIC_EXCLUDE_MQTT
@@ -756,20 +757,14 @@ void AdminModule::handleSetConfig(const meshtastic_Config &c)
         LOG_INFO("Set config: LoRa");
         config.has_lora = true;
 
-        if (validatedLora.coding_rate < 4 || validatedLora.coding_rate > 8) {
-            LOG_WARN("Invalid coding_rate %d, setting to 5", validatedLora.coding_rate);
-            validatedLora.coding_rate = 5;
+        if (validatedLora.coding_rate != clampCodingRate(validatedLora.coding_rate)) {
+            LOG_WARN("Invalid coding_rate %d, setting to %d", validatedLora.coding_rate, LORA_CR_DEFAULT);
+            validatedLora.coding_rate = LORA_CR_DEFAULT;
         }
 
-        if (validatedLora.spread_factor < 7 || validatedLora.spread_factor > 12) {
-            LOG_WARN("Invalid spread_factor %d, setting to 11", validatedLora.spread_factor);
-            validatedLora.spread_factor = 11;
-        }
-
-        if (validatedLora.bandwidth == 0) {
-            int originalBandwidth = validatedLora.bandwidth;
-            validatedLora.bandwidth = myRegion->wideLora ? 800 : 250;
-            LOG_WARN("Invalid bandwidth %d, setting to default", originalBandwidth);
+        if (validatedLora.spread_factor != clampSpreadFactor(validatedLora.spread_factor)) {
+            LOG_WARN("Invalid spread_factor %d, setting to %d", validatedLora.spread_factor, LORA_SF_DEFAULT);
+            validatedLora.spread_factor = LORA_SF_DEFAULT;
         }
 
         // If no lora radio parameters change, don't need to reboot