Limit flood advert packet forwarding

examples/simple_repeater/MyMesh.cpp

@@ -390,6 +390,14 @@ bool MyMesh::allowPacketForward(const mesh::Packet *packet) {
     MESH_DEBUG_PRINTLN("allowPacketForward: unknown transport code, or wildcard not allowed for FLOOD packet");
     return false;
   }
+  // Limit flood advert paket forwarding using a probabilistic reduction defined by P(h) = 0.308^(hops-1)
+  // https://github.com/meshcore-dev/MeshCore/issues/1223
+  double_t roll_dice = (double)rand() / RAND_MAX;
+  double_t forw_prob = pow(_prefs.flood_advert_base, packet->path_len - 1);
+  if (packet->getPayloadType() == PAYLOAD_TYPE_ADVERT && packet->isRouteFlood() && roll_dice > forw_prob)
+    return false;
+
+  // all other packets
   return true;
 }
 
@@ -783,6 +791,7 @@ MyMesh::MyMesh(mesh::MainBoard &board, mesh::Radio &radio, mesh::MillisecondCloc
   _prefs.tx_power_dbm = LORA_TX_POWER;
   _prefs.advert_interval = 1;        // default to 2 minutes for NEW installs
   _prefs.flood_advert_interval = 12; // 12 hours
+  _prefs.flood_advert_base = 0.308f;
   _prefs.flood_max = 64;
   _prefs.interference_threshold = 0; // disabled
 

examples/simple_room_server/MyMesh.cpp

@@ -275,6 +275,15 @@ uint32_t MyMesh::getDirectRetransmitDelay(const mesh::Packet *packet) {
 bool MyMesh::allowPacketForward(const mesh::Packet *packet) {
   if (_prefs.disable_fwd) return false;
   if (packet->isRouteFlood() && packet->path_len >= _prefs.flood_max) return false;
+
+  // Limit flood advert paket forwarding using a probabilistic reduction defined by P(h) = 0.308^(hops-1)
+  // https://github.com/meshcore-dev/MeshCore/issues/1223
+  double_t roll_dice = (double)rand() / RAND_MAX;
+  double_t forw_prob = pow(_prefs.flood_advert_base, packet->path_len - 1);
+  if (packet->getPayloadType() == PAYLOAD_TYPE_ADVERT && packet->isRouteFlood() && roll_dice > forw_prob)
+    return false;
+
+  // all other packets
   return true;
 }
 
@@ -613,6 +622,7 @@ MyMesh::MyMesh(mesh::MainBoard &board, mesh::Radio &radio, mesh::MillisecondCloc
   _prefs.disable_fwd = 1;
   _prefs.advert_interval = 1;        // default to 2 minutes for NEW installs
   _prefs.flood_advert_interval = 12; // 12 hours
+  _prefs.flood_advert_base = 0.308f;
   _prefs.flood_max = 64;
   _prefs.interference_threshold = 0; // disabled
 #ifdef ROOM_PASSWORD

src/helpers/CommonCLI.cpp

@@ -81,7 +81,9 @@ void CommonCLI::loadPrefsInt(FILESYSTEM* fs, const char* filename) {
     file.read((uint8_t *)&_prefs->discovery_mod_timestamp, sizeof(_prefs->discovery_mod_timestamp)); // 162
     file.read((uint8_t *)&_prefs->adc_multiplier, sizeof(_prefs->adc_multiplier)); // 166
     file.read((uint8_t *)_prefs->owner_info, sizeof(_prefs->owner_info));  // 170
-    // 290
+    file.read((uint8_t *)&_prefs->flood_advert_base, sizeof(_prefs->flood_advert_base));                 // 290
+
+    // 294
 
     // sanitise bad pref values
     _prefs->rx_delay_base = constrain(_prefs->rx_delay_base, 0, 20.0f);
@@ -108,6 +110,8 @@ void CommonCLI::loadPrefsInt(FILESYSTEM* fs, const char* filename) {
     _prefs->gps_enabled = constrain(_prefs->gps_enabled, 0, 1);
     _prefs->advert_loc_policy = constrain(_prefs->advert_loc_policy, 0, 2);
 
+    _prefs->flood_advert_base = constrain(_prefs->flood_advert_base, 0, 1);
+
     file.close();
   }
 }
@@ -165,7 +169,9 @@ void CommonCLI::savePrefs(FILESYSTEM* fs) {
     file.write((uint8_t *)&_prefs->discovery_mod_timestamp, sizeof(_prefs->discovery_mod_timestamp)); // 162
     file.write((uint8_t *)&_prefs->adc_multiplier, sizeof(_prefs->adc_multiplier));                 // 166
     file.write((uint8_t *)_prefs->owner_info, sizeof(_prefs->owner_info));  // 170
-    // 290
+    file.write((uint8_t *)&_prefs->flood_advert_base, sizeof(_prefs->flood_advert_base));                 // 290
+
+    // 294
 
     file.close();
   }
@@ -364,6 +370,8 @@ void CommonCLI::handleCommand(uint32_t sender_timestamp, const char* command, ch
         } else {
           sprintf(reply, "> %.3f", adc_mult);
         }
+      } else if (memcmp(config, "flood.advert.base", 17) == 0) {
+          sprintf(reply, "> %s", StrHelper::ftoa(_prefs->flood_advert_base));
       } else {
         sprintf(reply, "??: %s", config);
       }
@@ -583,6 +591,15 @@ void CommonCLI::handleCommand(uint32_t sender_timestamp, const char* command, ch
           _prefs->adc_multiplier = 0.0f;
           strcpy(reply, "Error: unsupported by this board");
         };
+      } else if (memcmp(config, "flood.advert.base ", 18) == 0) {
+        float f = atof(&config[18]);
+        if((f > 0) || (f<1)) {
+          _prefs->flood_advert_base = f;
+          savePrefs();
+          strcpy(reply, "OK");
+        } else {
+          strcpy(reply, "Error: base must be between 0 and 1");
+      }        
       } else {
         sprintf(reply, "unknown config: %s", config);
       }

src/helpers/CommonCLI.h

@@ -35,6 +35,7 @@ struct NodePrefs { // persisted to file
   uint8_t flood_max;
   uint8_t interference_threshold;
   uint8_t agc_reset_interval; // secs / 4
+  float flood_advert_base;
   // Bridge settings
   uint8_t bridge_enabled; // boolean
   uint16_t bridge_delay;  // milliseconds (default 500 ms)