For packets with a path set; auto try again if no echo was heard

src/Dispatcher.cpp

@@ -106,6 +106,7 @@ void Dispatcher::loop() {
 
       _radio->onSendFinished();
       logTx(outbound, 2 + outbound->getPathByteLen() + outbound->payload_len);
+      onSendComplete(outbound);
       if (outbound->isRouteFlood()) {
         n_sent_flood++;
       } else {
@@ -118,6 +119,7 @@ void Dispatcher::loop() {
 
       _radio->onSendFinished();
       logTxFail(outbound, 2 + outbound->getPathByteLen() + outbound->payload_len);
+      onSendFail(outbound);
 
       releasePacket(outbound);  // return to pool
       outbound = NULL;
@@ -386,4 +388,4 @@ unsigned long Dispatcher::futureMillis(int millis_from_now) const {
   return _ms->getMillis() + millis_from_now;
 }
 
-}
+}

src/Dispatcher.h

@@ -159,6 +159,8 @@ protected:
   virtual void logRx(Packet* packet, int len, float score) { }   // hooks for custom logging
   virtual void logTx(Packet* packet, int len) { }
   virtual void logTxFail(Packet* packet, int len) { }
+  virtual void onSendComplete(Packet* packet) { }
+  virtual void onSendFail(Packet* packet) { }
   virtual const char* getLogDateTime() { return ""; }
 
   virtual float getAirtimeBudgetFactor() const;

src/Mesh.cpp

@@ -4,11 +4,32 @@
 namespace mesh {
 
 void Mesh::begin() {
+  for (int i = 0; i < MAX_DIRECT_RETRY_SLOTS; i++) {
+    _direct_retries[i].packet = NULL;
+    _direct_retries[i].trigger_packet = NULL;
+    _direct_retries[i].retry_at = 0;
+    _direct_retries[i].retry_delay = 0;
+    _direct_retries[i].priority = 0;
+    _direct_retries[i].progress_marker = 0;
+    _direct_retries[i].expect_path_growth = false;
+    _direct_retries[i].queued = false;
+    _direct_retries[i].active = false;
+  }
   Dispatcher::begin();
 }
 
 void Mesh::loop() {
   Dispatcher::loop();
+
+  for (int i = 0; i < MAX_DIRECT_RETRY_SLOTS; i++) {
+    if (!_direct_retries[i].active || !_direct_retries[i].queued || !millisHasNowPassed(_direct_retries[i].retry_at)) {
+      continue;
+    }
+
+    if (!isDirectRetryQueued(_direct_retries[i].packet)) {
+      clearDirectRetrySlot(i);
+    }
+  }
 }
 
 bool Mesh::allowPacketForward(const mesh::Packet* packet) { 
@@ -22,10 +43,25 @@ uint32_t Mesh::getRetransmitDelay(const mesh::Packet* packet) {
 uint32_t Mesh::getDirectRetransmitDelay(const Packet* packet) {
   return 0;  // by default, no delay
 }
+bool Mesh::allowDirectRetry(const Packet* packet, const uint8_t* next_hop_hash, uint8_t next_hop_hash_len) const {
+  return false;
+}
+uint32_t Mesh::getDirectRetryEchoDelay(const Packet* packet) const {
+  // Keep the base fallback aligned with the repeater's minimum retry wait.
+  return 200;
+}
 uint8_t Mesh::getExtraAckTransmitCount() const {
   return 0;
 }
 
+void Mesh::onSendComplete(Packet* packet) {
+  armDirectRetryOnSendComplete(packet);
+}
+
+void Mesh::onSendFail(Packet* packet) {
+  clearPendingDirectRetryOnSendFail(packet);
+}
+
 uint32_t Mesh::getCADFailRetryDelay() const {
   return _rng->nextInt(1, 4)*120;
 }
@@ -39,6 +75,10 @@ int Mesh::searchChannelsByHash(const uint8_t* hash, GroupChannel channels[], int
 }
 
 DispatcherAction Mesh::onRecvPacket(Packet* pkt) {
+  if (pkt->isRouteDirect()) {
+    cancelDirectRetryOnEcho(pkt);
+  }
+
   if (pkt->isRouteDirect() && pkt->getPayloadType() == PAYLOAD_TYPE_TRACE) {
     if (pkt->path_len < MAX_PATH_SIZE) {
       uint8_t i = 0;
@@ -58,6 +98,7 @@ DispatcherAction Mesh::onRecvPacket(Packet* pkt) {
         pkt->path[pkt->path_len++] = (int8_t) (pkt->getSNR()*4);
 
         uint32_t d = getDirectRetransmitDelay(pkt);
+        maybeScheduleDirectRetry(pkt, 5);
         return ACTION_RETRANSMIT_DELAYED(5, d);  // schedule with priority 5 (for now), maybe make configurable?
       }
     }
@@ -98,6 +139,7 @@ DispatcherAction Mesh::onRecvPacket(Packet* pkt) {
         removeSelfFromPath(pkt);
 
         uint32_t d = getDirectRetransmitDelay(pkt);
+        maybeScheduleDirectRetry(pkt, 0);
         return ACTION_RETRANSMIT_DELAYED(0, d);  // Routed traffic is HIGHEST priority 
       }
     }
@@ -372,6 +414,7 @@ void Mesh::routeDirectRecvAcks(Packet* packet, uint32_t delay_millis) {
         a1->path_len = Packet::copyPath(a1->path, packet->path, packet->path_len);
         a1->header &= ~PH_ROUTE_MASK;
         a1->header |= ROUTE_TYPE_DIRECT;
+        maybeScheduleDirectRetry(a1, 0);
         sendPacket(a1, 0, delay_millis);
       }
       extra--;
@@ -382,11 +425,225 @@ void Mesh::routeDirectRecvAcks(Packet* packet, uint32_t delay_millis) {
       a2->path_len = Packet::copyPath(a2->path, packet->path, packet->path_len);
       a2->header &= ~PH_ROUTE_MASK;
       a2->header |= ROUTE_TYPE_DIRECT;
+      maybeScheduleDirectRetry(a2, 0);
       sendPacket(a2, 0, delay_millis);
     }
   }
 }
 
+void Mesh::clearDirectRetrySlot(int idx) {
+  _direct_retries[idx].packet = NULL;
+  _direct_retries[idx].trigger_packet = NULL;
+  _direct_retries[idx].retry_at = 0;
+  _direct_retries[idx].retry_delay = 0;
+  _direct_retries[idx].priority = 0;
+  _direct_retries[idx].progress_marker = 0;
+  _direct_retries[idx].expect_path_growth = false;
+  _direct_retries[idx].queued = false;
+  _direct_retries[idx].active = false;
+}
+
+bool Mesh::isDirectRetryQueued(const Packet* packet) const {
+  for (int i = 0; i < _mgr->getOutboundTotal(); i++) {
+    if (_mgr->getOutboundByIdx(i) == packet) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void Mesh::calculateDirectRetryKey(const Packet* packet, uint8_t* dest_key) const {
+  uint8_t type = packet->getPayloadType();
+  Utils::sha256(dest_key, MAX_HASH_SIZE, &type, 1, packet->payload, packet->payload_len);
+}
+
+bool Mesh::cancelDirectRetryOnEcho(const Packet* packet) {
+  uint8_t recv_key[MAX_HASH_SIZE];
+  calculateDirectRetryKey(packet, recv_key);
+
+  bool cleared = false;
+  for (int i = 0; i < MAX_DIRECT_RETRY_SLOTS; i++) {
+    if (!_direct_retries[i].active || memcmp(recv_key, _direct_retries[i].retry_key, MAX_HASH_SIZE) != 0) {
+      continue;
+    }
+
+    bool is_echo = _direct_retries[i].expect_path_growth
+      ? packet->path_len > _direct_retries[i].progress_marker
+      : packet->getPathHashCount() < _direct_retries[i].progress_marker;
+    if (!is_echo) {
+      continue;
+    }
+
+    if (_direct_retries[i].queued) {
+      for (int j = 0; j < _mgr->getOutboundTotal(); j++) {
+        if (_mgr->getOutboundByIdx(j) == _direct_retries[i].packet) {
+          Packet* pending = _mgr->removeOutboundByIdx(j);
+          if (pending) {
+            releasePacket(pending);
+          }
+          break;
+        }
+      }
+      clearDirectRetrySlot(i);
+    } else {
+      clearDirectRetrySlot(i);
+    }
+    cleared = true;
+  }
+
+  return cleared;
+}
+
+void Mesh::armDirectRetryOnSendComplete(const Packet* packet) {
+  for (int i = 0; i < MAX_DIRECT_RETRY_SLOTS; i++) {
+    if (!_direct_retries[i].active) {
+      continue;
+    }
+
+    if (_direct_retries[i].queued) {
+      if (_direct_retries[i].packet == packet) {
+        // The retry packet itself just finished transmitting; Dispatcher will release it after this hook.
+        clearDirectRetrySlot(i);
+      }
+      continue;
+    }
+
+    if (_direct_retries[i].trigger_packet != packet) {
+      continue;
+    }
+
+    // Allocate the retry packet only after TX-complete so busy repeaters do not reserve pool slots early.
+    Packet* retry = obtainNewPacket();
+    if (retry == NULL) {
+      clearDirectRetrySlot(i);
+      continue;
+    }
+
+    *retry = *packet;
+
+    // Start the echo wait only after the initial direct transmission actually completed.
+    sendPacket(retry, _direct_retries[i].priority, _direct_retries[i].retry_delay);
+    if (isDirectRetryQueued(retry)) {
+      _direct_retries[i].packet = retry;
+      _direct_retries[i].trigger_packet = NULL;
+      _direct_retries[i].queued = true;
+      _direct_retries[i].retry_at = futureMillis(_direct_retries[i].retry_delay);
+    } else {
+      clearDirectRetrySlot(i);
+    }
+  }
+}
+
+void Mesh::clearPendingDirectRetryOnSendFail(const Packet* packet) {
+  for (int i = 0; i < MAX_DIRECT_RETRY_SLOTS; i++) {
+    if (!_direct_retries[i].active) {
+      continue;
+    }
+
+    if (_direct_retries[i].queued) {
+      if (_direct_retries[i].packet == packet) {
+        // The queued retry itself failed; Dispatcher will release it after this hook.
+        clearDirectRetrySlot(i);
+      }
+      continue;
+    }
+
+    if (_direct_retries[i].trigger_packet == packet) {
+      clearDirectRetrySlot(i);
+    }
+  }
+}
+
+bool Mesh::getDirectRetryTarget(const Packet* packet, const uint8_t*& next_hop_hash, uint8_t& next_hop_hash_len,
+                                uint8_t& progress_marker, bool& expect_path_growth) const {
+  switch (packet->getPayloadType()) {
+    case PAYLOAD_TYPE_ACK:
+    case PAYLOAD_TYPE_PATH:
+    case PAYLOAD_TYPE_REQ:
+    case PAYLOAD_TYPE_RESPONSE:
+    case PAYLOAD_TYPE_TXT_MSG:
+    case PAYLOAD_TYPE_ANON_REQ:
+      if (packet->getPathHashCount() <= 1) {
+        return false;
+      }
+      next_hop_hash = packet->path;
+      next_hop_hash_len = packet->getPathHashSize();
+      progress_marker = packet->getPathHashCount();
+      expect_path_growth = false;
+      return true;
+
+    case PAYLOAD_TYPE_MULTIPART:
+      if (packet->payload_len < 1 || (packet->payload[0] & 0x0F) != PAYLOAD_TYPE_ACK || packet->getPathHashCount() <= 1) {
+        return false;
+      }
+      next_hop_hash = packet->path;
+      next_hop_hash_len = packet->getPathHashSize();
+      progress_marker = packet->getPathHashCount();
+      expect_path_growth = false;
+      return true;
+
+    case PAYLOAD_TYPE_TRACE: {
+      if (packet->payload_len < 9) {
+        return false;
+      }
+
+      uint8_t hash_size = 1 << (packet->payload[8] & 0x03);
+      uint8_t route_bytes = packet->payload_len - 9;
+      uint8_t offset = packet->path_len * hash_size;
+      if (offset + hash_size > route_bytes) {
+        return false;
+      }
+      if (offset + (2 * hash_size) > route_bytes) {
+        return false;  // no downstream repeater means there will be no forward echo to overhear.
+      }
+
+      next_hop_hash = &packet->payload[9 + offset];
+      next_hop_hash_len = hash_size;
+      progress_marker = packet->path_len;
+      expect_path_growth = true;
+      return true;
+    }
+
+    default:
+      return false;
+  }
+}
+
+void Mesh::maybeScheduleDirectRetry(const Packet* packet, uint8_t priority) {
+  const uint8_t* next_hop_hash;
+  uint8_t next_hop_hash_len;
+  uint8_t progress_marker;
+  bool expect_path_growth;
+  if (!getDirectRetryTarget(packet, next_hop_hash, next_hop_hash_len, progress_marker, expect_path_growth)
+      || !allowDirectRetry(packet, next_hop_hash, next_hop_hash_len)) {
+    return;
+  }
+
+  int slot_idx = -1;
+  for (int i = 0; i < MAX_DIRECT_RETRY_SLOTS; i++) {
+    if (!_direct_retries[i].active) {
+      slot_idx = i;
+      break;
+    }
+  }
+  if (slot_idx < 0) {
+    return;
+  }
+
+  // Only store retry metadata here; allocate the retry packet after the initial TX really completes.
+  uint32_t retry_delay = getDirectRetryEchoDelay(packet);
+  calculateDirectRetryKey(packet, _direct_retries[slot_idx].retry_key);
+  _direct_retries[slot_idx].packet = NULL;
+  _direct_retries[slot_idx].trigger_packet = const_cast<Packet*>(packet);
+  _direct_retries[slot_idx].retry_at = 0;
+  _direct_retries[slot_idx].retry_delay = retry_delay;
+  _direct_retries[slot_idx].priority = priority;
+  _direct_retries[slot_idx].progress_marker = progress_marker;
+  _direct_retries[slot_idx].expect_path_growth = expect_path_growth;
+  _direct_retries[slot_idx].queued = false;
+  _direct_retries[slot_idx].active = true;
+}
+
 Packet* Mesh::createAdvert(const LocalIdentity& id, const uint8_t* app_data, size_t app_data_len) {
   if (app_data_len > MAX_ADVERT_DATA_SIZE) return NULL;
 
@@ -634,7 +891,7 @@ void Mesh::sendFlood(Packet* packet, uint32_t delay_millis, uint8_t path_hash_si
   packet->header |= ROUTE_TYPE_FLOOD;
   packet->setPathHashSizeAndCount(path_hash_size, 0);
 
-  _tables->hasSeen(packet); // mark this packet as already sent in case it is rebroadcast back to us
+  _tables->markSent(packet); // mark this packet as already sent in case it is rebroadcast back to us
 
   uint8_t pri;
   if (packet->getPayloadType() == PAYLOAD_TYPE_PATH) {
@@ -663,7 +920,7 @@ void Mesh::sendFlood(Packet* packet, uint16_t* transport_codes, uint32_t delay_m
   packet->transport_codes[1] = transport_codes[1];
   packet->setPathHashSizeAndCount(path_hash_size, 0);
 
-  _tables->hasSeen(packet); // mark this packet as already sent in case it is rebroadcast back to us
+  _tables->markSent(packet); // mark this packet as already sent in case it is rebroadcast back to us
 
   uint8_t pri;
   if (packet->getPayloadType() == PAYLOAD_TYPE_PATH) {
@@ -696,7 +953,8 @@ void Mesh::sendDirect(Packet* packet, const uint8_t* path, uint8_t path_len, uin
       pri = 0;
     }
   }
-  _tables->hasSeen(packet); // mark this packet as already sent in case it is rebroadcast back to us
+  _tables->markSent(packet); // mark this packet as already sent in case it is rebroadcast back to us
+  maybeScheduleDirectRetry(packet, pri);
   sendPacket(packet, pri, delay_millis);
 }
 
@@ -706,7 +964,7 @@ void Mesh::sendZeroHop(Packet* packet, uint32_t delay_millis) {
 
   packet->path_len = 0;  // path_len of zero means Zero Hop
 
-  _tables->hasSeen(packet); // mark this packet as already sent in case it is rebroadcast back to us
+  _tables->markSent(packet); // mark this packet as already sent in case it is rebroadcast back to us
 
   sendPacket(packet, 0, delay_millis);
 }
@@ -719,9 +977,10 @@ void Mesh::sendZeroHop(Packet* packet, uint16_t* transport_codes, uint32_t delay
 
   packet->path_len = 0;  // path_len of zero means Zero Hop
 
-  _tables->hasSeen(packet); // mark this packet as already sent in case it is rebroadcast back to us
+  _tables->markSent(packet); // mark this packet as already sent in case it is rebroadcast back to us
 
   sendPacket(packet, 0, delay_millis);
 }
 
-}
+}
+

src/Mesh.h

@@ -4,6 +4,10 @@
 
 namespace mesh {
 
+#ifndef MAX_DIRECT_RETRY_SLOTS
+  #define MAX_DIRECT_RETRY_SLOTS  6
+#endif
+
 class GroupChannel {
 public:
   uint8_t hash[PATH_HASH_SIZE];
@@ -16,6 +20,7 @@ public:
 class MeshTables {
 public:
   virtual bool hasSeen(const Packet* packet) = 0;
+  virtual void markSent(const Packet* packet) = 0;
   virtual void clear(const Packet* packet) = 0;   // remove this packet hash from table
 };
 
@@ -24,17 +29,42 @@ public:
  *     and provides virtual methods for sub-classes on handling incoming, and also preparing outbound Packets.
 */
 class Mesh : public Dispatcher {
+  struct DirectRetryEntry {
+    Packet* packet;
+    Packet* trigger_packet;
+    unsigned long retry_at;
+    uint32_t retry_delay;
+    uint8_t retry_key[MAX_HASH_SIZE];
+    uint8_t priority;
+    uint8_t progress_marker;
+    bool expect_path_growth;
+    bool queued;
+    bool active;
+  };
+
   RTCClock* _rtc;
   RNG* _rng;
   MeshTables* _tables;
+  DirectRetryEntry _direct_retries[MAX_DIRECT_RETRY_SLOTS];
 
   void removeSelfFromPath(Packet* packet);
   void routeDirectRecvAcks(Packet* packet, uint32_t delay_millis);
+  void clearDirectRetrySlot(int idx);
+  bool isDirectRetryQueued(const Packet* packet) const;
+  void calculateDirectRetryKey(const Packet* packet, uint8_t* dest_key) const;
+  bool cancelDirectRetryOnEcho(const Packet* packet);
+  void armDirectRetryOnSendComplete(const Packet* packet);
+  void clearPendingDirectRetryOnSendFail(const Packet* packet);
+  bool getDirectRetryTarget(const Packet* packet, const uint8_t*& next_hop_hash, uint8_t& next_hop_hash_len,
+                            uint8_t& progress_marker, bool& expect_path_growth) const;
+  void maybeScheduleDirectRetry(const Packet* packet, uint8_t priority);
   //void routeRecvAcks(Packet* packet, uint32_t delay_millis);
   DispatcherAction forwardMultipartDirect(Packet* pkt);
 
 protected:
   DispatcherAction onRecvPacket(Packet* pkt) override;
+  void onSendComplete(Packet* packet) override;
+  void onSendFail(Packet* packet) override;
 
   virtual uint32_t getCADFailRetryDelay() const override;
 
@@ -65,6 +95,17 @@ protected:
    */
   virtual uint32_t getDirectRetransmitDelay(const Packet* packet);
 
+  /**
+   * \brief  Decide whether a DIRECT packet should get one delayed retry if the next hop echo is not overheard.
+   *         Sub-classes can use neighbour tables or other link-quality data to opt in selectively.
+   */
+  virtual bool allowDirectRetry(const Packet* packet, const uint8_t* next_hop_hash, uint8_t next_hop_hash_len) const;
+
+  /**
+   * \returns  milliseconds to wait for the next-hop echo before queueing one retry of the DIRECT packet.
+   */
+  virtual uint32_t getDirectRetryEchoDelay(const Packet* packet) const;
+
   /**
    * \returns  number of extra (Direct) ACK transmissions wanted.
    */

src/helpers/CommonCLI.cpp

@@ -8,6 +8,13 @@
 #define BRIDGE_MAX_BAUD 115200
 #endif
 
+// These bytes used to be reserved/unused in persisted prefs, so keep a marker before trusting them.
+#define DIRECT_RETRY_PREFS_MAGIC_0  0xD4
+#define DIRECT_RETRY_PREFS_MAGIC_1  0x52
+#define DIRECT_RETRY_RECENT_DEFAULT          0
+#define DIRECT_RETRY_SNR_MARGIN_DB_DEFAULT  5
+#define DIRECT_RETRY_SNR_MARGIN_DB_MAX     40
+
 // Believe it or not, this std C function is busted on some platforms!
 static uint32_t _atoi(const char* sp) {
   uint32_t n = 0;
@@ -60,7 +67,9 @@ void CommonCLI::loadPrefsInt(FILESYSTEM* fs, const char* filename) {
     file.read((uint8_t *)&_prefs->tx_delay_factor, sizeof(_prefs->tx_delay_factor));  // 84
     file.read((uint8_t *)&_prefs->guest_password[0], sizeof(_prefs->guest_password)); // 88
     file.read((uint8_t *)&_prefs->direct_tx_delay_factor, sizeof(_prefs->direct_tx_delay_factor)); // 104
-    file.read(pad, 4); // 108 : 4 bytes unused
+    file.read((uint8_t *)&_prefs->direct_retry_recent_enabled, sizeof(_prefs->direct_retry_recent_enabled)); // 108
+    file.read((uint8_t *)&_prefs->direct_retry_snr_margin_db, sizeof(_prefs->direct_retry_snr_margin_db));   // 109
+    file.read((uint8_t *)&_prefs->direct_retry_prefs_magic[0], sizeof(_prefs->direct_retry_prefs_magic));    // 110
     file.read((uint8_t *)&_prefs->sf, sizeof(_prefs->sf));                                         // 112
     file.read((uint8_t *)&_prefs->cr, sizeof(_prefs->cr));                                         // 113
     file.read((uint8_t *)&_prefs->allow_read_only, sizeof(_prefs->allow_read_only));               // 114
@@ -102,6 +111,15 @@ void CommonCLI::loadPrefsInt(FILESYSTEM* fs, const char* filename) {
     _prefs->multi_acks = constrain(_prefs->multi_acks, 0, 1);
     _prefs->adc_multiplier = constrain(_prefs->adc_multiplier, 0.0f, 10.0f);
     _prefs->path_hash_mode = constrain(_prefs->path_hash_mode, 0, 2);   // NOTE: mode 3 reserved for future
+    // Old firmware left offset 108..111 undefined, so require the marker before using the new retry prefs.
+    if (_prefs->direct_retry_prefs_magic[0] != DIRECT_RETRY_PREFS_MAGIC_0
+        || _prefs->direct_retry_prefs_magic[1] != DIRECT_RETRY_PREFS_MAGIC_1) {
+      _prefs->direct_retry_recent_enabled = DIRECT_RETRY_RECENT_DEFAULT;
+      _prefs->direct_retry_snr_margin_db = DIRECT_RETRY_SNR_MARGIN_DB_DEFAULT;
+    } else {
+      _prefs->direct_retry_recent_enabled = constrain(_prefs->direct_retry_recent_enabled, 0, 1);
+      _prefs->direct_retry_snr_margin_db = constrain(_prefs->direct_retry_snr_margin_db, 0, DIRECT_RETRY_SNR_MARGIN_DB_MAX);
+    }
 
     // sanitise bad bridge pref values
     _prefs->bridge_enabled = constrain(_prefs->bridge_enabled, 0, 1);
@@ -150,7 +168,11 @@ void CommonCLI::savePrefs(FILESYSTEM* fs) {
     file.write((uint8_t *)&_prefs->tx_delay_factor, sizeof(_prefs->tx_delay_factor));  // 84
     file.write((uint8_t *)&_prefs->guest_password[0], sizeof(_prefs->guest_password)); // 88
     file.write((uint8_t *)&_prefs->direct_tx_delay_factor, sizeof(_prefs->direct_tx_delay_factor)); // 104
-    file.write(pad, 4); // 108 : 4 byte unused
+    file.write((uint8_t *)&_prefs->direct_retry_recent_enabled, sizeof(_prefs->direct_retry_recent_enabled)); // 108
+    file.write((uint8_t *)&_prefs->direct_retry_snr_margin_db, sizeof(_prefs->direct_retry_snr_margin_db));   // 109
+    // Persist a marker so later loads can distinguish real values from legacy garbage in this reserved slot.
+    uint8_t retry_magic[2] = { DIRECT_RETRY_PREFS_MAGIC_0, DIRECT_RETRY_PREFS_MAGIC_1 };
+    file.write(retry_magic, sizeof(retry_magic)); // 110
     file.write((uint8_t *)&_prefs->sf, sizeof(_prefs->sf));                                         // 112
     file.write((uint8_t *)&_prefs->cr, sizeof(_prefs->cr));                                         // 113
     file.write((uint8_t *)&_prefs->allow_read_only, sizeof(_prefs->allow_read_only));               // 114
@@ -338,6 +360,10 @@ void CommonCLI::handleCommand(uint32_t sender_timestamp, const char* command, ch
         sprintf(reply, "> %d", (uint32_t)_prefs->flood_max);
       } else if (memcmp(config, "direct.txdelay", 14) == 0) {
         sprintf(reply, "> %s", StrHelper::ftoa(_prefs->direct_tx_delay_factor));
+      } else if (memcmp(config, "direct.retry.heard", 18) == 0) {
+        sprintf(reply, "> %s", _prefs->direct_retry_recent_enabled ? "on" : "off");
+      } else if (memcmp(config, "direct.retry.margin", 19) == 0) {
+        sprintf(reply, "> %d", (uint32_t)_prefs->direct_retry_snr_margin_db);
       } else if (memcmp(config, "owner.info", 10) == 0) {
         *reply++ = '>';
         *reply++ = ' ';
@@ -587,6 +613,27 @@ void CommonCLI::handleCommand(uint32_t sender_timestamp, const char* command, ch
         } else {
           strcpy(reply, "Error, cannot be negative");
         }
+      } else if (memcmp(config, "direct.retry.heard ", 19) == 0) {
+        if (memcmp(&config[19], "on", 2) == 0) {
+          _prefs->direct_retry_recent_enabled = 1;
+          savePrefs();
+          strcpy(reply, "OK");
+        } else if (memcmp(&config[19], "off", 3) == 0) {
+          _prefs->direct_retry_recent_enabled = 0;
+          savePrefs();
+          strcpy(reply, "OK");
+        } else {
+          strcpy(reply, "Error, must be on or off");
+        }
+      } else if (memcmp(config, "direct.retry.margin ", 20) == 0) {
+        int db = atoi(&config[20]);
+        if (db >= 0 && db <= DIRECT_RETRY_SNR_MARGIN_DB_MAX) {
+          _prefs->direct_retry_snr_margin_db = (uint8_t)db;
+          savePrefs();
+          strcpy(reply, "OK");
+        } else {
+          sprintf(reply, "Error, min 0 and max %d", DIRECT_RETRY_SNR_MARGIN_DB_MAX);
+        }
       } else if (memcmp(config, "owner.info ", 11) == 0) {
         config += 11;
         char *dp = _prefs->owner_info;

src/helpers/CommonCLI.h

@@ -32,7 +32,9 @@ struct NodePrefs { // persisted to file
   float tx_delay_factor;
   char guest_password[16];
   float direct_tx_delay_factor;
-  uint32_t guard;
+  uint8_t direct_retry_recent_enabled;
+  uint8_t direct_retry_snr_margin_db;
+  uint8_t direct_retry_prefs_magic[2];
   uint8_t sf;
   uint8_t cr;
   uint8_t allow_read_only;

src/helpers/SimpleMeshTables.h

@@ -8,13 +8,103 @@
 
 #define MAX_PACKET_HASHES  128
 #define MAX_PACKET_ACKS     64
+#define MAX_RECENT_REPEATERS  64
+#define MAX_ROUTE_HASH_BYTES   3
 
 class SimpleMeshTables : public mesh::MeshTables {
+public:
+  struct RecentRepeaterInfo {
+    // Just enough identity to match a next-hop path prefix plus the SNR that heard it.
+    uint8_t prefix[MAX_ROUTE_HASH_BYTES];
+    uint8_t prefix_len;
+    int8_t snr_x4;
+  };
+
+private:
   uint8_t _hashes[MAX_PACKET_HASHES*MAX_HASH_SIZE];
   int _next_idx;
   uint32_t _acks[MAX_PACKET_ACKS];
   int _next_ack_idx;
   uint32_t _direct_dups, _flood_dups;
+  RecentRepeaterInfo _recent_repeaters[MAX_RECENT_REPEATERS];
+  int _next_recent_repeater_idx;
+
+  bool hasSeenAck(uint32_t ack) const {
+    for (int i = 0; i < MAX_PACKET_ACKS; i++) {
+      if (ack == _acks[i]) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  void storeAck(uint32_t ack) {
+    _acks[_next_ack_idx] = ack;
+    _next_ack_idx = (_next_ack_idx + 1) % MAX_PACKET_ACKS;
+  }
+
+  bool hasSeenHash(const uint8_t* hash) const {
+    const uint8_t* sp = _hashes;
+    for (int i = 0; i < MAX_PACKET_HASHES; i++, sp += MAX_HASH_SIZE) {
+      if (memcmp(hash, sp, MAX_HASH_SIZE) == 0) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  void storeHash(const uint8_t* hash) {
+    memcpy(&_hashes[_next_idx*MAX_HASH_SIZE], hash, MAX_HASH_SIZE);
+    _next_idx = (_next_idx + 1) % MAX_PACKET_HASHES;
+  }
+
+  bool extractRecentRepeater(const mesh::Packet* packet, uint8_t* prefix, uint8_t& prefix_len) const {
+    // Learn repeater prefixes only from packet shapes that expose a trustworthy repeater ID.
+    if (packet->getPayloadType() == PAYLOAD_TYPE_ADVERT && packet->payload_len >= PUB_KEY_SIZE) {
+      memcpy(prefix, packet->payload, MAX_ROUTE_HASH_BYTES);
+      prefix_len = MAX_ROUTE_HASH_BYTES;
+      return true;
+    }
+
+    if (packet->getPayloadType() == PAYLOAD_TYPE_CONTROL
+        && packet->isRouteDirect()
+        && packet->getPathHashCount() == 0
+        && packet->payload_len >= 6 + MAX_ROUTE_HASH_BYTES
+        && (packet->payload[0] & 0xF0) == 0x90) {
+      memcpy(prefix, &packet->payload[6], MAX_ROUTE_HASH_BYTES);
+      prefix_len = MAX_ROUTE_HASH_BYTES;
+      return true;
+    }
+
+    if (packet->isRouteFlood() && packet->getPathHashCount() > 0) {
+      prefix_len = packet->getPathHashSize();
+      if (prefix_len > MAX_ROUTE_HASH_BYTES) {
+        prefix_len = MAX_ROUTE_HASH_BYTES;
+      }
+
+      const uint8_t* last_hop = &packet->path[(packet->getPathHashCount() - 1) * packet->getPathHashSize()];
+      memcpy(prefix, last_hop, prefix_len);
+      return true;
+    }
+
+    return false;
+  }
+
+  void recordRecentRepeater(const mesh::Packet* packet) {
+    uint8_t prefix[MAX_ROUTE_HASH_BYTES] = {0};
+    uint8_t prefix_len = 0;
+    if (!extractRecentRepeater(packet, prefix, prefix_len) || prefix_len == 0) {
+      return;
+    }
+
+    // Ring buffer is enough here; retry fallback only needs a recent prefix->SNR observation.
+    RecentRepeaterInfo& slot = _recent_repeaters[_next_recent_repeater_idx];
+    memset(slot.prefix, 0, sizeof(slot.prefix));
+    memcpy(slot.prefix, prefix, prefix_len);
+    slot.prefix_len = prefix_len;
+    slot.snr_x4 = packet->_snr;
+    _next_recent_repeater_idx = (_next_recent_repeater_idx + 1) % MAX_RECENT_REPEATERS;
+  }
 
 public:
   SimpleMeshTables() { 
@@ -23,6 +113,8 @@ public:
     memset(_acks, 0, sizeof(_acks));
     _next_ack_idx = 0;
     _direct_dups = _flood_dups = 0;
+    memset(_recent_repeaters, 0, sizeof(_recent_repeaters));
+    _next_recent_repeater_idx = 0;
   }
 
 #ifdef ESP32
@@ -31,12 +123,16 @@ public:
     f.read((uint8_t *) &_next_idx, sizeof(_next_idx));
     f.read((uint8_t *) &_acks[0], sizeof(_acks));
     f.read((uint8_t *) &_next_ack_idx, sizeof(_next_ack_idx));
+    f.read((uint8_t *) &_recent_repeaters[0], sizeof(_recent_repeaters));
+    f.read((uint8_t *) &_next_recent_repeater_idx, sizeof(_next_recent_repeater_idx));
   }
   void saveTo(File f) {
     f.write(_hashes, sizeof(_hashes));
     f.write((const uint8_t *) &_next_idx, sizeof(_next_idx));
     f.write((const uint8_t *) &_acks[0], sizeof(_acks));
     f.write((const uint8_t *) &_next_ack_idx, sizeof(_next_ack_idx));
+    f.write((const uint8_t *) &_recent_repeaters[0], sizeof(_recent_repeaters));
+    f.write((const uint8_t *) &_next_recent_repeater_idx, sizeof(_next_recent_repeater_idx));
   }
 #endif
 
@@ -44,28 +140,8 @@ public:
     if (packet->getPayloadType() == PAYLOAD_TYPE_ACK) {
       uint32_t ack;
       memcpy(&ack, packet->payload, 4);
-      for (int i = 0; i < MAX_PACKET_ACKS; i++) {
-        if (ack == _acks[i]) { 
-          if (packet->isRouteDirect()) {
-            _direct_dups++;   // keep some stats
-          } else {
-            _flood_dups++;
-          }
-          return true;
-        }
-      }
-  
-      _acks[_next_ack_idx] = ack;
-      _next_ack_idx = (_next_ack_idx + 1) % MAX_PACKET_ACKS;  // cyclic table  
-      return false;
-    }
 
-    uint8_t hash[MAX_HASH_SIZE];
-    packet->calculatePacketHash(hash);
-
-    const uint8_t* sp = _hashes;
-    for (int i = 0; i < MAX_PACKET_HASHES; i++, sp += MAX_HASH_SIZE) {
-      if (memcmp(hash, sp, MAX_HASH_SIZE) == 0) { 
+      if (hasSeenAck(ack)) {
         if (packet->isRouteDirect()) {
           _direct_dups++;   // keep some stats
         } else {
@@ -73,13 +149,46 @@ public:
         }
         return true;
       }
+
+      storeAck(ack);
+      return false;
     }
 
-    memcpy(&_hashes[_next_idx*MAX_HASH_SIZE], hash, MAX_HASH_SIZE);
-    _next_idx = (_next_idx + 1) % MAX_PACKET_HASHES;  // cyclic table
+    uint8_t hash[MAX_HASH_SIZE];
+    packet->calculatePacketHash(hash);
+
+    if (hasSeenHash(hash)) {
+      if (packet->isRouteDirect()) {
+        _direct_dups++;   // keep some stats
+      } else {
+        _flood_dups++;
+      }
+      return true;
+    }
+
+    storeHash(hash);
+    recordRecentRepeater(packet);
     return false;
   }
 
+  void markSent(const mesh::Packet* packet) override {
+    // Outbound packets must be marked as already-sent without teaching the recent-heard cache about ourselves.
+    if (packet->getPayloadType() == PAYLOAD_TYPE_ACK) {
+      uint32_t ack;
+      memcpy(&ack, packet->payload, 4);
+      if (!hasSeenAck(ack)) {
+        storeAck(ack);
+      }
+      return;
+    }
+
+    uint8_t hash[MAX_HASH_SIZE];
+    packet->calculatePacketHash(hash);
+    if (!hasSeenHash(hash)) {
+      storeHash(hash);
+    }
+  }
+
   void clear(const mesh::Packet* packet) override {
     if (packet->getPayloadType() == PAYLOAD_TYPE_ACK) {
       uint32_t ack;
@@ -107,5 +216,24 @@ public:
   uint32_t getNumDirectDups() const { return _direct_dups; }
   uint32_t getNumFloodDups() const { return _flood_dups; }
 
+  const RecentRepeaterInfo* findRecentRepeaterByHash(const uint8_t* hash, uint8_t hash_len) const {
+    if (hash == NULL || hash_len == 0) {
+      return NULL;
+    }
+
+    // Search newest-to-oldest so the retry gate prefers the freshest SNR sample for a prefix.
+    for (int i = 0; i < MAX_RECENT_REPEATERS; i++) {
+      int idx = (_next_recent_repeater_idx - 1 - i + MAX_RECENT_REPEATERS) % MAX_RECENT_REPEATERS;
+      const RecentRepeaterInfo* info = &_recent_repeaters[idx];
+      if (info->prefix_len < hash_len || info->prefix_len == 0) {
+        continue;
+      }
+      if (memcmp(info->prefix, hash, hash_len) == 0) {
+        return info;
+      }
+    }
+    return NULL;
+  }
+
   void resetStats() { _direct_dups = _flood_dups = 0; }
 };