Upon receiving ACK/reply directly, only update next-hop if we’re the *sole* relayer

src/mesh/NextHopRouter.cpp

@@ -71,10 +71,11 @@ void NextHopRouter::sniffReceived(const meshtastic_MeshPacket *p, const meshtast
         if (p->from != 0) {
             meshtastic_NodeInfoLite *origTx = nodeDB->getMeshNode(p->from);
             if (origTx) {
-                // Either relayer of ACK was also a relayer of the packet, or we were the relayer and the ACK came directly from
-                // the destination
+                // Either relayer of ACK was also a relayer of the packet, or we were the *only* relayer and the ACK came directly
+                // from the destination
                 if (wasRelayer(p->relay_node, p->decoded.request_id, p->to) ||
-                    (wasRelayer(ourRelayID, p->decoded.request_id, p->to) && p->hop_start != 0 && p->hop_start == p->hop_limit)) {
+                    (p->hop_start != 0 && p->hop_start == p->hop_limit &&
+                     wasSoleRelayer(ourRelayID, p->decoded.request_id, p->to))) {
                     if (origTx->next_hop != p->relay_node) { // Not already set
                         LOG_INFO("Update next hop of 0x%x to 0x%x based on ACK/reply", p->from, p->relay_node);
                         origTx->next_hop = p->relay_node;

src/mesh/PacketHistory.cpp

@@ -294,7 +294,7 @@ void PacketHistory::insert(const PacketRecord &r)
 
 /* Check if a certain node was a relayer of a packet in the history given an ID and sender
  * @return true if node was indeed a relayer, false if not */
-bool PacketHistory::wasRelayer(const uint8_t relayer, const uint32_t id, const NodeNum sender)
+bool PacketHistory::wasRelayer(const uint8_t relayer, const uint32_t id, const NodeNum sender, bool *wasSole)
 {
     if (!initOk()) {
         LOG_ERROR("PacketHistory - wasRelayer: NOT INITIALIZED!");
@@ -322,27 +322,42 @@ bool PacketHistory::wasRelayer(const uint8_t relayer, const uint32_t id, const N
               found->sender, found->id, found->next_hop, millis() - found->rxTimeMsec, found->relayed_by[0], found->relayed_by[1],
               found->relayed_by[2], relayer);
 #endif
-    return wasRelayer(relayer, *found);
+    return wasRelayer(relayer, *found, wasSole);
 }
 
 /* Check if a certain node was a relayer of a packet in the history given iterator
  * @return true if node was indeed a relayer, false if not */
-bool PacketHistory::wasRelayer(const uint8_t relayer, const PacketRecord &r)
+bool PacketHistory::wasRelayer(const uint8_t relayer, const PacketRecord &r, bool *wasSole)
 {
-    for (uint8_t i = 0; i < NUM_RELAYERS; i++) {
+    bool found = false;
+    bool other_present = false;
+
+    for (uint8_t i = 0; i < NUM_RELAYERS; ++i) {
         if (r.relayed_by[i] == relayer) {
-#if VERBOSE_PACKET_HISTORY
-            LOG_DEBUG("Packet History - was rel.PR.: s=%08x id=%08x rls=%02x %02x %02x / rl=%02x? YES", r.sender, r.id,
-                      r.relayed_by[0], r.relayed_by[1], r.relayed_by[2], relayer);
-#endif
-            return true;
+            found = true;
+        } else if (r.relayed_by[i] != 0) {
+            other_present = true;
         }
     }
+
+    if (wasSole) {
+        *wasSole = (found && !other_present);
+    }
+
 #if VERBOSE_PACKET_HISTORY
     LOG_DEBUG("Packet History - was rel.PR.: s=%08x id=%08x rls=%02x %02x %02x / rl=%02x? NO", r.sender, r.id, r.relayed_by[0],
               r.relayed_by[1], r.relayed_by[2], relayer);
 #endif
-    return false;
+
+    return found;
+}
+
+// Check if a certain node was the *only* relayer of a packet in the history given an ID and sender
+bool PacketHistory::wasSoleRelayer(const uint8_t relayer, const uint32_t id, const NodeNum sender)
+{
+    bool wasSole = false;
+    wasRelayer(relayer, id, sender, &wasSole);
+    return wasSole;
 }
 
 // Remove a relayer from the list of relayers of a packet in the history given an ID and sender

src/mesh/PacketHistory.h

@@ -34,8 +34,9 @@ class PacketHistory
     void insert(const PacketRecord &r); // Insert or replace a packet record in the history
 
     /* Check if a certain node was a relayer of a packet in the history given iterator
+     * If wasSole is not nullptr, it will be set to true if the relayer was the only relayer of that packet
      * @return true if node was indeed a relayer, false if not */
-    bool wasRelayer(const uint8_t relayer, const PacketRecord &r);
+    bool wasRelayer(const uint8_t relayer, const PacketRecord &r, bool *wasSole = nullptr);
 
     PacketHistory(const PacketHistory &);            // non construction-copyable
     PacketHistory &operator=(const PacketHistory &); // non copyable
@@ -54,8 +55,12 @@ class PacketHistory
                          bool *weWereNextHop = nullptr);
 
     /* Check if a certain node was a relayer of a packet in the history given an ID and sender
+     * If wasSole is not nullptr, it will be set to true if the relayer was the only relayer of that packet
      * @return true if node was indeed a relayer, false if not */
-    bool wasRelayer(const uint8_t relayer, const uint32_t id, const NodeNum sender);
+    bool wasRelayer(const uint8_t relayer, const uint32_t id, const NodeNum sender, bool *wasSole = nullptr);
+
+    // Check if a certain node was the *only* relayer of a packet in the history given an ID and sender
+    bool wasSoleRelayer(const uint8_t relayer, const uint32_t id, const NodeNum sender);
 
     // Remove a relayer from the list of relayers of a packet in the history given an ID and sender
     void removeRelayer(const uint8_t relayer, const uint32_t id, const NodeNum sender);