LoRa Scanner: MeshCore searches for nodes and their answers, read

The first two MeshCore packets heard were these: a search for repeaters
and a repeater answering. Both are in clear; they are the test's bytes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk

lib/meshcore/src/meshcore_packet.cpp

@@ -67,6 +67,27 @@ bool parseAdvert(const Packet& p, Advert& out) {
     return true;
 }
 
+bool parseDiscover(const Packet& p, Discover& out) {
+    if (p.type != Payload::Control || p.payloadLen < 6) return false;
+    uint8_t sub = p.payload[0] >> 4;
+    Discover d;
+    d.tag = static_cast<uint32_t>(le32(p.payload + 2));
+    if (sub == 0x8) {
+        d.kinds = p.payload[1];
+    } else if (sub == 0x9) {
+        d.response = true;
+        d.kind = p.payload[0] & 0x0F;
+        d.snr = static_cast<int8_t>(p.payload[1]) / 4.0f;
+        d.id = p.payload + 6;
+        d.idLen = p.payloadLen - 6;
+        if (d.idLen != 8 && d.idLen != 32) return false;
+    } else {
+        return false;
+    }
+    out = d;
+    return true;
+}
+
 const char* routeName(Route r) {
     switch (r) {
         case Route::TransportFlood: return "flood in a region";

lib/meshcore/src/meshcore_packet.h

@@ -58,6 +58,18 @@ struct Advert {
 };
 bool parseAdvert(const Packet& p, Advert& out);
 
+// Control packets that look for nodes nearby, and the answers: sent in clear, to neighbours only.
+struct Discover {
+    bool response = false;
+    uint8_t kinds = 0;     // a request: one bit per kind of node wanted (bit 2: repeaters)
+    uint8_t kind = 0;      // a response: what answers, as in an advert
+    float snr = 0;         // a response: how well it heard the request, dB
+    uint32_t tag = 0;      // random in the request, repeated in its responses
+    const uint8_t* id = nullptr;  // a response: the node's key, or its first 8 bytes
+    size_t idLen = 0;
+};
+bool parseDiscover(const Packet& p, Discover& out);
+
 const char* routeName(Route r);      // "flood", "direct", ...
 const char* payloadName(Payload t);  // "advert", "text", ...
 const char* payloadShort(Payload t); // for a list row: "adv", "txt", ...