Receive only what the receiver was listening for

bridge/main.cpp

@@ -53,6 +53,7 @@ void loop();
 // Defined by the host variant.
 extern uint32_t g_sim_millis;
 int g_stuck_irq_ms = 0;
+bool g_lenient_receive = false;
 // The receiver-noise stream the chip model draws from. Distinct per node so
 // two nodes do not read the same "random" bytes at the same instants - which
 // is what seeds each node's RNG, its CSMA backoff and its advert jitter. Left
@@ -81,6 +82,7 @@ constexpr uint8_t kChannelBusy = 0x08; // is another station on the air here?
 constexpr uint8_t kRadioStats = 0x09;  // node -> host: what the chip has seen
 constexpr uint8_t kFrameFailed = 0x0A; // host -> node: a frame locked onto and lost
 constexpr uint8_t kCapFrameFailed = 0x01; // stats byte 47: this bridge takes kFrameFailed
+constexpr uint8_t kCapNoLock = 0x02;      // and its chip reads failure 3 as never locked onto
 
 sock_t gFd = BAD_SOCK;
 std::deque<uint8_t> gConsoleIn;
@@ -201,6 +203,9 @@ int main(int argc, char** argv) {
     // without a way to reproduce it the difference between 1.16 and 1.17
     // cannot be observed at all.
     else if (!strcmp(argv[i], "--stuck-irq-ms")) g_stuck_irq_ms = atoi(next());
+    // The chip's inbox grace, back on: for reproducing a run made before this
+    // build received only what its receiver was listening for.
+    else if (!strcmp(argv[i], "--lenient-receive")) g_lenient_receive = true;
     else if (!strcmp(argv[i], "--print-airtime")) printAirtimeFor = atoi(next());
   }
 
@@ -234,6 +239,9 @@ int main(int argc, char** argv) {
                                                : (g_identity_seed ^ 0x9E3779B97F4A7C15ULL));
 
   if (g_stuck_irq_ms > 0) sim_hal.chip().setStuckIrqMs((uint32_t)g_stuck_irq_ms);
+  // This node's clock is the engine's, so the chip can judge when a frame began
+  // and refuse one its receiver was not listening for, as silicon does.
+  sim_hal.chip().setStrictReceive(!g_lenient_receive);
   setup();
   drainTx();
   flushConsole();
@@ -393,7 +401,9 @@ int main(int argc, char** argv) {
           // engine sends kFrameFailed only to a node that says so here, because
           // a bridge without that case ends its connection on a kind it does
           // not know, and the engine cannot tell the two apart any other way.
-          sb[47] = kCapFrameFailed;
+          // A chip older than ABI 1.7 reads failure 3 as a CRC error, so the
+          // engine sends it only where this bit says the chip knows better.
+          sb[47] = kCapFrameFailed | kCapNoLock;
           writeMsg(gFd, kRadioStats, sb, sizeof(sb));
         }
         if (!writeMsg(gFd, kAck, payload.data(), 4)) goto done;