Fix direct retry review nits

docs/cli_commands.md

@@ -953,7 +953,7 @@ region save
 ---
 ### Direct Retry
 
-Direct retry resends direct-routed packets when the downstream echo is not heard. It applies to direct messages and TRACE packets. It does not change ACK handling.
+Direct retry resends direct-routed packets when the downstream echo is not heard. It applies to direct messages, ACK packets, multipart packets carrying ACK payloads, and TRACE packets.
 
 #### View or change direct retry state
 **Usage:**

examples/simple_repeater/MyMesh.cpp

@@ -574,8 +574,8 @@ uint8_t MyMesh::getDirectRetryCodingRateForSNR(int8_t snr_x4) const {
   if (!_prefs.direct_retry_cr_enabled) return 0;
   if (snr_x4 >= _prefs.direct_retry_cr4_snr_x4) return 4;
   if (snr_x4 >= _prefs.direct_retry_cr5_snr_x4) return 5;
-  if (snr_x4 >= _prefs.direct_retry_cr7_snr_x4) return 7;
   if (snr_x4 <= _prefs.direct_retry_cr8_snr_x4) return 8;
+  if (snr_x4 >= _prefs.direct_retry_cr7_snr_x4) return 7;
   return 7;
 }
 

src/Dispatcher.cpp

@@ -348,19 +348,23 @@ void Dispatcher::checkSend() {
       outbound_restore_cr = 0;
       outbound_restore_preamble_len = 0;
       uint8_t default_cr = getDefaultTxCodingRate();
+      bool using_low_retry_cr = false;
       if (outbound->tx_cr >= 4 && outbound->tx_cr <= 8 && default_cr >= 4 && default_cr <= 8
           && outbound->tx_cr != default_cr) {
         if (_radio->setCodingRate(outbound->tx_cr)) {
           outbound_restore_cr = default_cr;
+          using_low_retry_cr = outbound->tx_cr == 4 || outbound->tx_cr == 5;
           max_airtime = _radio->getEstAirtimeFor(len)*3/2;
         } else {
           MESH_DEBUG_PRINTLN("%s Dispatcher::checkSend(): WARN: failed to set packet CR%d", getLogDateTime(), (uint32_t)outbound->tx_cr);
         }
+      } else if (outbound->tx_cr == 4 || outbound->tx_cr == 5) {
+        using_low_retry_cr = outbound->tx_cr == default_cr;
       }
       bool has_direct_path = outbound->getPathHashCount() > 0
           || (outbound->getPayloadType() == PAYLOAD_TYPE_TRACE && outbound->payload_len > 9);
       if (outbound->isRouteDirect() && has_direct_path
-          && (outbound->tx_cr == 4 || outbound->tx_cr == 5)) {
+          && using_low_retry_cr) {
         uint16_t default_preamble_len = _radio->getDefaultPreambleLength();
         if (default_preamble_len > 16 && _radio->setPreambleLength(16)) {
           outbound_restore_preamble_len = default_preamble_len;

src/Packet.cpp

@@ -87,4 +87,3 @@ bool Packet::readFrom(const uint8_t src[], uint8_t len) {
 }
 
 }
-