CanIOFlagAbortOnError - automatically enforced by TransferSender if the node is in passive mode

libuavcan/include/uavcan/driver/can.hpp

@@ -114,9 +114,17 @@ struct UAVCAN_EXPORT CanSelectMasks
 
 /**
  * Special IO flags.
+ *
+ * @ref CanIOFlagLoopback       - Send the frame back to RX with true TX timestamps.
+ *
+ * @ref CanIOFlagAbortOnError   - Abort transmission on first bus error instead of retransmitting. This does not
+ *                                affect the case of arbitration loss, in which case the retransmission will work
+ *                                as usual. This flag is used together with anonymous messages which allows to
+ *                                implement CSMA bus access. Read the spec for details.
  */
 typedef uint16_t CanIOFlags;
-static const CanIOFlags CanIOFlagLoopback = 1; ///< Send the frame back to RX with true TX timestamps
+static const CanIOFlags CanIOFlagLoopback = 1;
+static const CanIOFlags CanIOFlagAbortOnError = 2;
 
 /**
  * Single non-blocking CAN interface.

libuavcan/include/uavcan/transport/transfer_sender.hpp

@@ -100,6 +100,10 @@ public:
 
     /**
      * Send with automatic Transfer ID.
+     *
+     * Note that as long as the local node operates in passive mode, the
+     * flag @ref CanIOFlagAbortOnError will be set implicitly for all outgoing frames.
+     *
      * TID is managed by OutgoingTransferRegistry.
      */
     int send(const uint8_t* payload, unsigned payload_len, MonotonicTime tx_deadline,

libuavcan/src/transport/uc_transfer_sender.cpp

@@ -69,10 +69,15 @@ int TransferSender::send(const uint8_t* payload, unsigned payload_len, Monotonic
         frame.setEndOfTransfer(true);
         UAVCAN_ASSERT(frame.isStartOfTransfer() && frame.isEndOfTransfer() && !frame.getToggle());
 
-        return dispatcher_.send(frame, tx_deadline, blocking_deadline, qos_, flags_, iface_mask_);
+        const CanIOFlags flags = frame.getSrcNodeID().isUnicast() ? flags_ : (flags_ | CanIOFlagAbortOnError);
+
+        return dispatcher_.send(frame, tx_deadline, blocking_deadline, qos_, flags, iface_mask_);
     }
     else                                                   // Multi Frame Transfer
     {
+        UAVCAN_ASSERT(!dispatcher_.isPassiveMode());
+        UAVCAN_ASSERT(frame.getSrcNodeID().isUnicast());
+
         int offset = 0;
         {
             TransferCRC crc = crc_base_;

libuavcan/test/transport/can/can.hpp

@@ -23,21 +23,25 @@ public:
         uavcan::CanFrame frame;
         uavcan::MonotonicTime time;
         uavcan::UtcTime time_utc;
+        uavcan::CanIOFlags flags;
 
         FrameWithTime(const uavcan::CanFrame& frame, uavcan::MonotonicTime time)
             : frame(frame)
             , time(time)
+            , flags(0)
         { }
 
         FrameWithTime(const uavcan::CanFrame& frame, uavcan::MonotonicTime time, uavcan::UtcTime time_utc)
             : frame(frame)
             , time(time)
             , time_utc(time_utc)
+            , flags(0)
         { }
 
         FrameWithTime(const uavcan::CanFrame& frame, uint64_t time_usec)
             : frame(frame)
             , time(uavcan::MonotonicTime::fromUSec(time_usec))
+            , flags(0)
         { }
     };
 
@@ -115,6 +119,7 @@ public:
             return 0;
         }
         tx.push(FrameWithTime(frame, tx_deadline));
+        tx.back().flags = flags;
         if (flags & uavcan::CanIOFlagLoopback)
         {
             loopback.push(FrameWithTime(frame, iclock.getMonotonic()));
@@ -126,7 +131,6 @@ public:
                                     uavcan::UtcTime& out_ts_utc, uavcan::CanIOFlags& out_flags)
     {
         assert(this);
-        out_flags = uavcan::CanIOFlags();
         if (loopback.empty())
         {
             EXPECT_TRUE(rx.size());        // Shall never be called when not readable
@@ -143,6 +147,7 @@ public:
             out_frame = frame.frame;
             out_ts_monotonic = frame.time;
             out_ts_utc = frame.time_utc;
+            out_flags = frame.flags;
         }
         else
         {
@@ -151,6 +156,7 @@ public:
             loopback.pop();
             out_frame = frame.frame;
             out_ts_monotonic = frame.time;
+            out_ts_utc = frame.time_utc;
         }
 
         // Let's just all pretend that this code is autogenerated, instead of being carefully designed by a human.

libuavcan/test/transport/transfer_sender.cpp

@@ -257,6 +257,10 @@ TEST(TransferSender, PassiveMode)
               sender.send(Payload, sizeof(Payload), tsMono(1000), uavcan::MonotonicTime(),
                           uavcan::TransferTypeServiceRequest, uavcan::NodeID(42)));
 
+    // Making sure the abort flag is set
+    ASSERT_FALSE(driver.ifaces.at(0).tx.empty());
+    ASSERT_EQ(uavcan::CanIOFlagAbortOnError, driver.ifaces.at(0).tx.front().flags);
+
     EXPECT_EQ(0, dispatcher.getTransferPerfCounter().getErrorCount());
     EXPECT_EQ(1, dispatcher.getTransferPerfCounter().getTxTransferCount());
     EXPECT_EQ(0, dispatcher.getTransferPerfCounter().getRxTransferCount());