mavlink: add class for command retransmission

This adds a class to allow for retransmission of outgoing commands. The sent commands are kept in a timestamped list to check if they are acked as required by the mavlink protocol. If they are not acked within a timeout, they can be retransmitted.
2026-07-07 12:20:35 +08:00 · 2017-07-05 16:13:42 +02:00
parent 9854fc0d84
commit af0107ae0a
7 changed files with 527 additions and 18 deletions
@@ -0,0 +1,230 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2017 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file mavlink_command_sender.cpp
+ * Mavlink commands sender with support for retransmission.
+ *
+ * @author Julian Oes <julian@oes.ch>
+ */
+
+#include "mavlink_command_sender.h"
+#include <px4_log.h>
+#include <cassert>
+
+bool MavlinkCommandSender::_init = false;
+MavlinkCommandSender *MavlinkCommandSender::_instance = nullptr;
+px4_sem_t MavlinkCommandSender::_lock;
+
+void MavlinkCommandSender::initialize()
+{
+	if (_init) {
+		return;
+	}
+
+	px4_sem_init(&_lock, 1, 1);
+	_init = true;
+}
+
+MavlinkCommandSender &MavlinkCommandSender::instance()
+{
+	if (_instance == nullptr) {
+		_instance = new MavlinkCommandSender();
+	}
+
+	return *_instance;
+}
+
+MavlinkCommandSender::MavlinkCommandSender() :
+	_commands(5)
+{
+}
+
+MavlinkCommandSender::~MavlinkCommandSender()
+{
+	px4_sem_destroy(&_lock);
+}
+
+int MavlinkCommandSender::handle_vehicle_command(struct vehicle_command_s &command, mavlink_channel_t channel)
+{
+	assert(0 <= channel);
+	assert(channel < MAX_MAVLINK_CHANNEL);
+
+	lock();
+	PX4_INFO("getting vehicle command with timestamp %" PRIu64 ", channel: %d", command.timestamp, channel);
+
+	mavlink_command_long_t msg = {};
+	msg.target_system = command.target_system;
+	msg.target_component = command.target_component;
+	msg.command = command.command;
+	msg.confirmation = command.confirmation;
+	msg.param1 = command.param1;
+	msg.param2 = command.param2;
+	msg.param3 = command.param3;
+	msg.param4 = command.param4;
+	msg.param5 = command.param5;
+	msg.param6 = command.param6;
+	msg.param7 = command.param7;
+	mavlink_msg_command_long_send_struct(channel, &msg);
+
+	bool already_existing = false;
+	_commands.reset_to_start();
+
+	while (command_item_t *item = _commands.get_next()) {
+		if (item->timestamp_us == command.timestamp) {
+
+			// We should activate the channel by setting num_sent_per_channel from -1 to 0.
+			item->num_sent_per_channel[channel] = 0;
+
+			PX4_INFO("already existing");
+			already_existing = true;
+
+			break;
+		}
+	}
+
+	if (!already_existing) {
+
+		command_item_t new_item;
+		new_item.command = msg;
+		new_item.timestamp_us = command.timestamp;
+		new_item.num_sent_per_channel[channel] = 0;
+		new_item.last_time_sent_us = hrt_absolute_time();
+		_commands.put(new_item);
+	}
+
+	unlock();
+	return 0;
+}
+
+void MavlinkCommandSender::handle_mavlink_command_ack(const mavlink_command_ack_t &ack,
+		uint8_t from_sysid, uint8_t from_compid)
+{
+	PX4_INFO("handling result %d for command %d: %d from %d, %d",
+		 ack.result, ack.command, from_sysid, from_compid);
+	lock();
+
+	_commands.reset_to_start();
+
+	while (command_item_t *item = _commands.get_next()) {
+		// Check if the incoming ack matches any of the commands that we have sent.
+		if (item->command.command == ack.command &&
+		    from_sysid == item->command.target_system &&
+		    from_compid == item->command.target_component) {
+			PX4_INFO("handling result %d for command %d: %d", ack.result, ack.command);
+			// Drop it anyway because the command seems to have arrived at the destination, even if we
+			// receive IN_PROGRESS because we trust that it will be handled after that.
+			_commands.drop_current();
+			break;
+		}
+	}
+
+	unlock();
+}
+
+void MavlinkCommandSender::check_timeout(mavlink_channel_t channel)
+{
+	assert(0 <= channel);
+	assert(channel < MAX_MAVLINK_CHANNEL);
+
+	lock();
+
+	_commands.reset_to_start();
+
+	while (command_item_t *item = _commands.get_next()) {
+		if (hrt_elapsed_time(&item->last_time_sent_us) <= TIMEOUT_US) {
+			// We keep waiting for the timeout.
+			continue;
+		}
+
+		// The goal of this is to retry from all channels. Therefore, we keep
+		// track of the retry count for each channel.
+		//
+		// When the first channel does a retry, the timeout is reset.
+		// (e.g. all channel have done 2 retries, then channel 0 is called
+		// and does retry number 3, and also resets the timeout timestamp).
+
+		// First, we need to determine what the current max and min retry level
+		// are because we can only level up, if all have caught up.
+		// If num_sent_per_channel is at -1, the channel is inactive.
+		int8_t max_sent = 0;
+		int8_t min_sent = INT8_MAX;
+
+		for (unsigned i = 0; i < MAX_MAVLINK_CHANNEL; ++i) {
+			if (item->num_sent_per_channel[i] > max_sent) {
+				max_sent = item->num_sent_per_channel[i];
+			}
+
+			if ((item->num_sent_per_channel[i] != -1) &&
+			    (item->num_sent_per_channel[i] < min_sent)) {
+				min_sent = item->num_sent_per_channel[i];
+			}
+		}
+
+		if (item->num_sent_per_channel[channel] < max_sent) {
+			// We are behind and need to do a retransmission.
+			mavlink_msg_command_long_send_struct(channel, &item->command);
+			item->num_sent_per_channel[channel]++;
+
+			PX4_INFO("%x timeout (behind), retries: %d/%d, channel: %d",
+				 item, item->num_sent_per_channel[channel], max_sent, channel);
+
+		} else if (item->num_sent_per_channel[channel] == max_sent &&
+			   min_sent == max_sent) {
+
+			// If the next retry would be above the needed retries anyway, we can
+			// drop the item, and continue with other items.
+			if (item->num_sent_per_channel[channel] + 1 > RETRIES) {
+				_commands.drop_current();
+				PX4_INFO("%x, timeout dropped", item);
+				continue;
+			}
+
+			// We are the first of a new retransmission series.
+			mavlink_msg_command_long_send_struct(channel, &item->command);
+			item->num_sent_per_channel[channel]++;
+			// Therefore, we are the ones setting the timestamp of this retry round.
+			item->last_time_sent_us = hrt_absolute_time();
+
+			PX4_INFO("%x timeout (first), retries: %d/%d, channel: %d",
+				 item, item->num_sent_per_channel[channel], max_sent, channel);
+
+		} else {
+			// We are already ahead, so this should not happen.
+			// If it ever does, just ignore it. It will timeout eventually.
+			continue;
+		}
+	}
+
+	unlock();
+}