Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

generator/C: Don't parse messages outside CRC_EXTRA #990

Merged
merged 1 commit into from
Nov 13, 2024
Merged

generator/C: Don't parse messages outside CRC_EXTRA #990

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 15 additions & 9 deletions generator/C/include_v2.0/mavlink_helpers.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -742,18 +742,24 @@ MAVLINK_HELPER uint8_t mavlink_frame_char_buffer(mavlink_message_t* rxmsg,

case MAVLINK_PARSE_STATE_GOT_PAYLOAD: {
const mavlink_msg_entry_t *e = mavlink_get_msg_entry(rxmsg->msgid);
uint8_t crc_extra = e?e->crc_extra:0;
mavlink_update_checksum(rxmsg, crc_extra);
if (c != (rxmsg->checksum & 0xFF)) {
if (e == NULL) {
// Message not found in CRC_EXTRA table.
status->parse_state = MAVLINK_PARSE_STATE_GOT_BAD_CRC1;
Copy link
Contributor

@tridge tridge Nov 11, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

you also need to set rxmsg->ck[0] to the byte from the packet (c) so that this code works correctly for forwarding the message:

	if (status->msg_received == MAVLINK_FRAMING_BAD_CRC) {
		/*
		  the CRC came out wrong. We now need to overwrite the
		  msg CRC with the one on the wire so that if the
		  caller decides to forward the message anyway that
		  mavlink_msg_to_send_buffer() won't overwrite the
		  checksum
		 */
            if (r_message != NULL) {
                r_message->checksum = rxmsg->ck[0] | (rxmsg->ck[1]<<8);
            }
	}

Copy link
Contributor Author

@julianoes julianoes Nov 12, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I see, so you can still forward even if you can't fully parse a message. Do you have an example of such an implementation?

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

https://github.com/ArduPilot/ardupilot/blob/7d426f4741c7f77b03c26b98899e5d3d89503e8f/libraries/GCS_MAVLink/GCS_Common.cpp#L1889 is one related implementation

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Got it, thanks. That's interesting.

I will update as suggested to fix that case.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Fix pushed.

rxmsg->ck[0] = c;
} else {
status->parse_state = MAVLINK_PARSE_STATE_GOT_CRC1;
}
rxmsg->ck[0] = c;
uint8_t crc_extra = e->crc_extra;
mavlink_update_checksum(rxmsg, crc_extra);
if (c != (rxmsg->checksum & 0xFF)) {
status->parse_state = MAVLINK_PARSE_STATE_GOT_BAD_CRC1;
} else {
status->parse_state = MAVLINK_PARSE_STATE_GOT_CRC1;
}
rxmsg->ck[0] = c;

// zero-fill the packet to cope with short incoming packets
if (e && status->packet_idx < e->max_msg_len) {
memset(&_MAV_PAYLOAD_NON_CONST(rxmsg)[status->packet_idx], 0, e->max_msg_len - status->packet_idx);
// zero-fill the packet to cope with short incoming packets
if (e && status->packet_idx < e->max_msg_len) {
memset(&_MAV_PAYLOAD_NON_CONST(rxmsg)[status->packet_idx], 0, e->max_msg_len - status->packet_idx);
}
}
break;
}
Expand Down
Loading