Hi,

on github Ayoub Kaanich writes:

https://github.com/linux-can/can-utils/issues/291

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The SocketCAN API is a great initiative for standardizing the CAN
interface API. This request tries to extend this initiative for more use
cases.

Context:

The SocketCAN was adopted by libpcap and tcpdump as the standard format
for logging CAN Frames in PCAP and PCAP-NG. See:

https://www.tcpdump.org/linktypes/LINKTYPE_CAN_SOCKETCAN.html
https://github.com/wireshark/wireshark/blob/master/epan/dissectors/packet-socketcan.c
https://www.wireshark.org/docs/dfref/c/can.html

Problem:
Applications that perform logging, usually need more details that normal
applications, for the sake of debugging later on. Flags needs to be
reserved/allocated in the SocketCAN API, so that logging applications
can make use of them in the PCAP format. The flags does not need
necessary need to be implemented by SocketCAN, they just need to be
marked as reserved for such use case.

Needed Flags:
FDF Flag

- Since CAN Frames and CAN-FD frames can co-exist in the same bus,
  logging application needs to know if a normal CAN Frame was
  transmitted on a CAN-FD bus, namely was the FDF bit set or not.
  
 ACK bit in data frame
- Some logging hardware can act as a "spy", meaning that it records CAN
  Frames, but does not set the ACK bit
- A way to know for a given frame (FD or not), was the ACK bit set or
  not.
- Current API allow detecting missing ACK, but it does not report what
  Frame had a missing ACK.

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regards,
Marc

-- 
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