Wireshark-bugs: [Wireshark-bugs] [Bug 12687] SocketCAN dissector does not support CAN FD
Comment # 7
on bug 12687
from Michael Mann
(In reply to Oliver Hartkopp from comment #6)
> The capture was generated with Wireshark after selecting vcan0.
>
> How can I provide a capture file that fits your needs?
> Is there some magic config button I would have to press?
You're mixing two completely different pieces of functionality. Wireshark is a
network analysis tool that happens to have hooks for doing capturing as well.
Wireshark can only analyze what's been captured for it. After capturing, it
then gets passed to the analysis/dissector portion.
vcan0 is the "capture driver" and it's providing the capture data in the
socketCAN format as specified by LINKTYPE_ definition of:
u32 CAN_ID
u8 length
u8 pad1
u8 pad2
u8 pad3
u8 data[8];
If vcan0 writes a "CANFD" frame, I think it looks like this:
u32 CAN_ID
u8 length
u8 fd_flags
u8 pad2
u8 pad3
u8 data[64];
What I was hoping to get out of the capture file was a deterministic way to
tell if CANFD was present. In the capture file you did provide, CANFD is
piggybacking on the CAN format, so how is one supposed to know if its CAN or
CANFD? Can we assume the fd_flags field will be non-zero? (It appears to be
in all but the first packet of your capture). Are we to assume pad1 should
always be 0 with "regular" CAN?
The capture file format is why I also mentioned the SLL types. vcan0 doesn't
appear to write capture files in that format (and there isn't a magic button to
change it), so does that not need to be supported?
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