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Wireshark-bugs: [Wireshark-bugs] [Bug 12687] SocketCAN dissector does not support CAN FD

Date: Sun, 28 Aug 2016 10:14:59 +0000

Comment # 50 on bug 12687 from
Created attachment 14857 [details]
Screenshot from Wireshark with Patchset 10

The picture shows two issues aka space for improvements :-)

1. For CANFD protocol the 'FD Flags' are no optional flags which should be
expanded or collapsed in the "Controller Area Network FD" section. The 'Bit
Rate Setting' and 'Error State Indicator' flags should always be placed below
the 'Extended Flag' and before the 'Frame-Length'.

2. Up to now only the Packet type 1 (Broadcast) was displayed inside Wireshark.
With the use of PF_PACKET sockets we now see the type 1 and type 4 (from me)
packet types - so we see sent frames two times, which is not usual.
The IFF_ECHO mechanism for CAN interfaces 'echoes' all sent frames on netdev
driver level, so all type 4 frames will show up as type 1 frames anyway.
My suggestion would be to a new Controller Area Network preference (like the
'Byte-swap the CAN ID/flags flied').
E.g. 'Enable display of Packet Type 4 (sent from me)' which is disabled by
default.

ps. Is it possible to remove the 'Data' display from CAN frames with remote
transmission request (RTR)? RTR frames are really weird: RTR frames have NO
data bits on the wire EVEN when the data length value can carry values from 0
to 8. Is there any chance to display this technical detail in Wireshark?


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