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

Date: Thu, 25 Aug 2016 20:29:42 +0000

Comment # 43 on bug 12687 from
(In reply to Oliver Hartkopp from comment #42)
> (In reply to Guy Harris from comment #41)
> 
> > Or how about doing a cooked capture for ARPHRD_CAN, so that the link-layer
> > type is DLT_LINUX_SLL, add LINUX_SLL_P_CANFD (with the same numerical value
> > as ETH_P_CANFD) to libpcap's pcap/sll.h and Wireshark's
> > epan/dissectors/packet-sll.h,
> 
> In the latest Wireshark patch set on
> https://code.wireshark.org/review/#/c/16787/ Michael already defined
> LINUX_SLL_P_CANFD as suggested by you.
> 
> > add it to the byte-swapping code in libpcap's
> > pcap-common.c and Wireshark's wiretap/pcap-common.c, add it to the table in
> > epan/dissectors/packet-sll.c, and have epan/dissectors/packet-socketcan.c
> > register for it, as well as LINUX_SLL_P_CAN, in the "sll.ltype" dissector
> > table.
> > 
> > Then the dissector for LINUX_SLL_P_CANFD would dissect a CANFD header, and
> > the dissector for LINUX_SLL_P_CAN would dissect a non-CANFD header.
> > 
> > Then we don't need any DLT_/LINKTYPE_ values for CANFD, and might even not
> > need to bother with DLT_CAN_SOCKETCAN_HOSTENDIAN.
> 
> That would be great!
> 
> I hoped the possibility to remove some code paths would create this
> opportunity to simplify the interface provided by libpcap.
> 
> Even though I did not get completely behind your suggestion it seems the way
> of simplification I had in mind too :-)

Done on the libpcap master branch with change
https://github.com/the-tcpdump-group/libpcap/commit/93ca5ff7030aaf1219e1de05ec89a68384bfc50b.
 I reverted to just having DLT_CAN_SOCKETCAN/LINKTYPE_CAN_SOCKETCAN;
pcap-linux.c will now use DLT_LINUX_SLL/LINKTYPE_LINUX_SLL, so the protocol
field can be used to distinguish between "classic" CAN and CAN FD frames.


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