Re: [PATCH] SocketCAN support for libpcap - draft implementation

[Guy Harris <guy () alum mit edu>]

On Oct 11, 2009, at 2:58 AM, Felix Obenhuber wrote:

> On Fri, 2009-10-09 at 08:27 -0400, Alexander Dupuy wrote:

        ...

> Summing up the discussion till now, I'd like to request a new DLT for
> SocketCAN that is called
>
> DLT_CAN_SOCKETCAN

OK, I've assigned 227 to DLT_CAN_SOCKETCAN, and checked into the main  
branch and pushed changes for that

> Are there any conventions about the DLT naming?

Not really.

> > If you ever think that SocketCAN/libpcap will be used on big-endian
> > systems, you might want to "canonicalize" the layout in the big- 
> > endian
> > format above for a more comprehensible diagram, and because
> > little-endian systems have htonl/ntohl macros that are not no-ops,
> > making portable user-level coding simpler (if you standardize the
> > little-endian format, portable code has to use #ifdefs to determine
> > byte-order and then call a swap() function/macro on big-endian
> > systems).
>
> Think that the usage of SocketCAN/libpcap on BE machines may be need
> once. Think about a Linux and PPC based CAN data logger for example.

Linux USB leaves the pseudo-header in host byte order - and, in the  
code that reads the savefile, libpcap byte-swaps the fields, if the  
capture file was written on a machine with the opposite byte order, so  
that they appear to be in the byte order of the host reading the file.
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