[tcpdump-workers] Link type FlexRay

Guy Harris guy at alum.mit.edu
Tue Jan 19 20:50:32 EST 2016

On Jan 19, 2016, at 9:35 AM, Guenter Ebermann <guenter.ebermann at googlemail.com> wrote:

> I asked Hannes about DLT_FLEXRAY.
> He told me that they currently dont use pcap for FlexRay and have only
> used it in a limited scenario and that we are free to change the
> layout.
> The format represented the bitsream from the bus 1:1 without an
> additional header.
> The only deviation was the padding: the data was padded to align to 4
> byte boundaries.
> This is my suggestion for an extension:
> I want to extend the frame by a "measurement-header": This header is
> added by the measurement device. It contains one bit for the FlexRay
> channel (A or B), a "data-type" enumeration and error-flags.

OK, so the new format is that the frame begins with a measurement header, which is followed by the bitstream from the bus?

Is the bitstream from the bus padded in that fashion?

From the Wikipedia article on FlexRay (the first of the ISO standards the article mentions costs CHF 118, so I'm not going to buy them immediately):


a frame consists of some framing bits at each end of the frame, with each octet in the frame containing 2 bits of per-byte framing followed by the 8 bits of the octet.  Would LINKTYPE_FLEXRAY/DLT_FLEXRAY frames include all of those bits?  If so, where does the padding appear?

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