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On Sun, Oct 25, 2020 at 2:05 AM Guy Harris wrote:
>
> On Oct 21, 2020, at 1:56 PM, Aki Van Ness via tcpdump-workers
> wrote:
>
> > I'm working on a project that plans to store PCI and PCI-Express
> > packets in the pcapng format as that's the most appropriate storage
> > format and I really rather not roll something custom.
> >
> > As such what are thoughts on adding Link-Layer types for PCI, PCI-X,
> > and PCI-Express?
>
> It seems reasonable, given that we have USB, Infiniband, and the DisplayPort
> AUX channel.
>
> > And would you want to group all versions of PCI, PCI-X, and
> > PCI-Express together or have them be their own values?
>
> Would each version need its own LINKTYPE_ value, or would a single metadata
> header and payload suffice for all versions of PCI, all versions of PCI-X,
> and all versions of PCIe? From a quick look at the Wikipedia pages for
> those, for what that's worth, they changes for each seem to be at the
> physical layer, with full or at least significant backwards compatibility,
> so, other than additional bits of metadata, would LINKTYPE_PCI,
> LINKTYPE_PCI_X, and LINKTYPE_PCI_EXPRESS suffice?
>
> I'm assuming that the metadata would be different between PCI, PCI-X, and
> PCIe.
Yeah, so having a LINKTYPE_PCI, LINKTYPE_PCI_X, and LINKTYPE_PCI_E
would work, seeing as they are different enough to not be compatible
with each other.
As for the inter-version having common metadata then the content would
be fine, as long as the metadata could store the version of the
protocol. While they are mostl backwards compatible some versions add
/ remove commands or registers. So being able to interpret additional
metadata depending on the protocol version would be beneficial.
At least that's how I see it and how I think it makes the most sense.
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