Re: [RFC] Addition of link-layer header types for PCI, PCI-X, and PCI-Express

[Aki Van Ness via tcpdump-workers <tcpdump-workers () lists tcpdump org>]

> --- Begin Message ---
>
>
> From: Aki Van Ness <aki.vanness () gmail com>
>
> Date: Sun, 25 Oct 2020 16:01:18 -0400
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> On Sun, Oct 25, 2020 at 2:05 AM Guy Harris <gharris () sonic net> wrote:
> > On Oct 21, 2020, at 1:56 PM, Aki Van Ness via tcpdump-workers <tcpdump-workers () lists tcpdump org> 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.
>
> --- End Message ---
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