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Hello,
Back in 2019 I have requested Link-Layer Header Type for USB 2.0 [1].
Unfortunately, I didn't foresee the problems with dissecting packets at
effectively "unknown" capture speed. That is, while the host, device
and capture tool were all aware about the speed, the resul
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On Sun, May 8, 2022 at 8:53 PM Guy Harris wrote:
> At least from a quick look at section 5.2.3 "Physical Bus Topology" of the
> USB 2.0 spec, a given bus can either be a high-speed bus or a full/low-speed
> bus.
The full/low-speed bus applies only to upstream link from ful
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On Sun, May 8, 2022 at 11:15 PM Guy Harris wrote:
> On May 8, 2022, at 1:30 PM, Michael Richardson wrote:
> > I guess I would have thought that a physical bus could have a mix of
> > different devices which operate at different speeds. As such, I wondered if
> > you really
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On Mon, May 9, 2022 at 9:21 AM Guy Harris wrote:
> On May 8, 2022, at 11:09 PM, Tomasz Moń wrote:
> > Note that end nodes cannot directly communicate with each other. The
> > communication is always between host and a device.
>
> Those two sentences, when combined, imply tha
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On Mon, May 9, 2022 at 9:17 AM Guy Harris wrote:
> On May 8, 2022, at 10:47 PM, Tomasz Moń wrote:
> > On Sun, May 8, 2022 at 8:53 PM Guy Harris wrote:
> >> At least from a quick look at section 5.2.3 "Physical Bus Topology" of the
> >> USB 2.0 spec, a given bus can either
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On Mon, May 9, 2022 at 2:48 PM Michael Richardson wrote:
> Tomasz Moń via tcpdump-workers wrote:
> Guy> "super-speed" is USB 3.0, right? No LINKTYPE_/DLT_ has been
> Guy> proposed for the 3.0 link layer, as far as I know.
>
> >
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On Mon, 2022-05-09 at 07:47 +0200, Tomasz Moń wrote:
> The problematic case (and the reason why full/low-speed bus is
> mentioned) is the LINKTYPE_USB_2_0_FULL_SPEED. It is the case when
> you capture at the connection between full speed hub and the host
> (and possibly full s
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On Mon, 2022-05-09 at 08:44 -0400, Michael Richardson wrote:
> A capture from a host to a hub with a mix of downstream devices would
> seem to include transmissions at different speeds.
The problem is only when capturing at full-speed where either the host
or hub is full-spee
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On Mon, 2022-05-09 at 11:52 -0700, Guy Harris wrote:
> On May 9, 2022, at 1:58 AM, Tomasz Moń wrote:
>
> > On Mon, May 9, 2022 at 9:17 AM Guy Harris
> > wrote:
> > > On May 8, 2022, at 10:47 PM, Tomasz Moń
> > > wrote:
> > > > On Sun, May 8, 2022 at 8:53 PM Guy Harris
> >
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On Mon, 2022-05-09 at 12:02 -0700, Guy Harris wrote:
> On May 9, 2022, at 7:41 AM, Tomasz Moń wrote:
>
> > That would require defining pseudoheader that would have to be
> > included in every packet.
>
> Is that really a great burden?
I think it would make it harder to und
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On Mon, 2022-05-09 at 12:52 -0700, Guy Harris wrote:
> On May 9, 2022, at 12:40 PM, Tomasz Moń wrote:
>
> > On Mon, 2022-05-09 at 12:02 -0700, Guy Harris wrote:
> > > On May 9, 2022, at 7:41 AM, Tomasz Moń wrote:
> > >
> > > > That would require defining pseudoheader that
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On Mon, 2022-05-09 at 13:19 -0700, Guy Harris wrote:
> On May 9, 2022, at 1:02 PM, Tomasz Moń wrote:
>
> > The same as why URB level captures are confusing. Maybe not to the
> > same
> > level as that would be just a single byte (and the URB metadata
> > contains way more in
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On Tue, May 10, 2022 at 6:57 AM Guy Harris wrote:
> On May 9, 2022, at 9:41 PM, Tomasz Moń wrote:
> > Also Wireshark would have to show "USB Full/Low speed capture" section with
> > only the single byte denoting
> > full or low speed, followed by "USB Link Layer" (as shown
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On Mon, May 9, 2022 at 10:17 PM Guy Harris wrote:
> On May 9, 2022, at 12:31 PM, Tomasz Moń wrote:
> > There is no such thing as "low-speed bus" because low-speed is only
> > allowed for non-hub devices. USB hosts and hubs *must* support atleast
> > full and high speed. USB
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On Tue, 2022-05-10 at 07:28 +0200, Tomasz Moń wrote:
> On Mon, May 9, 2022 at 10:17 PM Guy Harris wrote:
> > On May 9, 2022, at 12:31 PM, Tomasz Moń wrote:
> > > It is important that the analysis engine know whether the packets
> > > were
> > > full or low-speed as there are
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On Tue, 2022-05-10 at 21:31 +0200, Tomasz Moń wrote:
> On Tue, 2022-05-10 at 07:28 +0200, Tomasz Moń wrote:
> > On Mon, May 9, 2022 at 10:17 PM Guy Harris wrote:
> > > It makes sense to indicate whether packets are full-speed or low-
> > > speed; nobody is arguing otherwise.
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On Tue, 2022-06-14 at 10:49 -0400, Michael Richardson wrote:
> Tomasz Moń via tcpdump-workers wrote:
> > I think I have summed up whole discussion in the libpcap commit
> > message. High-speed and Low-speed are pretty much clear, as these links
>
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On Mon, 2022-06-20 at 08:34 -0400, Michael Richardson wrote:
> Tomasz Moń wrote:
> > On Tue, 2022-06-14 at 10:49 -0400, Michael Richardson wrote:
> >> Tomasz Moń via tcpdump-workers wrote:
> >> > I think I have summed up whole di
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