Re: NFSv4 boot support?

[Antony Pavlov <antonynpavlov@gmail.com>]

On Wed, 28 Feb 2024 10:20:27 +0100
Sascha Hauer <sha@pengutronix.de> wrote:


Hi Sascha!

> On Wed, Feb 28, 2024 at 10:26:15AM +0300, Antony Pavlov wrote:
> > On Sat, 17 Feb 2024 09:51:02 +0100
> > Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
> > 
> > Hi All!
> > 
> > > Hello Antony,
> > > 
> > > On 05.02.24 10:59, Antony Pavlov wrote:
> > > > On Wed, 31 Jan 2024 22:37:50 +0100
> > > > Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
> > > > 
> > > > Hi All!
> > > > 
> > > >> Hello Dan,
> > > >>
> > > >> On 31.01.24 22:03, Dan Shelton wrote:
> > > >>> Hello!
> > > >>>
> > > >>> Does barebox support booting from a NFSv4 filesystem, e.g. boot from
> > > >>> NFSv4 filesystem into a Linux NFSv4 netroot (diskless machine)?
> > > >>
> > > >> The barebox network stack only does UDP/IP. There have been attempts to
> > > >> bring a TCP stack into barebox, but none have so far succeeded to
> > > >> make it mainline. This is a hard requirement before we can consider
> > > >> supporting NFSv4. I hope that lwIP could fill this gap in the future,
> > > >> but no one is actively continuing this work as far as I am aware[1].
> > > > 
> > > > I have started integration on picotcp into barebox in 2015, see
> > > >   https://lore.barebox.org/barebox/1436991230-14251-10-git-send-email-antonynpavlov@gmail.com/T/
> > 
> > Actually I made the first attempt to integrate picotcp into barebox in 2014,
> > see http://lists.infradead.org/pipermail/barebox/2014-May/019243.html
> > 
> > 10 years is too long for this task :)
> > 
> > In the message http://lists.infradead.org/pipermail/barebox/2015-July/024244.html
> > if I understand correctly Sascha asked me to keep network stuff
> > users (tftp, nfs, netconsole) as intact as possible.
> > 
> > At the moment I understand that this task is too hard.
> > 
> > The problem is: the network stuff users don't rely on "a network stack"
> > in the true sense. E.g. tftp_handler() takes an ETHERNET PACKET on
> > it's input, tftp_handler() skips Ethernet and IP stuff by itself
> > and modifies UDP fields directly!
> > 
> > This week I have connected picotcp code to the existing network code
> > in the way that makes it possible to keep dhcp_handler() and
> > ftp_handler() intact. The result is ugly: barebox netdevice driver
> > receives frame from network, pass it to picotcp, picotcp parses
> > network protocol headers and extracts udp payload, next
> > picotcp passes udp payload back to my picotcp-to-barebox adapter,
> > the adapter RECONSTRUCTS ETHERNET PACKET and give it to tftp/dhcp_handler()!
> > This horrible approach creates more problems than it solves!

> So if I understand correctly you tried passing *all* incoming packets to
> picotcp and route some of them back to the barebox network stack.

for every barebox network device I create picotcp network device
which can send packets by picotcp initiative.
net_receive() just calls pico_stack_recv() with corresponding
picotcp network device as an argument, so no code change in drivers/net/.
net_poll() just calls pico_stack_tick().
So all incoming packets go to picotcp only.
Picotcp can send packet if necessary without barebox interraction.

UDP datagrams processed by picotcp routed to corresponding dhcp/tftp_handler().
Are dhcp/tftp_handlers parts of barebox network stack?

> Instead of passing all packets to picotcp, can't we just dispatch the
> incoming packets on a per-port basis in barebox and only pass the ones
> picotcp shall handle to picotcp?

Good idea. I have to try. We can reroute IPv6 traffic to picotcp in net_receive()
and reroute TCP/IPv4 traffic to picotcp in net_handle_ip().

> So basically a struct net_connection with the handler set to the picotcp
> receive function?

net_connection handler is set to the normal unamended dhcp/tftp_handlers.

> That way it might be possible to have the barebox network stack and
> picotcp in parallel and port the handlers over to pictotcp one by one.

But I see a problem here. If there is a ARP respond in the incoming traffic
I have no idea there to send it. Both barebox network code and picotcp
can make ARP request. I suppose can just route ARP respond to the both stacks.

But what I have to do if an ARP or ICMP echo __request__ is received?

I suppose it is possible to add some simple dynamic incoming packet filtration rules
that can be changed on-the-fly for testing purposes.

-- 
Best regards,
  Antony Pavlov