Re: [PATCH v5 00/20] Introduce the lwIP network stack

[Tom Rini <trini@konsulko.com>]

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On Wed, Aug 07, 2024 at 08:54:08PM +0200, Michael Nazzareno Trimarchi wrote:
> Hi Jerome
> 
> On Thu, Jul 25, 2024 at 2:58 PM Jerome Forissier
> <jerome.forissier@linaro.org> wrote:
> >
> > This is a rework of a patch series by Maxim Uvarov: "net/lwip: add lwip
> > library for the network stack" [1]. The goal is to introduce the lwIP TCP/IP
> > stack [2] [3] as an alternative to the current implementation in net/,
> > selectable with Kconfig, and ultimately keep only lwIP if possible. Some
> > reasons for doing so are:
> > - Make the support of HTTPS in the wget command easier. Javier T. and
> > Raymond M. (CC'd) have some additional lwIP and Mbed TLS patches to do
> > so. With that it becomes possible to fetch and launch a distro installer
> > such as Debian etc. using a secure, authenticated connection directly
> > from the U-Boot shell. Several use cases:
> >   * Authentication: prevent MITM attack (third party replacing the
> > binary with a different one)
> >   * Confidentiality: prevent third parties from grabbing a copy of the
> > image as it is being downloaded
> >   * Allow connection to servers that do not support plain HTTP anymore
> > (this is becoming more and more common on the Internet these days)
> > - Possibly benefit from additional features implemented in lwIP
> > - Less code to maintain in U-Boot
> >
> > Prior to applying this series, the lwIP stack needs to be added as a
> > Git subtree with the following command:
> >
> >  $  git subtree add --squash --prefix lib/lwip/lwip https://git.savannah.gnu.org/git/lwip.git STABLE-2_2_0_RELEASE
> >
> > Notes:
> >
> > 1. A number of features are currently incompatible with NET_LWIP: SANDBOX,
> > DFU_TFTP, FASTBOOT, SPL_NET. All make assumptions on how the network
> > stack is implemented and/or pull sybols that are not trivially exported
> > from lwIP. Some interface rework may be needed.
> >
> > 2. Due to the above and in order to provide some level of testing, a new QEMU
> > configuration is introduced (qemu_arm64_lwip_defconfig) which is the same
> > as qemu_arm64_defconfig but with NET_LWIP and CMD_*_LWIP enabled.
> > Tests are added to test/py/tests/test_net.py for that configuration.
> >
> > 3. The default QEMU networking doesn't work with NET_LWIP. wget
> > pauses and resets the connection. Wireshark shows [TCP Window Full] and
> > [TCP ZeroWindow]. Wen using an emulated e1000 however all is fine
> > (that is "-nic tap,model=e1000" on the QEMU command line, with a bridge
> > configured on the host).
> >
> > Changes in v5:
> >
> > - Rebased on next
> > - Refactor Kconfig options to avoid duplicates
> > - Library functions use a more consistent naming (dhcp_loop(),
> > ping_loop() etc.) and take a struct udevice * parameter (Heinrich S.)
> > - Do not use net_process_receive_packet() for input anymore. Instead of
> > calling eth_rx() which would invoke net_process_receive_packet(), we
> > call a new net_lwip_rx(udev) function which invokes the device recv()
> > and pushes the packets up the lwIP stack. Thus everything is tied to
> > a udevice now. (Heinrich S.)
> > - Add "configs: replace '# CONFIG_NET is not set' with CONFIG_NO_NET=y"
> > (Tom R.)
> 
> Here I have some questions. You can have CONFIG_NET with two alternatives and
> the alternatives are exclusive. Why do we need a CONFIG_NO_NET definition?

For the platforms that today don't enable networking at all (of which
there are a small but reasonable number). Since it's a "choice"
statement we need a "none of the above" option.

-- 
Tom

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