Re: [PATCHv5 01/13] net/lwip: add doc/develop/net_lwip.rst

Simon Glass
2023-08-02T21:31:47Z

Hi Maxim,

On Wed, 2 Aug 2023 at 08:09, Maxim Uvarov <maxim.uvarov@linaro.org> wrote:
>
> Just add inital doc.
>
> Signed-off-by: Maxim Uvarov <maxim.uvarov@linaro.org>
> ---
> doc/develop/index.rst | 1 +
> doc/develop/net_lwip.rst | 55 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 56 insertions(+)
> create mode 100644 doc/develop/net_lwip.rst
>

Reviewed-by: Simon Glass <sjg@chromium.org>

> diff --git a/doc/develop/index.rst b/doc/develop/index.rst
> index ddbf8dad4a..f8ab6cb56e 100644
> --- a/doc/develop/index.rst
> +++ b/doc/develop/index.rst
> @@ -46,6 +46,7 @@ Implementation
> smbios
> spl
> uefi/index
> + net_lwip
> vbe
> version
>
> diff --git a/doc/develop/net_lwip.rst b/doc/develop/net_lwip.rst
> new file mode 100644
> index 0000000000..784b8f960c
> --- /dev/null
> +++ b/doc/develop/net_lwip.rst
> @@ -0,0 +1,55 @@
> +.. SPDX-License-Identifier: GPL-2.0+
> +
> +LWIP IP stack intergation for U-Boot

spelling

> +====================================
> +
> +Intro
> +-----
> +
> +LWIP is a library implementating network protocols, which is commonly used

spelling

> +on embedded devices.
> +
> +https://savannah.nongnu.org/projects/lwip/
> +
> +LwIP license:
> +LwIP is licensed under a BSD-style license: http://lwip.wikia.com/wiki/License.
> +
> +Main features include:
> +
> +* Protocols: IP, IPv6, ICMP, ND, MLD, UDP, TCP, IGMP, ARP, PPPoS, PPPoE
> +
> +* DHCP client, DNS client (incl. mDNS hostname resolver), AutoIP/APIPA (Zeroconf), SNMP agent (v1, v2c, v3, private MIB support & MIB compiler)
> +
> +* APIs: specialized APIs for enhanced performance, optional Berkeley-alike socket API
> +
> +* Extended features: IP forwarding over multiple network interfaces, TCP congestion control, RTT estimation and fast recovery/fast retransmit

Can we stick to 80cois for docs?

> +
> +* Addon applications: HTTP(S) server, SNTP client, SMTP(S) client, ping, NetBIOS nameserver, mDNS responder, MQTT client, TFTP server
> +
> +U-Boot implementation details
> +-----------------------------
> +
> +1. In general we can build lwIP as .a library and link it against u-boot or compile it in

as a

U-Boot (please check throughout)

> +the U-Boot tree in the same way as other U-Boot files. There are few reasons why I selected
> +the second variant: LwIP is very customizable with defines for features, memory size, types of
> +allocation, some internal types and platform specific code. It turned out easier to enable/disable
> +debug which is also done with defines, and is needed periodically.
> +
> +2. lwIP has 2 APIs - raw mode and sequential (as lwIP names it, or socket API as we name it in Linux).
> +For now only raw API is supported.
> +
> +In raw IP mode a callback function for RX path is registered and will be called when packet
> +is passed to the IP stack and is ready for the application.
> +
> +Example is unmodified working ping example from lwip sources which registeres the callback:

spelling

> +
> +.. code-block:: c
> +
> + ping_pcb = raw_new(IP_PROTO_ICMP);
> + raw_recv(ping_pcb, ping_recv, NULL); <- ping_recv is app callback.
> + raw_bind(ping_pcb, IP_ADDR_ANY)
> +
> +3. Input and output
> +
> +RX packet path is injected to U-Boot eth_rx() polling loop and TX patch is in eth_send() accordingly.
> +So we do not touch any drivers code and just eat packets when they are ready.
> --
> 2.30.2
>

Regards,
Simon