Hi Maxim, On Tue, 22 Aug 2023 at 03:38, Maxim Uvarov <maxim.uva...@linaro.org> wrote: > > Add initial documentation of lwIP network IP stack integration > to the U-Boot (net_lwip.rst). > > Signed-off-by: Maxim Uvarov <maxim.uva...@linaro.org> > Reviewed-by: Simon Glass <s...@chromium.org> > --- > doc/develop/index.rst | 1 + > doc/develop/net_lwip.rst | 76 ++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 77 insertions(+) > create mode 100644 doc/develop/net_lwip.rst > > diff --git a/doc/develop/index.rst b/doc/develop/index.rst > index 5b230d0321..4764990f25 100644 > --- a/doc/develop/index.rst > +++ b/doc/develop/index.rst > @@ -48,6 +48,7 @@ Implementation > spl > falcon > 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..cd85de92a1 > --- /dev/null > +++ b/doc/develop/net_lwip.rst > @@ -0,0 +1,76 @@ > +.. SPDX-License-Identifier: GPL-2.0+ > + > +LWIP IP stack intergation for U-Boot
spelling > +==================================== > + > +Intro > +----- > + > +LWIP is a library implementing network protocols, which is commonly used > +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 > + > +* 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 the U-Boot tree in the same way as other U-Boot files. There > + are few reasons why second variant was selected: 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. > + > +One example is the unmodified working ping example from lwip sources which > +registered the callback: > + > +.. 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. That way we can leave the driver code unmodified and > +consume packets once they are ready. So we do not touch any drivers code and > +just eat packets when they are ready. > + > +U-Boot lwIP Applications > +======================== > + > +.. kernel-doc:: include/net/lwip.h > + :internal: > + > +lwIP API to control polling loop > +================================ > + > +.. kernel-doc:: include/net/ulwip.h > + :internal: > -- > 2.30.2 > Regards, Simon
