Hi Maxim,
On Tue, 22 Aug 2023 at 03:38, Maxim Uvarov maxim.uvarov@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.uvarov@linaro.org Reviewed-by: Simon Glass sjg@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