Hi Maxim,
On Wed, 5 Jul 2023 at 09:17, 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 | 59 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 60 insertions(+) create mode 100644 doc/develop/net_lwip.rst
diff --git a/doc/develop/index.rst b/doc/develop/index.rst index 97c526e997..a092c33df0 100644 --- a/doc/develop/index.rst +++ b/doc/develop/index.rst @@ -43,6 +43,7 @@ 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..2520fe11b1 --- /dev/null +++ b/doc/develop/net_lwip.rst @@ -0,0 +1,59 @@ +.. SPDX-License-Identifier: GPL-2.0+
+LWIP IP stack intergation for U-boot
U-Boot
+====================================
+Intro +-----
+LWIP is a library for implementation 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 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. And it was more easy 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.
+Raw IP means that the call back function for RX path is registered and will be called when packet +data passes the IP stack and is ready for the application.
+Example is unmodified working ping example from lwip sources which registeres 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)+Socket API also gives nice advantages due it will be easy to port linux socket applications to u-boot. +I.e. LwIP sockets compatible with the linux ones. But that will require RX thread running in the background. +So that means we need some kind of scheduler, locking and threading support or find some other solution.
+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