Re: [lwip-devel] [PATCHv2 2/3] net/lwip: add README.lwip

[Ilias Apalodimas]

Hi Maxim,

On Thu, Jun 29, 2023 at 06:34:29PM +0600, Maxim Uvarov wrote:
> Just add inital README.lwip doc.

We'll need a more accurate description for this.  The first paragraph of
the documentation you are adding would do

>
> Signed-off-by: Maxim Uvarov <maxim.uvarov@linaro.org>
> ---
>  doc/README.lwip | 90 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 90 insertions(+)
>  create mode 100644 doc/README.lwip
>
> diff --git a/doc/README.lwip b/doc/README.lwip
> new file mode 100644
> index 0000000000..16f41049ab
> --- /dev/null
> +++ b/doc/README.lwip
> @@ -0,0 +1,90 @@
> +     RFC LWIP IP stack intergation for U-boot
> +        ----------------------------------------
> +
> +Reliable and bug free IP stack is usually an issue when you are trying to 
> write it

I am not sure about the bug free part :).  Just move this entire paragraph as
part of the commit message and remove the 'RFC' parts.

> +from scratch. It looks like not, but when addinging new features it will be 
> chelledging.
> +This RFC work is a demo to enable lwIP (lightweight IP) which is a widely 
> used open-source
> +TCP/IP stack designed for embedded systems for U-boot. That will allow using 
> already
> +written network applications for microcontrollers.
> +
> +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: iwIP 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).
> +  This RFC implements only raw API as the proof of work.
> +
> +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.
> +
> +This RFC has an unmodified working ping example from lwip sources which 
> registeres this callback.
> +  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.
> +
> +4. Testing
> +
> +Unmodified ping example can be used. I did ping from qemu/u-boot tap device 
> on the host:
> +
> +=> lwip init
> +=> lwip ping 192.168.1.2
> +ping: recv 3 ms
> +tcpdump on the host:
> +5:09:10.925951 ARP, Request who-has 192.168.1.200 tell 192.168.1.200, length 
> 28 15:09:12.114643 IP6 fe80::38e2:41ff:fec3:8bda > ip6-allrouters: ICMP6, 
> router solicitation, length 16 15:09:20.370725 ARP, Request who-has 
> 192.168.1.2 tell 192.168.1.200, length 28 15:09:20.370740 ARP, Reply 
> 192.168.1.2 is-at 3a:e2:41:c3:8b:da (oui Unknown), length 28 15:09:20.372789 
> IP 192.168.1.200 > 192.168.1.2: ICMP echo request, id 44975, seq 1, length 40 
> 15:09:20.372810 IP 192.168.1.2 > 192.168.1.200: ICMP echo reply, id 44975, 
> seq 1, length 40 15:09:25.426636 ARP, Request who-has 192.168.1.200 tell 
> 192.168.1.2, length 28 15:09:25.426870 ARP, Reply 192.168.1.200 is-at 
> f6:11:01:02:03:04 (oui Unknown), length 28
> +
> +
> +5. Wget example
> +
> +Http server has 192.168.1.2 IP address. (I did not port DNS resolving yet,
> +but it's also exist in lwip.) So example just downloads some file with http
> +protocol:
> +
> +Net:   eth0: virtio-net#30
> +Hit any key to stop autoboot:  0
> +=> lwip init
> +Starting lwIP, local interface IP is 192.168.1.200
> +Initialized LWIP stack
> +=> lwip wget http://192.168.1.2/
> +downloading http://192.168.1.2/ to addr 0x40200000

Does wget with lwip work with dns as well?

> +downloaded chunk size 294, to addr 0x40200000
> +downloaded chunk size 318, to addr 0x40200126
> +=> md 0x40200000 0x40
> +40200000: 4f44213c 50595443 74682045 0a3e6c6d  <!DOCTYPE html>.
> +40200010: 6d74683c 3c0a3e6c 64616568 743c0a3e  <html>.<head>.<t
> +40200020: 656c7469 6c65573e 656d6f63 206f7420  itle>Welcome to
> +40200030: 6e69676e 2f3c2178 6c746974 3c0a3e65  nginx!</title>.<
> +40200040: 6c797473 200a3e65 62202020 2079646f  style>.    body
> +40200050: 20200a7b 20202020 69772020 3a687464  {.        width:
> +40200060: 65353320 200a3b6d 20202020 6d202020   35em;.        m
> +40200070: 69677261 30203a6e 74756120 200a3b6f  argin: 0 auto;.
> +40200080: 20202020 66202020 2d746e6f 696d6166         font-fami
> +40200090: 203a796c 6f686154 202c616d 64726556  ly: Tahoma, Verd
> +402000a0: 2c616e61 69724120 202c6c61 736e6173  ana, Arial, sans
> +402000b0: 7265732d 0a3b6669 20202020 2f3c0a7d  -serif;.    }.</
> +402000c0: 6c797473 3c0a3e65 6165682f 3c0a3e64  style>.</head>.<
> +402000d0: 79646f62 683c0a3e 65573e31 6d6f636c  body>.<h1>Welcom
> +402000e0: 6f742065 69676e20 3c21786e 3e31682f  e to nginx!</h1>
> +402000f0: 3e703c0a 79206649 7320756f 74206565  .<p>If you see t
> --
> 2.30.2
>

Thanks
/Ilias