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

Mon Jul 3 18:22:03 CEST 2023

On Fri, 30 Jun 2023 at 16:01, Ilias Apalodimas <ilias.apalodimas at linaro.org>
wrote:

> 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 at 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?
>
>
Yes it works with dns also. But to test that I need to set up access to the
dns server. So dns is more likely the next command to implement.

> > +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
>