How to port a TCP/IP stack in your kernel TCP/IP stacks without an - - PowerPoint PPT Presentation

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How to port a TCP/IP stack in your kernel TCP/IP stacks without an - - PowerPoint PPT Presentation

Apr 05, 2023 196 likes •563 views

How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction How to port a TCP/IP stack in your kernel TCP/IP stacks without an Ethernet driver Focus on lw IP Conclusion Nassim Eddequiouaq July 20, 2014 Plan How to port a

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

How to port a TCP/IP stack in your kernel

without an Ethernet driver Nassim Eddequiouaq July 20, 2014

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Plan

1

Introduction

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Generic TCP/IP stack

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Plan

2

TCP/IP stacks

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Which free open source stacks ?

  • uIP
  • lwIP
  • tinytcp, wattcp..
  • fNET
  • Bentham’s TCP/IP stack
  • OpenBSD → not standalone
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Focus on what you need

  • embedded ?
  • bare metal ? (no operating system)
  • Keep It Simple, Stupid ?
  • fast ?
  • out of the box ?

Your choice.

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

uIP

  • world’s smallest TCP/IP Stack
  • used mostly for 8/16 bits microcontrollers
  • separates 32-bit arithmetic
  • useful for embedded systems
  • uses polling
  • handles TCP

, UDP (poorly), IPv4

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

uIP simple example

#define UIP_ACTIVE_OPEN 1 void setup() { connect_test(); } void loop() { uip_send("foo\n", 4); } void connect_test(void) { uip_ipaddr_t ipaddr; uip_ipaddr(&ipaddr , 192, 168, 1, 100); uip_connect(&ipaddr, HTONS(8080)); } [...]

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

lwIP

  • works with IRQs
  • which makes it VERY fast
  • DHCP

, AUTO-IP , ARP , UDP , PPP. . .

  • works well even with few RAM
  • several layouts of API
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

fNET structure

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

fNET

  • mostly for 32bits microcontrollers
  • supports ARM, Coldfire and Power Architecture
  • TCP

, UDP , IPv4, IPv6

  • HTTP server, DHCP client, DNS. . .
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Plan

3

Focus on lwIP Port lwIP Test and debug

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Plan

3

Focus on lwIP Port lwIP Test and debug

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

lwIP structure

lwIP offers 3 APIs:

  • Raw API
  • Netconn API
  • BSD Socket API

These APIs are layered in term of abstraction as follows: Very useful!

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

lwIP structure

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Raw API

This is the core API of lwIP

  • best performances
  • handles asynchronous events
  • does not need an OS, bare metal works
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Netconn API

This is the sequential API:

  • allows multi-threading
  • needs an OS
  • lower performances than Raw API
  • easier to use
  • needs much more memory
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

BSD Socket API

A Berkeley-like Socket implementation:

  • POSIX compliant
  • very portable
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Initialize the lwIP stack

Two ways:

  • single-threaded:

lwip_init()

  • multi-threaded:

tcpip_init(...) The second one calls implicitly the first one

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Your network interface

First, setup the compiler abstraction layer. In ‘cc.h’, define macros describing your processor and your compiler for :

  • types
  • byte ordering
  • structure packing
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Your network interface

lwIP is able to use higher-level mechanisms and structures. In ‘sys_arch.c’, you may define a set of wrappers in

  • rder to make it access:
  • semaphores
  • mailboxes
  • threads

This file is optional

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

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Conclusion

Start your network interface

Add the interface:

  • struct *netif netif_add(...)
  • specify IP address, netmask, gateway address

Set the interface up:

  • static IP address: netif_set_{up,down}
  • DHCP: dhcp_{start,stop}
  • AUTO-IP: autoip_{start,stop}
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Initialize your device driver

netif_add(...) takes (among other parameters) the init and input functions. You must provide these two functions with defined prototypes:

  • err_t foo_init(struct netif *netif)
  • err_t foo_input(struct pbuf *p,

struct netif *netif)

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

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Conclusion

Set your net interface properly

Set your struct netif during initialization:

  • state fields (i.e hardware address

and length, MTU, name. . . )

  • functions fields (output, link_output, input)
  • flag field: OR options you want to activate

(broadcast, PPP , ARP. . . )

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

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Conclusion

Your driver’s ouput functions

There are two function pointers that you need to set:

  • netif->linkoutput
  • netif->output

Implement the following functions:

  • err_t foo_linkoutput(...): called when a raw link

packet is ready to be send and does the actual transmission

  • err_t foo_output(...): called when an IP packet

is ready for transmission foo_output should call foo_linkoutput when the treated packet is ready.

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

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Conclusion

Your driver’s input management

When you receive a packet, pass it to foo_netif->input. This field has been set by your netif_add call, the last parameter being a function pointer:

  • err_t (*input)(struct pbuf *p, struct netif

*netif)

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

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Conclusion

Sum up

1

Call lwip_init() / tcpip_init(...)

2

Ethernet init function to pass to netif_add(...)

3

Ethernet input function to pass to netif_add(...)

4

Setup struct netif to pass to netif_add(...)

5

Ethernet link_output function and add it to struct netif

6

Ethernet output function and add it to struct netif

7

Call netif_add(...)

8

Set default network interface with netif_set_default(...)

9

Set interface to ‘UP’ with netif_set_up(...)

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

Plan

3

Focus on lwIP Port lwIP Test and debug

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

Port lwIP Test and debug

Conclusion

How to test your network interface ?

Remember, we have no Ethernet driver yet! Several solutions:

  • init another lwIP inside your kernel as a standalone

module

  • setup a protocol control block (PCB) and a TCP

connection associated to this PCB

  • activate the TCP connection
  • make it tcp_write(...) data to your network

interface

  • create a TAP device before starting qemu and make

it output/input data

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP

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Conclusion

Debugging your stack

There are some rough edges, you might want to tweak your stack:

  • a debugger, a JTAG → what if you don’t have one ?
  • printf / built-in debug → quite nice actually!

1

#define LWIP_DEBUG 1

2

#define IP_DEBUG LWIP_DBG_ON

3

configure debug messages in ‘opt.h’ and ‘lwipopts.h’

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Conclusion

Some useful data

Figure: Lines of code in lwIP

Linux networking stack had more than 25000 lines of code solely under net/ipv4 directory with ‘tcp_*.c’ files in 2012. . . Also, lwIP takes less than 14 kB in term of object code

  • size. In comparison, Linux TCP/IP minimal stack size

takes 153 kB.

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Plan

4

Conclusion

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Conclusion

If you want something scalable, lwIP is a very good solution! Currently porting it myself to Stos. Very active community around the project! Tons of examples.

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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Questions ?

Feel free to ask at:

  • nass@lse.epita.fr
  • nass on #lse @irc.rezosup.org
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How to port a TCP/IP stack in your kernel Nassim Eddequiouaq Introduction TCP/IP stacks Focus on lwIP Conclusion

Link

Adam Dunkels’ (uIP and lwIP creator) thesis:

http://static2.wikia.nocookie.net/__cb20100724070440/mini6/ images/0/0e/Lwip.pdf

lwIP Wiki:

http://lwip.wikia.com/wiki/LwIP_Wiki

lwIP -new- homepage, mailing list, forum:

http://savannah.nongnu.org/projects/lwip/