=========== You should know that some source code in this project is
= WARNING = not a best practice and immature.
===========                                            -- 2015/10/28

tapip

A user-mode TCP/IP stack based on linux tap device

Dependence

• linux tun/tap device (/dev/net/tun exists if supported)
• pthreads

Quick start

$ make
# ./tapip                    (run as root)
[net shell]: ping 10.0.0.2   (ping linux kernel TCP/IP stack)
(waiting icmp echo reply...)
[net shell]: help            (see all embedded commands)
...

The corresponding network topology is here.

More information for hacking TCP/UDP/IP/ICMP:
See doc/net_topology, and select a script from doc/test to do.

Socket Api

_socket,_read,_write,_send,_recv,_connect,_bind,_close and _listen are provided now.
Three socket types(SOCK_STREAM, SOCK_DGRAM, SOCK_RAW) can be used.
You can use these apis to write applications working on tapip.
Good examples are app/ping.c and app/snc.c.

How to implement

I refer to xinu and Linux 2.6.11 TCP/IP stack and use linux tap device to simulate net device(for l2).
A small shell is embedded in tapip.
So this is just user-mode TCP/IP stack :)

Any use

Tapip makes it easy to hack TCP/IP stack, just compiling it to run.
It can also do some network test: arp snooping, proxy, and NAT!
I think the most important is that tapip helps me learn TCP/IP, and understand linux TCP/IP stack.

Other

You can refer to saminiir/level-ip and its blog posts for more details.