Kernel_UDP

Two kernel modules that implement UDP client - server communication.
Tested using Ubuntu 17.4 kernel version 4.10.0-26-generic.

Once running, the client send HELLO to server, that answers OK.

Files

kern_udp/udp_client.c: kernel module for client
kern_udp/udp_server.c: kernel module for server

Each module has the equivalent in user space under the folder used_udp. They also have the same parameters and perform the same operations

Usage

1. Compile ( make in this folder)
2. Load server with sudo insmod udp_server.ko (see Parameters for optional parameters)
3. Load client with sudo insmod udp_client.ko (see Parameters for optional parameters)
4. Observe in /var/log/kern.log the message passing:
   Load server

[  +4.514179] k_server: opt: p
[  +0.000006] Socket created
[  +0.000008] Socket is bind to 127.0.0.1:4000
[  +0.000057] k_server: Thread running
[  +0.000031] k_server: Performing a simple test: this module will wait to receive HELLO from client, replying with OK

Load client

[ +11.079634] k_client: Destination is 127.0.0.1:4000
[  +0.000003] k_client: opt: p, ns: 1, tsec: -1, ntests:1
[  +0.000003] Socket created
[  +0.000007] Socket is bind to 127.0.0.1:3000
[  +0.000104] k_client: Thread running
[  +0.000046] k_client: Performing a simple test: this module will send OK and will wait to receive HELLO from server
[  +0.000103] k_client: Sent HELLO (size 6) to 127.0.0.1 : 4000
[  +0.000096] k_server: Received HELLO (size 6) from 127.0.0.1:3000
[  +0.000009] k_server: Sent OK (size 6) to 127.0.0.1:3000
[  +0.000002] k_client: Received OK (size 6) from 127.0.0.1:4000
[  +0.000001] k_client: All done, terminating client

If you want to have a dynamic view of the kern.log file, use the command tail -f /var/log/kern.log or dmesg -wH

Parameters:

On client, the server ip, server ip and port can be specified as module parameters when loading the module:
sudo insmod udp_client.ko myip=123.12.1.0 myport=2900 destip=123.12.1.2 destport=3000

On server, the server ip and port can be specified as module parameters when loading the module:
sudo insmod udp_server.ko myip=123.12.1.2 port=3000

For the other options, type modinfo module_name.ko in the terminal to get these informations.

The module features 4 operation types:

• PRINT simple HELLO-OK passing
  
• TROUGHPUT checks how many messages a client can send and how many the server can receive
  
• LATENCY checks the average latency
  
• SIMULATION simulates n clients sending messages and counting how many can be received back each second. Prints the result in a file.

u_run.sh and k_run

To make the loading / unloading of modules easier, I also created a script k_run.sh. This script calls make, insmod, wait a command to terminate and call rmmod.

1. Give appropriate executing permission using chmod
2. Run it ./k_run module_name [other optionals parameters]
3. Once unloaded the module, it will wait for enter or ctrl-c to either continue and unload the module or terminate.

If the module is already running and this script is called, the module is unloaded first, recompiled, and loaded again.

emanuele@emanuele-MacBookPro:~/Desktop/Kernel_Modules/Kernel_UDP$ ./run.sh udp_client
Module Successfully complied
Successfully loaded Module
Press enter to remove the module or Ctrl+C to exit...
Closing
Successfuly unloaded Module

Same is with u_run.sh for the user space applications.

Disclaimer

These are my first kernel modules, if you experience bugs, or simply want to improve it, any suggestion is appreciated.

In case the module blocks (impossible to unload it, lsmod returns Used by -1, whole screen freezes), the only thing you can do is force restart the computer (hold power button, or unplug it). If you manage to shut it down normally, but the interface still freeze and it does not shut down (ubuntu logo with moving dots), do a force shut down.
On restart, the kernel will be restored and module unloaded.
I am not responsible of any use you do or any damage it might create.