new-CWV kernel module (draft-ietf-tcpm-newcwv)

newcwv is a Linux kernel module that implements the TCP modification described in draft-ietf-tcpm-newcwv. It is based on the 'tcp_congestion_ops' kernel hooks for congestion control. We tested it with kernel 3.8.2.

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Installation

First, change the KDIR in Makefile to the linux source code folder and then use make command to compile the c file. It will create tcp_newcwv.ko file along with some other files. (Problem? look at problems faced section).

Then use these commands to insert the module. These commands require root privilege; so use sudo if in user mode.

1.The command for inserting the module in the running kernel:

insmod  tcp_newcwv.ko	 

it can be checked by

cat   /proc/modules

where the first entry should show the tcp_newcwv module.

2.Set the congestion control algorithm to 'newcwv' using the command: echo "newcwv" > /proc/sys/net/ipv4/tcp_congestion_control

3.Run a client-server application; whether the tcp_newcwv was used can be tested from the kernel log:

dmesg   |    grep "CWVDEBUG"

should show some TCP stats during the application data transfer.

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Troubleshooting

1.insmod: error inserting 'tcp_newcwv.ko': -1 Invalid module format

This problem occurred when the module was tried to be inserted into any kernel other than linux-3.8.2. By compiling it, with the current version, it can be resolved. In Ubuntu:

sudo apt-get install build-essential linux-headers-$(uname -r)

Then you need to change the Makefile as follows:

obj-m := tcp_newcwv.o
KVERSION = $(shell uname -r)
PWD := $(shell pwd)

all: 
	$(MAKE) -C /lib/modules/$(KVERSION)/build M=$(PWD) modules	
clean:
	$(MAKE) -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

And execute 'make' that compiles the .c into a kernel module.

2.insmod: error inserting 'tcp_newcwv.ko': -1 Required key not available

This problem is due to kernel compilation settings. It is required to sign the module for the current kernel using the following commands:

cd  /usr/src/linux   OR  cd ~/kernel/linux-3.8.2   (for Ubuntu) 
perl scripts/sign-file ./signing_key.priv ./signing_key.x509 /path_to/module

and then insert the module.