Ubuntu 14.04 LTS kernel with drop_monitor support

In this guide, I'll describe how you could build kernel for Ubuntu 14.04 with CONFIG_NET_DROP_MONITOR option. It's pretty standard reference copy-n-pasted from official manual of Ubuntu with very small changes.

If you got this error:

sudo ./dropwatch 
Unable to find NET_DM family, dropwatch can't work
Cleaning up on socket creation error

Then it means that your kernel does not have CONFIG_NET_DROP_MONITOR option compiled.

I use Ubuntu 14.04 and could provide guide how you could rebuild kernel with this option.

Rebuild kernel:

apt-get source linux-image-$(uname -r)

Install build deps:

sudo apt-get build-dep linux-image-$(uname -r) libncurses5-dev

Start process:

cd linux-lts-vivid-3.19.0 

Change options:

chmod a+x debian/rules
chmod a+x debian/scripts/*
chmod a+x debian/scripts/misc/*
fakeroot debian/rules clean 

fakeroot debian/rules editconfigs # you need to go through each (Y, Exit, Y, Exit..) or get a complaint about config later

Then specify it:

Do you want to edit config: amd64/config.flavour.generic? [Y/n] Y

Required option you could find here:

Networking support - Networking options - Network testing - Network packet drop alerting service - [M]

Build it:

fakeroot debian/rules binary-headers binary-generic binary-perarch 

Check it:

cat ./debian.vivid/config/amd64/config.flavour.generic
#
# Config options for config.flavour.generic automatically generated by splitconfig.pl
#
CONFIG_HZ=250
# CONFIG_HZ_1000 is not set
CONFIG_HZ_250=y
# CONFIG_IRQ_FORCED_THREADING_DEFAULT is not set
CONFIG_NET_DROP_MONITOR=m
# CONFIG_PREEMPT is not set 

CONFIG_PREEMPT_VOLUNTARY=y

And finally load it when you restart to new kernel:

modprobe drop_monitor