What is Dropwatch?
This tool will show place where kernel drops/discards UDP packets.
How to build on Ubuntu 14.04?
First of all you need to have CONFIG_NET_DROP_MONITOR enabled in your kernel https://github.com/pavel-odintsov/drop_watch/wiki/Ubuntu-14.04-LTS-kernel-with-drop_monitor-support
sudo apt-get install -y libnl-3-dev libnl-genl-3-dev binutils-dev libreadline6-dev
Then clone repo, cd to src folder and run make.
And finally run tool:
./dropwatch -l kas