netsniff-ng
A Swiss army knife for your daily Linux network plumbing
netsniff-ng is a free Linux networking toolkit, a Swiss army knife for your daily Linux network plumbing if you will. Its gain of performance is reached by zero-copy mechanisms, so that on packet reception and transmission the kernel does not need to copy packets from kernel space to user space and vice versa. Our toolkit can be used for network development and analysis, debugging, auditing, or network reconnaissance.