netsniff-ng is a free, performant linux network analyzer and networking toolkit. If you will, the Swiss army knife for network packets.
The gain of performance is reached by built-in 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.
It can be used for network development, debugging, analysis, auditing or network reconnaissance. It consists of the following fixed set of utilities:
* netsniff-ng: a zero-copy packet analyzer, pcap capturing/replaying tool * trafgen: a multithreaded low-level zero-copy network packet generator * mausezahn [*]: high-level packet generator for appliances with Cisco-CLI * ifpps: a top-like kernel networking and system statistics tool * curvetun [*]: a lightweight curve25519-based multiuser IP tunnel * astraceroute: an autonomous system trace route and DPI testing utility * flowtop: a top-like netfilter connection tracking tool * bpfc: a [seccomp-]BPF (Berkeley packet filter) compiler, JIT disassembler
Note that tools marked with [*] should be considered as experimental for now, and not used in production environments as they still need more work to be fully stable and in line with others.