tg

tg is a Linux-only, transmit-only traffic generator built on AF_XDP and written in Zig, optimized for high‑rate packet generation directly from user space. It creates one dedicated thread per NIC TX queue and drives AF_XDP sockets bound to those queues for predictable performance and NUMA‑friendly CPU affinity.

Features

• Transmit‑only AF_XDP packet generator (no RX path), focusing on high‑rate, low‑latency packet transmission from user space.
• Per‑TX‑queue worker threads, each pinned to the CPU set configured for that queue under /sys/class/net/<dev>/queues/tx-*/xps_cpus.
• YAML configuration of packet templates with protocol “layers” (Ethernet, IPv4/IPv6, UDP, etc.).
• Flexible Range abstraction for each field.
• Fully static, musl‑targeted binary with statically linked libbpf and libxdp for deployment on minimal systems.
• Attach XDP programs to NICs: pass / drop.

Architecture overview

tg uses AF_XDP sockets to bypass most of the kernel network stack and operate directly on UMEM‑backed packet buffers in user space. Each worker thread owns its UMEM and AF_XDP socket, which is bound to a single NIC TX queue, avoiding sharing and locking between threads.

The threading model is derived from Linux’s per‑queue transmit scheduling, using the xps_cpus mask to map queues to CPUs. By setting the thread’s CPU affinity before creating UMEM and the AF_XDP socket, tg keeps memory and NIC queue access local to the intended core.

Requirements

• OS: Linux with AF_XDP support enabled in the kernel (XDP and AF_XDP address family).
• Compiler: Zig 0.15.2.