shardnet

Shardnet A high-performance userspace TCP/IP stack written in Zig Shardnet is a full TCP/IP stack — IPv4/IPv6, TCP, UDP, ICMP/ICMPv6, ARP and DNS — that runs entirely in userspace over pluggable drivers (loopback, TAP, AFPACKET, AFXDP). It targets Linux and is built for throughput: modern TCP extensions, CUBIC/BBRv2 congestion control, zero-copy buffers, and a sharded, multi-queue-friendly core — wrapped in a portable, poll-based socket API and hardened against adversarial traffic (bounded state everywhere, fuzz-tested parsers). Architecture Overall Architecture System Context Quick start Requires the Zig 0.14.x toolchain. Linux has full support; macOS/BSD build with the loopback driver only. Features Protocols — IPv4 and IPv6 with fragment reassembly on both (RFC 5722 overlap rejection on v6), extension header chains, TCP (RFC 793), UDP, ICMP/ICMPv6 (echo, rate limiting, neighbor discovery, SLAAC), ARP (cache change detection), DNS (TTL + negative cache + hosts file). Sockets — portable high-level socket API (Socket.tcp/Socket.udp): bind/connect/listen/accept, send/recv, poll-based like smoltcp — the same code runs over any driver on any platform.