passt is an implementation of user-mode networking for qemu, focusing on security (no dynamic memory allocation, purpose-written codebase, strict seccomp policy), performance (packet and syscall batching, pre-cooked buffers, minimalistic TCP adaptation), network transparency: contrary to libslirp, NAT is not needed, as the guest inherits addressing and routing from the host via DHCP, NDP, DHCPv6.

The aim is to bring production readiness to user-mode networking with a simpler implementation, written with the specific goal in mind. passt is also being integrated inside the KubeVirt architecture, thanks to its superior (as compared to libslirp) performance and flexibility.