Native MPLS Support for FreeBSD

This proposal lays out plans to bring native MPLS support into the FreeBSD kernel. MPLS—Multi-Protocol Label Switching—is a fast packet-forwarding method you’ll find everywhere in big service provider and data center networks. Instead of making routers do complex IP lookups at every hop, MPLS uses simple label swapping. The magic happens with a tiny 32-bit shim header that holds a 20-bit label, a few bits for traffic class, a stack indicator, and an 8-bit TTL. This header sits snugly between Layer 2 and Layer 3 headers, letting routers in the core do blazing-fast forwarding while pushing tough routing decisions to the network edge. FreeBSD is famous for its solid IPv4 and IPv6 networking stack, but it’s been missing native Layer 2.5 switching. That gap has made it hard for FreeBSD to get traction in provider core networks. Meanwhile, OpenBSD and NetBSD have shipped MPLS support for ages, and Linux has had MPLS built in since kernel 4.3. FreeBSD’s overdue update doesn’t just catch up—it leapfrogs the other BSDs. This project stands out in two big ways: it adds ECMP multipath support using the modern nhgrp (Nexthop Group) subsystem, and it swaps out the old, hard-to-extend rtsock interface for a much more flexible Netlink-based control plane.