eTran: Extensible Kernel Transport with eBPF#
NSDI '25 digest Program Core pick 28–30 April 2025
- Authors / tier: Zhongjie Chen (Tsinghua); Qingkai Meng (Nanjing University); ChonLam Lao (Harvard); Yifan Liu, Fengyuan Ren (Tsinghua); Minlan Yu (Harvard); Yang Zhou (UC Berkeley and UC Davis). Core.
- Why: New transport designs almost never reach the mainline kernel, and when they do it takes years. eTran is a credible answer to "how do we get customizable transports into production without forking the kernel" — directly relevant to anyone reasoning about datapath internals and congestion control.
- What: A framework that makes kernel transport extensible: operators implement and customize transports (it ships DCTCP-style TCP and Homa) as eBPF rather than kernel patches, while keeping kernel-level safety and absorbing userspace-transport performance tricks.
- How: Core transport ops run in the kernel via eBPF; packets reach a thin, untrusted userspace library through AF_XDP sockets, where they are reassembled into TCP flows or Homa RPCs. All packets traverse eBPF hooks, so monitoring, access control, and rate limiting are modular eBPF programs chained via
bpf_tail_call. Reported up to ~7.5x lower P99 latency than Linux Homa on RPC workloads. Open source. - Where applicable: Datacenter Linux hosts (evaluated on kernel 6.6.0 with AF_XDP). General technique, but tied to a recent kernel and AF_XDP; synchronization support in eBPF is a noted limitation.