D. Fast, Simple User-Space Network Functions with Snabb (RIPE 77)
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By Andy Wingo. Snabb is an open-source toolkit for building fast, flexible network functions. Since its beginnings in 2012, Snabb has seen some modest deployment success ranging from simple one-off diagnosis tools to border routers that process all IPv4 traffic for entire countries. This talk will give an introduction to Snabb. After going over Snabb's fundamental components and how they combine, the talk will move on to examples of how network engineers are taking advantage of Snabb in practice, mentioning a few of the many open-source network functions built on Snabb. (c) RIPE 77 15 - 19 October 2018 Amsterdam, Netherlands https://ripe77.ripe.net
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struct packet {
uint16_t length;
unsigned char data[10*1024];
};
struct link {
struct packet *packets[1024];
// the next element to be read
int read;
// the next element to be written
int write;
};
// (Some statistics counters elided)](https://image.slidesharecdn.com/andywingo-d-181019101623/85/D-Fast-Simple-User-Space-Network-Functions-with-Snabb-RIPE-77-16-320.jpg)
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D. Fast, Simple User-Space Network Functions with Snabb (RIPE 77)
- 1. Snabb: Open Source Meets Dataplane RIPE77, October 2018, Amsterdam Andy Wingo | [email protected] | @andywingo
- 2. this talk Why? The problem solved by Snabb How? Snabb from the ground up What? What’s in the box Who? Snabb in the wild
- 3. why? Ever want to deploy a new RFC, but no vendor is selling it? Maybe it’s not even an RFC yet? 10 years ago – too bad Now – open source software + commodity servers
- 4. software? User-space data planes Avoid the kernel, handle all data in user-space Snabb, DPDK, VPP (fd.io)
- 5. user space Tell Linux to forget about NIC Mmap NIC’s PCI registers into address space Read and write memory == read and write PCI registers ❧ Poke registers as needed to bring up NIC Set up a ring buffer for RX/TX Busy-loop to take packets from RX, process, send to TX
- 6. advantage You get the whole packet No hazard for straying off device- supported hot-path Program using whatever technology you want: C, Rust, Lua, Scheme, ... “It’s just programming” Hire anyone you want to modify the programs
- 7. limits Limited by PCI bandwidth Limited to ~10-50Gbps/CPU core (parallelization possible) Tangential to containerization / kubernetes / openstack hellscape
- 8. an aside on snabb Goal: “rewritable software” The hard part: searching program- space for elegant hacks “Is that all? I could rewrite that in a weekend.”
- 9. in a nutshell A snabb program consists of a graph of apps Apps are connected by directional links A snabb program processes packets in units of breaths
- 11. local Intel82599 = require("apps.intel.intel_app").Intel82599 local PcapFilter = require("apps.packet_filter.pcap_filter").PcapFilter local c = config.new() config.app(c, "nic", Intel82599, {pciaddr="82:00.0"}) config.app(c, "filter", PcapFilter, {filter="tcp port 80"}) config.link(c, "nic.tx -> filter.input") config.link(c, "filter.output -> nic.rx") engine.configure(c) while true do engine.breathe() end
- 12. snabb is written in lua Short and sweet programs LuaJIT does the heavy lifting High-performance just-in-time compilation, applied to networking domain Lua all the way down – packet processing, not just configuration
- 13. breaths Each breath has two phases: Inhale a batch of packets into the network ❧ Process those packets❧ To inhale, run pull functions on apps that have them To process, run push functions on apps that have them
- 14. # Pull function for built-in Intel82599 app function Intel82599:pull () for i = 1, engine.pull_npackets do if not self.dev:can_receive() then break end local pkt = self.dev:receive() link.transmit(self.output.tx, pkt) end end
- 15. # Push function for built-in PcapFilter app function PcapFilter:push () while not link.empty(self.input.rx) do local p = link.receive(self.input.rx) if self.accept_fn(p.data, p.length) then link.transmit(self.output.tx, p) else packet.free(p) end end end
- 16. packets and links struct packet { uint16_t length; unsigned char data[10*1024]; }; struct link { struct packet *packets[1024]; // the next element to be read int read; // the next element to be written int write; }; // (Some statistics counters elided)
- 17. voilà At this point, you can rewrite Snabb (Please do!) But you might want to use it as-is...
- 18. unboxing $ git clone https://github.com/snabbco/snabb $ cd snabb $ make $ ./src/snabb What’s in there? How are people using it?
- 19. apps I/O: Intel i210/i350/82599, Mellanox ConnectX4/5, TAP, AF_PACKET, AF_XDP, vhost/virtio, pcap... L2: ARP, NDP, learning bridge, l2vpn... L3: IPsec, ICMP, fragmentation... +: IPFIX, lwAFTR, DPI, firewall, pflang... Apps: learning bridge, NIC
- 20. yang App graph as function of YANG- modelled configuration Run-time config/state query, reconfigure Multi-process Statistics aggregation https://snabbco.github.io/#ptree
- 21. libraries LPM, JSON, fast raw hash tables, protocol stack, timer wheel, profiling, packet match domain-specific language compilers, NUMA/CPU binding, RRD files... https://snabbco.github.io/
- 22. no full router yet Some support for receiving routes from Linux We would love to flesh this out!
- 23. snabb in the wild See lightning talk “8 ways network engineers use Snabb” for more examples
- 24. exploratory analysis Flexibility, expressiveness, and rapid development of scapy, the speed to run live A large CDN uses Snabb in this way internally
- 25. layer 2 vpn # github.com/alexandergall/snabb # l2vpn branch $ snabb l2vpn l2vpn.conf RFC 4664 layer 2 learning bridge over IPv6 Built by SWITCH network engineer Alexander Gall because what he needed wasn’t on offer In production linking academic sites in Switzerland
- 26. ipsec vpn Vita: https://github.com/inters/ vita Secure VPN between sites, IPSec, 1-10 Gbps/core Funded by NLnet Foundation
- 27. border router tunnel endpoint $ snabb lwaftr run lwaftr.conf Lightweight 4-over-6 AFTR: processes all IPv4 traffic for a network YANG-enabled, runtime reconfigurable Multi-process: one instance can manage many NICs in a machine See K. Zorbadelos (OTE) at RIPE76: https://ripe76.ripe.net/archives/ video/30/
- 28. join us! https://github.com/snabbco/snabb snabb.slack.com (see Github page for join link) [email protected], @andywingo Happy hacking!