SNABB

A TOOLKIT FOR BUILDING USER-SPACE NETWORKFUNCTIONS

ABOUT IGALIA

Consultancy specialized in open-sourceBase in Coruña but distributed all over the world (>60 people working from 15different countries)Contributors to projects such as WebKit, Chromium V8, etcOther areas: Graphics, Multimedia, Networking

https://www.igalia.com/networking

AGENDA

What is Snabb?How it works?Catalog and programsUse case: lwAFTR

WHAT IS SNABB?

Snabb is a toolkit for developing high-performance network functions in user-space

WHAT IS A NETWORK FUNCTION?

A program that manipulates traffic dataBasic operations: read, forward, drop, modify, create...Combining these primitives we can build any network function

EXAMPLES

Firewall: read incoming packets, compare to table of rules and execute anaction(forward or drop)NAT: read incoming packets, modify headers and forward packetTunelling: read incoming packets, create a new packet, embed packet into newone and send it

WHY SNABB?

Increasing improvement of commodity hardware: 10Gbps NICs at veryaffordable pricesHigh-performance equipment is still very expensiveIdea: build an analog high-performance router using commodity hardware

WHY SNABB?

What software to put into this hardware?Common intuition: LinuxDrawback: Linux is not suitable for high-performance networking

WHY NOT LINUX?

General-purpose operating systemAn OS abstracts hw resources to offer high-level interfaces: filesystems,processes, sockets...Our network function will be divided into two lands: user-space and kernel-spaceColorary: processing a packet has an inheritent cost => the cost of the OS

HIGH-PERFORMANCE NETWORKING

NIC: 10GbpsAvg Packet-size: 550-bytePPS: 2272727,271 packet every 440ns ((1/2272727,27)*10^9)CPU: 2,5 Ghz1100 cycles to process one packet (2,5 cycles/sec * 440 ns)

HIGH-PERFORMANCE NETWORKING

Packet-size: 64-byte: 51 ns per packet; 128 cycles per packetLock/Unlock: 16ns; Cache-miss: 32 nsSource: Jonathan Corbet's Small packet size => More packets per second => worseFaster CPU => better

"Improving Linux networking performance"

USER-SPACE DRIVER

Do a kernel by-pass and manage the hardware directly from user-space:Tell Linux not to manage the PCI device (unbind)Do a mmap of the registers of the PCI device into addressable memoryWhenever we read/write the addressable memory, we're actually poking theregisters of the NICFollow the NIC's datasheet to implement operations such as initialize,receive, transmit, etc

USER-SPACE NETWORKING

Snabb is not an isolated case of user-space networking:Snabb (2012)DPDK (2012)VPP/fd.io (2016)

DPDK (Data-plane Development Kit, Intel)VPP (Vector Packet Processing, Cisco)

RING-BUFFER

Very important to avoid packet drops

INSIDE SNABB

SNABB

Project started by Luke GorrieUser-space networking benefit: freedom of programming languageSnabb is mostly written in LuaNetwork functions are also written in LuaFast to run, fast to developSnabb means fast in Swedish :)

ABOUT LUA

Started in 1993 at University of Rio de Janeiro (PUC Rio)Very similar to JavaScript, easy to learnVery small and compact, it's generally embeded in other systemsUse cases: microcontrollers (NodeMCU), videogames (Grim Fandango), IA(Torch7)

ABOUT LUAJIT

Just-in-time compiler for LuaExtremely fast virtual machine!!Very good integration with C thanks to FFI (Foreign Function Interface)

FFI: EXAMPLE

ffi.cdef[[

void syslog(int priority, const char*format, ...);

]]

ffi.C.syslog(2, "error:...");

local ether_header_t = ffi.typeof [[

/* All values in network byte order. */

struct {

uint8_t dhost[6];

uint8_t shost[6];

uint16_t type;

} __attribute__((packed))

]]

SNABB IN A NUTSHELL

A snabb program is an app graphApps are conected together via linksSnabb processes the program in units called breadths

NF: APP GRAPH

BREADTHS

A breadth has two steps:inhale a batch of packets into the graphprocess those packets

To inhale, the method pull of the apps is executed (if defined)To process, the method push of the apps is executed (if defined)

# Pull function of included Intel 82599 driver

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

# Push function of included PcapFilter

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

PACKET PROCESSING

Normally only one app of the app graph introduces packets into the graphThe method push gives an opportunity to every app to do something with apacket

APP GRAPH DEFINITION

local c = config.new()

-- App definition.

config.add(c, "nic", Intel82599, {

pci = "0000:04:00.0"

})

config.add(c, "filter", PcapFilter, "src port 80")

config.add(c, "writer", Pcap.PcapWriter, "output.pcap")

-- Link definition.

config.link(c, "nic.tx -> filter.input")

config.link(c, "filter.output -> writer.input")

engine.configure(c)

engine.main({duration=1})

PACKETS

struct packet {

uint16_t length;

unsigned char data[10*1024];

};

LINKS

struct link {

struct packet *packets[1024];

// the next element to be read

int read;

// the next element to be written

int write;

};

SNABB: APP CATALOG AND PROGRAMS

INVENTARY

apps: software components that developers combine together to build networkfunctionsprograms: complete network functions

APPS I/O

Intel i210/i350/82599/XL710Mellanox Connectx-4/5Virtio host y guestUNIX socketLinux: tap and "raw" (e.g: eth0)Pcap files

APPS L2

Flooding and learning bridgeVLAN insert/removeARP/NDP

APPS L3

IPv4/v6 fragmentation and reassemblyIPv4/v6 splitterICMPv4/v6 echo responderControl-plane delegation (nh_fwd)

APPS L4

IPsec ESPLightweight 4-over-6 AFTRKeyed IPv6 Tunnel

APPS MONITORING

IPFix capturer and exporterL7 monitor/filtering (libndpi)Pcap expressions filter (with own backend for code generation)

APPS TESTING

Lots of load generators: loadgen, packetblaster, loadbench...

USE CASE: LWAFTR

CONTEXT

2012-2014: Several RIRs run out of IPv4 public addresses2008: IPv6 adoption starts to peak upStill big dependency on IPv4: services, websites, programs, etc

SOLUTIONS

Carrier-Grade NAT: temporal solution for IPv4 address exhaustion problemDeployment of Dual-Stack networks (IPv4 e IPv6)Dual-Stack implies increasing complexity and costs (maintenance of twoseparated networks)Dual-Stack Lite (IPv6-only network which also offers IPv4 connectivity relyingon CGN)Lightweight 4over6: iteration over Dual-Stack

LIGHTWEIGHT 4OVER6

LW4O6 - GOALS

RFC7596 fully complaint (lwAFTR part)Performance: 2MPPS; 550-byte (packet-size); Binding-table: 1M subscribers.No packet drops

LW4O6 - DEVELOPMENT

Version 1:PrototypeBasic functionality (encapsulating/decapsulating)Small binding-table (own format)Development of tools to measure performance

LW4O6 - DEVELOPMENT

Version 2Production qualityFully standard compliantBig binding-table: 1M subscribers (still customized format but much closerto standard)Add support for other necessary protocols: ARP, NDP, fragmentation,reassembly, pingTons of optimizations (use of AVX instructions to speed up lookups)

LW4O6 - DEVELOPMENT

Version 3:Added YANG support to SnabbSupport binding-table format according to standardSupport of execution as leader/worker (leader: control-plane/worker: data-plane)

LW4O6 - DEVELOPMENT

Version 4:Multiprocess (one leader, multiple workers)Improvement of the Intel 10Gbps driver (added support for RSS, ReceivedSide Scaling)Added alarms support according to latest draft

LIGHTWEIGHT 4OVER6 - TALKS

Juniper's vMX Lightweight 4over6 VNFCharla: Kostas Zordabelos's A real-world scale network VF using Snabb for lw4o6Charla:

Juniper Tech Club, Marzo 2017

SDN Meetup, Abril 2017

OTHER PROGRAMS

PROGRAM: PACKET BLASTER

Generally useful tool: fill TX buffer of NIC with packets and transmit them overand over againMeasures received traffic tooEasily saturates 10Gbps links

snabb packetblaster replay packets.pcap 82:00.1

PROGRAM: SNABBWALL

L7 firewall that optionally uses nDPICollaboration betwen Igalia and NLnet FoundationLanded upstream in 2017Website: http://snabbwall.org

PROGRAM: IPFIX

NETFLOW collector and exporter (v9 and IPFIX)Line-rate speed on a single core. Further improvement: parallel processing viaRSSLanded upstream very recently

PROGRAM: L2VPN

L2VPN over IPv6 (developed by Alexander Gall from SWITCH)Pending to land upstream; used in productionIdeal Snabb use case: programmer/operator builds bespoke tool

PROGRAM: YOUR VNF

Snabb upstream open to include new network functionsRepository will grow as people will build new thingsIgalia can build one for you

LAST NOTES ABOUT PERFORMANCE

CONSIDERATIONS

Isolcpus: Prevents the kernel to take a CPU to schedule processesDishable HyperThreadingUse HugePages (2MB) (Linux default is 4Kb)Do not neglect NUMA when launching programsMake use of SIMD instructions (AVX, AVX2) to speed up computations(checksum)Keep an eye on regressions: profile often

SUMMARY

Toolkit for developing high-performance network functions in user-spaceSnabb provides apps which can be combined together forming a graph (networkfunction)Snabb provides programs, complete network functions ready to useSnabb provides libraries, to easy the development of new network functionsCompletely written in Lua: easy to extendFast: kernel-by pass + high-level language + fast VM (LuaJIT)

THANKS!

Email: dpino@igalia.comTwitter: @diepg

$ git clone https://github.com/snabbco/snabb.git

$ cd snabb

$ make