© 2015 Steven Barth

Networking

Steven Barth

© 2015 Steven Barth

The Good ol’ Days…

Image: “legacy-caution” by Phil Benchoff; CC BY 2.0

Static Configuration- Fixed private addresses- DHCP to clients- Leases & hostnames stored- NAT hides dynamic changes

Bootstrapping

DHCP

EthernetCable etc.

PPP(oE/A)Modems (DSL, 3G, …)

IPCP

© 2015 Steven Barth

… and bootstrapping now

RA + DHCPV6

6rdIPv6 in IPv4

DHCP

EthernetCable etc.

PPP(oE/A)Modems (DSL, 3G, …)

IPCP

DS-LiteIPv4 in IPv6

MAP-E / LW4o6IPv4 in IPv6 + NAT

MAP-TNAT46 + 44

464XLATNAT46

MBIM3G / 4G

QMI3G / 4G

Other 3G/4GNCM, DirectIP, ...

© 2015 Steven Barth

Expose it to the user?

© 2015 Steven Barth

Configure only what is necessary!

Ethernet / WiFiconfig interface wan option ifname eth1 option proto dhcp

config interface wan6 option ifname eth1 option proto dhcpv6

DSL (PPPoE/A)config interface wan

option ifname eth1option proto pppoeoption username #user#option password #pass#

3G / 4Gconfig interface wan

option proto wwanoption pincode #code#option apn #apn#

© 2015 Steven Barth

Network Subsystem Overview

netifdconfig + management

firewall3iptables abstraction

ProtocolsDHCP, DHCPv6, ...

DNS cache

Client ConfigurationDHCP, RA, DHCPv6, ...

DevicesEthernet, WiFi, ... Other Services

PCP, MDNS, UPNP, ...

© 2015 Steven Barth

netifd: heart of the network subsystem

Device Setup

bring up / teardownhotplug & carrier-detectionbridges, 802.1q/ad, macvlansettings: L2-address, MTU, …

Configuration & Events

store and manage configurationcalculate minimal changesreact to events: kernel, ubus

Layer 3 Protocols

ubus + shell based APIstackable protocolsdependency support

Addresses & Route

manage and distributesend ubus + script eventshandle auxiliary data (DNS, ...)

© 2015 Steven Barth

Example Flowconfig interface wan option ifname eth1 option proto dhcp

option hostname foobar

Kernel device event eth1 available and cable plugged in

Configuration Eventnew interface using device eth1→ listen for eth1 device events

Run dhcp protocol handlerpass option hostname

Protocol Eventsuccess: IP=1.2.3.4, GW=2.3.4.5on wan (eth1)

Assign addresses and routesAssign 1.2.3.4 to eth1Setup default route to 2.3.4.5

© 2015 Steven Barth

Declaring protocolsfile: /lib/netifd/proto/dhcpv6.sh (simpl.)1. Some Preamble

2. Declare Configuration

3. Protocol setup functiona: retrieve configuration

b: spawn protocol daemon

4. Declare teardown function

5. Register protocol

© 2015 Steven Barth

Handling protocol repliesfile: /lib/netifd/dhcpv6.script (simpl.)1. Some Preamble

2. Declare a setup functionParse status data and turn it intonetifd configuration information

3. Declare a teardown function

4. Depending on daemon state, runsetup or teardown function

© 2015 Steven Barth

Stackable Protocols and Dependenciesconfig interface wan

option proto wwanoption pincode #code#option apn #apn#

Create interface wan_6 (dhcpv6)configure IPv6 layer 3detect if 464XLAT / DNS64 is used

Run interface wan (wwan)detect and bring up modem “link”(IPv6 modem “link” was brought up)

Create interface wan_6_4 (464xlat)configure virtual IPv4 layer 3

© 2015 Steven Barth

WiFi Featuresmulticast to unicast

generic conversion layerworkaround WiFi shortcomings

iwinfo: monitoring

status abstraction layerquery settings & capabilitiesquery associated stationsscan for nearby networks

netifd: configuration

change managementplugins to abstract driverswpad (hostapd) integration

client “pseudo-bridge”

in the absence of WDSrelayd: proxy ARP, DHCPodhcpd: proxy NDP, RA, DHCPv6

© 2015 Steven Barth

Custom IPv6 Stack

Uplink Configuration

auto-detected bootstrapmany painful ISP work-aroundsprefix distribution support

Client Configuration

designed for compatibilityoptimized power saving defaultssupport for downstream routers

Softwire support

lots of transitional technologiesencapsulation and nattingIPv4 address sharing support

© 2015 Steven Barth

Firewall

Zones

aggregation of interfacessource and destination of rulesassigned via config or protocol

Generic

event-triggered iptables rule generatorhooks and daemon integration (PCP, UPNP IGD, …)

Rules

filtering and NATstatic rules through UCI configdynamic rules from protocols

© 2015 Steven Barth

Other OpenWrt network projects in core

odhcp6c IPv6 Router Advertisement & DHCPv6+PD client

uhttpd2 http(s) daemon + json-rpc - ubus bridge

mdns DNS-SD querier & announcer

map + 464xlat MAP-E, MAP-T, LW4over6 & 464xlat implementation

umbim MBIM 3g/4g modem client

uqmi QMI 3g/4g modem client

omcproxy IGMPv3 / MLDv2 multicast proxy

© 2015 Steven Barth

QoS, SQM and Bufferbloat.net

Bufferbloat?High latency & congestion through lotsof large dumb buffers all over the data paths.

(TCP) packets clog queues → latency rises!

Solution?controlled delay (fq_codel) by defaultoptionally full smart queue management scriptsfor full control over the bottleneck

© 2015 Steven Barth

Multi-router and multi-ISP networks

What if I want to utilize multiple ISPs at once (ala multipath TCP or Google’s QUIC)?

→ IPv6 + source-address aware routing

What if I want to directly access my IOT devices without going through the cloud?

→ Layer 2 bridging? Take it to Layer 3!→ Multi Router SOHO networks

This is unmanageable… for a user!

Internet

?

© 2015 Steven Barth

Research in the IETF homenet WG...

We can build relatively universal more or less self-configuring IPv4 + IPv6 SOHO routers!

Can we take this one step further?Getting rid of WAN-port and LAN-bridge?

Can we scale this up to arbitrary networks?“Plug & Play” routers?But who “owns” the network(s)?

→ Find a consensus among equal routers→ DNCP: a distributed consensus protocol

→ Specify requirements for interoperability→ HNCP: autonomous networks using

DNCP

Firewall

DHCP

DHCPv6 6rd

LW4over6DS-LiteMAP

PCP

464XLAT

Source-Dest-Routing

?

© 2015 Steven Barth

… towards autonomous networks!→ Topology Detection

→ Border Discovery & Setup

→ Routing Setup

→ Naming & Service Discovery

→ Status Distribution

→ Security Bootstrap

Read more→ www.homewrt.org

© 2015 Steven Barth

Thank you for your attention! Questions?

Steven Barth<cyrus@openwrt.org>

Licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)