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• Launchpad entry: https://features.launchpad.net/distros/ubuntu/+spec/zero-configuration-networking

• Packages affected: avahi-autoipd, libnss-mdns

Summary

When a dynamic network configuration is desired and a local DHCP server is not available for a network, Ubuntu needs to correctly assign itself a link-local address. This is implemented by avahi-autoipd, but requires some additional configuration and packaging corrections to have the expected proper behavior.

Rationale

Using link-local addresses for communicating on adhoc networks or local LANs without a DHCP server works for other operating systems. Having Ubuntu work correctly in these situations makes users more productive because they will be able to communicate with other link-local devices without having to do anything special.

Use cases

1. Claudia's home network does not have a DHCP server, and does not want to have to define a static IP address for her laptop. She still be able to communicate with other devices on the network.
2. John's desktop computer was booted and it got a link-local address. Then he adds a DHCP server to his network, and boots a second computer that gets a regular DHCP-assigned address. He wants these two devices to communicate with eachother.

3. Mary uses a name server that makes a .local top-level-domain available, and she upgrades her computer from Edgy to Feisty, where link-local addresses are assigned. She needs notification that the unicast .local TLD and the link-local .local domain conflict with eachother, offering a hint on how to disable link-local assignments.

Scope

Design

Implementation

• basefiles(?) update to include description of link-local network
  • add "link-local 169.254.0.0" to /etc/networks
• dhclient hook for DNS changes to check for unicast "local" TLD

  • if ! host -t soa local. >/dev/null 2>&1; then dbus-msg OMGPONIES; fi

• zeroconf
  • remove package from archive
• libnss-mdns
  • start with version 0.8-5
  • audit and promote to main
  • read debian #393711
    • audit for error conditions around nsswitch.conf updating sanity

  • build package with --disable-legacy (drops ministack)

• network manager
  • patch with proper avahi ll hooks, especially adhoc modes
• avahi-autoipd

  • audit and promote to main (see http://avahi.org/wiki/SecurityConsiderations)

  • require both ll routes, as described in "Routes" at http://avahi.org/wiki/AvahiAutoipd

• avahi-daemon
  • enable by default
• in /etc/network/interfaces add some comments on how to set up manual ll addresses correctly.
• ifupdown, g-s-t
  • patch to include "ipv4ll" method for sane configuration in /etc/network/interfaces

Code

Data preservation and migration

Unresolved issues

BoF agenda and discussion

Clarification of terminology

Zeroconf is a collection of protocols including ipv4 link local, mdns, and dns service-discovery. Apple's implementation of zeroconf was named "Rendezvous", and was later renamed to "Bonjour". Avahi is a free software implementation of zeroconf. See http://avahi.org/wiki/AboutAvahi.

IPv4 link-local addresses are in the 165.254.0.0/16 space.

mDNS is DNS over multicast on the local network.

DNS-sd allows for service discovery using mDNS.

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