Zeroconf is a IETF standard protocol that allows stateless IP autoconfiguration on a network without a DHCP server. RFC RFC 3927 allocates the netblock 169.254/16 for this purposes and RFC RFC 5227 details how the automatic configuration is performed.

This, in turn, can be used to automatically assign IPs in the mesh and could be considered instead of our current policy.

Zeroconf also allows servers to announce services to a local network to alleviate the need for clients to lookup into DNS, search engines or similar directories to find services. For example, Zeroconf can be used to announce a local webserver or chat server on a LAN.

Usage

This fairly new protocol (in Internet history) is well implemented under different platforms.

Avahi automatic IP allocation

This should work on Linux and FreeBSD.

To automatically configure an IP on your interface:

# sudo avahi-autoipd eth0
Found user 'avahi-autoipd' (UID 103) and group 'avahi-autoipd' (GID 111).
Successfully called chroot().
Successfully dropped root privileges.
Starting with address 169.254.6.31
Callout BIND, address 169.254.6.31 on interface eth0
Successfully claimed IP address 169.254.6.31

Above, the Avahi process tried a random IP adress, and tested if it was allocated before assigning it to the interface.

Avahi DNS

Magic DNS! Only works on the "local" network: works over the VPN, but not non-local Babel links.

# apt-get install avahi-utils
# avahi-resolve-address fe80::7cd1:dbff:fea3:8fa6
fe80::7cd1:dbff:fea3:8fa6       phil-ThinkPad-T500-3.local

This can also be added to your nsswitch.conf so that regular DNS lookup routines will use Avahi for lookups:

hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4

References

See the excellent Arch Linux documentation.