Multicast DNS
Multicast DNS (mDNS) is a part of Zero Configuration Networking (Zeroconf) and provides the ability to address hosts using DNS-like names without the need of an existing (unicast), managed DNS server.
The project is divided into two phases each with a set of sub-projects. The sub-projects in phase 1 is more or less listed in the order they will be implemented in (they depend on each other), sub-projects in phase 2 is not listed in the same order as they will be implemented.
Quick start - If you want to play with it.
A public mercurial repository with snapshots is available at http://hg.h3q.net/mdns.
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wiki-admin note: as of 20240829 this address does not resolve.
Phase 1
Multicast DNS responder (mdnsd)
Status: Feature complete, requires testing and bugfixing.
This is the core responder daemon, performs multicast dns queries on behalf of clients and acts as a unified cache to all clients. Provides the ability to announce its own mdns records onto the network.
Client API (libmdns)
Status: Working
Provides a easy programming interface to the client side of responderd. Privileges operations include addition/removal of self-claimed records, while non-privileged operations are limited to basic host lookup routines.
NSS module
Status: Complete
Uses libmdns and hooks into the name-service switch system to expose mdns aware-versions of name lookup functions. Implements gethostby{name,name2,addr}, getaddrinfo and ghby{addr,name} (used by getipnodeby{name,addr} and getnameinfo). Configuration file /etc/mdns.conf (similar to resolv.conf) controld the search space. Default is .local and private ip-addresses.
Command line utility
Status: Working
Utility named mdns (or similar) to provide basic host name lookup for debugging purposes and to provide a way to dynamically add and remove self-claimed mdns records. It currently supports resolving names, add/remove/list names and resources and view/flush cache, its feature set is in sync with features provided by libmdns.
Phase 2
Service Discovery integration
Status: Not started (Open task)
Create an application to do both multicast (libmdns) and unicase service discovery. The previous idea with a separate library is probably overkill at the moment.
Avahi library wrapper (mdns_compat_avahi)
Status: Not started (Open task)
A wrapper library around libmdns to allow avahi-aware applications to work with mdns_responderd. It seems most normal avahi consumers performs queries through d-bus so this compat library will probably mimic this interface. The api avahi-core exposes will probably not be covered.
dns_sd library wrapper (mdns_compat_dns_sd)
Status: Not started (Open task)
A wrapper library around libmdns (and possibly libsd) to allow apple dns_sd-aware applications to work with mdns_responderd. The API header (dns_sd.h) is released by Apple under a BSD-license.