https://github.com/cnlohr/minimdnsd
Simple, dependency-less, and low-overhead MDNS server for Linux
https://github.com/cnlohr/minimdnsd
mdns
Last synced: about 1 month ago
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Simple, dependency-less, and low-overhead MDNS server for Linux
- Host: GitHub
- URL: https://github.com/cnlohr/minimdnsd
- Owner: cnlohr
- License: mit
- Created: 2024-06-01T04:59:04.000Z (over 1 year ago)
- Default Branch: master
- Last Pushed: 2024-10-26T05:06:57.000Z (12 months ago)
- Last Synced: 2025-08-23T10:31:54.626Z (about 2 months ago)
- Topics: mdns
- Language: C
- Homepage:
- Size: 72.3 KB
- Stars: 74
- Watchers: 3
- Forks: 3
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# minimdnsd (MDNS server)
Extremely simple MDNS server for Linux. Much smaller and lighter weight than Avahi.
⚠️ This has not been battle hardened, or even thoroughly checked ⚠️
Primarily MDNS Hostname responder - i.e. run this, and any computer on your network can say `ping your_hostname.local` and it will resolve to your PC. Specifically, it uses whatever name is in your `/etc/hostname`
* Uses no CPU unless event requested.
* Only needs around 32kB RAM.
* Compiles to between 15-45kB
* Can run as a user or root.
* Zero config + Watches for `/etc/hostname` changes. (Optionally: Can use -h to also watch for a host alias)
* Works on IPv6
⚠️ Caveats ⚠️
* This tool only replies to hostnames, so you can use `hostname.local` but not services, so you can't use it to find your printer.
* This tool automatically perform both a `UNICAST-RESPONSE` and `MULTICAST-RESPONSE` - whether true or not.
## General Motivation
1. To obviate need for avahi-daemon
2. To provide an MDNS server on very simple systems
3. To act as an educational tool for the following items
### To demonstrate the following:
1. Use of inotify to detect changes of `/etc/hostname`
2. Use of `getifaddrs` to iterate through all available interfaces
3. Use of `NETLINK_ROUTE` and `RTMGRP_IPV4_IFADDR` and `RTMGRP_IPV6_IFADDR` to monitor for any new network interfaces or addresses.
4. Use of multicast in IPv4 and IPv6 to join a multicast group
5. Use of `recvmsg` to get the interface and address that a UDP packet is received on
6. Use of `optarg` to handle command-line parameters.
7. Use of `fork()` and `wait3()` to handle workers. (Only used in DNS forwarding mode)
### And for general housekeeping:
7. Use of github workflows to build and test tool on Linux
8. Makefile example for building .deb files
9. Github workflow example for generating releases on new tags.
10. How to use/install a basic man page
## Building
### Prerequisits
* build-essential (make + GCC + system headers)
### Build process
* `make`
* or, optionally `make install` to install it to /usr/local/bin/minimdnsd, and install the initd service
## Long-Term
* Allow response to services (see original MDNS server here: https://github.com/cnlohr/esp82xx/blob/master/fwsrc/mdns.c)
* Keep it under or around 1k LoC
* Keep it < 32kB `.text`
## Things I learned
IPv6 is pain. this would have been a tiny fraction of its size if it weren't for IPv6.
Also IPv6 with MDNS is in a really sorry state, so I was barely able to test this with IPv6.
https://superuser.com/questions/1086954/how-do-i-use-mdns-for-ssh-6
And ping6 has a similar issue.
### Thanks
For code reviews: @GPSBabelDeveloper, @probonopd