Hey everyone!
I have a practical enhancement proposal for you to consider.
What should be changed?
(*) Dhcp-server static-mapping for 'ip-address' FROM [REQUIRED] TO [OPTIONAL]
# set service dhcp-server shared-network-name <NAME> subnet <SUBNET> static-mapping <HOST> [TAB] Possible completions: [...] ip-address Static mapping for specified IP address [REQUIRED] <-- change to: [OPTIONAL] mac-address Static mapping for specified MAC address [REQUIRED]
What would this change accomplish?
The dhcp static-mapping function in VyOS requires both 'ip-address' and 'mac-address', where the host{} declaration in ISC-DHCP server, to which this is "translated", only requires a 'hardware ethernet' (mac-address). The omitted 'fixed-address' is then dynamically assigned from the 'range' of IPs available in the subnet pool [1].
Why should we care?
Many IoT/Smart-Home devices rely on a dhcp server, but send "unfriendly" client hostnames and working around this to have a "clean" dns resolution for clients like:
- android-ed27272ab14acf44 --> TABLET
- amazon-acc8xdsfs --> FIRETV
- camera-12432XXwq --> IPCAM1
- yeelink-light-strip1_miio77908737 --> LICHT3
means either you have to change the client's hostname(often not trivial or even possible) or set a static mapping for the device!!
Dhcp static-mapping is the only viable option, but in VyOS you have to also manually assign a static IP address for every single one of those devices, just to get rid of the "unfriendly" client hostnames - even if you simply don't care what IP addresses they get assigned.
Why is this a hassle?
Scenario:
(1) Pick up a new IP-Camera, Smart-Lights, HA-Sensor, Android Tablet, etc... (2) Look up the HW/MAC-Address (usually on the back of the device/packaging) (3) vyos# set service dhcp-server shared-network-name LAN subnet 192.168.1.0/24 static-mapping TABLET mac-address 'AA:BB:CC:DD:EE:FF' (4) vyos# set service dhcp-server shared-network-name LAN subnet 192.168.1.0/24 static-mapping TABLET ip-address '192.168.1.155' (5) <DONE> ($> ping TABLET | adb connect TABLET | nslookup TABLET |...)
But the mandatory <ip-address> (step (4) above) requires you to search for a free IP address outside of your dhcp subnet range.
With a significant and growing number of static hosts and IoT-Devices inside your LAN this becomes more and more a tedious job.
To prevent IP address collisions you must maintain a list of mapped/assigned IP addresses. That's not practical at all!
Could this change lead to a potential regression or even break VyOS?
I don't think so, because:
- a host declaration like 'host TABLET { hardware ethernet 'AA:BB:CC:DD:EE:FF'; }' in dhcpd.conf is perfectly valid (see below [1])
- it should be a minimum effort job, which requires only a small modification of the existing code - no extensive rewrite is needed
- no need for special care of config migration scripts, since older Vyatta Core versions are no longer supported [2]
I think this could be considered a significant improvement for home and small office environments, where keeping track of statically assigned IPs for IoT/Smart-Devices is not desirable or practical.
Thank you all for the great work!
Cheers,
krassle
[1] https://kb.isc.org/docs/isc-dhcp-44-manual-pages-dhcpdconf
The host statement
...
The host declaration provides a way for the DHCP server to identify a DHCP or BOOTP client.
[...] The host declarations will only match a client if one of their fixed-address statements is viable on the subnet (or shared network) where the client is attached.
Conversely, for a host declaration to match a client being allocated a dynamic address, it must not have any fixed-address statements. [...]
[2] https://github.com/vyos/vyos-1x/commit/4c070a73a3fac283f5ab8ca679bc1ac191565ef6