[Kea-users] dhcp6 and ntp-server, version 3.0.3

[Karl Gaissmaier]

Hi Darren,

I've been experimenting with *dnsmasq*, and this DHCPv6 server packs 
multiple sub-option1 entries into a single option-56, and the *dhcpcd* 
client then recognizes both NTP servers:

dnsmasq.conf:
> dhcp-option=option6:dns-server,[2001:db8::77],[2001:db8::88]
> dhcp-option=option6:ntp-server,[2001:db8::33],[2001:db8::44]


tshark -V:
>     NTP Server
>         Option: NTP Server (56)
>         Length: 40
>         NTP Server Address
>             Suboption: NTP Server Address (1)
>             Length: 16
>             NTP Server Address: 2001:db8::33
>         NTP Server Address
>             Suboption: NTP Server Address (1)
>             Length: 16
>             NTP Server Address: 2001:db8::44
>     DNS recursive name server
>         Option: DNS recursive name server (23)
>         Length: 32
>          1 DNS server address: 2001:db8::77
>          2 DNS server address: 2001:db8::88


dhcpcd-lease.dump:
> reason=BOUND6
> interface=vlan351
> protocol=dhcp6
> dhcp6_client_id=0001000131510f2c001b21bc2db7
> dhcp6_server_id=00010001318b40e6001b21bc2db7
> dhcp6_ia_na1_iaid=ff00015f
> dhcp6_ia_na1_t1=1800
> dhcp6_ia_na1_t2=3150
> dhcp6_ia_na1_ia_addr1=2001:db8:3101:1a03::ba96
> dhcp6_ia_na1_ia_addr1_pltime=3600
> dhcp6_ia_na1_ia_addr1_vltime=3600
> dhcp6_status_code=0
> dhcp6_status_code_message=success
> dhcp6_ntp_server_addr=2001:db8::33
> dhcp6_ntp_server_addr=2001:db8::44
> dhcp6_name_servers=2001:db8::77 2001:db8::88
> dhcp6_fqdn_flags=S
> dhcp6_fqdn=vlan351

*dnsmasq* currently cannot return more than one option-56, which 
contradicts RFC 5908.

It would be interesting to see how the systemd-networkd DHCP client 
handles this.
I’ll try to figure that out in another test setup.

It would also be interesting to see how other operating systems, such as 
macOS and Windows 11, handle this option-56.

Best regards
    Charly