Update: Since writing this entry, Amazon have fixed this bug.
Those that have read my journal long enough may remember my old palmtop which had trouble keeping time. Its clock kept becoming slower and slower due to its age. One of the ways to deal with this was NTP. Then I found a bug that affects my Kindle.
I no longer have my old palmtop, so why am I still running an NTP server? There are a number of reasons. One of the most recent reasons to review Network Time Protocol was when I was researching for my IPv6 entry.
NTP being a protocol that runs over IP can run over either IPv4 or IPv6. Because of its nature it is best to keep routing fast and efficient, and that means using a server close to you. These servers are run over Internet, so no server needed.
All operating systems can act as NTP clients. However, in Ireland there are significantly less servers. Only a handful of them are available over IPv6.
All the more reason to run my own server. This also brings additional benefits. If you run your own server, it means all devices on the network can sync with it. Your whole network will have an equal time.
When a public server goes down, each client will have previously connected to it at different times. They each now have different offsets on the local network.
If you let your own NTP server connect to them, you can let your network clients connect to your server instead. Everything maintains the same time and same offset in the network.
You can use a DHCP option to specify to clients on the network what the address of the private NTP server is. The NTP server can also send out a broadcast message to the local subnet. Both on IPv4 and IPv6.
There is another option that does not require relying on public NTP servers at all. Using a GPS receiver connected to the machine on which the NTP server will run. I still have some research to do. There are a few different GPS constellations today. I need to figure out which is best.
But now, back to DHCP. Remember my Kindle? If you set the DHCP IPv6 NTP option it sends the IP address of the NTP server specified to the client. But then Kindle Oasis is not too happy. It will not connect at all to the Wi-Fi network.
Instead it tells you to contact your ISP. I can just imagine how confused IT support would be. I know I was. Strangely, when setting the same option for IPv4, it works just fine.
This bug also does not affect older Kindles, so it is unlikely to be a bug in dnsmasq. I would like to find a workaround however, but for the moment I will wait for the next Kindle software update. But it is a long shot.
I have been reading on Kindle for 7.5 years now and this is only the second major bug I have come across. And it is a fun and odd bug at that. It is quirks and hacking that got me into computers at the start, so in a way it is a digital reminder of who I once was.