Since I changed to Edgerouter X my Ubuntu client has over 350 IPv6 addresses, and gets new ones all the time. Theese are public IPv6, 2601:645:: (Comcast).
I didn't have this problem with the pevious router, I had about 5 public at a time.
What is the problem?
Monday - last edited Monday
Sounds like Ubuntu is just assigning itself lots of addresses. This is pretty normal. Each process can request its own temp IPv6 address or addresses. I forget what it's called, but it's to provide throwaway addresses not tied to the machine's hardware MAC since, as you mention, the addresses are publicly routable.
350 addresses does seem like a lot. however. My Ubuntu box has 8 at the moment.
I know of this concept with requiring new IP-addresses for privacy reasons, hiding the true MAC for the Internet. With my previous router I used to have 5-10 at a time, but since I switched to Edgerouter I have hundreds.
You might want to check your settings in:
# Acceptable values:
# 0 - don’t use privacy extensions.
# 1 - generate privacy addresses
# 2 - prefer privacy addresses and use them over the normal addresses.
net.ipv6.conf.all.use_tempaddr = 0
net.ipv6.conf.default.use_tempaddr = 0