After installing 21.02-RC3, I found that my browsing experience was miserable, on both wireless and wired connections. There were large delays in displaying content and many sites completely failed. After some investigations, I found that the issue appeared to be with DNS and in particular with DNS over IPv6. DNS over IPv4 is fine.
As a workaround, I disabled the WAN6 interface, and performance was great again. I'm still using IPv6 internally, but not externally.
Are there any commands that I can execute to provide further information? I am comfortable in the CLI but not expert.
What I see from ip addr
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
link/ether 60:e3:27:c8:4a:11 brd ff:ff:ff:ff:ff:ff
inet xxx.xxx.120.28/18 brd xxx.xxx.127.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 xxxx:xxxx:c002::1:b923/128 scope global dynamic noprefixroute
valid_lft 3586sec preferred_lft 3586sec
inet6 fe80::62e3:27ff:fec8:4a11/64 scope link
valid_lft forever preferred_lft forever
from Luci
Protocol: DHCPv6 client
Uptime: 0h 0m 18s
MAC: 60:E3:27:C8:4A:11
RX: 326.29 MB (44339348 Pkts.)
TX: 2.76 GB (20814158 Pkts.)
IPv6: xxxx:xxxx:c002::1:b923/128
IPv6-PD: xxxx:xxxx:c802:9c2a::/64
What I suspect is the issue: my ISP is providing short Valid and Preferred IPv6 lifetimes. The Valid lifetime is the same as Preferred, when Valid should be twice the Preferred lifetime.
This interacts with changes to odhcpd for 21.02-RC3 regarding the lifetime of IPv6 addresses and leases. All IPv6 addresses, both externally routed and internal fda6:xxx addresses on the internal network are given mostly 30 mins leases, occasional 60 mins leases, and occasionally no IPv6 leases is allocated at all.
After disabling the WAN6 interface, all devices are given 14d leases on the fda6:xxxx addresses.
The ISP (in Singapore) provides no means to report this issue - surprise, surprise.