[23.05.0-rc2] DHCPV6-PD/PPPoE doesn't work

[emss-github]

Describe the bug

Interface startup or restart establishes the link, the prefix delegations seems correct, but after a while the router stops forwarding ipv6 packets then from time to time forwards again then stops.

The issue seems to be related to odhcp6c as lines like the following pop up in the logs
odhcp6c[xxx]: Server returned IA_PD status 'No Binding (NO-BINDING)'

network config and ifstatus wan6 result are attached, a pcap of the dhcpv6 exchange is available on request.

ifstatus_wan6.txt
network.txt

OpenWrt version

r23228-cd17d8df2a

OpenWrt target/subtarget

x86/64

Device

AZW U59

Image kind

Official downloaded image

Steps to reproduce

No response

Actual behaviour

No response

Expected behaviour

No response

Additional info

No response

Diffconfig

No response

Terms

• I am reporting an issue for OpenWrt, not an unsupported fork.

[emss-github]

Changing wan configuration from :
option ipv6 'auto'
to
option ipv6 '1'
did improve the situation (router forwards ipv6 packets for longer periods before stopping)

[emss-github]

I've gathered further information related to this issue.
One host on the lan is pinging a valid ipv6 address on the outside
2 tcpdump captures are running on the router.
On br-lan interface to get destination unreachable packets sent by the router when it "looses" ipv6 connection.
tcpdump -evni br-lan "icmp6 and ip6[40] = 1"
lan.txt
On pppoe-wan interface to get dhcpv6 & router related multicast packets.
tcpdump -evni pppoe-wan "(icmp6 and (ip6[40] = 134 or ip6[40] = 133)) or (udp port 546 and port 547)"
wan.txt
Last odhcp6c logs
dhcpv6.log
For the record, relevant configuration files (AAAA record filtered by dnsmasq to mitigate the issue)
dhcp.txt
network.txt

[emss-github]

Seems to work fine in 23.05.0-rc3