[FS#1002] Dns ipv6 problem when interface restart

[LEDE Bugs]

The following task has a new comment added:

FS#1002 - Dns ipv6 problem when interface restart
User who did this - Hans Dedecker (dedeckeh)

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> The only issue I see is that you only get a /64 prefix from your provider. Means, only one network can have IPv6. In your case the prefix is assigned to the guest network instead of the lan. 

Assigning interface priority for prefix delegation in case less prefixes are available then interfaces to which a prefix needs to be delegated; can be done by means of the interface uci parameter ip6weight.
If lan needs to get the highest priority for prefix delegation; set ip6weight as follows:
uci set network.lan.ip6weight=10
uci set network.guest.ip6weight=0

Looking into the wireshark traces the DHCPv6 client requests both a non temporary IPv6 address and an IPv6 prefix; the Tim DHCPv6 server only returns an IPv6 prefix.
It seems the DHCPv6 client is unhappy only an IPv6 prefix is returned as it refuses to send out a DHCPv6 request in response to the received DHCPv6 advertise.
The IPv6 address in use  on the wan6 interfaces is a slaac based IPv6 address based on the received prefix in the RA messages.

Can you check which arguments are passed to the DHCPv6 client when started; eg I would like to see the output of ps -w | grep odhcp6c 
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1002#comment3445