[FS#635] IPv6 RA provides broken DNS

[LEDE Bugs]

The following task has a new comment added:

FS#635 - IPv6 RA provides broken DNS
User who did this - Hans Dedecker (dedeckeh)

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IPv6 DNS address selection has been reworked as follows :
*First consider all global/ULA IPv6 address having a valid lifetime
*Next give preference to global/ULA IPv6 addresses being not deprecated
*Give preference to ULA IPv6 addresses over IPv6 global addresses
*Give preference to the IPv6 address with the longest preferred lifetime in
its selected category (ULA or global)
*Finally if no global/ULA IPv6 address is present use the IPv6 link local address
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=635#comment2280