[FS#1379] IPv6 DNS setting Problem

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - PaTTeeL (PaTTeeL) 

Attached to Project - OpenWrt/LEDE Project
Summary - IPv6 DNS setting Problem
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - Software versions : Linux version 4.9.82 (buildbot at slashdirt-02) (gcc version 5.5.0 (OpenWrt GCC 5.5.0 r6194-138c763) ) #0 Mon Feb 19 22:54:38 2018
Device : WZR HP G300NH2 and PHICOMM K3

BUG : Can't set IPv6's DNS to Customized Server

I've set the IPv6 DNS to "2001:4860:4860::8888", but in Status->Overview , "IPv6 WAN Status"	still shows 
"pppoe-wan 	Type: dhcpv6-pd
Prefix Delegated: 240e:f2:xxxx:xxxx::/60
Address: 240e:f2:c01c:a9e:xxxx:xxxx:xxxx:xxxx/64
Gateway: fe80::e224:xxxx:xxxx:772
DNS 1: 240e:1c:200::1
DNS 2: 240e:1c:200::2
Connected: 11h 55m 17s"

cat /etc/config/network :
config interface 'loopback'
        option ifname 'lo'
        option proto 'static'
        option ipaddr '127.0.0.1'
        option netmask '255.0.0.0'

config globals 'globals'

config interface 'lan'
        option type 'bridge'
        option ifname 'eth0.1'
        option proto 'static'
        option ipaddr '192.168.1.1'
        option netmask '255.255.255.0'
        option ip6assign '64'
        option dns '8.8.8.8 8.8.4.4'

config interface 'wan'
        option ifname 'eth0.2'
        option _orig_ifname 'eth0.2'
        option _orig_bridge 'false'
        option proto 'pppoe'
        option username 'xxxxxxxx'
        option password 'xxxxxxxx'
        option ipv6 'auto'
        option dns '8.8.8.8 8.8.4.4'

config interface 'wan6'
        option ifname 'eth0.2'
        option proto 'dhcpv6'
        option reqaddress 'try'
        option reqprefix 'auto'
        option peerdns '0'
        option dns '2001:4860:4860::8888 2001:4860:4860::8844'

config switch
        option name 'switch0'
        option reset '1'
        option enable_vlan '1'

config switch_vlan
        option device 'switch0'
        option vlan '1'
        option ports '1 3 4 5 0t'

config switch_vlan
        option device 'switch0'
        option vlan '2'
        option ports '2 0t'

Here's IPv4 WAN Status	:

pppoe-wan 	Type: pppoe
Address: 122.232.xxx.xxx
Netmask: 255.255.255.255
Gateway: 122.232.xxx.xxx
DNS 1: 8.8.8.8
DNS 2: 8.8.4.4
DNS 3: 220.189.127.106
DNS 4: 220.189.127.107
Connected: 11h 58m 29s   

cat /etc/config/dhcp shows:
config dnsmasq
        option domainneeded '1'
        option boguspriv '1'
        option filterwin2k '0'
        option localise_queries '1'
        option rebind_protection '1'
        option rebind_localhost '1'
        option local '/lan/'
        option domain 'lan'
        option expandhosts '1'
        option nonegcache '0'
        option authoritative '1'
        option readethers '1'
        option leasefile '/tmp/dhcp.leases'
        option resolvfile '/tmp/resolv.conf.auto'
        option nonwildcard '1'
        option localservice '1'

config dhcp 'lan'
        option interface 'lan'
        option start '100'
        option limit '150'
        option leasetime '12h'
        option ra 'hybrid'
        option dhcpv6 'hybrid'
        option ra_management '1'

config dhcp 'wan'
        option interface 'wan'
        option ignore '1'

config odhcpd 'odhcpd'
        option maindhcp '0'
        option leasefile '/tmp/hosts/odhcpd'
        option leasetrigger '/usr/sbin/odhcpd-update'
        option loglevel '4'


More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1379