System logs filled with "IPv6: MLD: clamping QRV from 1 to 2"

Installing and Using OpenWrt
1

When I use the logread command to check the system logs I can see a lot of messages like this:

I'm using the latest OpenWRT snapshot (from the master branch) with a BPI-R3 board

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Every 6 seconds this log is getting thrown out, when I set the mld_qrv variable manually to 1 using this command sysctl net.ipv6.mld_qrv=1 it seems to go away. But I don't really know the implications of it, is it safe to do that?

My /etc/config/network:

config interface 'loopback'
	option device 'lo'
	option proto 'static'
	option ipaddr '127.0.0.1'
	option netmask '255.0.0.0'

config globals 'globals'
	option ula_prefix 'fdd4:a656:665c::/48'

config device
	option name 'br-lan'
	option type 'bridge'
	list ports 'lan1'
	list ports 'lan2'
	list ports 'lan3'
	list ports 'lan4'
	list ports 'sfp2'

config interface 'lan'
	option device 'br-lan'
	option proto 'static'
	option ipaddr '192.168.1.1'
	option netmask '255.255.255.0'
	option ip6assign '60'

config device
	option name 'br-wan'
	option type 'bridge'
	list ports 'eth1'
	list ports 'wan'

config device
	option name 'eth1'
	option macaddr '4e:7b:37:ba:28:8f'

config device
	option name 'wan'
	option macaddr '4e:7b:37:ba:28:8f'

config interface 'wan'
	option device 'br-wan'
	option proto 'dhcp'
	option metric '10'

config interface 'wan6'
	option device 'br-wan'
	option proto 'dhcpv6'
	option metric '10'

config interface '4G'
	option proto 'qmi'
	option auth 'none'
	option pdptype 'ipv4v6'
	option device '/dev/cdc-wdm0'
	option metric '50'
	option delegate '0'

/etc/config/firewall:

config defaults
	option syn_flood '1'
	option input 'REJECT'
	option output 'ACCEPT'
	option forward 'REJECT'

config zone
	option name 'lan'
	list network 'lan'
	option input 'ACCEPT'
	option output 'ACCEPT'
	option forward 'ACCEPT'

config zone
	option name 'wan'
	option input 'REJECT'
	option output 'ACCEPT'
	option forward 'REJECT'
	option masq '1'
	option masq6 '1'
	option mtu_fix '1'
	list network 'wan'
	list network 'wan6'
	list network '4G'

config forwarding
	option src 'lan'
	option dest 'wan'

config ipset
	option name 'f2bset-v4'
	option family 'ipv4'
	option match 'src_ip'
	option enabled '1'

config ipset
	option name 'f2bset-v6'
	option family 'ipv6'
	option match 'src_ip'
	option enabled '1'

config rule
	option name 'fail2ban-v4'
	option src 'wan'
	option target 'REJECT'
	option proto 'all'
	option family 'ipv4'
	option ipset 'f2bset-v4'

config rule
	option name 'fail2ban-v6'
	option src 'wan'
	option target 'REJECT'
	option proto 'all'
	option family 'ipv6'
	option ipset 'f2bset-v6'

config rule
	option name 'Allow-DHCP-Renew'
	option src 'wan'
	option proto 'udp'
	option dest_port '68'
	option target 'ACCEPT'
	option family 'ipv4'

config rule
	option name 'Allow-Ping'
	option src 'wan'
	option proto 'icmp'
	option icmp_type 'echo-request'
	option family 'ipv4'
	option target 'ACCEPT'

config rule
	option name 'Allow-IGMP'
	option src 'wan'
	option proto 'igmp'
	option family 'ipv4'
	option target 'ACCEPT'

config rule
	option name 'Allow-DHCPv6'
	option src 'wan'
	option proto 'udp'
	option dest_port '546'
	option family 'ipv6'
	option target 'ACCEPT'

config rule
        option name 'Allow-MLD'
        option src 'wan'
        option proto 'icmp'
        option src_ip 'fe80::/10'
        list icmp_type '130/0'
        list icmp_type '131/0'
        list icmp_type '132/0'
        list icmp_type '143/0'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
	option name 'Allow-ICMPv6-Input'
	option src 'wan'
	option proto 'icmp'
	list icmp_type 'echo-request'
	list icmp_type 'echo-reply'
	list icmp_type 'destination-unreachable'
	list icmp_type 'packet-too-big'
	list icmp_type 'time-exceeded'
	list icmp_type 'bad-header'
	list icmp_type 'unknown-header-type'
	list icmp_type 'router-solicitation'
	list icmp_type 'neighbour-solicitation'
	list icmp_type 'router-advertisement'
	list icmp_type 'neighbour-advertisement'
	option limit '1000/sec'
	option family 'ipv6'
	option target 'ACCEPT'

config rule
	option name 'Allow-ICMPv6-Forward'
	option src 'wan'
	option dest '*'
	option proto 'icmp'
	list icmp_type 'echo-request'
	list icmp_type 'echo-reply'
	list icmp_type 'destination-unreachable'
	list icmp_type 'packet-too-big'
	list icmp_type 'time-exceeded'
	list icmp_type 'bad-header'
	list icmp_type 'unknown-header-type'
	option limit '1000/sec'
	option family 'ipv6'
	option target 'ACCEPT'

config rule
	option name 'Allow-IPSec-ESP'
	option src 'wan'
	option dest 'lan'
	option proto 'esp'
	option target 'ACCEPT'

config rule
	option name 'Allow-ISAKMP'
	option src 'wan'
	option dest 'lan'
	option dest_port '500'
	option proto 'udp'
	option target 'ACCEPT'
2

Most likely some multicast client is not v2 capable and it falls back to v1.
The question is if you are using multicast in your network. If not, you had better disable it completely.
Also why is wan interface bridged? This is usually a bad idea.