file: /proc/sys/net/ipv6/conf/interface/accept_ra_from_local
variable: net.ipv6.conf.interface.accept_ra_from_local
Official reference

Accept RA with source-address that is found on local machine if the RA is otherwise proper and able to be accepted. Default is to NOT accept these as it may be an un-intended network loop.

Functional default: enabled if accept_ra_from_local is enabled on a specific interface. disabled if accept_ra_from_local is disabled on a specific interface.

Nb: per interface setting (where “interface” is the name of your network interface); “all” is a special interface: changes the settings for all interfaces.