file: /proc/sys/net/ipv4/conf/interface/accept_local
variable: net.ipv4.conf.interface.accept_local
Official reference

Accept packets with local source addresses. In combination with suitable routing, this can be used to direct packets between two local interfaces over the wire and have them accepted properly. default FALSE

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