forwarding

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

Enable IP forwarding on this interface. This controls whether packets received on this interface can be forwarded.

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

source