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

Send redirects, if router. send_redirects for the interface will be enabled if at least one of conf/{all,interface}/send_redirects is set to TRUE, it will be disabled otherwise Default: TRUE

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