file: /proc/sys/net/ipv4/tcp_orphan_retries
variable: net.ipv4.tcp_orphan_retries
Official reference

This value influences the timeout of a locally closed TCP connection, when RTO retransmissions remain unacknowledged. See tcp_retries2 for more details.

The default value is 8. If your machine is a loaded WEB server, you should think about lowering this value, such sockets may consume significant resources. Cf. tcp_max_orphans.