Vector of 3 integers: min, default, max.

• min - minimal size of receive buffer used by TCP sockets. It is guaranteed to each TCP socket, even under moderate memory pressure. The default value is 4096 bytes.
• default - default size of receive buffer used by TCP sockets. This value overrides rmem_default used by other protocols. The default value is 87380 bytes. This value results in window of 65535 with default setting of tcp_adv_win_scale and tcp_app_win is 0, and a bit less for default tcp_app_win.
• max - maximal size of receive buffer allowed for automatically selected receiver buffers for TCP socket. This value does not override rmem_max, "static" selection via SO_RCVBUF does not use this. The default value is 4194304 bytes.