Onload 201811 implements the Early Retransmit (RFC 5827) algorithm for TCP, and also the Limited Transmit (RFC 3042) algorithm, on which Early Retransmit depends. As for tail-drop probes, the purpose of these algorithms is to allow fast retransmissions to happen more readily. The use of these algorithms is controlled by the following environment variable:
The default value is read from the kernel configuration at /proc/sys/net/ipv4/tcp_early_retrans.
For more information, see EF_TCP_EARLY_RETRANSMIT.