The environment variable, EF_INVALID_ACK_RATELIMIT enables Onload support for the Linux
tcp_invalid_ratelimit where the aim is to reduce the number of duplicate ACKs in response packets on an existing connection, but invalid for any of the following reasons:
- out-of-window ACK number
- out-of-window sequence number
- ACK for PAWS check failure.
The rate limit, applied per-socket, is the minimal time gap between sending dupacks.
The default rate is that from /proc/sys/net/ipv4/tcp_invalid_ratelimit.