Active socket caching, supported from the Onload 201509 release, means Onload will re-use socket buffers and file descriptors from active-open sockets when an established TCP connection has terminated.
Active-open sockets setting the IP_TRANSPARENT socket option can be cached.
From Onload 201805, socket caching can be enabled for active-open sockets but disabled for passive-open sockets. To do so, set EF_PER_SOCKET_CACHE_MAX to 0.