Hi. I use ESX 6.5.
When I added datastore via NFSv3 or NFSv4 protocol I got a lot of RST packets from ESX due to NFS server didn't answer on keepalive TCP messages that was previously sent by ESX.
Investigation shown that ESX was sending keepalive TCP message without TSopt, but connection was initiated with timestamp.
This behaviour does not conform to RFC7323:
Once TSopt has been successfully negotiated, that is both <SYN>
and <SYN,ACK> contain TSopt, the TSopt MUST be sent in every non-<RST>
segment for the duration of the connection, and SHOULD be sent in
an <RST> segment (see Section 5.2 for details). The TCP SHOULD
remember this state by setting a flag, referred to as Snd.TS.OK,
to one. If a non-<RST> segment is received without a TSopt, a TCP SHOULD
silently drop the segment. A TCP MUST NOT abort a TCP connection
because any segment lacks an expected TSopt.