This morning I noticed that one of my directory servers has hundreds of "ESTABLISHED" connections from a coworker's Linux host. The directory server is running RHEL4, kernel 2.6.9-55.ELsmp, and tcp_keepalive_time is set to 600. The client no longer shows an ESTABLISHED connection on the port that is reported by netstat on the directory server. It reports less than ten open connections. I'm not sure whether or not an intermediary firewall is doing something bad, but I expected that the directory server would use setsockopt() to set SO_KEEPALIVE on its connections so that it could detect connections that die off. After 600 seconds of inactivity, the server should start sending probes, and then notify ns-slapd that the connection is closed. I'm not sure how I might filter keepalive packets with tcpdump, so I'm not sure if I can verify that they're being used with that tool. Can anyone identify the code that *should* be setting SO_KEEPALIVE on the sockets, or otherwise speculate on why they might not be working?
