I have a http proxy running on Linux (RHEL 5.5), intermittently it doesn't reply [SYN,ACK] packet after received a [SYN] packet from the client. This issue can be recovered by restarting the proxy. I ran the gstack against the proxy process, however the stack of each thread doesn't indicate any problems(hanging). And there were less than 100 connections staying at the "SYN_RECV" state during this issue.
Any ideas? For such issue, where should i start to debug?
Any suggestions would be greatly appreciated.