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Hi, Not sure if this post should be here or the kernel forum. Let me know. I'm developing a simple TCP server. 99% of incoming connections terminate correctly and the ...
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- 07-17-2009 #1
- Join Date
- Jul 2009
Connections stuck in FIN_WAIT2 for days
Not sure if this post should be here or the kernel forum. Let me know.
I'm developing a simple TCP server. 99% of incoming connections terminate correctly and the sockets disappear from netstat output. However, a few connections hang around for indefinitely in the FIN_WAIT2 state. Now, I know that the clients in this case are misbehaving by not sending a FIN,ACK to close the connection. However, regardless of client behaviour, the connections should only remain in this state for a maximum of 60 seconds (set globally by /proc/sys/net/ipv4/tcp_fin_timeout)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Timer tcp 0 0 10.0.0.12:2000 10.0.0.6:50990 FIN_WAIT2 9507/perl off (0.00/0/0) tcp 0 0 10.0.0.12:2000 10.0.0.6:57896 FIN_WAIT2 7247/perl off (0.00/0/0) tcp 0 0 10.0.0.12:2000 10.0.0.6:60683 FIN_WAIT2 6835/perl off (0.00/0/0)
tcp_fin_timeout (integer; default: 60) This specifies how many seconds to wait for a final FIN packet before the socket is forcibly closed. This is strictly a violation of the TCP specifica- tion, but required to prevent denial-of-service attacks. In Linux 2.2, the default value was 180.
I'm running RHEL 5.3 with 2.6.18-128.1.6.el5.PAE (i386) as my kernel.
Is there anything I can do to find out why these connections are not being forcibly closed by the kernel? Why are these connections NOT being timed?