Sockets stuck at FIN_WAIT_1/2

[Michael D'Aulerio]

Does anyone know of a good resource that explains the various states of socket connections as reported by nestat?

I have a system running HP-UX 10.20 that is connected to a PC running Red Hat Linux. Our system sets up a socket connection to a process running on the Linux box. When the network connection is broken or the Linux system is rebooted, the socket on the HP-UX side goes to FIN_WAIT_1 and then FIN_WAIT_2 and doesn't always close. Sometimes we have a bunch of sockets at FIN_WAIT.

I need to get a better understanding of how HP-UX handles sockets and whether there are any kernel parameters that control the behavior.
Thanks for any help.

Mike

[Steve Steel · Accepted solution]

Hi


see man nettune to
modify certain kernel parameters that control networking defaults
such as keepalive timers.

Nettune is found in /usr/contrib/bin.

type: "nettune -h" for help
type: "nettune -l" to display current values



To set the keepalive start time to 60 seconds type:
"nettune -s tcp_keepstart 60"

To set the keepalive frequency to sending every 10 second type:
"nettune -s tcp_keepfreq 10"

To set the keepalive stop time to 3 minutes type:
"nettune -s tcp_keepstop 180"

For help on these three variables type:
"nettune -h tcp_keepstart"
"nettune -h tcp_keepfreq"
"nettune -h tcp_keepstop"


Steve Steel

[Muthukumar_5]

You can know the socket connections report on netstat over at,
http://support.microsoft.com/default.aspx?scid=kb;en-us;q137984 (it is from ms :) )
or see linux man netstat.8 man page

After data transactions,

After connection setup from HP-UX client to Linux server data's transaction are made. After it's completion,
Hp-ux client sends a active close(FIN) to server as (FIN_WAIT_1) and server goes to passive close (CLOSE_WAIT) to make active close. It sends ACK to FIN_WAIT_1. After getting this acknowledgement client went to FIN_WAIT_2 stage to get the postive close from server. Until that client is at TIMED_WAIT stage. After successful active close on server, server sends LAST_ACK (FIN) to the client. After recieving this client sends CLOSED message (ACK) to server

To avoid to get FIN_WAIT_2 state of sockets use, setsockopt() with SO_KEEPALIVE option to keep tcp connection alive.
To make finite timeout to get LAST_ACK from server then tune tcp_fin_wait_2_timeout parameter with ndd

by default ndd -h tcp_fin_wait_2_timeout will be infinite. Change to your requirement.

Regards
MuthuYou can know the socket connections report on netstat over at,
http://support.microsoft.com/default.aspx?scid=kb;en-us;q137984 (it is from ms :) )
or see linux man netstat.8 man page

After data transactions,

After connection setup from HP-UX client to Linux server data's transaction are made. After it's completion,
Hp-ux client sends a active close(FIN) to server as (FIN_WAIT_1) and server goes to passive close (CLOSE_WAIT) to make active close. It sends ACK to FIN_WAIT_1. After getting this acknowledgement client went to FIN_WAIT_2 stage to get the postive close from server. Until that client is at TIMED_WAIT stage. After successful active close on server, server sends LAST_ACK (FIN) to the client. After recieving this client sends CLOSED message (ACK) to server

To avoid to get FIN_WAIT_2 state of sockets use, setsockopt() with SO_KEEPALIVE option to keep tcp connection alive.
To make finite timeout to get LAST_ACK from server then tune tcp_fin_wait_2_timeout parameter with ndd

by default ndd -h tcp_fin_wait_2_timeout will be infinite. Change to your requirement.

Regards
Muthu

[Michael D'Aulerio]

Steve & Muthu,

Thanks you both for the information. I have quite a lot to work with now. I'm going to defer assigning points til I go through the info you provided, but you both get somewhere from 7-10.

Mike D'.

[Dave Olker]

Hi Mike,

My friend and colleague Pat Kilfoyle recently put together a presentation on Network Troubleshooting, and part of the presentation was to document the various TCP connection states and how connections transition from one state to another state.

I've stripped out the 4 slides that detailed the connection states and how/why they transition between them into the attached .PDF file.

Hope this helps,

Dave

[Paul Thomson_2]

Dave , that document is very good.

Mike, we once had this problem on HPUX 10.20 , to close these FIN_WAIT_2 we added patch PHNE_19936 and in /sbin/init.d/net added the line

/usr/contrib/bin/nettune -s tcp_fin_wait_timer 675

This will clear the statuses (normally) without reboot

Thanks
Paul

[Michael D'Aulerio]

Excellent info from all of you.

Dave, you must be running on an 800 series. We run on a HP744. The latest equivalent 700 series patch is PHNE_22506.

Muthu, I couldn't find the ndd command (must be for 11.x). I'm trying the nettune command as Steve and Dave suggested.

Thank you all again.