Ulrich Windl wrote:

OK, I don't know about the allowable range of the timeout and the scale of problem you are having, but we had idle connections that were inactive for days or weeks, so we set the timeout to one day. That worked.

Considering that a closed connection may stay around for several seconds, a timeout of 5 seconds seems extremely short to me, however.

Sure, it is short and it was just for my test case, not for production. The original problem was found with 5 minute idle timeout, which we wanted to use for production.

However, I do not see any evidence in the code that it would treat these differently, and what led me to ask here is that I did not manage to spot any code that would set timers that even could expire in idle conditions. I wonder if something else have happening within the one-day mark which then triggers disconnect?

-- Tero ________________________________ From: Ulrich Windl Ulrich.Windl@rz.uni-regensburg.de Sent: Tuesday, December 1, 2020 11:08 To: Tero Saarni tero.saarni@est.tech; openldap-technical@openldap.org openldap-technical@openldap.org Subject: Re: Antw: [EXT] LDAP proxy backend does not drop idle connections

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Tero Saarni tero.saarni@est.tech schrieb am 01.12.2020 um 09:20 in

Nachricht HE1P189MB0491BEEEFFF202642C4145A988F40@HE1P189MB0491.EURP189.PROD.OUTLOOK.COM:

Ulrich Windl wrote:

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It may depend on the version, but for us it worked. How did you check that

it doesn't work?

I have tested by setting up "idassert‑bind" configuration which results in cached connection. I set idle‑timeout to 5 (seconds). I did packet capture

with Wireshark to see that the connection is still up.

OK, I don't know about the allowable range of the timeout and the scale of problem you are having, but we had idle connections that were inactive for days or weeks, so we set the timeout to one day. That worked.

Considering that a closed connection may stay around for several seconds, a timeout of 5 seconds seems extremely short to me, however.

Regards, Ulrich

To test I have executed:

1. execute search from client
2. wait for the duration of idle‑timeout to expire
3. observe from LDAP protocol capture that the connection is still up

Secondly I tested:

1. execute search from client
2. wait for the duration of idle‑timeout to expire
3. execute search from client again
4. observe that unbind and TCP connection tear down happened immediately

after step 3

I also tested that search before idle timeout extends the timeout:

1. execute search from client
2. execute search from client again before idle‑timeout
3. observe that nothing happens
4. execute search after idle‑timeout has passed when measuring the time from

step 2. 5. observe that unbind and TCP connection tear down happened immediately after step 4

I also tried to find the function within back‑ldap code that compares the idle timeout value. This is the only place in the code I found idle timeout

being compared

https://git.openldap.org/openldap/openldap/%E2%80%91/blob/master/servers/sla...

dap/bind.c#L1133 and it is in function ldap_back_getconn(). I attached gdb

to slapd and breakpoint to the function. Debugger shows that it does not seem to get called unless there is activity from client to proxy i.e. not during connection from proxy to remote LDAP remains idle.

I tested only with recent releases and git master, not with very old versions since they are bit harder to compile with modern distros. But I have compared the code from a random historical release. It seems to be the

same as today.

Quanah also replied "back‑ldap likely needs a task to check for idle connections" so I'm bit puzzled if this has worked previously. Maybe ldap_back_getconn() can be called in some other scenario also without having

traffic from client towards the proxy?

‑‑ Tero