We are using IPSEC on linux with kernel 2.6.8.1.
We are facing one problem:
We created a TCP association with the peer. We set-up a security association with this IP and port pair and protocol as TCP for a certain duration. After hard life time of Security Association expires, the
kernel switches to another Security Association.
Since we were continuously pumping data on this TCP association, it is possible that the application might be trying to send a data on this TCP association while the kernel was trying to switch to another security association. We noticed that in high load scenario, the Application is not able to send any more Data on same TCP association and
gets error as "Resources not available" for all outgoing Data.
But some other application can send data using the Same newly created security Association.

TCPDUMP shows it tried on new SA but was not able to continue.

You also asked us for the print of the scenario. Could you please let us know on how to enable the kernel level printing so that we could enable them too.

Please help us in getting around of it.
If you know some better person and mailing lists etc. which can provide any help.
Please provide me same also.