Ostra is a KernelDevelopment tool created by ArnaldoMelo to track objects in the LinuxKernel. It depends on Sparse.
It was originally created for use in debugging DCCP but has also examples for TCP and can be used for many other purposes.
At the moment (25 Aug 05) Ostra won't compile against Sparse without a patch that LinusTorvalds has not yet committed. ArnaldoMelo has supplied a patch and you can contact him or IanMcDonald for it.
A little bit of bit-rot has set in for Ostra so may not be a good tool to use right now.