FD policies offer a configurable way to handle file descriptors that haven't been closed by application. Currently it is possible to forcefully close open sockets, but not reopen them as in the case of FDs pointing to files.

While it does not seem practical to reopen sockets that represent actual connections (because CRaC cannot reconstruct the other side of the connection), a listening socket can be reopened on the same address.

FD policy like this is not intended to be a final solution for the application, but can provide a workaround when POCing the benefit of CRaC.