I had the same problem with pidentd and found that it apparently tries to use a NETLINK-socket with "protocol" NETLINK_TCPDIAG, probably to inquire about the "owners" of tcp connections. For this to work, the kernel needs to have CONFIG_IP_TCPDIAG, called "IP: TCP socket monitoring interface" in the networking options section of the kernel configuration. I had configured that as a module, not knowing what it was needed for; obviously it does not load automatically on demand, but after loading it manually, the error with pidentd is gone.
Regards, Daniel
