You should be able to run 'netstat' against a corefile using the -M option. This lets you do things such as display the TCP connections (and the addresses of their associated control blocks).
In FreeBSD-CURRENT, if you run 'netstat -Aan -M <corefile>', it will return output. However, the output is taken from the running system, rather than the coredump. I believe there is no warning that this is the case.
We need to either:
(a) Restore the old behavior (preferred), or
(b) Return an error when a user tries to read from a corefile.
This functionality was broken by r315662 (Hide struct inpcb, struct tcpcb from the userland.) Unfortunately, that change also removed the test of the "live" flag, so it blindly shows connections for the current system rather than from the core file.
Belatedly notify committer of r315662.