netstat(1): teach netstat to attach to jails

[dfr]

Summary

Add -j <jail> flag to netstat(1) to allow access to network information
from a jail.

MFC after: 1 week

[dfr]

The code change here is fairly straightforward and brings netstat in line with similar support in ifconfig and route. The manpage change is larger and it would be nice to get a review if possible. I know people are busy this week preparing for the stable/14 branch - I'll leave the review up for another day. If someone has time to give it a review then great, otherwise I'll commit anyway and we can fix any manpage issues as followups.

[freebsd_igalic.co]

late to the party, but the man page is missing a .Dd update.

[dfr]

In D41446#944772, @freebsd_igalic.co wrote:

late to the party, but the man page is missing a .Dd update.

Well spotted, thanks - I've pushed an update.