rc.d: add a service jails config to all base system services

This gives more permissions to services (e.g. network access to
services which require this) when they are started as an automatic
service jail.

The sshd patch is important for the sshd-related functionality as
described in the man-page in the service jails part.

The location of the added env vars is supposed to allow overriding them
in rc.conf, and to hard-disable the use of svcj for some parts where it
doesn't make sense or will not work.

Only a subset of all of the services are fully tested (I'm running this
since more than a year with various services started as service jails).
The untested parts should be most of the time ok, in some edge-cases
more permissions are needed inside the service jail.
Differential Revision: https://reviews.freebsd.org/D40371

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

rc.d: Fix NFS server startup scripts to enable vnet prison use

Now that commit cbbb22031f9b is in main,
it is possible to run nfsd(8), nfsuserd(8), mountd(8),
gssd(8) and rpc.tlsservd(8) in an appropriately configured vnet
prison if the "allow.nfsd" option is specified in jail.conf.

This patch fixes the rc scripts for this.
Mostly just replaces the "nojail" KEYWORD with "nojailvnet",
but also avoids setting vfs.nfsd.srvmaxio in a prison, since it
must be set outside of the prisons and applies to all
nfsd(8) instances.

Reviewed by: jamie
MFC after: 3 months
Differential Revision: https://reviews.freebsd.org/D38809

mountd startup: enable NFSv4 if needed on restart

The mountd script in rc.d sets vfs.nfsd.server_max_nfsvers correctly
when it is run at system startup, relying on the kernel default.
However, if NFSv4 was enabled in /etc/rc.conf later, and the script
was re-run to restart mountd, the sysctl was still set to 3.
Set the sysctl to the right value in all cases.

Reviewed by: rmacklem
MFC after: 1 week

mountd: Delay starting mountd until after mountlate

PR#254282 reports a problem where nullfs mounts cannot be
exported via mountd for FreeBSD 13.0.

The problem seems to be that, to do the nullfs mounts in
/etc/fstab, they require the "late" mount option, so that the
underlying filesystem is mounted (ZFS for the PR).

Adding "mountlate" to the REQUIRE list in /etc/rc.d/mountd
fixes the problem, but that results in a dependency cycle
because /etc/rc.d/lockd specifies:

REQUIRE: nfsd
BEFORE: DAEMON
--> which forces mountd to preceed DAEMON.

This patch removes "nfsd" from REQUIRE for lockd and statd,
then adds mountlate to REQUIRE for mountd, to fix this
problem. Having lockd REQUIRE nfsd was done in the NetBSD
code when it was pulled into FreeBSD and there does not
seem to be a need for this.

In case this causes problems, a long MFC has been specified.

PR: 254282
Differential Revision: https://reviews.freebsd.org/D33256
MFC after: 3 months

mountd(8): generate a syslog message when the "V4:" line is missing

Daniel reported that NFSv4 mounts were not working despite having
set "nfsv4_server_enable=YES" in /etc/rc.conf. Mountd was logging a
message that there was no /etc/exports file.
He noted that creating a /etc/exports file with a "V4:" line in it
was needed make NFSv4 mounts work.
At least one "V4:" line in one of the exports(5) file(s) is needed to
make NFSv4 mounts work. This patch fixes mountd.c so that it logs a
message indicting that there is no "V4:" line in any exports(5)
file when NFSv4 mounts are enabled.
To avoid this message being generated erroneously, /etc/rc.d/mountd
is updated to make sure vfs.nfsd.server_max_nfsvers is properly set
before mountd(8) is started.

Reported by: debdrup
PR: 253901
MFC after: 2 weeks

Add support for the new mountd -R option.

r376026 added a new "-R" option to mountd, which tells it to
not support the Mount protocol (not used by NFSv4) and not
register with rpcbind.
Rpcbind is considered a security issue by some sites now.

This patch adds a new yes/no variable called nfsv4_server_only.
When that is set, make vfs.nfsd.server_min_vers=4 and set "=R"
for mountd.
Setting vfs.nfsd.server_min_vers=4 tells nfsd to not register with rpcbind.
While here, add a check for "load_kld nfsd" failing to nfsd.

Reviewed by: 0mp
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D26938

Move the rc framework out of sbin/init into libexec/rc.

The reasons for this are forward looking to pkgbase:
* /sbin/init is a special binary; try not to replace it with
every package update because an rc script was touched.
(a follow-up commit will make init its own package)
* having rc in its own place will allow more easy replacement
of the rc framework with alternatives, such as openrc.

Discussed with: brd (during BSDCam), kmoore
Requested by: cem, bz
PR: 231522
Approved by: re (gjb)