Update the nfsv4 man page to reflect recent changes to support

the newer RFCs (5661 and 7530). The main man changes are for the
case of "numbers in strings" for user/groups that RFC7530 allows
and avoids use of nfsuserd(8).

This is a content change.

Reviewed by:	trasz (earlier version)
MFC after:	1 week

usr.sbin/nfsd/nfsv4.4

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 1, 2013
+.Dd July 19, 2017
 .Dt NFSV4 4
 .Os
 .Sh NAME
@@ -34,7 +34,8 @@
 The NFS client and server provides support for the
 .Tn NFSv4
 specification; see
-.%T "Network File System (NFS) Version 4 Protocol RFC 3530" .
+.%T "Network File System (NFS) Version 4 Protocol RFC 7530" and
+.%T "Network File System (NFS) Version 4 Minor Version 1 Protocol RFC 5661" .
 The protocol is somewhat similar to NFS Version 3, but differs in significant
 ways.
 It uses a single compound RPC that concatenates operations to-gether.
@@ -74,6 +75,7 @@ It provides several optional features not present in NFS Version 3:
 - Referrals, which redirect subtrees to other servers
   (not yet implemented)
 - Delegations, which allow a client to operate on a file locally
+- pNFS, where I/O operations are separated from Metadata operations
 .Ed
 .Pp
 The
@@ -115,8 +117,8 @@ multiple server file systems, although not all clients are capable of doing
 this.
 .Pp
 .Nm
-uses names for users and groups instead of numbers.
-On the wire, they
+uses strings for users and groups instead of numbers.
+On the wire, these strings can either have the numbers in the string or
 take the form:
 .sp
 .Bd -literal -offset indent -compact
@@ -136,15 +138,37 @@ Under FreeBSD, the mapping daemon is called
 .Xr nfsuserd 8
 and has a command line option that overrides the domain component of the
 machine's hostname.
-For use of
+For use of this form of string on
 .Nm ,
 either client or server, this daemon must be running.
-If this ``<dns.domain>'' is not set correctly or the daemon is not running, ``ls -l'' will typically
+.Pp
+The form where the numbers are in the strings can only be used for AUTH_SYS.
+To configure your systems this way, the
+.Xr nfsuserd 8
+daemon does not need to be running on the server, but the following sysctls need to be
+set to 1 on the server.
+.sp
+.Bd -literal -offset indent -compact
+vfs.nfs.enable_uidtostring
+vfs.nfsd.enable_stringtouid
+.Ed
+.sp
+On the client, the sysctl
+.sp
+.Bd -literal -offset indent -compact
+vfs.nfs.enable_uidtostring
+.Ed
+.sp
+must be set to 1 and the
+.Xr nfsuserd 8
+daemon does not need to be running.
+.Pp
+If these strings are not configured correctly, ``ls -l'' will typically
 report a lot of ``nobody'' and ``nogroup'' ownerships.
 .Pp
 Although uid/gid numbers are no longer used in the
 .Nm
-protocol, they will still be in the RPC authentication fields when
+protocol except optionally in the above strings, they will still be in the RPC authentication fields when
 using AUTH_SYS (sec=sys), which is the default.
 As such, in this case both the user/group name and number spaces must
 be consistent between the client and server.
@@ -156,24 +180,24 @@ will go on the wire.
 .Sh SERVER SETUP
 To set up the NFS server that supports
 .Nm ,
-you will need to either set the variables in
+you will need to set the variables in
 .Xr rc.conf 5
 as follows:
 .sp
 .Bd -literal -offset indent -compact
 nfs_server_enable="YES"
 nfsv4_server_enable="YES"
+.Ed
+.sp
+plus
+.sp
+.Bd -literal -offset indent -compact
 nfsuserd_enable="YES"
 .Ed
 .sp
-or start
-.Xr mountd 8
-and
-.Xr nfsd 8
-without the ``-o'' option, which would force use of the old server.
-The
-.Xr nfsuserd 8
-daemon must also be running.
+if the server is using the ``<user>@<domain>'' form of user/group strings or
+is using the ``-manage-gids'' option for
+.Xr nfsuserd 8 .
 .Pp
 You will also need to add at least one ``V4:'' line to the
 .Xr exports 5
@@ -232,7 +256,7 @@ plus set ``tcp'' and
 .Pp
 The
 .Xr nfsuserd 8
-must be running, as above.
+must be running if name<->uid/gid mapping is being used, as above.
 Also, since an
 .Nm
 mount uses the host uuid to identify the client uniquely to the server,
@@ -255,7 +279,7 @@ daemon to handle client side callbacks.
 This will occur if
 .sp
 .Bd -literal -offset indent -compact
-nfsuserd_enable="YES"
+nfsuserd_enable="YES"	<-- If name<->uid/gid mapping is being used.
 nfscbd_enable="YES"
 .Ed
 .sp
@@ -265,7 +289,7 @@ are set in
 Without a functioning callback path, a server will never issue Delegations
 to a client.
 .sp
-By default, the callback address will be set to the IP address acquired via
+For NFSv4.0, by default, the callback address will be set to the IP address acquired via
 rtalloc() in the kernel and port# 7745.
 To override the default port#, a command line option for
 .Xr nfscbd 8
@@ -282,6 +306,10 @@ N.N.N.N.N.N
 where the first 4 Ns are the host IP address and the last two are the
 port# in network byte order (all decimal #s in the range 0-255).
 .Pp
+For NFSv4.1, the callback path (called a backchannel) uses the same TCP connection as the mount,
+so none of the above applies and should work through gateways without
+any issues.
+.Pp
 To build a kernel with the client that supports
 .Nm
 linked into it, the option