From 6a3450e17844175e68319d0033e99226ca26c337 Mon Sep 17 00:00:00 2001
From: Edward Tomasz Napierala <trasz@FreeBSD.org>
Date: Mon, 26 Jun 2017 13:11:21 +0000
Subject: [PATCH] Add vfs.nfsd.nfsd_enable_uidtostring, which works just like
 vfs.nfsd.nfsd_enable_stringtouid, but in reverse - when set to 1, it forces
 the NFSv4 server to return numeric UIDs and GIDs instead of "user@domain"
 strings. This helps with clients that can't translate returned identifiers,
 eg when rerooting.

The same can be achieved by just never running nfsuserd(8),
but the sysctl is useful to toggle the behaviour back and forth
without rebooting.

Reviewed by:	rmacklem (earlier version)
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D11326
---
 sys/fs/nfs/nfs_commonsubs.c     | 7 ++++---
 sys/fs/nfsserver/nfs_nfsdport.c | 3 +++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/sys/fs/nfs/nfs_commonsubs.c b/sys/fs/nfs/nfs_commonsubs.c
index 3b62ef18af11..5367440bbd83 100644
--- a/sys/fs/nfs/nfs_commonsubs.c
+++ b/sys/fs/nfs/nfs_commonsubs.c
@@ -68,6 +68,7 @@ gid_t nfsrv_defaultgid = GID_NOGROUP;
 int nfsrv_lease = NFSRV_LEASE;
 int ncl_mbuf_mlen = MLEN;
 int nfsd_enable_stringtouid = 0;
+int nfsd_enable_uidtostring = 0;
 NFSNAMEIDMUTEX;
 NFSSOCKMUTEX;
 extern int nfsrv_lughashsize;
@@ -2561,7 +2562,7 @@ nfsv4_uidtostr(uid_t uid, u_char **cpp, int *retlenp, NFSPROC_T *p)
 
 	cnt = 0;
 tryagain:
-	if (nfsrv_dnsnamelen > 0) {
+	if (nfsrv_dnsnamelen > 0 && !nfsd_enable_uidtostring) {
 		/*
 		 * Always map nfsrv_defaultuid to "nobody".
 		 */
@@ -2671,7 +2672,7 @@ nfsrv_getgrpscred(struct ucred *oldcred)
 	cnt = 0;
 	uid = oldcred->cr_uid;
 tryagain:
-	if (nfsrv_dnsnamelen > 0) {
+	if (nfsrv_dnsnamelen > 0 && !nfsd_enable_uidtostring) {
 		hp = NFSUSERHASH(uid);
 		mtx_lock(&hp->mtx);
 		TAILQ_FOREACH(usrp, &hp->lughead, lug_numhash) {
@@ -2823,7 +2824,7 @@ nfsv4_gidtostr(gid_t gid, u_char **cpp, int *retlenp, NFSPROC_T *p)
 
 	cnt = 0;
 tryagain:
-	if (nfsrv_dnsnamelen > 0) {
+	if (nfsrv_dnsnamelen > 0 && !nfsd_enable_uidtostring) {
 		/*
 		 * Always map nfsrv_defaultgid to "nogroup".
 		 */
diff --git a/sys/fs/nfsserver/nfs_nfsdport.c b/sys/fs/nfsserver/nfs_nfsdport.c
index e6380238d1e6..8e4ed0c03277 100644
--- a/sys/fs/nfsserver/nfs_nfsdport.c
+++ b/sys/fs/nfsserver/nfs_nfsdport.c
@@ -87,6 +87,7 @@ static int nfs_commit_miss;
 extern int nfsrv_issuedelegs;
 extern int nfsrv_dolocallocks;
 extern int nfsd_enable_stringtouid;
+extern int nfsd_enable_uidtostring;
 
 SYSCTL_NODE(_vfs, OID_AUTO, nfsd, CTLFLAG_RW, 0, "NFS server");
 SYSCTL_INT(_vfs_nfsd, OID_AUTO, mirrormnt, CTLFLAG_RW,
@@ -103,6 +104,8 @@ SYSCTL_INT(_vfs_nfsd, OID_AUTO, debuglevel, CTLFLAG_RW, &nfsd_debuglevel,
     0, "Debug level for NFS server");
 SYSCTL_INT(_vfs_nfsd, OID_AUTO, enable_stringtouid, CTLFLAG_RW,
     &nfsd_enable_stringtouid, 0, "Enable nfsd to accept numeric owner_names");
+SYSCTL_INT(_vfs_nfsd, OID_AUTO, enable_uidtostring, CTLFLAG_RW,
+    &nfsd_enable_uidtostring, 0, "Make nfsd always send numeric owner_names");
 
 #define	MAX_REORDERED_RPC	16
 #define	NUM_HEURISTIC		1031