diff --git a/sys/fs/nfsclient/nfs_clport.c b/sys/fs/nfsclient/nfs_clport.c
index 8ea50d80ae1..c0318b692d8 100644
--- a/sys/fs/nfsclient/nfs_clport.c
+++ b/sys/fs/nfsclient/nfs_clport.c
@@ -264,10 +264,10 @@ nfscl_nget(struct mount *mntp, struct vnode *dvp, struct nfsfh *nfhp,
 
 	np->n_fhp = nfhp;
 	/*
-	 * For NFSv4, we have to attach the directory file handle and
+	 * For NFSv4.0, we have to attach the directory file handle and
 	 * file name, so that Open Ops can be done later.
 	 */
-	if (nmp->nm_flag & NFSMNT_NFSV4) {
+	if (NFSHASNFSV4(nmp) && !NFSHASNFSV4N(nmp)) {
 		np->n_v4 = malloc(sizeof (struct nfsv4node)
 		    + dnp->n_fhp->nfh_len + cnp->cn_namelen - 1, M_NFSV4NODE,
 		    M_WAITOK);
diff --git a/sys/fs/nfsclient/nfs_clrpcops.c b/sys/fs/nfsclient/nfs_clrpcops.c
index 14351d915ba..2276e09f6e7 100644
--- a/sys/fs/nfsclient/nfs_clrpcops.c
+++ b/sys/fs/nfsclient/nfs_clrpcops.c
@@ -392,16 +392,6 @@ nfsrpc_open(vnode_t vp, int amode, struct ucred *cred, NFSPROC_T *p)
 	nfhp = np->n_fhp;
 
 	retrycnt = 0;
-#ifdef notdef
-{ char name[100]; int namel;
-namel = (np->n_v4->n4_namelen < 100) ? np->n_v4->n4_namelen : 99;
-bcopy(NFS4NODENAME(np->n_v4), name, namel);
-name[namel] = '\0';
-printf("rpcopen p=0x%x name=%s",p->p_pid,name);
-if (nfhp->nfh_len > 0) printf(" fh=0x%x\n",nfhp->nfh_fh[12]);
-else printf(" fhl=0\n");
-}
-#endif
 	do {
 	    dp = NULL;
 	    error = nfscl_open(vp, nfhp->nfh_fh, nfhp->nfh_len, mode, 1,
@@ -452,6 +442,39 @@ else printf(" fhl=0\n");
 				    op->nfso_own->nfsow_clp,
 				    nfhp->nfh_fh, nfhp->nfh_len, cred, p, &dp);
 			}
+		} else if (NFSHASNFSV4N(nmp)) {
+			/*
+			 * For the first attempt, try and get a layout, if
+			 * pNFS is enabled for the mount.
+			 */
+			if (!NFSHASPNFS(nmp) || nfscl_enablecallb == 0 ||
+			    nfs_numnfscbd == 0 ||
+			    (np->n_flag & NNOLAYOUT) != 0 || retrycnt > 0)
+				error = nfsrpc_openrpc(nmp, vp, nfhp->nfh_fh,
+				    nfhp->nfh_len, nfhp->nfh_fh, nfhp->nfh_len,
+				    mode, op, NULL, 0, &dp, 0, 0x0, cred, p, 0,
+				    0);
+			else
+				error = nfsrpc_getopenlayout(nmp, vp,
+				    nfhp->nfh_fh, nfhp->nfh_len, nfhp->nfh_fh,
+				    nfhp->nfh_len, mode, op, NULL, 0, &dp,
+				    cred, p);
+			if (dp != NULL) {
+				NFSLOCKNODE(np);
+				np->n_flag &= ~NDELEGMOD;
+				/*
+				 * Invalidate the attribute cache, so that
+				 * attributes that pre-date the issue of a
+				 * delegation are not cached, since the
+				 * cached attributes will remain valid while
+				 * the delegation is held.
+				 */
+				NFSINVALATTRCACHE(np);
+				NFSUNLOCKNODE(np);
+				(void) nfscl_deleg(nmp->nm_mountp,
+				    op->nfso_own->nfsow_clp,
+				    nfhp->nfh_fh, nfhp->nfh_len, cred, p, &dp);
+			}
 		} else {
 			error = EIO;
 		}
@@ -538,19 +561,40 @@ nfsrpc_openrpc(struct nfsmount *nmp, vnode_t vp, u_int8_t *nfhp, int fhlen,
 		*tl = txdr_unsigned(delegtype);
 	} else {
 		if (dp != NULL) {
-			*tl = txdr_unsigned(NFSV4OPEN_CLAIMDELEGATECUR);
-			NFSM_BUILD(tl, u_int32_t *, NFSX_STATEID);
-			if (NFSHASNFSV4N(nmp))
-				*tl++ = 0;
-			else
+			if (NFSHASNFSV4N(nmp)) {
+				*tl = txdr_unsigned(
+				    NFSV4OPEN_CLAIMDELEGATECURFH);
+				NFSLOCKMNT(nmp);
+				if ((nmp->nm_privflag & NFSMNTP_BUGGYFBSDSRV) !=
+				    0) {
+					NFSUNLOCKMNT(nmp);
+					/*
+					 * Add a stateID argument to make old
+					 * broken FreeBSD NFSv4.1/4.2 servers
+					 * happy.
+					 */
+					NFSM_BUILD(tl, uint32_t *,NFSX_STATEID);
+					*tl++ = 0;
+					*tl++ = dp->nfsdl_stateid.other[0];
+					*tl++ = dp->nfsdl_stateid.other[1];
+					*tl = dp->nfsdl_stateid.other[2];
+				} else
+					NFSUNLOCKMNT(nmp);
+			} else {
+				*tl = txdr_unsigned(NFSV4OPEN_CLAIMDELEGATECUR);
+				NFSM_BUILD(tl, u_int32_t *, NFSX_STATEID);
 				*tl++ = dp->nfsdl_stateid.seqid;
-			*tl++ = dp->nfsdl_stateid.other[0];
-			*tl++ = dp->nfsdl_stateid.other[1];
-			*tl = dp->nfsdl_stateid.other[2];
+				*tl++ = dp->nfsdl_stateid.other[0];
+				*tl++ = dp->nfsdl_stateid.other[1];
+				*tl = dp->nfsdl_stateid.other[2];
+				(void)nfsm_strtom(nd, name, namelen);
+			}
+		} else if (NFSHASNFSV4N(nmp)) {
+			*tl = txdr_unsigned(NFSV4OPEN_CLAIMFH);
 		} else {
 			*tl = txdr_unsigned(NFSV4OPEN_CLAIMNULL);
+			(void)nfsm_strtom(nd, name, namelen);
 		}
-		(void) nfsm_strtom(nd, name, namelen);
 	}
 	NFSM_BUILD(tl, u_int32_t *, NFSX_UNSIGNED);
 	*tl = txdr_unsigned(NFSV4OP_GETATTR);
@@ -2713,6 +2757,8 @@ nfsrpc_createv4(vnode_t dvp, char *name, int namelen, struct vattr *vap,
 		if ((rflags & NFSV4OPEN_RESULTCONFIRM) &&
 		    (owp->nfsow_clp->nfsc_flags & NFSCLFLAGS_GOTDELEG) &&
 		    !error && dp == NULL) {
+		    KASSERT(!NFSHASNFSV4N(nmp),
+			("nfsrpc_createv4: result confirm"));
 		    do {
 			ret = nfsrpc_openrpc(VFSTONFS(dvp->v_mount), dvp,
 			    np->n_fhp->nfh_fh, np->n_fhp->nfh_len,
@@ -8009,8 +8055,12 @@ nfsrpc_openlayoutrpc(struct nfsmount *nmp, vnode_t vp, u_int8_t *nfhp,
 	nfsm_strtom(nd, op->nfso_own->nfsow_owner, NFSV4CL_LOCKNAMELEN);
 	NFSM_BUILD(tl, uint32_t *, 2 * NFSX_UNSIGNED);
 	*tl++ = txdr_unsigned(NFSV4OPEN_NOCREATE);
-	*tl = txdr_unsigned(NFSV4OPEN_CLAIMNULL);
-	nfsm_strtom(nd, name, namelen);
+	if (NFSHASNFSV4N(nmp)) {
+		*tl = txdr_unsigned(NFSV4OPEN_CLAIMFH);
+	} else {
+		*tl = txdr_unsigned(NFSV4OPEN_CLAIMNULL);
+		nfsm_strtom(nd, name, namelen);
+	}
 	NFSM_BUILD(tl, uint32_t *, NFSX_UNSIGNED);
 	*tl = txdr_unsigned(NFSV4OP_GETATTR);
 	NFSZERO_ATTRBIT(&attrbits);
diff --git a/sys/fs/nfsclient/nfs_clstate.c b/sys/fs/nfsclient/nfs_clstate.c
index 74d6a14fc4c..57921094180 100644
--- a/sys/fs/nfsclient/nfs_clstate.c
+++ b/sys/fs/nfsclient/nfs_clstate.c
@@ -4383,9 +4383,15 @@ nfscl_moveopen(vnode_t vp, struct nfsclclient *clp, struct nfsmount *nmp,
 	nfscl_newopen(clp, NULL, &owp, NULL, &op, &nop, owp->nfsow_owner,
 	    lop->nfso_fh, lop->nfso_fhlen, cred, &newone);
 	ndp = dp;
-	error = nfscl_tryopen(nmp, vp, np->n_v4->n4_data, np->n_v4->n4_fhlen,
-	    lop->nfso_fh, lop->nfso_fhlen, lop->nfso_mode, op,
-	    NFS4NODENAME(np->n_v4), np->n_v4->n4_namelen, &ndp, 0, 0, cred, p);
+	if (NFSHASNFSV4N(nmp))
+		error = nfscl_tryopen(nmp, vp, lop->nfso_fh, lop->nfso_fhlen,
+		    lop->nfso_fh, lop->nfso_fhlen, lop->nfso_mode, op,
+		    NULL, 0, &ndp, 0, 0, cred, p);
+	else
+		error = nfscl_tryopen(nmp, vp, np->n_v4->n4_data,
+		    np->n_v4->n4_fhlen, lop->nfso_fh, lop->nfso_fhlen,
+		    lop->nfso_mode, op, NFS4NODENAME(np->n_v4),
+		    np->n_v4->n4_namelen, &ndp, 0, 0, cred, p);
 	if (error) {
 		if (newone)
 			nfscl_freeopen(op, 0, true);
@@ -4476,14 +4482,16 @@ nfsrpc_reopen(struct nfsmount *nmp, u_int8_t *fhp, int fhlen,
 	if (error)
 		return (error);
 	vp = NFSTOV(np);
-	if (np->n_v4 != NULL) {
+	if (NFSHASNFSV4N(nmp))
+		error = nfscl_tryopen(nmp, vp, fhp, fhlen, fhp, fhlen, mode, op,
+		    NULL, 0, dpp, 0, 0, cred, p);
+	else if (np->n_v4 != NULL)
 		error = nfscl_tryopen(nmp, vp, np->n_v4->n4_data,
 		    np->n_v4->n4_fhlen, fhp, fhlen, mode, op,
 		    NFS4NODENAME(np->n_v4), np->n_v4->n4_namelen, dpp, 0, 0,
 		    cred, p);
-	} else {
+	else
 		error = EINVAL;
-	}
 	vrele(vp);
 	return (error);
 }
@@ -4500,18 +4508,43 @@ nfscl_tryopen(struct nfsmount *nmp, vnode_t vp, u_int8_t *fhp, int fhlen,
     int reclaim, u_int32_t delegtype, struct ucred *cred, NFSPROC_T *p)
 {
 	int error;
+	struct nfscldeleg *dp;
+	bool try_busted_xdr;
 
+	dp = *ndpp;
 	do {
+		*ndpp = dp;	/* *ndpp needs to be set for retries. */
 		error = nfsrpc_openrpc(nmp, vp, fhp, fhlen, newfhp, newfhlen,
 		    mode, op, name, namelen, ndpp, reclaim, delegtype, cred, p,
 		    0, 0);
+		try_busted_xdr = false;
 		if (error == NFSERR_DELAY)
 			(void) nfs_catnap(PZERO, error, "nfstryop");
-	} while (error == NFSERR_DELAY);
+		else if (error == NFSERR_EXPIRED && NFSHASNFSV4N(nmp) &&
+		    reclaim == 0 && dp != NULL) {
+			/* This case is a Claim_Deleg_Cur_FH Open. */
+			NFSLOCKMNT(nmp);
+			if ((nmp->nm_privflag & NFSMNTP_BUGGYFBSDSRV) == 0) {
+				/*
+				 * Old FreeBSD NFSv4.1/4.2 servers erroneously
+				 * expect a stateID argument for Open
+				 * Claim_Deleg_Cur_FH and interpret the
+				 * Getattr reply as a stateID.  This results
+				 * in an NFSERR_EXPIRED failure.
+				 * Setting NFSMNTP_BUGGYFBSDSRV makes the Open
+				 * send a stateID, in violation of RFC8881.
+				 */
+				try_busted_xdr = true;
+				nmp->nm_privflag |= NFSMNTP_BUGGYFBSDSRV;
+			}
+			NFSUNLOCKMNT(nmp);
+		}
+	} while (error == NFSERR_DELAY || try_busted_xdr);
 	if (error == EAUTH || error == EACCES) {
 		/* Try again using system credentials */
 		newnfs_setroot(cred);
 		do {
+		    *ndpp = dp;	/* *ndpp needs to be set for retries. */
 		    error = nfsrpc_openrpc(nmp, vp, fhp, fhlen, newfhp,
 			newfhlen, mode, op, name, namelen, ndpp, reclaim,
 			delegtype, cred, p, 1, 0);
diff --git a/sys/fs/nfsclient/nfs_clvnops.c b/sys/fs/nfsclient/nfs_clvnops.c
index fd88531789d..00b6c761710 100644
--- a/sys/fs/nfsclient/nfs_clvnops.c
+++ b/sys/fs/nfsclient/nfs_clvnops.c
@@ -2052,14 +2052,6 @@ nfs_rename(struct vop_rename_args *ap)
 		      tdnp->n_fhp->nfh_len != fnp->n_v4->n4_fhlen ||
 		      NFSBCMP(tdnp->n_fhp->nfh_fh, fnp->n_v4->n4_data,
 			tdnp->n_fhp->nfh_len))) {
-#ifdef notdef
-{ char nnn[100]; int nnnl;
-nnnl = (tcnp->cn_namelen < 100) ? tcnp->cn_namelen : 99;
-bcopy(tcnp->cn_nameptr, nnn, nnnl);
-nnn[nnnl] = '\0';
-printf("ren replace=%s\n",nnn);
-}
-#endif
 			free(fnp->n_v4, M_NFSV4NODE);
 			fnp->n_v4 = newv4;
 			newv4 = NULL;
@@ -2713,14 +2705,6 @@ nfs_lookitup(struct vnode *dvp, char *name, int len, struct ucred *cred,
 			 dnp->n_fhp->nfh_len != np->n_v4->n4_fhlen ||
 			 NFSBCMP(dnp->n_fhp->nfh_fh, np->n_v4->n4_data,
 			 dnp->n_fhp->nfh_len))) {
-#ifdef notdef
-{ char nnn[100]; int nnnl;
-nnnl = (len < 100) ? len : 99;
-bcopy(name, nnn, nnnl);
-nnn[nnnl] = '\0';
-printf("replace=%s\n",nnn);
-}
-#endif
 			    free(np->n_v4, M_NFSV4NODE);
 			    np->n_v4 = malloc(
 				sizeof (struct nfsv4node) +
diff --git a/sys/fs/nfsclient/nfsmount.h b/sys/fs/nfsclient/nfsmount.h
index 37b84a015da..7571add27b9 100644
--- a/sys/fs/nfsclient/nfsmount.h
+++ b/sys/fs/nfsclient/nfsmount.h
@@ -124,6 +124,7 @@ struct	nfsmount {
 #define	NFSMNTP_DELEGISSUED	0x00000400
 #define	NFSMNTP_NODEALLOCATE	0x00000800
 #define	NFSMNTP_FAKEROOTFH	0x00001000
+#define	NFSMNTP_BUGGYFBSDSRV	0x00002000
 
 /* New mount flags only used by the kernel via nmount(2). */
 #define	NFSMNT_TLS		0x00000001