exports: let kernel decide which flags vary by flavor

Query the kernel to ask which flavors vary by pseudoflavor, and use that
instead of a fixed constant.  To allow the possibility of more flags
varying by pseudoflavor, use the set/clear_flags functions for all
options instead of setting some by hand.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

3 files changed, 75 insertions, 27 deletions

diff --git a/support/include/exportfs.h b/support/include/exportfs.h
index a5cf482..ce7eac0 100644
--- a/support/include/exportfs.h
+++ b/support/include/exportfs.h
@@ -103,6 +103,13 @@ int				rmtab_read(void);
 
 struct nfskey *			key_lookup(char *hname);
 
+struct export_features {
+	unsigned int flags;
+	unsigned int secinfo_flags;
+};
+
+struct export_features *get_export_features(void);
+
 /* Record export error.  */
 extern int export_errno;
 
diff --git a/support/include/nfs/export.h b/support/include/nfs/export.h
index f7a99ba..d3e188c 100644
--- a/support/include/nfs/export.h
+++ b/support/include/nfs/export.h
@@ -24,6 +24,16 @@
 #define NFSEXP_FSID		0x2000
 #define	NFSEXP_CROSSMOUNT	0x4000
 #define NFSEXP_NOACL		0x8000 /* reserved for possible ACL related use */
-#define NFSEXP_ALLFLAGS		0xFFFF
+/*
+ * All flags supported by the kernel before addition of the
+ * export_features interface:
+ */
+#define NFSEXP_OLDFLAGS		0x7E3F
+/*
+ * Flags that can vary per flavor, for kernels before addition of the
+ * export_features interface:
+ */
+#define NFSEXP_OLD_SECINFO_FLAGS (NFSEXP_READONLY | NFSEXP_ROOTSQUASH \
+					| NFSEXP_ALLSQUASH)
 
 #endif /* _NSF_EXPORT_H */
diff --git a/support/nfs/exports.c b/support/nfs/exports.c
index f1ca632..ef31a85 100644
--- a/support/nfs/exports.c
+++ b/support/nfs/exports.c
@@ -467,9 +467,6 @@ static void clearflags(int mask, unsigned int active, struct exportent *ep)
 	}
 }
 
-/* options that can vary per flavor: */
-#define NFSEXP_SECINFO_FLAGS (NFSEXP_READONLY | NFSEXP_ROOTSQUASH \
-					| NFSEXP_ALLSQUASH)
 /*
  * For those flags which are not allowed to vary by pseudoflavor,
  * ensure that the export flags agree with the flags on each
@@ -477,10 +474,12 @@ static void clearflags(int mask, unsigned int active, struct exportent *ep)
  */
 static void fix_pseudoflavor_flags(struct exportent *ep)
 {
+	struct export_features *ef;
 	struct sec_entry *p;
 
+	ef = get_export_features();
 	for (p = ep->e_secinfo; p->flav; p++)
-		p->flags |= ep->e_flags & ~NFSEXP_SECINFO_FLAGS;
+		p->flags |= ep->e_flags & ~ef->secinfo_flags;
 }
 
 /*
@@ -518,25 +517,25 @@ parseopts(char *cp, struct exportent *ep, int warn, int *had_subtree_opt_ptr)
 		else if (strcmp(opt, "rw") == 0)
 			clearflags(NFSEXP_READONLY, active, ep);
 		else if (!strcmp(opt, "secure"))
-			ep->e_flags &= ~NFSEXP_INSECURE_PORT;
+			clearflags(NFSEXP_INSECURE_PORT, active, ep);
 		else if (!strcmp(opt, "insecure"))
-			ep->e_flags |= NFSEXP_INSECURE_PORT;
+			setflags(NFSEXP_INSECURE_PORT, active, ep);
 		else if (!strcmp(opt, "sync"))
-			ep->e_flags &= ~NFSEXP_ASYNC;
+			clearflags(NFSEXP_ASYNC, active, ep);
 		else if (!strcmp(opt, "async"))
-			ep->e_flags |= NFSEXP_ASYNC;
+			setflags(NFSEXP_ASYNC, active, ep);
 		else if (!strcmp(opt, "nohide"))
-			ep->e_flags |= NFSEXP_NOHIDE;
+			setflags(NFSEXP_NOHIDE, active, ep);
 		else if (!strcmp(opt, "hide"))
-			ep->e_flags &= ~NFSEXP_NOHIDE;
+			clearflags(NFSEXP_NOHIDE, active, ep);
 		else if (!strcmp(opt, "crossmnt"))
-			ep->e_flags |= NFSEXP_CROSSMOUNT;
+			setflags(NFSEXP_CROSSMOUNT, active, ep);
 		else if (!strcmp(opt, "nocrossmnt"))
-			ep->e_flags &= ~NFSEXP_CROSSMOUNT;
+			clearflags(NFSEXP_CROSSMOUNT, active, ep);
 		else if (!strcmp(opt, "wdelay"))
-			ep->e_flags |= NFSEXP_GATHERED_WRITES;
+			setflags(NFSEXP_GATHERED_WRITES, active, ep);
 		else if (!strcmp(opt, "no_wdelay"))
-			ep->e_flags &= ~NFSEXP_GATHERED_WRITES;
+			clearflags(NFSEXP_GATHERED_WRITES, active, ep);
 		else if (strcmp(opt, "root_squash") == 0)
 			setflags(NFSEXP_ROOTSQUASH, active, ep);
 		else if (!strcmp(opt, "no_root_squash"))
@@ -547,22 +546,22 @@ parseopts(char *cp, struct exportent *ep, int warn, int *had_subtree_opt_ptr)
 			clearflags(NFSEXP_ALLSQUASH, active, ep);
 		else if (strcmp(opt, "subtree_check") == 0) {
 			had_subtree_opt = 1;
-			ep->e_flags &= ~NFSEXP_NOSUBTREECHECK;
+			clearflags(NFSEXP_NOSUBTREECHECK, active, ep);
 		} else if (strcmp(opt, "no_subtree_check") == 0) {
 			had_subtree_opt = 1;
-			ep->e_flags |= NFSEXP_NOSUBTREECHECK;
+			setflags(NFSEXP_NOSUBTREECHECK, active, ep);
 		} else if (strcmp(opt, "auth_nlm") == 0)
-			ep->e_flags &= ~NFSEXP_NOAUTHNLM;
+			clearflags(NFSEXP_NOAUTHNLM, active, ep);
 		else if (strcmp(opt, "no_auth_nlm") == 0)
-			ep->e_flags |= NFSEXP_NOAUTHNLM;
+			setflags(NFSEXP_NOAUTHNLM, active, ep);
 		else if (strcmp(opt, "secure_locks") == 0)
-			ep->e_flags &= ~NFSEXP_NOAUTHNLM;
+			clearflags(NFSEXP_NOAUTHNLM, active, ep);
 		else if (strcmp(opt, "insecure_locks") == 0)
-			ep->e_flags |= NFSEXP_NOAUTHNLM;
+			setflags(NFSEXP_NOAUTHNLM, active, ep);
 		else if (strcmp(opt, "acl") == 0)
-			ep->e_flags &= ~NFSEXP_NOACL;
+			clearflags(NFSEXP_NOACL, active, ep);
 		else if (strcmp(opt, "no_acl") == 0)
-			ep->e_flags |= NFSEXP_NOACL;
+			setflags(NFSEXP_NOACL, active, ep);
 		else if (strncmp(opt, "anonuid=", 8) == 0) {
 			char *oe;
 			ep->e_anonuid = strtol(opt+8, &oe, 10);
@@ -594,11 +593,11 @@ bad_option:
 			char *oe;
 			if (strcmp(opt+5, "root") == 0) {
 				ep->e_fsid = 0;
-				ep->e_flags |= NFSEXP_FSID;
+				setflags(NFSEXP_FSID, active, ep);
 			} else {
 				ep->e_fsid = strtoul(opt+5, &oe, 0);
 				if (opt[5]!='\0' && *oe == '\0') 
-					ep->e_flags |= NFSEXP_FSID;
+					setflags(NFSEXP_FSID, active, ep);
 				else if (valid_uuid(opt+5))
 					ep->e_uuid = strdup(opt+5);
 				else {
@@ -639,19 +638,20 @@ bad_option:
 		} else {
 			xlog(L_ERROR, "%s:%d: unknown keyword \"%s\"\n",
 					flname, flline, opt);
-			ep->e_flags |= NFSEXP_ALLSQUASH | NFSEXP_READONLY;
+			setflags(NFSEXP_ALLSQUASH | NFSEXP_READONLY, active, ep);
 			goto bad_option;
 		}
 		free(opt);
 		while (isblank(*cp))
 			cp++;
 	}
+
 	/*
 	 * Turn on nohide which will allow this export to cross over
 	 * the 'mount --bind' mount point.
 	 */
 	if (ep->e_fslocdata)
-		ep->e_flags |= NFSEXP_NOHIDE;
+		setflags(NFSEXP_NOHIDE, active, ep);
 	fix_pseudoflavor_flags(ep);
 	ep->e_squids = squids;
 	ep->e_sqgids = sqgids;
@@ -769,3 +769,34 @@ syntaxerr(char *msg)
 	xlog(L_ERROR, "%s:%d: syntax error: %s",
 			efname, efp?efp->x_line:0, msg);
 }
+struct export_features *get_export_features(void)
+{
+	static char *path = "/proc/fs/nfsd/export_features";
+	static struct export_features ef;
+	static int cached = 0;
+	char buf[50];
+	int c;
+	int fd;
+
+	if (cached)
+		return &ef;
+
+	ef.flags = NFSEXP_OLDFLAGS;
+	ef.secinfo_flags = NFSEXP_OLD_SECINFO_FLAGS;
+
+	fd = open(path, O_RDONLY);
+	if (fd == -1)
+		goto good;
+	fd = read(fd, buf, 50);
+	if (fd == -1)
+		goto err;
+	c = sscanf(buf, "%x %x", &ef.flags, &ef.secinfo_flags);
+	if (c != 2)
+		goto err;
+good:
+	cached = 1;
+	return &ef;
+err:
+	xlog(L_WARNING, "unexpected error reading %s", path);
+	return &ef;
+}