1 files changed, 47 insertions, 16 deletions

diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
index f33184868089..61e63001f52a 100644
--- a/sys/kern/kern_sysctl.c
+++ b/sys/kern/kern_sysctl.c
@@ -296,6 +296,8 @@ sysctl_register_oid(struct sysctl_oid *oidp)
 	struct sysctl_oid_list *parent = oidp->oid_parent;
 	struct sysctl_oid *p;
 	struct sysctl_oid *q;
+	int oid_number;
+	int timeout = 2;
 
 	/*
 	 * First check if another oid with the same name already
@@ -312,37 +314,66 @@ sysctl_register_oid(struct sysctl_oid *oidp)
 			return;
 		}
 	}
+	/* get current OID number */
+	oid_number = oidp->oid_number;
+
+#if (OID_AUTO >= 0)
+#error "OID_AUTO is expected to be a negative value"
+#endif	
 	/*
-	 * If this oid has a number OID_AUTO, give it a number which
-	 * is greater than any current oid.
+	 * Any negative OID number qualifies as OID_AUTO. Valid OID
+	 * numbers should always be positive.
+	 *
 	 * NOTE: DO NOT change the starting value here, change it in
 	 * <sys/sysctl.h>, and make sure it is at least 256 to
 	 * accomodate e.g. net.inet.raw as a static sysctl node.
 	 */
-	if (oidp->oid_number == OID_AUTO) {
-		static int newoid = CTL_AUTO_START;
+	if (oid_number < 0) {
+		static int newoid;
 
-		oidp->oid_number = newoid++;
-		if (newoid == 0x7fffffff)
-			panic("out of oids");
-	}
-#if 0
-	else if (oidp->oid_number >= CTL_AUTO_START) {
-		/* do not panic; this happens when unregistering sysctl sets */
-		printf("static sysctl oid too high: %d", oidp->oid_number);
+		/*
+		 * By decrementing the next OID number we spend less
+		 * time inserting the OIDs into a sorted list.
+		 */
+		if (--newoid < CTL_AUTO_START)
+			newoid = 0x7fffffff;
+
+		oid_number = newoid;
 	}
-#endif
 
 	/*
-	 * Insert the oid into the parent's list in order.
+	 * Insert the OID into the parent's list sorted by OID number.
 	 */
+retry:
 	q = NULL;
 	SLIST_FOREACH(p, parent, oid_link) {
-		if (oidp->oid_number < p->oid_number)
+		/* check if the current OID number is in use */
+		if (oid_number == p->oid_number) {
+			/* get the next valid OID number */
+			if (oid_number < CTL_AUTO_START ||
+			    oid_number == 0x7fffffff) {
+				/* wraparound - restart */
+				oid_number = CTL_AUTO_START;
+				/* don't loop forever */
+				if (!timeout--)
+					panic("sysctl: Out of OID numbers\n");
+				goto retry;
+			} else {
+				oid_number++;
+			}
+		} else if (oid_number < p->oid_number)
 			break;
 		q = p;
 	}
-	if (q)
+	/* check for non-auto OID number collision */
+	if (oidp->oid_number >= 0 && oidp->oid_number < CTL_AUTO_START &&
+	    oid_number >= CTL_AUTO_START) {
+		printf("sysctl: OID number(%d) is already in use for '%s'\n",
+		    oidp->oid_number, oidp->oid_name);
+	}
+	/* update the OID number, if any */
+	oidp->oid_number = oid_number;
+	if (q != NULL)
 		SLIST_INSERT_AFTER(q, oidp, oid_link);
 	else
 		SLIST_INSERT_HEAD(parent, oidp, oid_link);