Function sysctl_register_oid

freebsd/kern/kern_sysctl.c:423–522

#endif

void
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
	 * exists in the parent's list.
	 */
	SYSCTL_ASSERT_WLOCKED();
	p = sysctl_find_oidname(oidp->oid_name, parent);
	if (p != NULL) {
		if ((p->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
			p->oid_refcnt++;
			return;
		} else {
			sysctl_warn_reuse(__func__, p);
			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	
	/*
	 * 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
	 * accommodate e.g. net.inet.raw as a static sysctl node.
	 */
	if (oid_number < 0) {
		static int newoid;

		/*
		 * 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;
	}

	/*
	 * Insert the OID into the parent's list sorted by OID number.
	 */
retry:
	q = NULL;
	SLIST_FOREACH(p, parent, oid_link) {
		/* check if the current OID number is in use */