Function unp_pcblist

freebsd/kern/uipc_usrreq.c:1794–1930

* unp_pcblist() walks the global list of struct unpcb's to generate a * pointer list, bumping the refcount on each unpcb. It then copies them out * sequentially, validating the generation number on each to see if it has * been detached. All of this is necessary because copyout() may sleep on * disk I/O. */

 * disk I/O.
 */
static int
unp_pcblist(SYSCTL_HANDLER_ARGS)
{
	struct unpcb *unp, **unp_list;
	unp_gen_t gencnt;
	struct xunpgen *xug;
	struct unp_head *head;
	struct xunpcb *xu;
	u_int i;
	int error, n;

	switch ((intptr_t)arg1) {
	case SOCK_STREAM:
		head = &unp_shead;
		break;

	case SOCK_DGRAM:
		head = &unp_dhead;
		break;

	case SOCK_SEQPACKET:
		head = &unp_sphead;
		break;

	default:
		panic("unp_pcblist: arg1 %d", (int)(intptr_t)arg1);
	}

	/*
	 * The process of preparing the PCB list is too time-consuming and
	 * resource-intensive to repeat twice on every request.
	 */
	if (req->oldptr == NULL) {
		n = unp_count;
		req->oldidx = 2 * (sizeof *xug)
			+ (n + n/8) * sizeof(struct xunpcb);
		return (0);
	}

	if (req->newptr != NULL)
		return (EPERM);

	/*
	 * OK, now we're committed to doing something.
	 */
	xug = malloc(sizeof(*xug), M_TEMP, M_WAITOK | M_ZERO);
	UNP_LINK_RLOCK();
	gencnt = unp_gencnt;
	n = unp_count;
	UNP_LINK_RUNLOCK();

	xug->xug_len = sizeof *xug;
	xug->xug_count = n;
	xug->xug_gen = gencnt;
	xug->xug_sogen = so_gencnt;
	error = SYSCTL_OUT(req, xug, sizeof *xug);
	if (error) {
		free(xug, M_TEMP);