2 * Copyright (C) 2013-2014 Universita` di Pisa. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * This module implements netmap support on top of standard,
28 * unmodified device drivers.
30 * A NIOCREGIF request is handled here if the device does not
31 * have native support. TX and RX rings are emulated as follows:
34 * We preallocate a block of TX mbufs (roughly as many as
35 * tx descriptors; the number is not critical) to speed up
36 * operation during transmissions. The refcount on most of
37 * these buffers is artificially bumped up so we can recycle
38 * them more easily. Also, the destructor is intercepted
39 * so we use it as an interrupt notification to wake up
40 * processes blocked on a poll().
42 * For each receive ring we allocate one "struct mbq"
43 * (an mbuf tailq plus a spinlock). We intercept packets
45 * on the receive path and put them in the mbq from which
46 * netmap receive routines can grab them.
49 * in the generic_txsync() routine, netmap buffers are copied
50 * (or linked, in a future) to the preallocated mbufs
51 * and pushed to the transmit queue. Some of these mbufs
52 * (those with NS_REPORT, or otherwise every half ring)
53 * have the refcount=1, others have refcount=2.
54 * When the destructor is invoked, we take that as
55 * a notification that all mbufs up to that one in
56 * the specific ring have been completed, and generate
57 * the equivalent of a transmit interrupt.
65 #include <sys/cdefs.h> /* prerequisite */
66 __FBSDID("$FreeBSD$");
68 #include <sys/types.h>
69 #include <sys/errno.h>
70 #include <sys/malloc.h>
71 #include <sys/lock.h> /* PROT_EXEC */
72 #include <sys/rwlock.h>
73 #include <sys/socket.h> /* sockaddrs */
74 #include <sys/selinfo.h>
76 #include <net/if_var.h>
77 #include <machine/bus.h> /* bus_dmamap_* in netmap_kern.h */
79 // XXX temporary - D() defined here
80 #include <net/netmap.h>
81 #include <dev/netmap/netmap_kern.h>
82 #include <dev/netmap/netmap_mem2.h>
84 #define rtnl_lock() D("rtnl_lock called");
85 #define rtnl_unlock() D("rtnl_unlock called");
86 #define MBUF_TXQ(m) ((m)->m_pkthdr.flowid)
87 #define MBUF_RXQ(m) ((m)->m_pkthdr.flowid)
95 * we allocate an EXT_PACKET
97 #define netmap_get_mbuf(len) m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR|M_NOFREE)
99 /* mbuf destructor, also need to change the type to EXT_EXTREF,
100 * add an M_NOFREE flag, and then clear the flag and
101 * chain into uma_zfree(zone_pack, mf)
102 * (or reinstall the buffer ?)
104 #define SET_MBUF_DESTRUCTOR(m, fn) do { \
105 (m)->m_ext.ext_free = (void *)fn; \
106 (m)->m_ext.ext_type = EXT_EXTREF; \
110 #define GET_MBUF_REFCNT(m) ((m)->m_ext.ref_cnt ? *(m)->m_ext.ref_cnt : -1)
116 #include "bsd_glue.h"
118 #include <linux/rtnetlink.h> /* rtnl_[un]lock() */
119 #include <linux/ethtool.h> /* struct ethtool_ops, get_ringparam */
120 #include <linux/hrtimer.h>
122 //#define RATE /* Enables communication statistics. */
129 /* Common headers. */
130 #include <net/netmap.h>
131 #include <dev/netmap/netmap_kern.h>
132 #include <dev/netmap/netmap_mem2.h>
136 /* ======================== usage stats =========================== */
142 unsigned long txsync;
146 unsigned long rxsync;
149 struct rate_context {
151 struct timer_list timer;
152 struct rate_stats new;
153 struct rate_stats old;
156 #define RATE_PRINTK(_NAME_) \
157 printk( #_NAME_ " = %lu Hz\n", (cur._NAME_ - ctx->old._NAME_)/RATE_PERIOD);
158 #define RATE_PERIOD 2
159 static void rate_callback(unsigned long arg)
161 struct rate_context * ctx = (struct rate_context *)arg;
162 struct rate_stats cur = ctx->new;
174 r = mod_timer(&ctx->timer, jiffies +
175 msecs_to_jiffies(RATE_PERIOD * 1000));
177 D("[v1000] Error: mod_timer()");
180 static struct rate_context rate_ctx;
187 /* =============== GENERIC NETMAP ADAPTER SUPPORT ================= */
188 #define GENERIC_BUF_SIZE netmap_buf_size /* Size of the mbufs in the Tx pool. */
191 * Wrapper used by the generic adapter layer to notify
192 * the poller threads. Differently from netmap_rx_irq(), we check
193 * only IFCAP_NETMAP instead of NAF_NATIVE_ON to enable the irq.
196 netmap_generic_irq(struct ifnet *ifp, u_int q, u_int *work_done)
198 if (unlikely(!(ifp->if_capenable & IFCAP_NETMAP)))
201 netmap_common_irq(ifp, q, work_done);
205 /* Enable/disable netmap mode for a generic network interface. */
207 generic_netmap_register(struct netmap_adapter *na, int enable)
209 struct ifnet *ifp = na->ifp;
210 struct netmap_generic_adapter *gna = (struct netmap_generic_adapter *)na;
219 error = ifp->netdev_ops->ndo_stop(ifp);
223 #endif /* REG_RESET */
225 if (enable) { /* Enable netmap mode. */
226 /* Init the mitigation support. */
227 gna->mit = malloc(na->num_rx_rings * sizeof(struct nm_generic_mit),
228 M_DEVBUF, M_NOWAIT | M_ZERO);
230 D("mitigation allocation failed");
234 for (r=0; r<na->num_rx_rings; r++)
235 netmap_mitigation_init(&gna->mit[r], na);
237 /* Initialize the rx queue, as generic_rx_handler() can
238 * be called as soon as netmap_catch_rx() returns.
240 for (r=0; r<na->num_rx_rings; r++) {
241 mbq_safe_init(&na->rx_rings[r].rx_queue);
245 * Preallocate packet buffers for the tx rings.
247 for (r=0; r<na->num_tx_rings; r++)
248 na->tx_rings[r].tx_pool = NULL;
249 for (r=0; r<na->num_tx_rings; r++) {
250 na->tx_rings[r].tx_pool = malloc(na->num_tx_desc * sizeof(struct mbuf *),
251 M_DEVBUF, M_NOWAIT | M_ZERO);
252 if (!na->tx_rings[r].tx_pool) {
253 D("tx_pool allocation failed");
257 for (i=0; i<na->num_tx_desc; i++)
258 na->tx_rings[r].tx_pool[i] = NULL;
259 for (i=0; i<na->num_tx_desc; i++) {
260 m = netmap_get_mbuf(GENERIC_BUF_SIZE);
262 D("tx_pool[%d] allocation failed", i);
266 na->tx_rings[r].tx_pool[i] = m;
270 /* Prepare to intercept incoming traffic. */
271 error = netmap_catch_rx(na, 1);
273 D("netdev_rx_handler_register() failed (%d)", error);
274 goto register_handler;
276 ifp->if_capenable |= IFCAP_NETMAP;
278 /* Make netmap control the packet steering. */
279 netmap_catch_tx(gna, 1);
284 if (rate_ctx.refcount == 0) {
286 memset(&rate_ctx, 0, sizeof(rate_ctx));
287 setup_timer(&rate_ctx.timer, &rate_callback, (unsigned long)&rate_ctx);
288 if (mod_timer(&rate_ctx.timer, jiffies + msecs_to_jiffies(1500))) {
289 D("Error: mod_timer()");
295 } else if (na->tx_rings[0].tx_pool) {
296 /* Disable netmap mode. We enter here only if the previous
297 generic_netmap_register(na, 1) was successfull.
298 If it was not, na->tx_rings[0].tx_pool was set to NULL by the
299 error handling code below. */
302 ifp->if_capenable &= ~IFCAP_NETMAP;
304 /* Release packet steering control. */
305 netmap_catch_tx(gna, 0);
307 /* Do not intercept packets on the rx path. */
308 netmap_catch_rx(na, 0);
312 /* Free the mbufs going to the netmap rings */
313 for (r=0; r<na->num_rx_rings; r++) {
314 mbq_safe_purge(&na->rx_rings[r].rx_queue);
315 mbq_safe_destroy(&na->rx_rings[r].rx_queue);
318 for (r=0; r<na->num_rx_rings; r++)
319 netmap_mitigation_cleanup(&gna->mit[r]);
320 free(gna->mit, M_DEVBUF);
322 for (r=0; r<na->num_tx_rings; r++) {
323 for (i=0; i<na->num_tx_desc; i++) {
324 m_freem(na->tx_rings[r].tx_pool[i]);
326 free(na->tx_rings[r].tx_pool, M_DEVBUF);
330 if (--rate_ctx.refcount == 0) {
332 del_timer(&rate_ctx.timer);
338 error = ifp->netdev_ops->ndo_open(ifp);
349 for (r=0; r<na->num_tx_rings; r++) {
350 if (na->tx_rings[r].tx_pool == NULL)
352 for (i=0; i<na->num_tx_desc; i++)
353 if (na->tx_rings[r].tx_pool[i])
354 m_freem(na->tx_rings[r].tx_pool[i]);
355 free(na->tx_rings[r].tx_pool, M_DEVBUF);
356 na->tx_rings[r].tx_pool = NULL;
358 for (r=0; r<na->num_rx_rings; r++) {
359 netmap_mitigation_cleanup(&gna->mit[r]);
360 mbq_safe_destroy(&na->rx_rings[r].rx_queue);
362 free(gna->mit, M_DEVBUF);
369 * Callback invoked when the device driver frees an mbuf used
370 * by netmap to transmit a packet. This usually happens when
371 * the NIC notifies the driver that transmission is completed.
374 generic_mbuf_destructor(struct mbuf *m)
377 D("Tx irq (%p) queue %d", m, MBUF_TXQ(m));
378 netmap_generic_irq(MBUF_IFP(m), MBUF_TXQ(m), NULL);
380 m->m_ext.ext_type = EXT_PACKET;
381 m->m_ext.ext_free = NULL;
382 if (*(m->m_ext.ref_cnt) == 0)
383 *(m->m_ext.ref_cnt) = 1;
384 uma_zfree(zone_pack, m);
385 #endif /* __FreeBSD__ */
386 IFRATE(rate_ctx.new.txirq++);
389 /* Record completed transmissions and update hwtail.
391 * The oldest tx buffer not yet completed is at nr_hwtail + 1,
392 * nr_hwcur is the first unsent buffer.
395 generic_netmap_tx_clean(struct netmap_kring *kring)
397 u_int const lim = kring->nkr_num_slots - 1;
398 u_int nm_i = nm_next(kring->nr_hwtail, lim);
399 u_int hwcur = kring->nr_hwcur;
401 struct mbuf **tx_pool = kring->tx_pool;
403 while (nm_i != hwcur) { /* buffers not completed */
404 struct mbuf *m = tx_pool[nm_i];
406 if (unlikely(m == NULL)) {
407 /* this is done, try to replenish the entry */
408 tx_pool[nm_i] = m = netmap_get_mbuf(GENERIC_BUF_SIZE);
409 if (unlikely(m == NULL)) {
410 D("mbuf allocation failed, XXX error");
411 // XXX how do we proceed ? break ?
414 } else if (GET_MBUF_REFCNT(m) != 1) {
415 break; /* This mbuf is still busy: its refcnt is 2. */
418 nm_i = nm_next(nm_i, lim);
420 kring->nr_hwtail = nm_prev(nm_i, lim);
421 ND("tx completed [%d] -> hwtail %d", n, kring->nr_hwtail);
428 * We have pending packets in the driver between nr_hwtail +1 and hwcur.
429 * Compute a position in the middle, to be used to generate
433 generic_tx_event_middle(struct netmap_kring *kring, u_int hwcur)
435 u_int n = kring->nkr_num_slots;
436 u_int ntc = nm_next(kring->nr_hwtail, n-1);
440 e = (hwcur + ntc) / 2;
441 } else { /* wrap around */
442 e = (hwcur + n + ntc) / 2;
448 if (unlikely(e >= n)) {
449 D("This cannot happen");
457 * We have pending packets in the driver between nr_hwtail+1 and hwcur.
458 * Schedule a notification approximately in the middle of the two.
459 * There is a race but this is only called within txsync which does
463 generic_set_tx_event(struct netmap_kring *kring, u_int hwcur)
468 if (nm_next(kring->nr_hwtail, kring->nkr_num_slots -1) == hwcur) {
469 return; /* all buffers are free */
471 e = generic_tx_event_middle(kring, hwcur);
473 m = kring->tx_pool[e];
475 /* This can happen if there is already an event on the netmap
476 slot 'e': There is nothing to do. */
479 ND("Event at %d mbuf %p refcnt %d", e, m, GET_MBUF_REFCNT(m));
480 kring->tx_pool[e] = NULL;
481 SET_MBUF_DESTRUCTOR(m, generic_mbuf_destructor);
484 /* Decrement the refcount an free it if we have the last one. */
491 * generic_netmap_txsync() transforms netmap buffers into mbufs
492 * and passes them to the standard device driver
493 * (ndo_start_xmit() or ifp->if_transmit() ).
494 * On linux this is not done directly, but using dev_queue_xmit(),
495 * since it implements the TX flow control (and takes some locks).
498 generic_netmap_txsync(struct netmap_adapter *na, u_int ring_nr, int flags)
500 struct ifnet *ifp = na->ifp;
501 struct netmap_kring *kring = &na->tx_rings[ring_nr];
502 struct netmap_ring *ring = kring->ring;
503 u_int nm_i; /* index into the netmap ring */ // j
504 u_int const lim = kring->nkr_num_slots - 1;
505 u_int const head = kring->rhead;
507 IFRATE(rate_ctx.new.txsync++);
509 // TODO: handle the case of mbuf allocation failure
514 * First part: process new packets to send.
516 nm_i = kring->nr_hwcur;
517 if (nm_i != head) { /* we have new packets to send */
518 while (nm_i != head) {
519 struct netmap_slot *slot = &ring->slot[nm_i];
520 u_int len = slot->len;
521 void *addr = NMB(slot);
523 /* device-specific */
527 NM_CHECK_ADDR_LEN(addr, len);
529 /* Tale a mbuf from the tx pool and copy in the user packet. */
530 m = kring->tx_pool[nm_i];
532 RD(5, "This should never happen");
533 kring->tx_pool[nm_i] = m = netmap_get_mbuf(GENERIC_BUF_SIZE);
534 if (unlikely(m == NULL)) {
535 D("mbuf allocation failed");
539 /* XXX we should ask notifications when NS_REPORT is set,
540 * or roughly every half frame. We can optimize this
541 * by lazily requesting notifications only when a
542 * transmission fails. Probably the best way is to
543 * break on failures and set notifications when
544 * ring->cur == ring->tail || nm_i != cur
546 tx_ret = generic_xmit_frame(ifp, m, addr, len, ring_nr);
547 if (unlikely(tx_ret)) {
548 RD(5, "start_xmit failed: err %d [nm_i %u, head %u, hwtail %u]",
549 tx_ret, nm_i, head, kring->nr_hwtail);
551 * No room for this mbuf in the device driver.
552 * Request a notification FOR A PREVIOUS MBUF,
553 * then call generic_netmap_tx_clean(kring) to do the
554 * double check and see if we can free more buffers.
555 * If there is space continue, else break;
556 * NOTE: the double check is necessary if the problem
557 * occurs in the txsync call after selrecord().
558 * Also, we need some way to tell the caller that not
559 * all buffers were queued onto the device (this was
560 * not a problem with native netmap driver where space
561 * is preallocated). The bridge has a similar problem
562 * and we solve it there by dropping the excess packets.
564 generic_set_tx_event(kring, nm_i);
565 if (generic_netmap_tx_clean(kring)) { /* space now available */
571 slot->flags &= ~(NS_REPORT | NS_BUF_CHANGED);
572 nm_i = nm_next(nm_i, lim);
573 IFRATE(rate_ctx.new.txpkt ++);
576 /* Update hwcur to the next slot to transmit. */
577 kring->nr_hwcur = nm_i; /* not head, we could break early */
581 * Second, reclaim completed buffers
583 if (flags & NAF_FORCE_RECLAIM || nm_kr_txempty(kring)) {
584 /* No more available slots? Set a notification event
585 * on a netmap slot that will be cleaned in the future.
586 * No doublecheck is performed, since txsync() will be
587 * called twice by netmap_poll().
589 generic_set_tx_event(kring, nm_i);
591 ND("tx #%d, hwtail = %d", n, kring->nr_hwtail);
593 generic_netmap_tx_clean(kring);
595 nm_txsync_finalize(kring);
602 * This handler is registered (through netmap_catch_rx())
603 * within the attached network interface
604 * in the RX subsystem, so that every mbuf passed up by
605 * the driver can be stolen to the network stack.
606 * Stolen packets are put in a queue where the
607 * generic_netmap_rxsync() callback can extract them.
610 generic_rx_handler(struct ifnet *ifp, struct mbuf *m)
612 struct netmap_adapter *na = NA(ifp);
613 struct netmap_generic_adapter *gna = (struct netmap_generic_adapter *)na;
615 u_int rr = MBUF_RXQ(m); // receive ring number
617 if (rr >= na->num_rx_rings) {
618 rr = rr % na->num_rx_rings; // XXX expensive...
621 /* limit the size of the queue */
622 if (unlikely(mbq_len(&na->rx_rings[rr].rx_queue) > 1024)) {
625 mbq_safe_enqueue(&na->rx_rings[rr].rx_queue, m);
628 if (netmap_generic_mit < 32768) {
629 /* no rx mitigation, pass notification up */
630 netmap_generic_irq(na->ifp, rr, &work_done);
631 IFRATE(rate_ctx.new.rxirq++);
633 /* same as send combining, filter notification if there is a
634 * pending timer, otherwise pass it up and start a timer.
636 if (likely(netmap_mitigation_active(&gna->mit[rr]))) {
637 /* Record that there is some pending work. */
638 gna->mit[rr].mit_pending = 1;
640 netmap_generic_irq(na->ifp, rr, &work_done);
641 IFRATE(rate_ctx.new.rxirq++);
642 netmap_mitigation_start(&gna->mit[rr]);
648 * generic_netmap_rxsync() extracts mbufs from the queue filled by
649 * generic_netmap_rx_handler() and puts their content in the netmap
651 * Access must be protected because the rx handler is asynchronous,
654 generic_netmap_rxsync(struct netmap_adapter *na, u_int ring_nr, int flags)
656 struct netmap_kring *kring = &na->rx_rings[ring_nr];
657 struct netmap_ring *ring = kring->ring;
658 u_int nm_i; /* index into the netmap ring */ //j,
660 u_int const lim = kring->nkr_num_slots - 1;
661 u_int const head = nm_rxsync_prologue(kring);
662 int force_update = (flags & NAF_FORCE_READ) || kring->nr_kflags & NKR_PENDINTR;
665 return netmap_ring_reinit(kring);
668 * First part: import newly received packets.
670 if (netmap_no_pendintr || force_update) {
671 /* extract buffers from the rx queue, stop at most one
672 * slot before nr_hwcur (stop_i)
674 uint16_t slot_flags = kring->nkr_slot_flags;
675 u_int stop_i = nm_prev(kring->nr_hwcur, lim);
677 nm_i = kring->nr_hwtail; /* first empty slot in the receive ring */
678 for (n = 0; nm_i != stop_i; n++) {
680 void *addr = NMB(&ring->slot[nm_i]);
683 /* we only check the address here on generic rx rings */
684 if (addr == netmap_buffer_base) { /* Bad buffer */
685 return netmap_ring_reinit(kring);
688 * Call the locked version of the function.
689 * XXX Ideally we could grab a batch of mbufs at once
690 * and save some locking overhead.
692 m = mbq_safe_dequeue(&kring->rx_queue);
693 if (!m) /* no more data */
696 m_copydata(m, 0, len, addr);
697 ring->slot[nm_i].len = len;
698 ring->slot[nm_i].flags = slot_flags;
700 nm_i = nm_next(nm_i, lim);
703 kring->nr_hwtail = nm_i;
704 IFRATE(rate_ctx.new.rxpkt += n);
706 kring->nr_kflags &= ~NKR_PENDINTR;
709 // XXX should we invert the order ?
711 * Second part: skip past packets that userspace has released.
713 nm_i = kring->nr_hwcur;
715 /* Userspace has released some packets. */
716 for (n = 0; nm_i != head; n++) {
717 struct netmap_slot *slot = &ring->slot[nm_i];
719 slot->flags &= ~NS_BUF_CHANGED;
720 nm_i = nm_next(nm_i, lim);
722 kring->nr_hwcur = head;
724 /* tell userspace that there might be new packets. */
725 nm_rxsync_finalize(kring);
726 IFRATE(rate_ctx.new.rxsync++);
732 generic_netmap_dtor(struct netmap_adapter *na)
734 struct ifnet *ifp = na->ifp;
735 struct netmap_generic_adapter *gna = (struct netmap_generic_adapter*)na;
736 struct netmap_adapter *prev_na = gna->prev;
738 if (prev_na != NULL) {
739 D("Released generic NA %p", gna);
741 netmap_adapter_put(prev_na);
745 D("Restored native NA %p", prev_na);
751 * generic_netmap_attach() makes it possible to use netmap on
752 * a device without native netmap support.
753 * This is less performant than native support but potentially
754 * faster than raw sockets or similar schemes.
756 * In this "emulated" mode, netmap rings do not necessarily
757 * have the same size as those in the NIC. We use a default
758 * value and possibly override it if the OS has ways to fetch the
759 * actual configuration.
762 generic_netmap_attach(struct ifnet *ifp)
764 struct netmap_adapter *na;
765 struct netmap_generic_adapter *gna;
767 u_int num_tx_desc, num_rx_desc;
769 num_tx_desc = num_rx_desc = netmap_generic_ringsize; /* starting point */
771 generic_find_num_desc(ifp, &num_tx_desc, &num_rx_desc);
772 ND("Netmap ring size: TX = %d, RX = %d", num_tx_desc, num_rx_desc);
774 gna = malloc(sizeof(*gna), M_DEVBUF, M_NOWAIT | M_ZERO);
776 D("no memory on attach, give up");
779 na = (struct netmap_adapter *)gna;
781 na->num_tx_desc = num_tx_desc;
782 na->num_rx_desc = num_rx_desc;
783 na->nm_register = &generic_netmap_register;
784 na->nm_txsync = &generic_netmap_txsync;
785 na->nm_rxsync = &generic_netmap_rxsync;
786 na->nm_dtor = &generic_netmap_dtor;
787 /* when using generic, IFCAP_NETMAP is set so we force
788 * NAF_SKIP_INTR to use the regular interrupt handler
790 na->na_flags = NAF_SKIP_INTR | NAF_HOST_RINGS;
792 ND("[GNA] num_tx_queues(%d), real_num_tx_queues(%d), len(%lu)",
793 ifp->num_tx_queues, ifp->real_num_tx_queues,
795 ND("[GNA] num_rx_queues(%d), real_num_rx_queues(%d)",
796 ifp->num_rx_queues, ifp->real_num_rx_queues);
798 generic_find_num_queues(ifp, &na->num_tx_rings, &na->num_rx_rings);
800 retval = netmap_attach_common(na);