freebsd/sys/dev/netmap/netmap.c

/*
 * Copyright (C) 2011-2013 Matteo Landi, Luigi Rizzo. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


/*
 * This module supports memory mapped access to network devices,
 * see netmap(4).
 *
 * The module uses a large, memory pool allocated by the kernel
 * and accessible as mmapped memory by multiple userspace threads/processes.
 * The memory pool contains packet buffers and "netmap rings",
 * i.e. user-accessible copies of the interface's queues.
 *
 * Access to the network card works like this:
 * 1. a process/thread issues one or more open() on /dev/netmap, to create
 *    select()able file descriptor on which events are reported.
 * 2. on each descriptor, the process issues an ioctl() to identify
 *    the interface that should report events to the file descriptor.
 * 3. on each descriptor, the process issues an mmap() request to
 *    map the shared memory region within the process' address space.
 *    The list of interesting queues is indicated by a location in
 *    the shared memory region.
 * 4. using the functions in the netmap(4) userspace API, a process
 *    can look up the occupation state of a queue, access memory buffers,
 *    and retrieve received packets or enqueue packets to transmit.
 * 5. using some ioctl()s the process can synchronize the userspace view
 *    of the queue with the actual status in the kernel. This includes both
 *    receiving the notification of new packets, and transmitting new
 *    packets on the output interface.
 * 6. select() or poll() can be used to wait for events on individual
 *    transmit or receive queues (or all queues for a given interface).
 *

		SYNCHRONIZATION (USER)

The netmap rings and data structures may be shared among multiple
user threads or even independent processes.
Any synchronization among those threads/processes is delegated
to the threads themselves. Only one thread at a time can be in
a system call on the same netmap ring. The OS does not enforce
this and only guarantees against system crashes in case of
invalid usage.

		LOCKING (INTERNAL)

Within the kernel, access to the netmap rings is protected as follows:

- a spinlock on each ring, to handle producer/consumer races on
  RX rings attached to the host stack (against multiple host
  threads writing from the host stack to the same ring),
  and on 'destination' rings attached to a VALE switch
  (i.e. RX rings in VALE ports, and TX rings in NIC/host ports)
  protecting multiple active senders for the same destination)

- an atomic variable to guarantee that there is at most one
  instance of *_*xsync() on the ring at any time.
  For rings connected to user file
  descriptors, an atomic_test_and_set() protects this, and the
  lock on the ring is not actually used.
  For NIC RX rings connected to a VALE switch, an atomic_test_and_set()
  is also used to prevent multiple executions (the driver might indeed
  already guarantee this).
  For NIC TX rings connected to a VALE switch, the lock arbitrates
  access to the queue (both when allocating buffers and when pushing
  them out).

- *xsync() should be protected against initializations of the card.
  On FreeBSD most devices have the reset routine protected by
  a RING lock (ixgbe, igb, em) or core lock (re). lem is missing
  the RING protection on rx_reset(), this should be added.

  On linux there is an external lock on the tx path, which probably
  also arbitrates access to the reset routine. XXX to be revised

- a per-interface core_lock protecting access from the host stack
  while interfaces may be detached from netmap mode.
  XXX there should be no need for this lock if we detach the interfaces
  only while they are down.


--- VALE SWITCH ---

NMG_LOCK() serializes all modifications to switches and ports.
A switch cannot be deleted until all ports are gone.

For each switch, an SX lock (RWlock on linux) protects
deletion of ports. When configuring or deleting a new port, the
lock is acquired in exclusive mode (after holding NMG_LOCK).
When forwarding, the lock is acquired in shared mode (without NMG_LOCK).
The lock is held throughout the entire forwarding cycle,
during which the thread may incur in a page fault.
Hence it is important that sleepable shared locks are used.

On the rx ring, the per-port lock is grabbed initially to reserve
a number of slot in the ring, then the lock is released,
packets are copied from source to destination, and then
the lock is acquired again and the receive ring is updated.
(A similar thing is done on the tx ring for NIC and host stack
ports attached to the switch)

 */

/*
 * OS-specific code that is used only within this file.
 * Other OS-specific code that must be accessed by drivers
 * is present in netmap_kern.h
 */

#if defined(__FreeBSD__)
#include <sys/cdefs.h> /* prerequisite */
__FBSDID("$FreeBSD$");

#include <sys/types.h>
#include <sys/module.h>
#include <sys/errno.h>
#include <sys/param.h>	/* defines used in kernel.h */
#include <sys/jail.h>
#include <sys/kernel.h>	/* types used in module initialization */
#include <sys/conf.h>	/* cdevsw struct */
#include <sys/uio.h>	/* uio struct */
#include <sys/sockio.h>
#include <sys/socketvar.h>	/* struct socket */
#include <sys/malloc.h>
#include <sys/mman.h>	/* PROT_EXEC */
#include <sys/poll.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <vm/vm.h>	/* vtophys */
#include <vm/pmap.h>	/* vtophys */
#include <vm/vm_param.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/uma.h>
#include <sys/socket.h> /* sockaddrs */
#include <sys/selinfo.h>
#include <sys/sysctl.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/bpf.h>		/* BIOCIMMEDIATE */
#include <net/vnet.h>
#include <machine/bus.h>	/* bus_dmamap_* */
#include <sys/endian.h>
#include <sys/refcount.h>

#define prefetch(x)	__builtin_prefetch(x)

#define BDG_RWLOCK_T		struct rwlock // struct rwlock

#define	BDG_RWINIT(b)		\
	rw_init_flags(&(b)->bdg_lock, "bdg lock", RW_NOWITNESS)
#define BDG_WLOCK(b)		rw_wlock(&(b)->bdg_lock)
#define BDG_WUNLOCK(b)		rw_wunlock(&(b)->bdg_lock)
#define BDG_RLOCK(b)		rw_rlock(&(b)->bdg_lock)
#define BDG_RTRYLOCK(b)		rw_try_rlock(&(b)->bdg_lock)
#define BDG_RUNLOCK(b)		rw_runlock(&(b)->bdg_lock)
#define BDG_RWDESTROY(b)	rw_destroy(&(b)->bdg_lock)


/* netmap global lock.
 * normally called within the user thread (upon a system call)
 * or when a file descriptor or process is terminated
 * (last close or last munmap)
 */

#define NMG_LOCK_T		struct mtx
#define NMG_LOCK_INIT()		mtx_init(&netmap_global_lock, "netmap global lock", NULL, MTX_DEF)
#define NMG_LOCK_DESTROY()	mtx_destroy(&netmap_global_lock)
#define NMG_LOCK()		mtx_lock(&netmap_global_lock)
#define NMG_UNLOCK()		mtx_unlock(&netmap_global_lock)
#define NMG_LOCK_ASSERT()	mtx_assert(&netmap_global_lock, MA_OWNED)


/* atomic operations */
#include <machine/atomic.h>
#define NM_ATOMIC_TEST_AND_SET(p)	(!atomic_cmpset_acq_int((p), 0, 1))
#define NM_ATOMIC_CLEAR(p)		atomic_store_rel_int((p), 0)


#elif defined(linux)

#include "bsd_glue.h"

static netdev_tx_t linux_netmap_start_xmit(struct sk_buff *, struct net_device *);

static struct device_driver*
linux_netmap_find_driver(struct device *dev)
{
	struct device_driver *dd;

	while ( (dd = dev->driver) == NULL ) {
		if ( (dev = dev->parent) == NULL )
			return NULL;
	}
	return dd;
}

static struct net_device*
ifunit_ref(const char *name)
{
	struct net_device *ifp = dev_get_by_name(&init_net, name);
	struct device_driver *dd;

	if (ifp == NULL)
		return NULL;

	if ( (dd = linux_netmap_find_driver(&ifp->dev)) == NULL )
		goto error;

	if (!try_module_get(dd->owner))
		goto error;

	return ifp;
error:
	dev_put(ifp);
	return NULL;
}

static void
if_rele(struct net_device *ifp)
{
	struct device_driver *dd;
	dd = linux_netmap_find_driver(&ifp->dev);
	dev_put(ifp);
	if (dd)
		module_put(dd->owner);
}

// XXX a mtx would suffice here too 20130404 gl
#define NMG_LOCK_T		struct semaphore
#define NMG_LOCK_INIT()		sema_init(&netmap_global_lock, 1)
#define NMG_LOCK_DESTROY()	
#define NMG_LOCK()		down(&netmap_global_lock)
#define NMG_UNLOCK()		up(&netmap_global_lock)
#define NMG_LOCK_ASSERT()	//	XXX to be completed


#elif defined(__APPLE__)

#warning OSX support is only partial
#include "osx_glue.h"

#else

#error	Unsupported platform

#endif /* unsupported */

/*
 * common headers
 */
#include <net/netmap.h>
#include <dev/netmap/netmap_kern.h>
#include <dev/netmap/netmap_mem2.h>


MALLOC_DEFINE(M_NETMAP, "netmap", "Network memory map");

/*
 * The following variables are used by the drivers and replicate
 * fields in the global memory pool. They only refer to buffers
 * used by physical interfaces.
 */
u_int netmap_total_buffers;
u_int netmap_buf_size;
char *netmap_buffer_base;	/* also address of an invalid buffer */

/* user-controlled variables */
int netmap_verbose;

static int netmap_no_timestamp; /* don't timestamp on rxsync */

SYSCTL_NODE(_dev, OID_AUTO, netmap, CTLFLAG_RW, 0, "Netmap args");
SYSCTL_INT(_dev_netmap, OID_AUTO, verbose,
    CTLFLAG_RW, &netmap_verbose, 0, "Verbose mode");
SYSCTL_INT(_dev_netmap, OID_AUTO, no_timestamp,
    CTLFLAG_RW, &netmap_no_timestamp, 0, "no_timestamp");
int netmap_mitigate = 1;
SYSCTL_INT(_dev_netmap, OID_AUTO, mitigate, CTLFLAG_RW, &netmap_mitigate, 0, "");
int netmap_no_pendintr = 1;
SYSCTL_INT(_dev_netmap, OID_AUTO, no_pendintr,
    CTLFLAG_RW, &netmap_no_pendintr, 0, "Always look for new received packets.");
int netmap_txsync_retry = 2;
SYSCTL_INT(_dev_netmap, OID_AUTO, txsync_retry, CTLFLAG_RW,
    &netmap_txsync_retry, 0 , "Number of txsync loops in bridge's flush.");

int netmap_drop = 0;	/* debugging */
int netmap_flags = 0;	/* debug flags */
int netmap_fwd = 0;	/* force transparent mode */
int netmap_mmap_unreg = 0; /* allow mmap of unregistered fds */

SYSCTL_INT(_dev_netmap, OID_AUTO, drop, CTLFLAG_RW, &netmap_drop, 0 , "");
SYSCTL_INT(_dev_netmap, OID_AUTO, flags, CTLFLAG_RW, &netmap_flags, 0 , "");
SYSCTL_INT(_dev_netmap, OID_AUTO, fwd, CTLFLAG_RW, &netmap_fwd, 0 , "");
SYSCTL_INT(_dev_netmap, OID_AUTO, mmap_unreg, CTLFLAG_RW, &netmap_mmap_unreg, 0, "");

NMG_LOCK_T	netmap_global_lock;

/*
 * protect against multiple threads using the same ring.
 * also check that the ring has not been stopped.
 */
#define NM_KR_BUSY	1
#define NM_KR_STOPPED	2
static void nm_kr_put(struct netmap_kring *kr);
static __inline int nm_kr_tryget(struct netmap_kring *kr)
{
	/* check a first time without taking the lock 
	 * to avoid starvation for nm_kr_get()
	 */
	if (unlikely(kr->nkr_stopped)) {
		ND("ring %p stopped (%d)", kr, kr->nkr_stopped);
		return NM_KR_STOPPED;
	}
	if (unlikely(NM_ATOMIC_TEST_AND_SET(&kr->nr_busy)))
		return NM_KR_BUSY;
	/* check a second time with lock held */
	if (unlikely(kr->nkr_stopped)) {
		ND("ring %p stopped (%d)", kr, kr->nkr_stopped);
		nm_kr_put(kr);
		return NM_KR_STOPPED;
	}
	return 0;
}

static __inline void nm_kr_put(struct netmap_kring *kr)
{
	NM_ATOMIC_CLEAR(&kr->nr_busy);
}

static void nm_kr_get(struct netmap_kring *kr)
{
	while (NM_ATOMIC_TEST_AND_SET(&kr->nr_busy))
		tsleep(kr, 0, "NM_KR_GET", 4);
}

static void nm_disable_ring(struct netmap_kring *kr)
{
	kr->nkr_stopped = 1;
	nm_kr_get(kr);
	mtx_lock(&kr->q_lock);
	mtx_unlock(&kr->q_lock);
	nm_kr_put(kr);
}

void netmap_disable_all_rings(struct ifnet *ifp)
{
	struct netmap_adapter *na;
	int i;

	if (!(ifp->if_capenable & IFCAP_NETMAP))
		return;

	na = NA(ifp);

	for (i = 0; i < na->num_tx_rings + 1; i++) {
		nm_disable_ring(na->tx_rings + i);
		selwakeuppri(&na->tx_rings[i].si, PI_NET);
	}
	for (i = 0; i < na->num_rx_rings + 1; i++) {
		nm_disable_ring(na->rx_rings + i);
		selwakeuppri(&na->rx_rings[i].si, PI_NET);
	}
	selwakeuppri(&na->tx_si, PI_NET);
	selwakeuppri(&na->rx_si, PI_NET);
}

void netmap_enable_all_rings(struct ifnet *ifp)
{
	struct netmap_adapter *na;
	int i;

	if (!(ifp->if_capenable & IFCAP_NETMAP))
		return;

	na = NA(ifp);
	for (i = 0; i < na->num_tx_rings + 1; i++) {
		D("enabling %p", na->tx_rings + i);
		na->tx_rings[i].nkr_stopped = 0;
	}
	for (i = 0; i < na->num_rx_rings + 1; i++) {
		D("enabling %p", na->rx_rings + i);
		na->rx_rings[i].nkr_stopped = 0;
	}
}


/*
 * generic bound_checking function
 */
u_int
nm_bound_var(u_int *v, u_int dflt, u_int lo, u_int hi, const char *msg)
{
	u_int oldv = *v;
	const char *op = NULL;

	if (dflt < lo)
		dflt = lo;
	if (dflt > hi)
		dflt = hi;
	if (oldv < lo) {
		*v = dflt;
		op = "Bump";
	} else if (oldv > hi) {
		*v = hi;
		op = "Clamp";
	}
	if (op && msg)
		printf("%s %s to %d (was %d)\n", op, msg, *v, oldv);
	return *v;
}

/*
 * packet-dump function, user-supplied or static buffer.
 * The destination buffer must be at least 30+4*len
 */
const char *
nm_dump_buf(char *p, int len, int lim, char *dst)
{
	static char _dst[8192];
        int i, j, i0;
	static char hex[] ="0123456789abcdef";
	char *o;	/* output position */

#define P_HI(x)	hex[((x) & 0xf0)>>4]
#define P_LO(x)	hex[((x) & 0xf)]
#define P_C(x)	((x) >= 0x20 && (x) <= 0x7e ? (x) : '.')
	if (!dst)
		dst = _dst;
	if (lim <= 0 || lim > len)
		lim = len;
	o = dst;
	sprintf(o, "buf 0x%p len %d lim %d\n", p, len, lim);
	o += strlen(o);
	/* hexdump routine */
	for (i = 0; i < lim; ) {
		sprintf(o, "%5d: ", i);
		o += strlen(o);
		memset(o, ' ', 48);
		i0 = i;
		for (j=0; j < 16 && i < lim; i++, j++) {
			o[j*3] = P_HI(p[i]);
			o[j*3+1] = P_LO(p[i]);
		}
		i = i0;
		for (j=0; j < 16 && i < lim; i++, j++)
			o[j + 48] = P_C(p[i]);
		o[j+48] = '\n';
		o += j+49;
	}
	*o = '\0';
#undef P_HI
#undef P_LO
#undef P_C
	return dst;
}

/*
 * system parameters (most of them in netmap_kern.h)
 * NM_NAME	prefix for switch port names, default "vale"
 * NM_BDG_MAXPORTS	number of ports
 * NM_BRIDGES	max number of switches in the system.
 *	XXX should become a sysctl or tunable
 *
 * Switch ports are named valeX:Y where X is the switch name and Y
 * is the port. If Y matches a physical interface name, the port is
 * connected to a physical device.
 *
 * Unlike physical interfaces, switch ports use their own memory region
 * for rings and buffers.
 * The virtual interfaces use per-queue lock instead of core lock.
 * In the tx loop, we aggregate traffic in batches to make all operations
 * faster. The batch size is bridge_batch.
 */
#define NM_BDG_MAXRINGS		16	/* XXX unclear how many. */
#define NM_BDG_MAXSLOTS		4096	/* XXX same as above */
#define NM_BRIDGE_RINGSIZE	1024	/* in the device */
#define NM_BDG_HASH		1024	/* forwarding table entries */
#define NM_BDG_BATCH		1024	/* entries in the forwarding buffer */
#define NM_MULTISEG		64	/* max size of a chain of bufs */
/* actual size of the tables */
#define NM_BDG_BATCH_MAX	(NM_BDG_BATCH + NM_MULTISEG)
/* NM_FT_NULL terminates a list of slots in the ft */
#define NM_FT_NULL		NM_BDG_BATCH_MAX
#define	NM_BRIDGES		8	/* number of bridges */


/*
 * bridge_batch is set via sysctl to the max batch size to be
 * used in the bridge. The actual value may be larger as the
 * last packet in the block may overflow the size.
 */
int bridge_batch = NM_BDG_BATCH; /* bridge batch size */
SYSCTL_INT(_dev_netmap, OID_AUTO, bridge_batch, CTLFLAG_RW, &bridge_batch, 0 , "");


/*
 * These are used to handle reference counters for bridge ports.
 */
#define	ADD_BDG_REF(ifp)	refcount_acquire(&NA(ifp)->na_bdg_refcount)
#define	DROP_BDG_REF(ifp)	refcount_release(&NA(ifp)->na_bdg_refcount)

/* The bridge references the buffers using the device specific look up table */
static inline void *
BDG_NMB(struct netmap_mem_d *nmd, struct netmap_slot *slot)
{
	struct lut_entry *lut = nmd->pools[NETMAP_BUF_POOL].lut;
	uint32_t i = slot->buf_idx;
	return (unlikely(i >= nmd->pools[NETMAP_BUF_POOL].objtotal)) ?  lut[0].vaddr : lut[i].vaddr;
}

static int bdg_netmap_attach(struct netmap_adapter *);
static int bdg_netmap_reg(struct ifnet *ifp, int onoff);
int kern_netmap_regif(struct nmreq *nmr);

/*
 * Each transmit queue accumulates a batch of packets into
 * a structure before forwarding. Packets to the same
 * destination are put in a list using ft_next as a link field.
 * ft_frags and ft_next are valid only on the first fragment.
 */
struct nm_bdg_fwd {	/* forwarding entry for a bridge */
	void *ft_buf;		/* netmap or indirect buffer */
	uint8_t ft_frags;	/* how many fragments (only on 1st frag) */
	uint8_t _ft_port;	/* dst port (unused) */
	uint16_t ft_flags;	/* flags, e.g. indirect */
	uint16_t ft_len;	/* src fragment len */
	uint16_t ft_next;	/* next packet to same destination */
};

/*
 * For each output interface, nm_bdg_q is used to construct a list.
 * bq_len is the number of output buffers (we can have coalescing
 * during the copy).
 */
struct nm_bdg_q {
	uint16_t bq_head;
	uint16_t bq_tail;
	uint32_t bq_len;	/* number of buffers */
};

/* XXX revise this */
struct nm_hash_ent {
	uint64_t	mac;	/* the top 2 bytes are the epoch */
	uint64_t	ports;
};

/*
 * nm_bridge is a descriptor for a VALE switch.
 * Interfaces for a bridge are all in bdg_ports[].
 * The array has fixed size, an empty entry does not terminate
 * the search, but lookups only occur on attach/detach so we
 * don't mind if they are slow.
 *
 * The bridge is non blocking on the transmit ports: excess
 * packets are dropped if there is no room on the output port.
 *
 * bdg_lock protects accesses to the bdg_ports array.
 * This is a rw lock (or equivalent).
 */
struct nm_bridge {
	/* XXX what is the proper alignment/layout ? */
	BDG_RWLOCK_T	bdg_lock;	/* protects bdg_ports */
	int		bdg_namelen;
	uint32_t	bdg_active_ports; /* 0 means free */
	char		bdg_basename[IFNAMSIZ];

	/* Indexes of active ports (up to active_ports)
	 * and all other remaining ports.
	 */
	uint8_t		bdg_port_index[NM_BDG_MAXPORTS];

	struct netmap_adapter *bdg_ports[NM_BDG_MAXPORTS];


	/*
	 * The function to decide the destination port.
	 * It returns either of an index of the destination port,
	 * NM_BDG_BROADCAST to broadcast this packet, or NM_BDG_NOPORT not to
	 * forward this packet.  ring_nr is the source ring index, and the
	 * function may overwrite this value to forward this packet to a
	 * different ring index.
	 * This function must be set by netmap_bdgctl().
	 */
	bdg_lookup_fn_t nm_bdg_lookup;

	/* the forwarding table, MAC+ports.
	 * XXX should be changed to an argument to be passed to
	 * the lookup function, and allocated on attach
	 */
	struct nm_hash_ent ht[NM_BDG_HASH];
};


/*
 * XXX in principle nm_bridges could be created dynamically
 * Right now we have a static array and deletions are protected
 * by an exclusive lock.
 */
struct nm_bridge nm_bridges[NM_BRIDGES];


/*
 * A few function to tell which kind of port are we using.
 * XXX should we hold a lock ?
 *
 * nma_is_vp()		virtual port
 * nma_is_host()	port connected to the host stack
 * nma_is_hw()		port connected to a NIC
 */
int nma_is_vp(struct netmap_adapter *na);
int
nma_is_vp(struct netmap_adapter *na)
{
	return na->nm_register == bdg_netmap_reg;
}

static __inline int
nma_is_host(struct netmap_adapter *na)
{
	return na->nm_register == NULL;
}

static __inline int
nma_is_hw(struct netmap_adapter *na)
{
	/* In case of sw adapter, nm_register is NULL */
	return !nma_is_vp(na) && !nma_is_host(na);
}


/*
 * If the NIC is owned by the kernel
 * (i.e., bridge), neither another bridge nor user can use it;
 * if the NIC is owned by a user, only users can share it.
 * Evaluation must be done under NMG_LOCK().
 */
#define NETMAP_OWNED_BY_KERN(ifp)	(!nma_is_vp(NA(ifp)) && NA(ifp)->na_bdg)
#define NETMAP_OWNED_BY_ANY(ifp) \
	(NETMAP_OWNED_BY_KERN(ifp) || (NA(ifp)->refcount > 0))

/*
 * NA(ifp)->bdg_port	port index
 */


/*
 * this is a slightly optimized copy routine which rounds
 * to multiple of 64 bytes and is often faster than dealing
 * with other odd sizes. We assume there is enough room
 * in the source and destination buffers.
 *
 * XXX only for multiples of 64 bytes, non overlapped.
 */
static inline void
pkt_copy(void *_src, void *_dst, int l)
{
        uint64_t *src = _src;
        uint64_t *dst = _dst;
        if (unlikely(l >= 1024)) {
                memcpy(dst, src, l);
                return;
        }
        for (; likely(l > 0); l-=64) {
                *dst++ = *src++;
                *dst++ = *src++;
                *dst++ = *src++;
                *dst++ = *src++;
                *dst++ = *src++;
                *dst++ = *src++;
                *dst++ = *src++;
                *dst++ = *src++;
        }
}


/*
 * locate a bridge among the existing ones.
 * MUST BE CALLED WITH NMG_LOCK()
 *
 * a ':' in the name terminates the bridge name. Otherwise, just NM_NAME.
 * We assume that this is called with a name of at least NM_NAME chars.
 */
static struct nm_bridge *
nm_find_bridge(const char *name, int create)
{
	int i, l, namelen;
	struct nm_bridge *b = NULL;

	NMG_LOCK_ASSERT();

	namelen = strlen(NM_NAME);	/* base length */
	l = name ? strlen(name) : 0;		/* actual length */
	if (l < namelen) {
		D("invalid bridge name %s", name ? name : NULL);
		return NULL;
	}
	for (i = namelen + 1; i < l; i++) {
		if (name[i] == ':') {
			namelen = i;
			break;
		}
	}
	if (namelen >= IFNAMSIZ)
		namelen = IFNAMSIZ;
	ND("--- prefix is '%.*s' ---", namelen, name);

	/* lookup the name, remember empty slot if there is one */
	for (i = 0; i < NM_BRIDGES; i++) {
		struct nm_bridge *x = nm_bridges + i;

		if (x->bdg_active_ports == 0) {
			if (create && b == NULL)
				b = x;	/* record empty slot */
		} else if (x->bdg_namelen != namelen) {
			continue;
		} else if (strncmp(name, x->bdg_basename, namelen) == 0) {
			ND("found '%.*s' at %d", namelen, name, i);
			b = x;
			break;
		}
	}
	if (i == NM_BRIDGES && b) { /* name not found, can create entry */
		/* initialize the bridge */
		strncpy(b->bdg_basename, name, namelen);
		ND("create new bridge %s with ports %d", b->bdg_basename,
			b->bdg_active_ports);
		b->bdg_namelen = namelen;
		b->bdg_active_ports = 0;
		for (i = 0; i < NM_BDG_MAXPORTS; i++)
			b->bdg_port_index[i] = i;
		/* set the default function */
		b->nm_bdg_lookup = netmap_bdg_learning;
		/* reset the MAC address table */
		bzero(b->ht, sizeof(struct nm_hash_ent) * NM_BDG_HASH);
	}
	return b;
}


/*
 * Free the forwarding tables for rings attached to switch ports.
 */
static void
nm_free_bdgfwd(struct netmap_adapter *na)
{
	int nrings, i;
	struct netmap_kring *kring;

	NMG_LOCK_ASSERT();
	nrings = nma_is_vp(na) ? na->num_tx_rings : na->num_rx_rings;
	kring = nma_is_vp(na) ? na->tx_rings : na->rx_rings;
	for (i = 0; i < nrings; i++) {
		if (kring[i].nkr_ft) {
			free(kring[i].nkr_ft, M_DEVBUF);
			kring[i].nkr_ft = NULL; /* protect from freeing twice */
		}
	}
	if (nma_is_hw(na))
		nm_free_bdgfwd(SWNA(na->ifp));
}


/*
 * Allocate the forwarding tables for the rings attached to the bridge ports.
 */
static int
nm_alloc_bdgfwd(struct netmap_adapter *na)
{
	int nrings, l, i, num_dstq;
	struct netmap_kring *kring;

	NMG_LOCK_ASSERT();
	/* all port:rings + broadcast */
	num_dstq = NM_BDG_MAXPORTS * NM_BDG_MAXRINGS + 1;
	l = sizeof(struct nm_bdg_fwd) * NM_BDG_BATCH_MAX;
	l += sizeof(struct nm_bdg_q) * num_dstq;
	l += sizeof(uint16_t) * NM_BDG_BATCH_MAX;

	nrings = nma_is_vp(na) ? na->num_tx_rings : na->num_rx_rings;
	kring = nma_is_vp(na) ? na->tx_rings : na->rx_rings;
	for (i = 0; i < nrings; i++) {
		struct nm_bdg_fwd *ft;
		struct nm_bdg_q *dstq;
		int j;

		ft = malloc(l, M_DEVBUF, M_NOWAIT | M_ZERO);
		if (!ft) {
			nm_free_bdgfwd(na);
			return ENOMEM;
		}
		dstq = (struct nm_bdg_q *)(ft + NM_BDG_BATCH_MAX);
		for (j = 0; j < num_dstq; j++) {
			dstq[j].bq_head = dstq[j].bq_tail = NM_FT_NULL;
			dstq[j].bq_len = 0;
		}
		kring[i].nkr_ft = ft;
	}
	if (nma_is_hw(na))
		nm_alloc_bdgfwd(SWNA(na->ifp));
	return 0;
}


/*
 * Fetch configuration from the device, to cope with dynamic
 * reconfigurations after loading the module.
 */
static int
netmap_update_config(struct netmap_adapter *na)
{
	struct ifnet *ifp = na->ifp;
	u_int txr, txd, rxr, rxd;

	txr = txd = rxr = rxd = 0;
	if (na->nm_config) {
		na->nm_config(ifp, &txr, &txd, &rxr, &rxd);
	} else {
		/* take whatever we had at init time */
		txr = na->num_tx_rings;
		txd = na->num_tx_desc;
		rxr = na->num_rx_rings;
		rxd = na->num_rx_desc;
	}

	if (na->num_tx_rings == txr && na->num_tx_desc == txd &&
	    na->num_rx_rings == rxr && na->num_rx_desc == rxd)
		return 0; /* nothing changed */
	if (netmap_verbose || na->refcount > 0) {
		D("stored config %s: txring %d x %d, rxring %d x %d",
			ifp->if_xname,
			na->num_tx_rings, na->num_tx_desc,
			na->num_rx_rings, na->num_rx_desc);
		D("new config %s: txring %d x %d, rxring %d x %d",
			ifp->if_xname, txr, txd, rxr, rxd);
	}
	if (na->refcount == 0) {
		D("configuration changed (but fine)");
		na->num_tx_rings = txr;
		na->num_tx_desc = txd;
		na->num_rx_rings = rxr;
		na->num_rx_desc = rxd;
		return 0;
	}
	D("configuration changed while active, this is bad...");
	return 1;
}

static struct netmap_if *
netmap_if_new(const char *ifname, struct netmap_adapter *na)
{
	if (netmap_update_config(na)) {
		/* configuration mismatch, report and fail */
		return NULL;
	}
	return netmap_mem_if_new(ifname, na);
}


/* Structure associated to each thread which registered an interface.
 *
 * The first 4 fields of this structure are written by NIOCREGIF and
 * read by poll() and NIOC?XSYNC.
 * There is low contention among writers (actually, a correct user program
 * should have no contention among writers) and among writers and readers,
 * so we use a single global lock to protect the structure initialization.
 * Since initialization involves the allocation of memory, we reuse the memory
 * allocator lock.
 * Read access to the structure is lock free. Readers must check that
 * np_nifp is not NULL before using the other fields.
 * If np_nifp is NULL initialization has not been performed, so they should
 * return an error to userlevel.
 *
 * The ref_done field is used to regulate access to the refcount in the
 * memory allocator. The refcount must be incremented at most once for
 * each open("/dev/netmap"). The increment is performed by the first
 * function that calls netmap_get_memory() (currently called by
 * mmap(), NIOCGINFO and NIOCREGIF).
 * If the refcount is incremented, it is then decremented when the
 * private structure is destroyed.
 */
struct netmap_priv_d {
	struct netmap_if * volatile np_nifp;	/* netmap if descriptor. */

	struct ifnet	*np_ifp;	/* device for which we hold a ref. */
	int		np_ringid;	/* from the ioctl */
	u_int		np_qfirst, np_qlast;	/* range of rings to scan */
	uint16_t	np_txpoll;

	struct netmap_mem_d *np_mref;	/* use with NMG_LOCK held */
#ifdef __FreeBSD__
	int		np_refcount;	/* use with NMG_LOCK held */
#endif /* __FreeBSD__ */
};

/* grab a reference to the memory allocator, if we don't have one already.  The
 * reference is taken from the netmap_adapter registered with the priv.
 *
 */
static int
netmap_get_memory_locked(struct netmap_priv_d* p)
{
	struct netmap_mem_d *nmd;
	int error = 0;

	if (p->np_ifp == NULL) {
		if (!netmap_mmap_unreg)
			return ENODEV;
		/* for compatibility with older versions of the API
 		 * we use the global allocator when no interface has been
 		 * registered
 		 */
		nmd = &nm_mem;
	} else {
		nmd = NA(p->np_ifp)->nm_mem;
	}
	if (p->np_mref == NULL) {
		error = netmap_mem_finalize(nmd);
		if (!error)
			p->np_mref = nmd;
	} else if (p->np_mref != nmd) {
		/* a virtual port has been registered, but previous
 		 * syscalls already used the global allocator.
 		 * We cannot continue
 		 */
		error = ENODEV;
	}
	return error;
}

static int
netmap_get_memory(struct netmap_priv_d* p)
{
	int error;
	NMG_LOCK();
	error = netmap_get_memory_locked(p);
	NMG_UNLOCK();
	return error;
}

static int
netmap_have_memory_locked(struct netmap_priv_d* p)
{
	return p->np_mref != NULL;
}

static void
netmap_drop_memory_locked(struct netmap_priv_d* p)
{
	if (p->np_mref) {
		netmap_mem_deref(p->np_mref);
		p->np_mref = NULL;
	}
}

/*
 * File descriptor's private data destructor.
 *
 * Call nm_register(ifp,0) to stop netmap mode on the interface and
 * revert to normal operation. We expect that np_ifp has not gone.
 * The second argument is the nifp to work on. In some cases it is
 * not attached yet to the netmap_priv_d so we need to pass it as
 * a separate argument.
 */
/* call with NMG_LOCK held */
static void
netmap_do_unregif(struct netmap_priv_d *priv, struct netmap_if *nifp)
{
	struct ifnet *ifp = priv->np_ifp;
	struct netmap_adapter *na = NA(ifp);

	NMG_LOCK_ASSERT();
	na->refcount--;
	if (na->refcount <= 0) {	/* last instance */
		u_int i;

		if (netmap_verbose)
			D("deleting last instance for %s", ifp->if_xname);
		/*
		 * (TO CHECK) This function is only called
		 * when the last reference to this file descriptor goes
		 * away. This means we cannot have any pending poll()
		 * or interrupt routine operating on the structure.
		 * XXX The file may be closed in a thread while
		 * another thread is using it.
		 * Linux keeps the file opened until the last reference
		 * by any outstanding ioctl/poll or mmap is gone.
		 * FreeBSD does not track mmap()s (but we do) and
		 * wakes up any sleeping poll(). Need to check what
		 * happens if the close() occurs while a concurrent
		 * syscall is running.
		 */
		na->nm_register(ifp, 0); /* off, clear IFCAP_NETMAP */
		/* Wake up any sleeping threads. netmap_poll will
		 * then return POLLERR
		 * XXX The wake up now must happen during *_down(), when
		 * we order all activities to stop. -gl
		 */
		nm_free_bdgfwd(na);
		for (i = 0; i < na->num_tx_rings + 1; i++) {
			mtx_destroy(&na->tx_rings[i].q_lock);
		}
		for (i = 0; i < na->num_rx_rings + 1; i++) {
			mtx_destroy(&na->rx_rings[i].q_lock);
		}
		/* XXX kqueue(9) needed; these will mirror knlist_init. */
		/* knlist_destroy(&na->tx_si.si_note); */
		/* knlist_destroy(&na->rx_si.si_note); */
		if (nma_is_hw(na))
			SWNA(ifp)->tx_rings = SWNA(ifp)->rx_rings = NULL;
	}
	/*
	 * netmap_mem_if_delete() deletes the nifp, and if this is
	 * the last instance also buffers, rings and krings.
	 */
	netmap_mem_if_delete(na, nifp);
}


/* we assume netmap adapter exists
 * Called with NMG_LOCK held
 */
static void
nm_if_rele(struct ifnet *ifp)
{
	int i, is_hw, hw, sw, lim;
	struct nm_bridge *b;
	struct netmap_adapter *na;
	uint8_t tmp[NM_BDG_MAXPORTS];

	NMG_LOCK_ASSERT();
	/* I can be called not only for get_ifp()-ed references where netmap's
	 * capability is guaranteed, but also for non-netmap-capable NICs.
	 */
	if (!NETMAP_CAPABLE(ifp) || !NA(ifp)->na_bdg) {
		if_rele(ifp);
		return;
	}
	na = NA(ifp);
	b = na->na_bdg;
	is_hw = nma_is_hw(na);

	ND("%s has %d references", ifp->if_xname, NA(ifp)->na_bdg_refcount);

	if (!DROP_BDG_REF(ifp))
		return;

	/*
	New algorithm:
	make a copy of bdg_port_index;
	lookup NA(ifp)->bdg_port and SWNA(ifp)->bdg_port
	in the array of bdg_port_index, replacing them with
	entries from the bottom of the array;
	decrement bdg_active_ports;
	acquire BDG_WLOCK() and copy back the array.
	 */
	
	hw = NA(ifp)->bdg_port;
	sw = (is_hw && SWNA(ifp)->na_bdg) ? SWNA(ifp)->bdg_port : -1;
	lim = b->bdg_active_ports;

	ND("detach %d and %d (lim %d)", hw, sw, lim);
	/* make a copy of the list of active ports, update it,
	 * and then copy back within BDG_WLOCK().
	 */
	memcpy(tmp, b->bdg_port_index, sizeof(tmp));
	for (i = 0; (hw >= 0 || sw >= 0) && i < lim; ) {
		if (hw >= 0 && tmp[i] == hw) {
			ND("detach hw %d at %d", hw, i);
			lim--; /* point to last active port */
			tmp[i] = tmp[lim]; /* swap with i */
			tmp[lim] = hw;	/* now this is inactive */
			hw = -1;
		} else if (sw >= 0 && tmp[i] == sw) {
			ND("detach sw %d at %d", sw, i);
			lim--;
			tmp[i] = tmp[lim];
			tmp[lim] = sw;
			sw = -1;
		} else {
			i++;
		}
	}
	if (hw >= 0 || sw >= 0) {
		D("XXX delete failed hw %d sw %d, should panic...", hw, sw);
	}
	hw = NA(ifp)->bdg_port;
	sw = (is_hw && SWNA(ifp)->na_bdg) ?  SWNA(ifp)->bdg_port : -1;

	BDG_WLOCK(b);
	b->bdg_ports[hw] = NULL;
	na->na_bdg = NULL;
	if (sw >= 0) {
		b->bdg_ports[sw] = NULL;
		SWNA(ifp)->na_bdg = NULL;
	}
	memcpy(b->bdg_port_index, tmp, sizeof(tmp));
	b->bdg_active_ports = lim;
	BDG_WUNLOCK(b);

	ND("now %d active ports", lim);
	if (lim == 0) {
		ND("marking bridge %s as free", b->bdg_basename);
		b->nm_bdg_lookup = NULL;
	}

	if (is_hw) {
		if_rele(ifp);
	} else {
		if (na->na_flags & NAF_MEM_OWNER)
			netmap_mem_private_delete(na->nm_mem);
		bzero(na, sizeof(*na));
		free(na, M_DEVBUF);
		bzero(ifp, sizeof(*ifp));
		free(ifp, M_DEVBUF);
	}
}


/*
 * returns 1 if this is the last instance and we can free priv
 */
static int
netmap_dtor_locked(struct netmap_priv_d *priv)
{
	struct ifnet *ifp = priv->np_ifp;

#ifdef __FreeBSD__
	/*
	 * np_refcount is the number of active mmaps on
	 * this file descriptor
	 */
	if (--priv->np_refcount > 0) {
		return 0;
	}
#endif /* __FreeBSD__ */
	if (ifp) {
		netmap_do_unregif(priv, priv->np_nifp);
	}
	netmap_drop_memory_locked(priv);
	if (ifp) {
		nm_if_rele(ifp); /* might also destroy *na */
	}
	return 1;
}

static void
netmap_dtor(void *data)
{
	struct netmap_priv_d *priv = data;
	int last_instance;

	NMG_LOCK();
	last_instance = netmap_dtor_locked(priv);
	NMG_UNLOCK();
	if (last_instance) {
		bzero(priv, sizeof(*priv));	/* for safety */
		free(priv, M_DEVBUF);
	}
}


#ifdef __FreeBSD__

/*
 * In order to track whether pages are still mapped, we hook into
 * the standard cdev_pager and intercept the constructor and
 * destructor.
 */

struct netmap_vm_handle_t {
	struct cdev 		*dev;
	struct netmap_priv_d	*priv;
};

static int
netmap_dev_pager_ctor(void *handle, vm_ooffset_t size, vm_prot_t prot,
    vm_ooffset_t foff, struct ucred *cred, u_short *color)
{
	struct netmap_vm_handle_t *vmh = handle;
	D("handle %p size %jd prot %d foff %jd",
		handle, (intmax_t)size, prot, (intmax_t)foff);
	dev_ref(vmh->dev);	
	return 0;	
}


static void
netmap_dev_pager_dtor(void *handle)
{
	struct netmap_vm_handle_t *vmh = handle;
	struct cdev *dev = vmh->dev;
	struct netmap_priv_d *priv = vmh->priv;
	D("handle %p", handle);
	netmap_dtor(priv);
	free(vmh, M_DEVBUF);
	dev_rel(dev);
}

static int
netmap_dev_pager_fault(vm_object_t object, vm_ooffset_t offset,
	int prot, vm_page_t *mres)
{
	struct netmap_vm_handle_t *vmh = object->handle;
	struct netmap_priv_d *priv = vmh->priv;
	vm_paddr_t paddr;
	vm_page_t page;
	vm_memattr_t memattr;
	vm_pindex_t pidx;

	ND("object %p offset %jd prot %d mres %p",
			object, (intmax_t)offset, prot, mres);
	memattr = object->memattr;
	pidx = OFF_TO_IDX(offset);
	paddr = netmap_mem_ofstophys(priv->np_mref, offset);
	if (paddr == 0)
		return VM_PAGER_FAIL;

	if (((*mres)->flags & PG_FICTITIOUS) != 0) {
		/*
		 * If the passed in result page is a fake page, update it with
		 * the new physical address.
		 */
		page = *mres;
		vm_page_updatefake(page, paddr, memattr);
	} else {
		/*
		 * Replace the passed in reqpage page with our own fake page and
		 * free up the all of the original pages.
		 */
#ifndef VM_OBJECT_WUNLOCK	/* FreeBSD < 10.x */
#define VM_OBJECT_WUNLOCK VM_OBJECT_UNLOCK
#define VM_OBJECT_WLOCK	VM_OBJECT_LOCK
#endif /* VM_OBJECT_WUNLOCK */

		VM_OBJECT_WUNLOCK(object);
		page = vm_page_getfake(paddr, memattr);
		VM_OBJECT_WLOCK(object);
		vm_page_lock(*mres);
		vm_page_free(*mres);
		vm_page_unlock(*mres);
		*mres = page;
		vm_page_insert(page, object, pidx);
	}
	page->valid = VM_PAGE_BITS_ALL;
	return (VM_PAGER_OK);
}


static struct cdev_pager_ops netmap_cdev_pager_ops = {
        .cdev_pg_ctor = netmap_dev_pager_ctor,
        .cdev_pg_dtor = netmap_dev_pager_dtor,
        .cdev_pg_fault = netmap_dev_pager_fault,
};


static int
netmap_mmap_single(struct cdev *cdev, vm_ooffset_t *foff,
	vm_size_t objsize,  vm_object_t *objp, int prot)
{
	int error;
	struct netmap_vm_handle_t *vmh;
	struct netmap_priv_d *priv;
	vm_object_t obj;

	D("cdev %p foff %jd size %jd objp %p prot %d", cdev,
	    (intmax_t )*foff, (intmax_t )objsize, objp, prot);
	
	vmh = malloc(sizeof(struct netmap_vm_handle_t), M_DEVBUF,
			      M_NOWAIT | M_ZERO);
	if (vmh == NULL)
		return ENOMEM;
	vmh->dev = cdev;

	NMG_LOCK();
	error = devfs_get_cdevpriv((void**)&priv);
	if (error)
		goto err_unlock;
	vmh->priv = priv;
	priv->np_refcount++;
	NMG_UNLOCK();

	error = netmap_get_memory(priv);
	if (error)
		goto err_deref;

	obj = cdev_pager_allocate(vmh, OBJT_DEVICE, 
		&netmap_cdev_pager_ops, objsize, prot,
		*foff, NULL);
	if (obj == NULL) {
		D("cdev_pager_allocate failed");
		error = EINVAL;
		goto err_deref;
	}
		
	*objp = obj;
	return 0;

err_deref:
	NMG_LOCK();
	priv->np_refcount--;
err_unlock:
	NMG_UNLOCK();
// err:
	free(vmh, M_DEVBUF);
	return error;
}


// XXX can we remove this ?
static int
netmap_close(struct cdev *dev, int fflag, int devtype, struct thread *td)
{
	if (netmap_verbose)
		D("dev %p fflag 0x%x devtype %d td %p",
			dev, fflag, devtype, td);
	return 0;
}


static int
netmap_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
{
	struct netmap_priv_d *priv;
	int error;

	(void)dev;
	(void)oflags;
	(void)devtype;
	(void)td;

	// XXX wait or nowait ?
	priv = malloc(sizeof(struct netmap_priv_d), M_DEVBUF,
			      M_NOWAIT | M_ZERO);
	if (priv == NULL)
		return ENOMEM;

	error = devfs_set_cdevpriv(priv, netmap_dtor);
	if (error)
	        return error;

	priv->np_refcount = 1;

	return 0;
}
#endif /* __FreeBSD__ */


/*
 * Handlers for synchronization of the queues from/to the host.
 * Netmap has two operating modes:
 * - in the default mode, the rings connected to the host stack are
 *   just another ring pair managed by userspace;
 * - in transparent mode (XXX to be defined) incoming packets
 *   (from the host or the NIC) are marked as NS_FORWARD upon
 *   arrival, and the user application has a chance to reset the
 *   flag for packets that should be dropped.
 *   On the RXSYNC or poll(), packets in RX rings between
 *   kring->nr_kcur and ring->cur with NS_FORWARD still set are moved
 *   to the other side.
 * The transfer NIC --> host is relatively easy, just encapsulate
 * into mbufs and we are done. The host --> NIC side is slightly
 * harder because there might not be room in the tx ring so it
 * might take a while before releasing the buffer.
 */


/*
 * pass a chain of buffers to the host stack as coming from 'dst'
 */
static void
netmap_send_up(struct ifnet *dst, struct mbuf *head)
{
	struct mbuf *m;

	/* send packets up, outside the lock */
	while ((m = head) != NULL) {
		head = head->m_nextpkt;
		m->m_nextpkt = NULL;
		if (netmap_verbose & NM_VERB_HOST)
			D("sending up pkt %p size %d", m, MBUF_LEN(m));
		NM_SEND_UP(dst, m);
	}
}

struct mbq {
	struct mbuf *head;
	struct mbuf *tail;
	int count;
};


/*
 * put a copy of the buffers marked NS_FORWARD into an mbuf chain.
 * Run from hwcur to cur - reserved
 */
static void
netmap_grab_packets(struct netmap_kring *kring, struct mbq *q, int force)
{
	/* Take packets from hwcur to cur-reserved and pass them up.
	 * In case of no buffers we give up. At the end of the loop,
	 * the queue is drained in all cases.
	 * XXX handle reserved
	 */
	u_int lim = kring->nkr_num_slots - 1;
	struct mbuf *m, *tail = q->tail;
	u_int k = kring->ring->cur, n = kring->ring->reserved;
	struct netmap_mem_d *nmd = kring->na->nm_mem;

	/* compute the final position, ring->cur - ring->reserved */
	if (n > 0) {
		if (k < n)
			k += kring->nkr_num_slots;
		k += n;
	}
	for (n = kring->nr_hwcur; n != k;) {
		struct netmap_slot *slot = &kring->ring->slot[n];

		n = nm_next(n, lim);
		if ((slot->flags & NS_FORWARD) == 0 && !force)
			continue;
		if (slot->len < 14 || slot->len > NETMAP_BDG_BUF_SIZE(nmd)) {
			D("bad pkt at %d len %d", n, slot->len);
			continue;
		}
		slot->flags &= ~NS_FORWARD; // XXX needed ?
		/* XXX adapt to the case of a multisegment packet */
		m = m_devget(BDG_NMB(nmd, slot), slot->len, 0, kring->na->ifp, NULL);

		if (m == NULL)
			break;
		if (tail)
			tail->m_nextpkt = m;
		else
			q->head = m;
		tail = m;
		q->count++;
		m->m_nextpkt = NULL;
	}
	q->tail = tail;
}


/*
 * The host ring has packets from nr_hwcur to (cur - reserved)
 * to be sent down to the NIC.
 * We need to use the queue lock on the source (host RX ring)
 * to protect against netmap_transmit.
 * If the user is well behaved we do not need to acquire locks
 * on the destination(s),
 * so we only need to make sure that there are no panics because
 * of user errors.
 * XXX verify
 *
 * We scan the tx rings, which have just been
 * flushed so nr_hwcur == cur. Pushing packets down means
 * increment cur and decrement avail.
 * XXX to be verified
 */
static void
netmap_sw_to_nic(struct netmap_adapter *na)
{
	struct netmap_kring *kring = &na->rx_rings[na->num_rx_rings];
	struct netmap_kring *k1 = &na->tx_rings[0];
	u_int i, howmany, src_lim, dst_lim;

	/* XXX we should also check that the carrier is on */
	if (kring->nkr_stopped)
		return;

	mtx_lock(&kring->q_lock);

	if (kring->nkr_stopped)
		goto out;

	howmany = kring->nr_hwavail;	/* XXX otherwise cur - reserved - nr_hwcur */

	src_lim = kring->nkr_num_slots - 1;
	for (i = 0; howmany > 0 && i < na->num_tx_rings; i++, k1++) {
		ND("%d packets left to ring %d (space %d)", howmany, i, k1->nr_hwavail);
		dst_lim = k1->nkr_num_slots - 1;
		while (howmany > 0 && k1->ring->avail > 0) {
			struct netmap_slot *src, *dst, tmp;
			src = &kring->ring->slot[kring->nr_hwcur];
			dst = &k1->ring->slot[k1->ring->cur];
			tmp = *src;
			src->buf_idx = dst->buf_idx;
			src->flags = NS_BUF_CHANGED;

			dst->buf_idx = tmp.buf_idx;
			dst->len = tmp.len;
			dst->flags = NS_BUF_CHANGED;
			ND("out len %d buf %d from %d to %d",
				dst->len, dst->buf_idx,
				kring->nr_hwcur, k1->ring->cur);

			kring->nr_hwcur = nm_next(kring->nr_hwcur, src_lim);
			howmany--;
			kring->nr_hwavail--;
			k1->ring->cur = nm_next(k1->ring->cur, dst_lim);
			k1->ring->avail--;
		}
		kring->ring->cur = kring->nr_hwcur; // XXX
		k1++; // XXX why?
	}
out:
	mtx_unlock(&kring->q_lock);
}


/*
 * netmap_txsync_to_host() passes packets up. We are called from a
 * system call in user process context, and the only contention
 * can be among multiple user threads erroneously calling
 * this routine concurrently.
 */
static void
netmap_txsync_to_host(struct netmap_adapter *na)
{
	struct netmap_kring *kring = &na->tx_rings[na->num_tx_rings];
	struct netmap_ring *ring = kring->ring;
	u_int k, lim = kring->nkr_num_slots - 1;
	struct mbq q = { NULL, NULL, 0 };

	if (nm_kr_tryget(kring)) {
		D("ring %p busy (user error)", kring);
		return;
	}
	k = ring->cur;
	if (k > lim) {
		D("invalid ring index in stack TX kring %p", kring);
		netmap_ring_reinit(kring);
		nm_kr_put(kring);
		return;
	}

	/* Take packets from hwcur to cur and pass them up.
	 * In case of no buffers we give up. At the end of the loop,
	 * the queue is drained in all cases.
	 */
	netmap_grab_packets(kring, &q, 1);
	kring->nr_hwcur = k;
	kring->nr_hwavail = ring->avail = lim;

	nm_kr_put(kring);
	netmap_send_up(na->ifp, q.head);
}


/*
 * This is the 'txsync' handler to send from a software ring to the
 * host stack.
 */
/* SWNA(ifp)->txrings[0] is always NA(ifp)->txrings[NA(ifp)->num_txrings] */
static int
netmap_bdg_to_host(struct ifnet *ifp, u_int ring_nr, int flags)
{
	(void)ring_nr;
	(void)flags;
	if (netmap_verbose > 255)
		RD(5, "sync to host %s ring %d", ifp->if_xname, ring_nr);
	netmap_txsync_to_host(NA(ifp));
	return 0;
}


/*
 * rxsync backend for packets coming from the host stack.
 * They have been put in the queue by netmap_transmit() so we
 * need to protect access to the kring using a lock.
 *
 * This routine also does the selrecord if called from the poll handler
 * (we know because td != NULL).
 *
 * NOTE: on linux, selrecord() is defined as a macro and uses pwait
 *     as an additional hidden argument.
 */
static void
netmap_rxsync_from_host(struct netmap_adapter *na, struct thread *td, void *pwait)
{
	struct netmap_kring *kring = &na->rx_rings[na->num_rx_rings];
	struct netmap_ring *ring = kring->ring;
	u_int j, n, lim = kring->nkr_num_slots;
	u_int k = ring->cur, resvd = ring->reserved;

	(void)pwait;	/* disable unused warnings */

	if (kring->nkr_stopped) /* check a first time without lock */
		return;

	/* XXX as an optimization we could reuse na->core_lock */
	mtx_lock(&kring->q_lock);

	if (kring->nkr_stopped)  /* check again with lock held */
		goto unlock_out;

	if (k >= lim) {
		netmap_ring_reinit(kring);
		goto unlock_out;
	}
	/* new packets are already set in nr_hwavail */
	/* skip past packets that userspace has released */
	j = kring->nr_hwcur;
	if (resvd > 0) {
		if (resvd + ring->avail >= lim + 1) {
			D("XXX invalid reserve/avail %d %d", resvd, ring->avail);
			ring->reserved = resvd = 0; // XXX panic...
		}
		k = (k >= resvd) ? k - resvd : k + lim - resvd;
        }
	if (j != k) {
		n = k >= j ? k - j : k + lim - j;
		kring->nr_hwavail -= n;
		kring->nr_hwcur = k;
	}
	k = ring->avail = kring->nr_hwavail - resvd;
	if (k == 0 && td)
		selrecord(td, &kring->si);
	if (k && (netmap_verbose & NM_VERB_HOST))
		D("%d pkts from stack", k);
unlock_out:

	mtx_unlock(&kring->q_lock);
}


/*
 * MUST BE CALLED UNDER NMG_LOCK()
 *
 * get a refcounted reference to an interface.
 * This is always called in the execution of an ioctl().
 *
 * Return ENXIO if the interface does not exist, EINVAL if netmap
 * is not supported by the interface.
 * If successful, hold a reference.
 *
 * When the NIC is attached to a bridge, reference is managed
 * at na->na_bdg_refcount using ADD/DROP_BDG_REF() as well as
 * virtual ports.  Hence, on the final DROP_BDG_REF(), the NIC
 * is detached from the bridge, then ifp's refcount is dropped (this
 * is equivalent to that ifp is destroyed in case of virtual ports.
 *
 * This function uses if_rele() when we want to prevent the NIC from
 * being detached from the bridge in error handling.  But once refcount
 * is acquired by this function, it must be released using nm_if_rele().
 */
static int
get_ifp(struct nmreq *nmr, struct ifnet **ifp, int create)
{
	const char *name = nmr->nr_name;
	int namelen = strlen(name);
	struct ifnet *iter = NULL;
	int no_prefix = 0;

	/* first try to see if this is a bridge port. */
	struct nm_bridge *b;
	struct netmap_adapter *na;
	int i, j, cand = -1, cand2 = -1;
	int needed;

	NMG_LOCK_ASSERT();
	*ifp = NULL;	/* default */
	if (strncmp(name, NM_NAME, sizeof(NM_NAME) - 1)) {
		no_prefix = 1;	/* no VALE prefix */
		goto no_bridge_port;
	}

	b = nm_find_bridge(name, create);
	if (b == NULL) {
		D("no bridges available for '%s'", name);
		return (ENXIO);
	}

	/* Now we are sure that name starts with the bridge's name,
	 * lookup the port in the bridge. We need to scan the entire
	 * list. It is not important to hold a WLOCK on the bridge
	 * during the search because NMG_LOCK already guarantees
	 * that there are no other possible writers.
	 */

	/* lookup in the local list of ports */
	for (j = 0; j < b->bdg_active_ports; j++) {
		i = b->bdg_port_index[j];
		na = b->bdg_ports[i];
		// KASSERT(na != NULL);
		iter = na->ifp;
		/* XXX make sure the name only contains one : */
		if (!strcmp(iter->if_xname, name) /* virtual port */ ||
		    (namelen > b->bdg_namelen && !strcmp(iter->if_xname,
		    name + b->bdg_namelen + 1)) /* NIC */) {
			ADD_BDG_REF(iter);
			ND("found existing if %s refs %d", name,
				NA(iter)->na_bdg_refcount);
			*ifp = iter;
			/* we are done, this is surely netmap capable */
			return 0;
		}
	}
	/* not found, should we create it? */
	if (!create)
		return ENXIO;
	/* yes we should, see if we have space to attach entries */
	needed = 2; /* in some cases we only need 1 */
	if (b->bdg_active_ports + needed >= NM_BDG_MAXPORTS) {
		D("bridge full %d, cannot create new port", b->bdg_active_ports);
		return EINVAL;
	}
	/* record the next two ports available, but do not allocate yet */
	cand = b->bdg_port_index[b->bdg_active_ports];
	cand2 = b->bdg_port_index[b->bdg_active_ports + 1];
	ND("+++ bridge %s port %s used %d avail %d %d",
		b->bdg_basename, name, b->bdg_active_ports, cand, cand2);

	/*
	 * try see if there is a matching NIC with this name
	 * (after the bridge's name)
	 */
	iter = ifunit_ref(name + b->bdg_namelen + 1);
	if (!iter) { /* this is a virtual port */
		/* Create a temporary NA with arguments, then
		 * bdg_netmap_attach() will allocate the real one
		 * and attach it to the ifp
		 */
		struct netmap_adapter tmp_na;
		int error;

		if (nmr->nr_cmd) {
			/* nr_cmd must be 0 for a virtual port */
			return EINVAL;
		}
		bzero(&tmp_na, sizeof(tmp_na));
		/* bound checking */
		tmp_na.num_tx_rings = nmr->nr_tx_rings;
		nm_bound_var(&tmp_na.num_tx_rings, 1, 1, NM_BDG_MAXRINGS, NULL);
		nmr->nr_tx_rings = tmp_na.num_tx_rings; // write back
		tmp_na.num_rx_rings = nmr->nr_rx_rings;
		nm_bound_var(&tmp_na.num_rx_rings, 1, 1, NM_BDG_MAXRINGS, NULL);
		nmr->nr_rx_rings = tmp_na.num_rx_rings; // write back
		nm_bound_var(&nmr->nr_tx_slots, NM_BRIDGE_RINGSIZE,
				1, NM_BDG_MAXSLOTS, NULL);
		tmp_na.num_tx_desc = nmr->nr_tx_slots;
		nm_bound_var(&nmr->nr_rx_slots, NM_BRIDGE_RINGSIZE,
				1, NM_BDG_MAXSLOTS, NULL);
		tmp_na.num_rx_desc = nmr->nr_rx_slots;

	 	/* create a struct ifnet for the new port.
		 * need M_NOWAIT as we are under nma_lock
		 */
		iter = malloc(sizeof(*iter), M_DEVBUF, M_NOWAIT | M_ZERO);
		if (!iter)
			return ENOMEM;

		strcpy(iter->if_xname, name);
		tmp_na.ifp = iter;
		/* bdg_netmap_attach creates a struct netmap_adapter */
		error = bdg_netmap_attach(&tmp_na);
		if (error) {
			D("error %d", error);
			free(iter, M_DEVBUF);
			return error;
		}
		cand2 = -1;	/* only need one port */
	} else if (NETMAP_CAPABLE(iter)) { /* this is a NIC */
		/* make sure the NIC is not already in use */
		if (NETMAP_OWNED_BY_ANY(iter)) {
			D("NIC %s busy, cannot attach to bridge",
				iter->if_xname);
			if_rele(iter); /* don't detach from bridge */
			return EINVAL;
		}
		if (nmr->nr_arg1 != NETMAP_BDG_HOST)
			cand2 = -1; /* only need one port */
	} else { /* not a netmap-capable NIC */
		if_rele(iter); /* don't detach from bridge */
		return EINVAL;
	}
	na = NA(iter);

	BDG_WLOCK(b);
	na->bdg_port = cand;
	ND("NIC  %p to bridge port %d", NA(iter), cand);
	/* bind the port to the bridge (virtual ports are not active) */
	b->bdg_ports[cand] = na;
	na->na_bdg = b;
	b->bdg_active_ports++;
	if (cand2 >= 0) {
		/* also bind the host stack to the bridge */
		b->bdg_ports[cand2] = SWNA(iter);
		SWNA(iter)->bdg_port = cand2;
		SWNA(iter)->na_bdg = b;
		b->bdg_active_ports++;
		ND("host %p to bridge port %d", SWNA(iter), cand2);
	}
	ADD_BDG_REF(iter);	// XXX one or two ?
	ND("if %s refs %d", name, NA(iter)->na_bdg_refcount);
	BDG_WUNLOCK(b);
	*ifp = iter;
	return 0;

no_bridge_port:
	*ifp = iter;
	if (! *ifp)
		*ifp = ifunit_ref(name);
	if (*ifp == NULL)
		return (ENXIO);

	if (NETMAP_CAPABLE(*ifp)) {
		/* Users cannot use the NIC attached to a bridge directly */
		if (no_prefix && NETMAP_OWNED_BY_KERN(*ifp)) {
			if_rele(*ifp); /* don't detach from bridge */
			return EINVAL;
		} else
			return 0;	/* valid pointer, we hold the refcount */
	}
	nm_if_rele(*ifp);
	return EINVAL;	// not NETMAP capable
}


/*
 * Error routine called when txsync/rxsync detects an error.
 * Can't do much more than resetting cur = hwcur, avail = hwavail.
 * Return 1 on reinit.
 *
 * This routine is only called by the upper half of the kernel.
 * It only reads hwcur (which is changed only by the upper half, too)
 * and hwavail (which may be changed by the lower half, but only on
 * a tx ring and only to increase it, so any error will be recovered
 * on the next call). For the above, we don't strictly need to call
 * it under lock.
 */
int
netmap_ring_reinit(struct netmap_kring *kring)
{
	struct netmap_ring *ring = kring->ring;
	u_int i, lim = kring->nkr_num_slots - 1;
	int errors = 0;

	// XXX KASSERT nm_kr_tryget
	RD(10, "called for %s", kring->na->ifp->if_xname);
	if (ring->cur > lim)
		errors++;
	for (i = 0; i <= lim; i++) {
		u_int idx = ring->slot[i].buf_idx;
		u_int len = ring->slot[i].len;
		if (idx < 2 || idx >= netmap_total_buffers) {
			if (!errors++)
				D("bad buffer at slot %d idx %d len %d ", i, idx, len);
			ring->slot[i].buf_idx = 0;
			ring->slot[i].len = 0;
		} else if (len > NETMAP_BDG_BUF_SIZE(kring->na->nm_mem)) {
			ring->slot[i].len = 0;
			if (!errors++)
				D("bad len %d at slot %d idx %d",
					len, i, idx);
		}
	}
	if (errors) {
		int pos = kring - kring->na->tx_rings;
		int n = kring->na->num_tx_rings + 1;

		RD(10, "total %d errors", errors);
		errors++;
		RD(10, "%s %s[%d] reinit, cur %d -> %d avail %d -> %d",
			kring->na->ifp->if_xname,
			pos < n ?  "TX" : "RX", pos < n ? pos : pos - n,
			ring->cur, kring->nr_hwcur,
			ring->avail, kring->nr_hwavail);
		ring->cur = kring->nr_hwcur;
		ring->avail = kring->nr_hwavail;
	}
	return (errors ? 1 : 0);
}


/*
 * Set the ring ID. For devices with a single queue, a request
 * for all rings is the same as a single ring.
 */
static int
netmap_set_ringid(struct netmap_priv_d *priv, u_int ringid)
{
	struct ifnet *ifp = priv->np_ifp;
	struct netmap_adapter *na = NA(ifp);
	u_int i = ringid & NETMAP_RING_MASK;
	/* initially (np_qfirst == np_qlast) we don't want to lock */
	u_int lim = na->num_rx_rings;

	if (na->num_tx_rings > lim)
		lim = na->num_tx_rings;
	if ( (ringid & NETMAP_HW_RING) && i >= lim) {
		D("invalid ring id %d", i);
		return (EINVAL);
	}
	priv->np_ringid = ringid;
	if (ringid & NETMAP_SW_RING) {
		priv->np_qfirst = NETMAP_SW_RING;
		priv->np_qlast = 0;
	} else if (ringid & NETMAP_HW_RING) {
		priv->np_qfirst = i;
		priv->np_qlast = i + 1;
	} else {
		priv->np_qfirst = 0;
		priv->np_qlast = NETMAP_HW_RING ;
	}
	priv->np_txpoll = (ringid & NETMAP_NO_TX_POLL) ? 0 : 1;
    if (netmap_verbose) {
	if (ringid & NETMAP_SW_RING)
		D("ringid %s set to SW RING", ifp->if_xname);
	else if (ringid & NETMAP_HW_RING)
		D("ringid %s set to HW RING %d", ifp->if_xname,
			priv->np_qfirst);
	else
		D("ringid %s set to all %d HW RINGS", ifp->if_xname, lim);
    }
	return 0;
}


/*
 * possibly move the interface to netmap-mode.
 * If success it returns a pointer to netmap_if, otherwise NULL.
 * This must be called with NMG_LOCK held.
 */
static struct netmap_if *
netmap_do_regif(struct netmap_priv_d *priv, struct ifnet *ifp,
	uint16_t ringid, int *err)
{
	struct netmap_adapter *na = NA(ifp);
	struct netmap_if *nifp = NULL;
	int error, need_mem;

	NMG_LOCK_ASSERT();
	/* ring configuration may have changed, fetch from the card */
	netmap_update_config(na);
	priv->np_ifp = ifp;     /* store the reference */
	error = netmap_set_ringid(priv, ringid);
	if (error)
		goto out;
	/* ensure allocators are ready */
	need_mem = !netmap_have_memory_locked(priv);
	if (need_mem) {
		error = netmap_get_memory_locked(priv);
		ND("get_memory returned %d", error);
		if (error)
			goto out;
	}
	nifp = netmap_if_new(ifp->if_xname, na);
	if (nifp == NULL) { /* allocation failed */
		/* we should drop the allocator, but only
		 * if we were the ones who grabbed it
		 */
		if (need_mem)
			netmap_drop_memory_locked(priv);
		error = ENOMEM;
		goto out;
	}
	na->refcount++;
	if (ifp->if_capenable & IFCAP_NETMAP) {
		/* was already set */
	} else {
		u_int i;
		/* Otherwise set the card in netmap mode
		 * and make it use the shared buffers.
		 *
		 * If the interface is attached to a bridge, lock it.
		 */
		if (NETMAP_OWNED_BY_KERN(ifp))
			BDG_WLOCK(NA(ifp)->na_bdg);
		for (i = 0 ; i < na->num_tx_rings + 1; i++)
			mtx_init(&na->tx_rings[i].q_lock, "nm_txq_lock",
			    NULL, MTX_DEF);
		for (i = 0 ; i < na->num_rx_rings + 1; i++) {
			mtx_init(&na->rx_rings[i].q_lock, "nm_rxq_lock",
			    NULL, MTX_DEF);
		}
		if (nma_is_hw(na)) {
			SWNA(ifp)->tx_rings = &na->tx_rings[na->num_tx_rings];
			SWNA(ifp)->rx_rings = &na->rx_rings[na->num_rx_rings];
		}
		/*
		 * do not core lock because the race is harmless here,
		 * there cannot be any traffic to netmap_transmit()
		 */
		error = na->nm_register(ifp, 1); /* mode on */
		// XXX do we need to nm_alloc_bdgfwd() in all cases ?
		if (!error)
			error = nm_alloc_bdgfwd(na);
		if (error) {
			netmap_do_unregif(priv, nifp);
			nifp = NULL;
		}
		if (NETMAP_OWNED_BY_KERN(ifp))
			BDG_WUNLOCK(NA(ifp)->na_bdg);

	}
out:
	*err = error;
	if (nifp != NULL) {
		/*
		 * advertise that the interface is ready bt setting ni_nifp.
		 * The barrier is needed because readers (poll and *SYNC)
		 * check for priv->np_nifp != NULL without locking
		 */
		wmb(); /* make sure previous writes are visible to all CPUs */
		priv->np_nifp = nifp;
	}
	return nifp;
}

/* Process NETMAP_BDG_ATTACH and NETMAP_BDG_DETACH */
static int
nm_bdg_attach(struct nmreq *nmr)
{
	struct ifnet *ifp;
	struct netmap_if *nifp;
	struct netmap_priv_d *npriv;
	int error;

	npriv = malloc(sizeof(*npriv), M_DEVBUF, M_NOWAIT|M_ZERO);
	if (npriv == NULL)
		return ENOMEM;
	NMG_LOCK();
	error = get_ifp(nmr, &ifp, 1 /* create if not exists */);
	if (error) /* no device, or another bridge or user owns the device */
		goto unlock_exit;
	/* get_ifp() sets na_bdg if this is a physical interface
	 * that we can attach to a switch.
	 */
	if (!NETMAP_OWNED_BY_KERN(ifp)) {
		/* got reference to a virtual port or direct access to a NIC.
		 * perhaps specified no bridge prefix or wrong NIC name
		 */
		error = EINVAL;
		goto unref_exit;
	}

	if (NA(ifp)->refcount > 0) { /* already registered */
		error = EBUSY;
		DROP_BDG_REF(ifp);
		goto unlock_exit;
	}

	nifp = netmap_do_regif(npriv, ifp, nmr->nr_ringid, &error);
	if (!nifp) {
		goto unref_exit;
	}

	NA(ifp)->na_kpriv = npriv;
	NMG_UNLOCK();
	ND("registered %s to netmap-mode", ifp->if_xname);
	return 0;

unref_exit:
	nm_if_rele(ifp);
unlock_exit:
	NMG_UNLOCK();
	bzero(npriv, sizeof(*npriv));
	free(npriv, M_DEVBUF);
	return error;
}

static int
nm_bdg_detach(struct nmreq *nmr)
{
	struct ifnet *ifp;
	int error;
	int last_instance;

	NMG_LOCK();
	error = get_ifp(nmr, &ifp, 0 /* don't create */);
	if (error) { /* no device, or another bridge or user owns the device */
		goto unlock_exit;
	}
	/* XXX do we need to check this ? */
	if (!NETMAP_OWNED_BY_KERN(ifp)) {
		/* got reference to a virtual port or direct access to a NIC.
		 * perhaps specified no bridge's prefix or wrong NIC's name
		 */
		error = EINVAL;
		goto unref_exit;
	}

	if (NA(ifp)->refcount == 0) { /* not registered */
		error = EINVAL;
		goto unref_exit;
	}

	DROP_BDG_REF(ifp); /* the one from get_ifp */
	last_instance = netmap_dtor_locked(NA(ifp)->na_kpriv); /* unregister */
	NMG_UNLOCK();
	if (!last_instance) {
		D("--- error, trying to detach an entry with active mmaps");
		error = EINVAL;
	} else {
		struct netmap_priv_d *npriv = NA(ifp)->na_kpriv;
		NA(ifp)->na_kpriv = NULL;

		bzero(npriv, sizeof(*npriv));
		free(npriv, M_DEVBUF);
	}
	return error;

unref_exit:
	nm_if_rele(ifp);
unlock_exit:
	NMG_UNLOCK();
	return error;
}


/* Initialize necessary fields of sw adapter located in right after hw's
 * one.  sw adapter attaches a pair of sw rings of the netmap-mode NIC.
 * It is always activated and deactivated at the same tie with the hw's one.
 * Thus we don't need refcounting on the sw adapter.
 * Regardless of NIC's feature we use separate lock so that anybody can lock
 * me independently from the hw adapter.
 * Make sure nm_register is NULL to be handled as FALSE in nma_is_hw
 */
static void
netmap_attach_sw(struct ifnet *ifp)
{
	struct netmap_adapter *hw_na = NA(ifp);
	struct netmap_adapter *na = SWNA(ifp);

	na->ifp = ifp;
	na->num_rx_rings = na->num_tx_rings = 1;
	na->num_tx_desc = hw_na->num_tx_desc;
	na->num_rx_desc = hw_na->num_rx_desc;
	na->nm_txsync = netmap_bdg_to_host;
	/* we use the same memory allocator as the
	 * the hw adapter */
	na->nm_mem = hw_na->nm_mem;
}


/* exported to kernel callers, e.g. OVS ?
 * Entry point.
 * Called without NMG_LOCK.
 */
int
netmap_bdg_ctl(struct nmreq *nmr, bdg_lookup_fn_t func)
{
	struct nm_bridge *b;
	struct netmap_adapter *na;
	struct ifnet *iter;
	char *name = nmr->nr_name;
	int cmd = nmr->nr_cmd, namelen = strlen(name);
	int error = 0, i, j;

	switch (cmd) {
	case NETMAP_BDG_ATTACH:
		error = nm_bdg_attach(nmr);
		break;

	case NETMAP_BDG_DETACH:
		error = nm_bdg_detach(nmr);
		break;

	case NETMAP_BDG_LIST:
		/* this is used to enumerate bridges and ports */
		if (namelen) { /* look up indexes of bridge and port */
			if (strncmp(name, NM_NAME, strlen(NM_NAME))) {
				error = EINVAL;
				break;
			}
			NMG_LOCK();
			b = nm_find_bridge(name, 0 /* don't create */);
			if (!b) {
				error = ENOENT;
				NMG_UNLOCK();
				break;
			}

			error = ENOENT;
			for (j = 0; j < b->bdg_active_ports; j++) {
				i = b->bdg_port_index[j];
				na = b->bdg_ports[i];
				if (na == NULL) {
					D("---AAAAAAAAARGH-------");
					continue;
				}
				iter = na->ifp;
				/* the former and the latter identify a
				 * virtual port and a NIC, respectively
				 */
				if (!strcmp(iter->if_xname, name) ||
				    (namelen > b->bdg_namelen &&
				    !strcmp(iter->if_xname,
				    name + b->bdg_namelen + 1))) {
					/* bridge index */
					nmr->nr_arg1 = b - nm_bridges;
					nmr->nr_arg2 = i; /* port index */
					error = 0;
					break;
				}
			}
			NMG_UNLOCK();
		} else {
			/* return the first non-empty entry starting from
			 * bridge nr_arg1 and port nr_arg2.
			 *
			 * Users can detect the end of the same bridge by
			 * seeing the new and old value of nr_arg1, and can
			 * detect the end of all the bridge by error != 0
			 */
			i = nmr->nr_arg1;
			j = nmr->nr_arg2;

			NMG_LOCK();
			for (error = ENOENT; i < NM_BRIDGES; i++) {
				b = nm_bridges + i;
				if (j >= b->bdg_active_ports) {
					j = 0; /* following bridges scan from 0 */
					continue;
				}
				nmr->nr_arg1 = i;
				nmr->nr_arg2 = j;
				j = b->bdg_port_index[j];
				na = b->bdg_ports[j];
				iter = na->ifp;
				strncpy(name, iter->if_xname, (size_t)IFNAMSIZ);
				error = 0;
				break;
			}
			NMG_UNLOCK();
		}
		break;

	case NETMAP_BDG_LOOKUP_REG:
		/* register a lookup function to the given bridge.
		 * nmr->nr_name may be just bridge's name (including ':'
		 * if it is not just NM_NAME).
		 */
		if (!func) {
			error = EINVAL;
			break;
		}
		NMG_LOCK();
		b = nm_find_bridge(name, 0 /* don't create */);
		if (!b) {
			error = EINVAL;
		} else {
			b->nm_bdg_lookup = func;
		}
		NMG_UNLOCK();
		break;

	default:
		D("invalid cmd (nmr->nr_cmd) (0x%x)", cmd);
		error = EINVAL;
		break;
	}
	return error;
}


/*
 * ioctl(2) support for the "netmap" device.
 *
 * Following a list of accepted commands:
 * - NIOCGINFO
 * - SIOCGIFADDR	just for convenience
 * - NIOCREGIF
 * - NIOCUNREGIF
 * - NIOCTXSYNC
 * - NIOCRXSYNC
 *
 * Return 0 on success, errno otherwise.
 */
static int
netmap_ioctl(struct cdev *dev, u_long cmd, caddr_t data,
	int fflag, struct thread *td)
{
	struct netmap_priv_d *priv = NULL;
	struct ifnet *ifp = NULL;
	struct nmreq *nmr = (struct nmreq *) data;
	struct netmap_adapter *na = NULL;
	int error;
	u_int i, lim;
	struct netmap_if *nifp;
	struct netmap_kring *krings;

	(void)dev;	/* UNUSED */
	(void)fflag;	/* UNUSED */
#ifdef linux
#define devfs_get_cdevpriv(pp)				\
	({ *(struct netmap_priv_d **)pp = ((struct file *)td)->private_data; 	\
		(*pp ? 0 : ENOENT); })

/* devfs_set_cdevpriv cannot fail on linux */
#define devfs_set_cdevpriv(p, fn)				\
	({ ((struct file *)td)->private_data = p; (p ? 0 : EINVAL); })


#define devfs_clear_cdevpriv()	do {				\
		netmap_dtor(priv); ((struct file *)td)->private_data = 0;	\
	} while (0)
#endif /* linux */

	CURVNET_SET(TD_TO_VNET(td));

	error = devfs_get_cdevpriv((void **)&priv);
	if (error) {
		CURVNET_RESTORE();
		/* XXX ENOENT should be impossible, since the priv
		 * is now created in the open */
		return (error == ENOENT ? ENXIO : error);
	}

	nmr->nr_name[sizeof(nmr->nr_name) - 1] = '\0';	/* truncate name */
	switch (cmd) {
	case NIOCGINFO:		/* return capabilities etc */
		if (nmr->nr_version != NETMAP_API) {
			D("API mismatch got %d have %d",
				nmr->nr_version, NETMAP_API);
			nmr->nr_version = NETMAP_API;
			error = EINVAL;
			break;
		}
		if (nmr->nr_cmd == NETMAP_BDG_LIST) {
			error = netmap_bdg_ctl(nmr, NULL);
			break;
		}

		NMG_LOCK();
		do {
			/* memsize is always valid */
			struct netmap_mem_d *nmd = &nm_mem;
			u_int memflags;

			if (nmr->nr_name[0] != '\0') {
				/* get a refcount */
				error = get_ifp(nmr, &ifp, 1 /* create */);
				if (error)
					break;
				na = NA(ifp);  /* retrieve the netmap adapter */
				nmd = na->nm_mem; /* and its memory allocator */
			}
			
			error = netmap_mem_get_info(nmd, &nmr->nr_memsize, &memflags);
			if (error)
				break;
			if (na == NULL) /* only memory info */
				break;
			nmr->nr_offset = 0;
			nmr->nr_rx_slots = nmr->nr_tx_slots = 0;
			netmap_update_config(na);
			nmr->nr_rx_rings = na->num_rx_rings;
			nmr->nr_tx_rings = na->num_tx_rings;
			nmr->nr_rx_slots = na->num_rx_desc;
			nmr->nr_tx_slots = na->num_tx_desc;
			if (memflags & NETMAP_MEM_PRIVATE)
				nmr->nr_ringid |= NETMAP_PRIV_MEM;
		} while (0);
		if (ifp)
			nm_if_rele(ifp);	/* return the refcount */
		NMG_UNLOCK();
		break;

	case NIOCREGIF:
		if (nmr->nr_version != NETMAP_API) {
			nmr->nr_version = NETMAP_API;
			error = EINVAL;
			break;
		}
		/* possibly attach/detach NIC and VALE switch */
		i = nmr->nr_cmd;
		if (i == NETMAP_BDG_ATTACH || i == NETMAP_BDG_DETACH) {
			error = netmap_bdg_ctl(nmr, NULL);
			break;
		} else if (i != 0) {
			D("nr_cmd must be 0 not %d", i);
			error = EINVAL;
			break;
		}

		/* protect access to priv from concurrent NIOCREGIF */
		NMG_LOCK();
		do {
			u_int memflags;

			if (priv->np_ifp != NULL) {	/* thread already registered */
				error = netmap_set_ringid(priv, nmr->nr_ringid);
				break;
			}
			/* find the interface and a reference */
			error = get_ifp(nmr, &ifp, 1 /* create */); /* keep reference */
			if (error)
				break;
			if (NETMAP_OWNED_BY_KERN(ifp)) {
				nm_if_rele(ifp);
				error = EBUSY;
				break;
			}
			nifp = netmap_do_regif(priv, ifp, nmr->nr_ringid, &error);
			if (!nifp) {    /* reg. failed, release priv and ref */
				nm_if_rele(ifp);        /* return the refcount */
				priv->np_ifp = NULL;
				priv->np_nifp = NULL;
				break;
			}

			/* return the offset of the netmap_if object */
			na = NA(ifp); /* retrieve netmap adapter */
			nmr->nr_rx_rings = na->num_rx_rings;
			nmr->nr_tx_rings = na->num_tx_rings;
			nmr->nr_rx_slots = na->num_rx_desc;
			nmr->nr_tx_slots = na->num_tx_desc;
			error = netmap_mem_get_info(na->nm_mem, &nmr->nr_memsize, &memflags);
			if (error) {
				nm_if_rele(ifp);
				break;
			}
			if (memflags & NETMAP_MEM_PRIVATE) {
				nmr->nr_ringid |= NETMAP_PRIV_MEM;
				*(uint32_t *)(uintptr_t)&nifp->ni_flags |= NI_PRIV_MEM;
			}
			nmr->nr_offset = netmap_mem_if_offset(na->nm_mem, nifp);
		} while (0);
		NMG_UNLOCK();
		break;

	case NIOCUNREGIF:
		// XXX we have no data here ?
		D("deprecated, data is %p", nmr);
		error = EINVAL;
		break;

	case NIOCTXSYNC:
	case NIOCRXSYNC:
		nifp = priv->np_nifp;

		if (nifp == NULL) {
			error = ENXIO;
			break;
		}
		rmb(); /* make sure following reads are not from cache */

		ifp = priv->np_ifp;	/* we have a reference */

		if (ifp == NULL) {
			D("Internal error: nifp != NULL && ifp == NULL");
			error = ENXIO;
			break;
		}

		na = NA(ifp); /* retrieve netmap adapter */
		if (priv->np_qfirst == NETMAP_SW_RING) { /* host rings */
			if (cmd == NIOCTXSYNC)
				netmap_txsync_to_host(na);
			else
				netmap_rxsync_from_host(na, NULL, NULL);
			break;
		}
		/* find the last ring to scan */
		lim = priv->np_qlast;
		if (lim == NETMAP_HW_RING)
			lim = (cmd == NIOCTXSYNC) ?
			    na->num_tx_rings : na->num_rx_rings;

		krings = (cmd == NIOCTXSYNC) ? na->tx_rings : na->rx_rings;
		for (i = priv->np_qfirst; i < lim; i++) {
			struct netmap_kring *kring = krings + i;
			if (nm_kr_tryget(kring)) {
				error = EBUSY;
				goto out;
			}
			if (cmd == NIOCTXSYNC) {
				if (netmap_verbose & NM_VERB_TXSYNC)
					D("pre txsync ring %d cur %d hwcur %d",
					    i, kring->ring->cur,
					    kring->nr_hwcur);
				na->nm_txsync(ifp, i, NAF_FORCE_RECLAIM);
				if (netmap_verbose & NM_VERB_TXSYNC)
					D("post txsync ring %d cur %d hwcur %d",
					    i, kring->ring->cur,
					    kring->nr_hwcur);
			} else {
				na->nm_rxsync(ifp, i, NAF_FORCE_READ);
				microtime(&na->rx_rings[i].ring->ts);
			}
			nm_kr_put(kring);
		}

		break;

#ifdef __FreeBSD__
	case BIOCIMMEDIATE:
	case BIOCGHDRCMPLT:
	case BIOCSHDRCMPLT:
	case BIOCSSEESENT:
		D("ignore BIOCIMMEDIATE/BIOCSHDRCMPLT/BIOCSHDRCMPLT/BIOCSSEESENT");
		break;

	default:	/* allow device-specific ioctls */
	    {
		struct socket so;

		bzero(&so, sizeof(so));
		NMG_LOCK();
		error = get_ifp(nmr, &ifp, 0 /* don't create */); /* keep reference */
		if (error) {
			NMG_UNLOCK();
			break;
		}
		so.so_vnet = ifp->if_vnet;
		// so->so_proto not null.
		error = ifioctl(&so, cmd, data, td);
		nm_if_rele(ifp);
		NMG_UNLOCK();
		break;
	    }

#else /* linux */
	default:
		error = EOPNOTSUPP;
#endif /* linux */
	}
out:

	CURVNET_RESTORE();
	return (error);
}


/*
 * select(2) and poll(2) handlers for the "netmap" device.
 *
 * Can be called for one or more queues.
 * Return true the event mask corresponding to ready events.
 * If there are no ready events, do a selrecord on either individual
 * selinfo or on the global one.
 * Device-dependent parts (locking and sync of tx/rx rings)
 * are done through callbacks.
 *
 * On linux, arguments are really pwait, the poll table, and 'td' is struct file *
 * The first one is remapped to pwait as selrecord() uses the name as an
 * hidden argument.
 */
static int
netmap_poll(struct cdev *dev, int events, struct thread *td)
{
	struct netmap_priv_d *priv = NULL;
	struct netmap_adapter *na;
	struct ifnet *ifp;
	struct netmap_kring *kring;
	u_int i, check_all_tx, check_all_rx, want_tx, want_rx, revents = 0;
	u_int lim_tx, lim_rx, host_forwarded = 0;
	struct mbq q = { NULL, NULL, 0 };
	void *pwait = dev;	/* linux compatibility */

		int retry_tx = 1;

	(void)pwait;

	if (devfs_get_cdevpriv((void **)&priv) != 0 || priv == NULL)
		return POLLERR;

	if (priv->np_nifp == NULL) {
		D("No if registered");
		return POLLERR;
	}
	rmb(); /* make sure following reads are not from cache */

	ifp = priv->np_ifp;
	// XXX check for deleting() ?
	if ( (ifp->if_capenable & IFCAP_NETMAP) == 0)
		return POLLERR;

	if (netmap_verbose & 0x8000)
		D("device %s events 0x%x", ifp->if_xname, events);
	want_tx = events & (POLLOUT | POLLWRNORM);
	want_rx = events & (POLLIN | POLLRDNORM);

	na = NA(ifp); /* retrieve netmap adapter */

	lim_tx = na->num_tx_rings;
	lim_rx = na->num_rx_rings;

	if (priv->np_qfirst == NETMAP_SW_RING) {
		/* handle the host stack ring */
		if (priv->np_txpoll || want_tx) {
			/* push any packets up, then we are always ready */
			netmap_txsync_to_host(na);
			revents |= want_tx;
		}
		if (want_rx) {
			kring = &na->rx_rings[lim_rx];
			if (kring->ring->avail == 0)
				netmap_rxsync_from_host(na, td, dev);
			if (kring->ring->avail > 0) {
				revents |= want_rx;
			}
		}
		return (revents);
	}

	/* if we are in transparent mode, check also the host rx ring */
	kring = &na->rx_rings[lim_rx];
	if ( (priv->np_qlast == NETMAP_HW_RING) // XXX check_all
			&& want_rx
			&& (netmap_fwd || kring->ring->flags & NR_FORWARD) ) {
		if (kring->ring->avail == 0)
			netmap_rxsync_from_host(na, td, dev);
		if (kring->ring->avail > 0)
			revents |= want_rx;
	}

	/*
	 * check_all is set if the card has more than one queue AND
	 * the client is polling all of them. If true, we sleep on
	 * the "global" selinfo, otherwise we sleep on individual selinfo
	 * (FreeBSD only allows two selinfo's per file descriptor).
	 * The interrupt routine in the driver wake one or the other
	 * (or both) depending on which clients are active.
	 *
	 * rxsync() is only called if we run out of buffers on a POLLIN.
	 * txsync() is called if we run out of buffers on POLLOUT, or
	 * there are pending packets to send. The latter can be disabled
	 * passing NETMAP_NO_TX_POLL in the NIOCREG call.
	 */
	check_all_tx = (priv->np_qlast == NETMAP_HW_RING) && (lim_tx > 1);
	check_all_rx = (priv->np_qlast == NETMAP_HW_RING) && (lim_rx > 1);

	if (priv->np_qlast != NETMAP_HW_RING) {
		lim_tx = lim_rx = priv->np_qlast;
	}

	/*
	 * We start with a lock free round which is good if we have
	 * data available. If this fails, then lock and call the sync
	 * routines.
	 */
	for (i = priv->np_qfirst; want_rx && i < lim_rx; i++) {
		kring = &na->rx_rings[i];
		if (kring->ring->avail > 0) {
			revents |= want_rx;
			want_rx = 0;	/* also breaks the loop */
		}
	}
	for (i = priv->np_qfirst; want_tx && i < lim_tx; i++) {
		kring = &na->tx_rings[i];
		if (kring->ring->avail > 0) {
			revents |= want_tx;
			want_tx = 0;	/* also breaks the loop */
		}
	}

	/*
	 * If we to push packets out (priv->np_txpoll) or want_tx is
	 * still set, we do need to run the txsync calls (on all rings,
	 * to avoid that the tx rings stall).
	 */
	if (priv->np_txpoll || want_tx) {
		/* If we really want to be woken up (want_tx),
		 * do a selrecord, either on the global or on
		 * the private structure.  Then issue the txsync
		 * so there is no race in the selrecord/selwait
		 */
flush_tx:
		for (i = priv->np_qfirst; i < lim_tx; i++) {
			kring = &na->tx_rings[i];
			/*
			 * Skip this ring if want_tx == 0
			 * (we have already done a successful sync on
			 * a previous ring) AND kring->cur == kring->hwcur
			 * (there are no pending transmissions for this ring).
			 */
			if (!want_tx && kring->ring->cur == kring->nr_hwcur)
				continue;
			/* make sure only one user thread is doing this */
			if (nm_kr_tryget(kring)) {
				ND("ring %p busy is %d", kring, (int)kring->nr_busy);
				revents |= POLLERR;
				goto out;
			}

			if (netmap_verbose & NM_VERB_TXSYNC)
				D("send %d on %s %d",
					kring->ring->cur, ifp->if_xname, i);
			if (na->nm_txsync(ifp, i, 0))
				revents |= POLLERR;

			/* Check avail/call selrecord only if called with POLLOUT */
			if (want_tx) {
				if (kring->ring->avail > 0) {
					/* stop at the first ring. We don't risk
					 * starvation.
					 */
					revents |= want_tx;
					want_tx = 0;
				}
			}
			nm_kr_put(kring);
		}
		if (want_tx && retry_tx) {
			selrecord(td, check_all_tx ?
			    &na->tx_si : &na->tx_rings[priv->np_qfirst].si);
			retry_tx = 0;
			goto flush_tx;
		}
	}

	/*
	 * now if want_rx is still set we need to lock and rxsync.
	 * Do it on all rings because otherwise we starve.
	 */
	if (want_rx) {
		int retry_rx = 1;
do_retry_rx:
		for (i = priv->np_qfirst; i < lim_rx; i++) {
			kring = &na->rx_rings[i];

			if (nm_kr_tryget(kring)) {
				revents |= POLLERR;
				goto out;
			}

			/* XXX NR_FORWARD should only be read on
			 * physical or NIC ports
			 */
			if (netmap_fwd ||kring->ring->flags & NR_FORWARD) {
				ND(10, "forwarding some buffers up %d to %d",
				    kring->nr_hwcur, kring->ring->cur);
				netmap_grab_packets(kring, &q, netmap_fwd);
			}

			if (na->nm_rxsync(ifp, i, 0))
				revents |= POLLERR;
			if (netmap_no_timestamp == 0 ||
					kring->ring->flags & NR_TIMESTAMP) {
				microtime(&kring->ring->ts);
			}

			if (kring->ring->avail > 0) {
				revents |= want_rx;
				retry_rx = 0;
			}
			nm_kr_put(kring);
		}
		if (retry_rx) {
			retry_rx = 0;
			selrecord(td, check_all_rx ?
			    &na->rx_si : &na->rx_rings[priv->np_qfirst].si);
			goto do_retry_rx;
		}
	}

	/* forward host to the netmap ring.
	 * I am accessing nr_hwavail without lock, but netmap_transmit
	 * can only increment it, so the operation is safe.
	 */
	kring = &na->rx_rings[lim_rx];
	if ( (priv->np_qlast == NETMAP_HW_RING) // XXX check_all
			&& (netmap_fwd || kring->ring->flags & NR_FORWARD)
			 && kring->nr_hwavail > 0 && !host_forwarded) {
		netmap_sw_to_nic(na);
		host_forwarded = 1; /* prevent another pass */
		want_rx = 0;
		goto flush_tx;
	}

	if (q.head)
		netmap_send_up(na->ifp, q.head);

out:

	return (revents);
}

/*------- driver support routines ------*/


/*
 * Initialize a ``netmap_adapter`` object created by driver on attach.
 * We allocate a block of memory with room for a struct netmap_adapter
 * plus two sets of N+2 struct netmap_kring (where N is the number
 * of hardware rings):
 * krings	0..N-1	are for the hardware queues.
 * kring	N	is for the host stack queue
 * kring	N+1	is only used for the selinfo for all queues.
 * Return 0 on success, ENOMEM otherwise.
 *
 * By default the receive and transmit adapter ring counts are both initialized
 * to num_queues.  na->num_tx_rings can be set for cards with different tx/rx
 * setups.
 */
int
netmap_attach(struct netmap_adapter *arg, u_int num_queues)
{
	struct netmap_adapter *na = NULL;
	struct ifnet *ifp = arg ? arg->ifp : NULL;
	size_t len;

	if (arg == NULL || ifp == NULL)
		goto fail;
	/* a VALE port uses two endpoints */
	len = nma_is_vp(arg) ? sizeof(*na) : sizeof(*na) * 2;
	na = malloc(len, M_DEVBUF, M_NOWAIT | M_ZERO);
	if (na == NULL)
		goto fail;
	WNA(ifp) = na;
	*na = *arg; /* copy everything, trust the driver to not pass junk */
	NETMAP_SET_CAPABLE(ifp);
	if (na->num_tx_rings == 0)
		na->num_tx_rings = num_queues;
	na->num_rx_rings = num_queues;
	na->refcount = na->na_single = na->na_multi = 0;
	/* Core lock initialized here, others after netmap_if_new. */
	mtx_init(&na->core_lock, "netmap core lock", MTX_NETWORK_LOCK, MTX_DEF);
#ifdef linux
	if (ifp->netdev_ops) {
		ND("netdev_ops %p", ifp->netdev_ops);
		/* prepare a clone of the netdev ops */
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 28)
		na->nm_ndo.ndo_start_xmit = ifp->netdev_ops;
#else
		na->nm_ndo = *ifp->netdev_ops;
#endif
	}
	na->nm_ndo.ndo_start_xmit = linux_netmap_start_xmit;
#endif /* linux */
	na->nm_mem = arg->nm_mem ? arg->nm_mem : &nm_mem;
	if (!nma_is_vp(arg))
		netmap_attach_sw(ifp);
	D("success for %s", ifp->if_xname);
	return 0;

fail:
	D("fail, arg %p ifp %p na %p", arg, ifp, na);
	netmap_detach(ifp);
	return (na ? EINVAL : ENOMEM);
}


/*
 * Free the allocated memory linked to the given ``netmap_adapter``
 * object.
 */
void
netmap_detach(struct ifnet *ifp)
{
	struct netmap_adapter *na = NA(ifp);

	if (!na)
		return;

	mtx_destroy(&na->core_lock);

	if (na->tx_rings) { /* XXX should not happen */
		D("freeing leftover tx_rings");
		free(na->tx_rings, M_DEVBUF);
	}
	if (na->na_flags & NAF_MEM_OWNER)
		netmap_mem_private_delete(na->nm_mem);
	bzero(na, sizeof(*na));
	WNA(ifp) = NULL;
	free(na, M_DEVBUF);
}


int
nm_bdg_flush(struct nm_bdg_fwd *ft, u_int n,
	struct netmap_adapter *na, u_int ring_nr);


/*
 * Intercept packets from the network stack and pass them
 * to netmap as incoming packets on the 'software' ring.
 * We rely on the OS to make sure that the ifp and na do not go
 * away (typically the caller checks for IFF_DRV_RUNNING or the like).
 * In nm_register() or whenever there is a reinitialization,
 * we make sure to access the core lock and per-ring locks
 * so that IFCAP_NETMAP is visible here.
 */
int
netmap_transmit(struct ifnet *ifp, struct mbuf *m)
{
	struct netmap_adapter *na = NA(ifp);
	struct netmap_kring *kring;
	u_int i, len = MBUF_LEN(m);
	u_int error = EBUSY, lim;
	struct netmap_slot *slot;

	// XXX [Linux] we do not need this lock
	// if we follow the down/configure/up protocol -gl
	// mtx_lock(&na->core_lock);
	if ( (ifp->if_capenable & IFCAP_NETMAP) == 0) {
		/* interface not in netmap mode anymore */
		error = ENXIO;
		goto done;
	}

	kring = &na->rx_rings[na->num_rx_rings];
	lim = kring->nkr_num_slots - 1;
	if (netmap_verbose & NM_VERB_HOST)
		D("%s packet %d len %d from the stack", ifp->if_xname,
			kring->nr_hwcur + kring->nr_hwavail, len);
	// XXX reconsider long packets if we handle fragments
	if (len > NETMAP_BDG_BUF_SIZE(na->nm_mem)) { /* too long for us */
		D("%s from_host, drop packet size %d > %d", ifp->if_xname,
			len, NETMAP_BDG_BUF_SIZE(na->nm_mem));
		goto done;
	}
	if (SWNA(ifp)->na_bdg) {
		struct nm_bdg_fwd *ft;
		char *dst;

		na = SWNA(ifp); /* we operate on the host port */
		ft = na->rx_rings[0].nkr_ft;
		dst = BDG_NMB(na->nm_mem, &na->rx_rings[0].ring->slot[0]);

		/* use slot 0 in the ft, there is nothing queued here */
		/* XXX we can save the copy calling m_copydata in nm_bdg_flush,
		 * need a special flag for this.
		 */
		m_copydata(m, 0, (int)len, dst);
		ft->ft_flags = 0;
		ft->ft_len = len;
		ft->ft_buf = dst;
		ft->ft_next = NM_FT_NULL;
		ft->ft_frags = 1;
		if (netmap_verbose & NM_VERB_HOST)
			RD(5, "pkt %p size %d to bridge port %d",
				dst, len, na->bdg_port);
		nm_bdg_flush(ft, 1, na, 0);
		na = NA(ifp);	/* back to the regular object/lock */
		error = 0;
		goto done;
	}

	/* protect against other instances of netmap_transmit,
	 * and userspace invocations of rxsync().
	 * XXX could reuse core_lock
	 */
	// XXX [Linux] there can be no other instances of netmap_transmit
	// on this same ring, but we still need this lock to protect
	// concurrent access from netmap_sw_to_nic() -gl
	mtx_lock(&kring->q_lock);
	if (kring->nr_hwavail >= lim) {
		if (netmap_verbose)
			D("stack ring %s full\n", ifp->if_xname);
	} else {
		/* compute the insert position */
		i = nm_kr_rxpos(kring);
		slot = &kring->ring->slot[i];
		m_copydata(m, 0, (int)len, BDG_NMB(na->nm_mem, slot));
		slot->len = len;
		slot->flags = kring->nkr_slot_flags;
		kring->nr_hwavail++;
		if (netmap_verbose  & NM_VERB_HOST)
			D("wake up host ring %s %d", na->ifp->if_xname, na->num_rx_rings);
		selwakeuppri(&kring->si, PI_NET);
		error = 0;
	}
	mtx_unlock(&kring->q_lock);

done:
	// mtx_unlock(&na->core_lock);

	/* release the mbuf in either cases of success or failure. As an
	 * alternative, put the mbuf in a free list and free the list
	 * only when really necessary.
	 */
	m_freem(m);

	return (error);
}


/*
 * netmap_reset() is called by the driver routines when reinitializing
 * a ring. The driver is in charge of locking to protect the kring.
 * If netmap mode is not set just return NULL.
 */
struct netmap_slot *
netmap_reset(struct netmap_adapter *na, enum txrx tx, u_int n,
	u_int new_cur)
{
	struct netmap_kring *kring;
	int new_hwofs, lim;

	if (na == NULL) {
		D("NULL na, should not happen");
		return NULL;	/* no netmap support here */
	}
	if (!(na->ifp->if_capenable & IFCAP_NETMAP)) {
		D("interface not in netmap mode");
		return NULL;	/* nothing to reinitialize */
	}

	/* XXX note- in the new scheme, we are not guaranteed to be
	 * under lock (e.g. when called on a device reset).
	 * In this case, we should set a flag and do not trust too
	 * much the values. In practice: TODO
	 * - set a RESET flag somewhere in the kring
	 * - do the processing in a conservative way
	 * - let the *sync() fixup at the end.
	 */
	if (tx == NR_TX) {
		if (n >= na->num_tx_rings)
			return NULL;
		kring = na->tx_rings + n;
		new_hwofs = kring->nr_hwcur - new_cur;
	} else {
		if (n >= na->num_rx_rings)
			return NULL;
		kring = na->rx_rings + n;
		new_hwofs = kring->nr_hwcur + kring->nr_hwavail - new_cur;
	}
	lim = kring->nkr_num_slots - 1;
	if (new_hwofs > lim)
		new_hwofs -= lim + 1;

	/* Always set the new offset value and realign the ring. */
	D("%s hwofs %d -> %d, hwavail %d -> %d",
		tx == NR_TX ? "TX" : "RX",
		kring->nkr_hwofs, new_hwofs,
		kring->nr_hwavail,
		tx == NR_TX ? lim : kring->nr_hwavail);
	kring->nkr_hwofs = new_hwofs;
	if (tx == NR_TX)
		kring->nr_hwavail = lim;

#if 0 // def linux
	/* XXX check that the mappings are correct */
	/* need ring_nr, adapter->pdev, direction */
	buffer_info->dma = dma_map_single(&pdev->dev, addr, adapter->rx_buffer_len, DMA_FROM_DEVICE);
	if (dma_mapping_error(&adapter->pdev->dev, buffer_info->dma)) {
		D("error mapping rx netmap buffer %d", i);
		// XXX fix error handling
	}

#endif /* linux */
	/*
	 * Wakeup on the individual and global selwait
	 * We do the wakeup here, but the ring is not yet reconfigured.
	 * However, we are under lock so there are no races.
	 */
	selwakeuppri(&kring->si, PI_NET);
	selwakeuppri(tx == NR_TX ? &na->tx_si : &na->rx_si, PI_NET);
	return kring->ring->slot;
}


/*
 * Grab packets from a kring, move them into the ft structure
 * associated to the tx (input) port. Max one instance per port,
 * filtered on input (ioctl, poll or XXX).
 * Returns the next position in the ring.
 */
static int
nm_bdg_preflush(struct netmap_adapter *na, u_int ring_nr,
	struct netmap_kring *kring, u_int end)
{
	struct netmap_ring *ring = kring->ring;
	struct nm_bdg_fwd *ft;
	u_int j = kring->nr_hwcur, lim = kring->nkr_num_slots - 1;
	u_int ft_i = 0;	/* start from 0 */
	u_int frags = 1; /* how many frags ? */
	struct nm_bridge *b = na->na_bdg;

	/* To protect against modifications to the bridge we acquire a
	 * shared lock, waiting if we can sleep (if the source port is
	 * attached to a user process) or with a trylock otherwise (NICs).
	 */
	ND("wait rlock for %d packets", ((j > end ? lim+1 : 0) + end) - j);
	if (na->na_flags & NAF_BDG_MAYSLEEP)
		BDG_RLOCK(b);
	else if (!BDG_RTRYLOCK(b))
		return 0;
	ND(5, "rlock acquired for %d packets", ((j > end ? lim+1 : 0) + end) - j);
	ft = kring->nkr_ft;

	for (; likely(j != end); j = nm_next(j, lim)) {
		struct netmap_slot *slot = &ring->slot[j];
		char *buf;

		ft[ft_i].ft_len = slot->len;
		ft[ft_i].ft_flags = slot->flags;

		ND("flags is 0x%x", slot->flags);
		/* this slot goes into a list so initialize the link field */
		ft[ft_i].ft_next = NM_FT_NULL;
		buf = ft[ft_i].ft_buf = (slot->flags & NS_INDIRECT) ?
			(void *)(uintptr_t)slot->ptr : BDG_NMB(na->nm_mem, slot);
		prefetch(buf);
		++ft_i;
		if (slot->flags & NS_MOREFRAG) {
			frags++;
			continue;
		}
		if (unlikely(netmap_verbose && frags > 1))
			RD(5, "%d frags at %d", frags, ft_i - frags);
		ft[ft_i - frags].ft_frags = frags;
		frags = 1;
		if (unlikely((int)ft_i >= bridge_batch))
			ft_i = nm_bdg_flush(ft, ft_i, na, ring_nr);
	}
	if (frags > 1) {
		D("truncate incomplete fragment at %d (%d frags)", ft_i, frags);
		// ft_i > 0, ft[ft_i-1].flags has NS_MOREFRAG
		ft[ft_i - 1].ft_frags &= ~NS_MOREFRAG;
		ft[ft_i - frags].ft_frags = frags - 1;
	}
	if (ft_i)
		ft_i = nm_bdg_flush(ft, ft_i, na, ring_nr);
	BDG_RUNLOCK(b);
	return j;
}


/*
 * Pass packets from nic to the bridge.
 * XXX TODO check locking: this is called from the interrupt
 * handler so we should make sure that the interface is not
 * disconnected while passing down an interrupt.
 *
 * Note, no user process can access this NIC so we can ignore
 * the info in the 'ring'.
 */
static void
netmap_nic_to_bdg(struct ifnet *ifp, u_int ring_nr)
{
	struct netmap_adapter *na = NA(ifp);
	struct netmap_kring *kring = &na->rx_rings[ring_nr];
	struct netmap_ring *ring = kring->ring;
	u_int j, k;

	/* make sure that only one thread is ever in here,
	 * after which we can unlock. Probably unnecessary XXX.
	 */
	if (nm_kr_tryget(kring)) 
		return;
	/* fetch packets that have arrived.
	 * XXX maybe do this in a loop ?
	 */
	if (na->nm_rxsync(ifp, ring_nr, 0))
		goto put_out;
	if (kring->nr_hwavail == 0 && netmap_verbose) {
		D("how strange, interrupt with no packets on %s",
			ifp->if_xname);
		goto put_out;
	}
	k = nm_kr_rxpos(kring);

	j = nm_bdg_preflush(na, ring_nr, kring, k);

	/* we consume everything, but we cannot update kring directly
	 * because the nic may have destroyed the info in the NIC ring.
	 * So we need to call rxsync again to restore it.
	 */
	ring->cur = j;
	ring->avail = 0;
	na->nm_rxsync(ifp, ring_nr, 0);

put_out:
	nm_kr_put(kring);
	return;
}


/*
 * Default functions to handle rx/tx interrupts from a physical device.
 * "work_done" is non-null on the RX path, NULL for the TX path.
 * We rely on the OS to make sure that there is only one active
 * instance per queue, and that there is appropriate locking.
 *
 * If the card is not in netmap mode, simply return 0,
 * so that the caller proceeds with regular processing.
 *
 * If the card is connected to a netmap file descriptor,
 * do a selwakeup on the individual queue, plus one on the global one
 * if needed (multiqueue card _and_ there are multiqueue listeners),
 * and return 1.
 *
 * Finally, if called on rx from an interface connected to a switch,
 * calls the proper forwarding routine, and return 1.
 */
int
netmap_rx_irq(struct ifnet *ifp, u_int q, u_int *work_done)
{
	struct netmap_adapter *na;
	struct netmap_kring *kring;

	if (!(ifp->if_capenable & IFCAP_NETMAP))
		return 0;

	q &= NETMAP_RING_MASK;

	if (netmap_verbose)
		RD(5, "received %s queue %d", work_done ? "RX" : "TX" , q);
	na = NA(ifp);
	if (na->na_flags & NAF_SKIP_INTR) {
		ND("use regular interrupt");
		return 0;
	}

	if (work_done) { /* RX path */
		if (q >= na->num_rx_rings)
			return 0;	// not a physical queue
		kring = na->rx_rings + q;
		kring->nr_kflags |= NKR_PENDINTR;	// XXX atomic ?
		if (na->na_bdg != NULL) {
			netmap_nic_to_bdg(ifp, q);
		} else {
			selwakeuppri(&kring->si, PI_NET);
			if (na->num_rx_rings > 1 /* or multiple listeners */ )
				selwakeuppri(&na->rx_si, PI_NET);
		}
		*work_done = 1; /* do not fire napi again */
	} else { /* TX path */
		if (q >= na->num_tx_rings)
			return 0;	// not a physical queue
		kring = na->tx_rings + q;
		selwakeuppri(&kring->si, PI_NET);
		if (na->num_tx_rings > 1 /* or multiple listeners */ )
			selwakeuppri(&na->tx_si, PI_NET);
	}
	return 1;
}


#ifdef linux	/* linux-specific routines */


/*
 * Remap linux arguments into the FreeBSD call.
 * - pwait is the poll table, passed as 'dev';
 *   If pwait == NULL someone else already woke up before. We can report
 *   events but they are filtered upstream.
 *   If pwait != NULL, then pwait->key contains the list of events.
 * - events is computed from pwait as above.
 * - file is passed as 'td';
 */
static u_int
linux_netmap_poll(struct file * file, struct poll_table_struct *pwait)
{
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,28)
	int events = POLLIN | POLLOUT; /* XXX maybe... */
#elif LINUX_VERSION_CODE < KERNEL_VERSION(3,4,0)
	int events = pwait ? pwait->key : POLLIN | POLLOUT;
#else /* in 3.4.0 field 'key' was renamed to '_key' */
	int events = pwait ? pwait->_key : POLLIN | POLLOUT;
#endif
	return netmap_poll((void *)pwait, events, (void *)file);
}


static int
linux_netmap_mmap(struct file *f, struct vm_area_struct *vma)
{
	int error = 0;
	unsigned long off, va;
	vm_ooffset_t pa;
	struct netmap_priv_d *priv = f->private_data;
	/*
	 * vma->vm_start: start of mapping user address space
	 * vma->vm_end: end of the mapping user address space
	 * vma->vm_pfoff: offset of first page in the device
	 */

	// XXX security checks

	error = netmap_get_memory(priv);
	ND("get_memory returned %d", error);
	if (error)
	    return -error;

	if ((vma->vm_start & ~PAGE_MASK) || (vma->vm_end & ~PAGE_MASK)) {
		ND("vm_start = %lx vm_end = %lx", vma->vm_start, vma->vm_end);
		return -EINVAL;
	}

	for (va = vma->vm_start, off = vma->vm_pgoff;
	     va < vma->vm_end;
	     va += PAGE_SIZE, off++)
	{
		pa = netmap_mem_ofstophys(priv->np_mref, off << PAGE_SHIFT);
		if (pa == 0) 
			return -EINVAL;
	
		ND("va %lx pa %p", va, pa);	
		error = remap_pfn_range(vma, va, pa >> PAGE_SHIFT, PAGE_SIZE, vma->vm_page_prot);
		if (error) 
			return error;
	}
	return 0;
}


/*
 * This one is probably already protected by the netif lock XXX
 */
static netdev_tx_t
linux_netmap_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	netmap_transmit(dev, skb);
	return (NETDEV_TX_OK);
}


#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)	// XXX was 37
#define LIN_IOCTL_NAME	.ioctl
int
linux_netmap_ioctl(struct inode *inode, struct file *file, u_int cmd, u_long data /* arg */)
#else
#define LIN_IOCTL_NAME	.unlocked_ioctl
long
linux_netmap_ioctl(struct file *file, u_int cmd, u_long data /* arg */)
#endif
{
	int ret;
	struct nmreq nmr;
	bzero(&nmr, sizeof(nmr));

	if (cmd == NIOCTXSYNC || cmd == NIOCRXSYNC) {
		data = 0;	/* no argument required here */
	}
	if (data && copy_from_user(&nmr, (void *)data, sizeof(nmr) ) != 0)
		return -EFAULT;
	ret = netmap_ioctl(NULL, cmd, (caddr_t)&nmr, 0, (void *)file);
	if (data && copy_to_user((void*)data, &nmr, sizeof(nmr) ) != 0)
		return -EFAULT;
	return -ret;
}


static int
netmap_release(struct inode *inode, struct file *file)
{
	(void)inode;	/* UNUSED */
	if (file->private_data)
		netmap_dtor(file->private_data);
	return (0);
}


static int
linux_netmap_open(struct inode *inode, struct file *file)
{
	struct netmap_priv_d *priv;
	(void)inode;	/* UNUSED */

	priv = malloc(sizeof(struct netmap_priv_d), M_DEVBUF,
			      M_NOWAIT | M_ZERO);
	if (priv == NULL)
		return -ENOMEM;

	file->private_data = priv;

	return (0);
}


static struct file_operations netmap_fops = {
    .owner = THIS_MODULE,
    .open = linux_netmap_open,
    .mmap = linux_netmap_mmap,
    LIN_IOCTL_NAME = linux_netmap_ioctl,
    .poll = linux_netmap_poll,
    .release = netmap_release,
};


static struct miscdevice netmap_cdevsw = {	/* same name as FreeBSD */
	MISC_DYNAMIC_MINOR,
	"netmap",
	&netmap_fops,
};

static int netmap_init(void);
static void netmap_fini(void);


/* Errors have negative values on linux */
static int linux_netmap_init(void)
{
	return -netmap_init();
}

module_init(linux_netmap_init);
module_exit(netmap_fini);
/* export certain symbols to other modules */
EXPORT_SYMBOL(netmap_attach);		// driver attach routines
EXPORT_SYMBOL(netmap_detach);		// driver detach routines
EXPORT_SYMBOL(netmap_ring_reinit);	// ring init on error
EXPORT_SYMBOL(netmap_buffer_lut);
EXPORT_SYMBOL(netmap_total_buffers);	// index check
EXPORT_SYMBOL(netmap_buffer_base);
EXPORT_SYMBOL(netmap_reset);		// ring init routines
EXPORT_SYMBOL(netmap_buf_size);
EXPORT_SYMBOL(netmap_rx_irq);		// default irq handler
EXPORT_SYMBOL(netmap_no_pendintr);	// XXX mitigation - should go away
EXPORT_SYMBOL(netmap_bdg_ctl);		// bridge configuration routine
EXPORT_SYMBOL(netmap_bdg_learning);	// the default lookup function
EXPORT_SYMBOL(netmap_disable_all_rings);
EXPORT_SYMBOL(netmap_enable_all_rings);


MODULE_AUTHOR("http://info.iet.unipi.it/~luigi/netmap/");
MODULE_DESCRIPTION("The netmap packet I/O framework");
MODULE_LICENSE("Dual BSD/GPL"); /* the code here is all BSD. */

#else /* __FreeBSD__ */


static struct cdevsw netmap_cdevsw = {
	.d_version = D_VERSION,
	.d_name = "netmap",
	.d_open = netmap_open,
	.d_mmap_single = netmap_mmap_single,
	.d_ioctl = netmap_ioctl,
	.d_poll = netmap_poll,
	.d_close = netmap_close,
};
#endif /* __FreeBSD__ */

/*
 *---- support for virtual bridge -----
 */

/* ----- FreeBSD if_bridge hash function ------- */

/*
 * The following hash function is adapted from "Hash Functions" by Bob Jenkins
 * ("Algorithm Alley", Dr. Dobbs Journal, September 1997).
 *
 * http://www.burtleburtle.net/bob/hash/spooky.html
 */
#define mix(a, b, c)                                                    \
do {                                                                    \
        a -= b; a -= c; a ^= (c >> 13);                                 \
        b -= c; b -= a; b ^= (a << 8);                                  \
        c -= a; c -= b; c ^= (b >> 13);                                 \
        a -= b; a -= c; a ^= (c >> 12);                                 \
        b -= c; b -= a; b ^= (a << 16);                                 \
        c -= a; c -= b; c ^= (b >> 5);                                  \
        a -= b; a -= c; a ^= (c >> 3);                                  \
        b -= c; b -= a; b ^= (a << 10);                                 \
        c -= a; c -= b; c ^= (b >> 15);                                 \
} while (/*CONSTCOND*/0)

static __inline uint32_t
nm_bridge_rthash(const uint8_t *addr)
{
        uint32_t a = 0x9e3779b9, b = 0x9e3779b9, c = 0; // hask key

        b += addr[5] << 8;
        b += addr[4];
        a += addr[3] << 24;
        a += addr[2] << 16;
        a += addr[1] << 8;
        a += addr[0];

        mix(a, b, c);
#define BRIDGE_RTHASH_MASK	(NM_BDG_HASH-1)
        return (c & BRIDGE_RTHASH_MASK);
}

#undef mix


static int
bdg_netmap_reg(struct ifnet *ifp, int onoff)
{
	/* the interface is already attached to the bridge,
	 * so we only need to toggle IFCAP_NETMAP.
	 */
	if (onoff) {
		ifp->if_capenable |= IFCAP_NETMAP;
	} else {
		ifp->if_capenable &= ~IFCAP_NETMAP;
	}
	return 0;
}


/*
 * Lookup function for a learning bridge.
 * Update the hash table with the source address,
 * and then returns the destination port index, and the
 * ring in *dst_ring (at the moment, always use ring 0)
 */
u_int
netmap_bdg_learning(char *buf, u_int buf_len, uint8_t *dst_ring,
		struct netmap_adapter *na)
{
	struct nm_hash_ent *ht = na->na_bdg->ht;
	uint32_t sh, dh;
	u_int dst, mysrc = na->bdg_port;
	uint64_t smac, dmac;

	if (buf_len < 14) {
		D("invalid buf length %d", buf_len);
		return NM_BDG_NOPORT;
	}
	dmac = le64toh(*(uint64_t *)(buf)) & 0xffffffffffff;
	smac = le64toh(*(uint64_t *)(buf + 4));
	smac >>= 16;

	/*
	 * The hash is somewhat expensive, there might be some
	 * worthwhile optimizations here.
	 */
	if ((buf[6] & 1) == 0) { /* valid src */
		uint8_t *s = buf+6;
		sh = nm_bridge_rthash(s); // XXX hash of source
		/* update source port forwarding entry */
		ht[sh].mac = smac;	/* XXX expire ? */
		ht[sh].ports = mysrc;
		if (netmap_verbose)
		    D("src %02x:%02x:%02x:%02x:%02x:%02x on port %d",
			s[0], s[1], s[2], s[3], s[4], s[5], mysrc);
	}
	dst = NM_BDG_BROADCAST;
	if ((buf[0] & 1) == 0) { /* unicast */
		dh = nm_bridge_rthash(buf); // XXX hash of dst
		if (ht[dh].mac == dmac) {	/* found dst */
			dst = ht[dh].ports;
		}
		/* XXX otherwise return NM_BDG_UNKNOWN ? */
	}
	*dst_ring = 0;
	return dst;
}


/*
 * This flush routine supports only unicast and broadcast but a large
 * number of ports, and lets us replace the learn and dispatch functions.
 */
int
nm_bdg_flush(struct nm_bdg_fwd *ft, u_int n, struct netmap_adapter *na,
		u_int ring_nr)
{
	struct nm_bdg_q *dst_ents, *brddst;
	uint16_t num_dsts = 0, *dsts;
	struct nm_bridge *b = na->na_bdg;
	u_int i, j, me = na->bdg_port;

	/*
	 * The work area (pointed by ft) is followed by an array of
	 * pointers to queues , dst_ents; there are NM_BDG_MAXRINGS
	 * queues per port plus one for the broadcast traffic.
	 * Then we have an array of destination indexes.
	 */
	dst_ents = (struct nm_bdg_q *)(ft + NM_BDG_BATCH_MAX);
	dsts = (uint16_t *)(dst_ents + NM_BDG_MAXPORTS * NM_BDG_MAXRINGS + 1);

	/* first pass: find a destination for each packet in the batch */
	for (i = 0; likely(i < n); i += ft[i].ft_frags) {
		uint8_t dst_ring = ring_nr; /* default, same ring as origin */
		uint16_t dst_port, d_i;
		struct nm_bdg_q *d;

		ND("slot %d frags %d", i, ft[i].ft_frags);
		dst_port = b->nm_bdg_lookup(ft[i].ft_buf, ft[i].ft_len,
			&dst_ring, na);
		if (netmap_verbose > 255)
			RD(5, "slot %d port %d -> %d", i, me, dst_port);
		if (dst_port == NM_BDG_NOPORT)
			continue; /* this packet is identified to be dropped */
		else if (unlikely(dst_port > NM_BDG_MAXPORTS))
			continue;
		else if (dst_port == NM_BDG_BROADCAST)
			dst_ring = 0; /* broadcasts always go to ring 0 */
		else if (unlikely(dst_port == me ||
		    !b->bdg_ports[dst_port]))
			continue;

		/* get a position in the scratch pad */
		d_i = dst_port * NM_BDG_MAXRINGS + dst_ring;
		d = dst_ents + d_i;

		/* append the first fragment to the list */
		if (d->bq_head == NM_FT_NULL) { /* new destination */
			d->bq_head = d->bq_tail = i;
			/* remember this position to be scanned later */
			if (dst_port != NM_BDG_BROADCAST)
				dsts[num_dsts++] = d_i;
		} else {
			ft[d->bq_tail].ft_next = i;
			d->bq_tail = i;
		}
		d->bq_len += ft[i].ft_frags;
	}

	/*
	 * Broadcast traffic goes to ring 0 on all destinations.
	 * So we need to add these rings to the list of ports to scan.
	 * XXX at the moment we scan all NM_BDG_MAXPORTS ports, which is
	 * expensive. We should keep a compact list of active destinations
	 * so we could shorten this loop.
	 */
	brddst = dst_ents + NM_BDG_BROADCAST * NM_BDG_MAXRINGS;
	if (brddst->bq_head != NM_FT_NULL) {
		for (j = 0; likely(j < b->bdg_active_ports); j++) {
			uint16_t d_i;
			i = b->bdg_port_index[j];
			if (unlikely(i == me))
				continue;
			d_i = i * NM_BDG_MAXRINGS;
			if (dst_ents[d_i].bq_head == NM_FT_NULL)
				dsts[num_dsts++] = d_i;
		}
	}

	ND(5, "pass 1 done %d pkts %d dsts", n, num_dsts);
	/* second pass: scan destinations (XXX will be modular somehow) */
	for (i = 0; i < num_dsts; i++) {
		struct ifnet *dst_ifp;
		struct netmap_adapter *dst_na;
		struct netmap_kring *kring;
		struct netmap_ring *ring;
		u_int dst_nr, is_vp, lim, j, sent = 0, d_i, next, brd_next;
		u_int needed, howmany;
		int retry = netmap_txsync_retry;
		struct nm_bdg_q *d;
		uint32_t my_start = 0, lease_idx = 0;
		int nrings;

		d_i = dsts[i];
		ND("second pass %d port %d", i, d_i);
		d = dst_ents + d_i;
		// XXX fix the division
		dst_na = b->bdg_ports[d_i/NM_BDG_MAXRINGS];
		/* protect from the lookup function returning an inactive
		 * destination port
		 */
		if (unlikely(dst_na == NULL))
			goto cleanup;
		if (dst_na->na_flags & NAF_SW_ONLY)
			goto cleanup;
		dst_ifp = dst_na->ifp;
		/*
		 * The interface may be in !netmap mode in two cases:
		 * - when na is attached but not activated yet;
		 * - when na is being deactivated but is still attached.
		 */
		if (unlikely(!(dst_ifp->if_capenable & IFCAP_NETMAP))) {
			ND("not in netmap mode!");
			goto cleanup;
		}

		/* there is at least one either unicast or broadcast packet */
		brd_next = brddst->bq_head;
		next = d->bq_head;
		/* we need to reserve this many slots. If fewer are
		 * available, some packets will be dropped.
		 * Packets may have multiple fragments, so we may not use
		 * there is a chance that we may not use all of the slots
		 * we have claimed, so we will need to handle the leftover
		 * ones when we regain the lock.
		 */
		needed = d->bq_len + brddst->bq_len;

		is_vp = nma_is_vp(dst_na);
		ND(5, "pass 2 dst %d is %x %s",
			i, d_i, is_vp ? "virtual" : "nic/host");
		dst_nr = d_i & (NM_BDG_MAXRINGS-1);
		if (is_vp) { /* virtual port */
			nrings = dst_na->num_rx_rings;
		} else {
			nrings = dst_na->num_tx_rings;
		}
		if (dst_nr >= nrings)
			dst_nr = dst_nr % nrings;
		kring = is_vp ?  &dst_na->rx_rings[dst_nr] :
				&dst_na->tx_rings[dst_nr];
		ring = kring->ring;
		lim = kring->nkr_num_slots - 1;

retry:

		/* reserve the buffers in the queue and an entry
		 * to report completion, and drop lock.
		 * XXX this might become a helper function.
		 */
		mtx_lock(&kring->q_lock);
		if (kring->nkr_stopped) {
			mtx_unlock(&kring->q_lock);
			goto cleanup;
		}
		/* on physical interfaces, do a txsync to recover
		 * slots for packets already transmitted.
		 * XXX maybe we could be optimistic and rely on a retry
		 * in case of failure.
		 */
		if (nma_is_hw(dst_na)) {
			dst_na->nm_txsync(dst_ifp, dst_nr, 0);
		}
		my_start = j = kring->nkr_hwlease;
		howmany = nm_kr_space(kring, is_vp);
		if (needed < howmany)
			howmany = needed;
		lease_idx = nm_kr_lease(kring, howmany, is_vp);
		mtx_unlock(&kring->q_lock);

		/* only retry if we need more than available slots */
		if (retry && needed <= howmany)
			retry = 0;

		/* copy to the destination queue */
		while (howmany > 0) {
			struct netmap_slot *slot;
			struct nm_bdg_fwd *ft_p, *ft_end;
			u_int cnt;

			/* find the queue from which we pick next packet.
			 * NM_FT_NULL is always higher than valid indexes
			 * so we never dereference it if the other list
			 * has packets (and if both are empty we never
			 * get here).
			 */
			if (next < brd_next) {
				ft_p = ft + next;
				next = ft_p->ft_next;
			} else { /* insert broadcast */
				ft_p = ft + brd_next;
				brd_next = ft_p->ft_next;
			}
			cnt = ft_p->ft_frags; // cnt > 0
			if (unlikely(cnt > howmany))
			    break; /* no more space */
			howmany -= cnt;
			if (netmap_verbose && cnt > 1)
				RD(5, "rx %d frags to %d", cnt, j);
			ft_end = ft_p + cnt;
			do {
			    void *dst, *src = ft_p->ft_buf;
			    size_t len = (ft_p->ft_len + 63) & ~63;

			    slot = &ring->slot[j];
			    dst = BDG_NMB(dst_na->nm_mem, slot);
			    /* round to a multiple of 64 */

			    ND("send %d %d bytes at %s:%d",
				i, ft_p->ft_len, dst_ifp->if_xname, j);
			    if (ft_p->ft_flags & NS_INDIRECT) {
				if (copyin(src, dst, len)) {
					// invalid user pointer, pretend len is 0
					ft_p->ft_len = 0;
				}
			    } else {
				//memcpy(dst, src, len);
				pkt_copy(src, dst, (int)len);
			    }
			    slot->len = ft_p->ft_len;
			    slot->flags = (cnt << 8)| NS_MOREFRAG;
			    j = nm_next(j, lim);
			    ft_p++;
			    sent++;
			} while (ft_p != ft_end);
			slot->flags = (cnt << 8); /* clear flag on last entry */
			/* are we done ? */
			if (next == NM_FT_NULL && brd_next == NM_FT_NULL)
				break;
		}
		{
		    /* current position */
		    uint32_t *p = kring->nkr_leases; /* shorthand */
		    uint32_t update_pos;
		    int still_locked = 1;

		    mtx_lock(&kring->q_lock);
		    if (unlikely(howmany > 0)) {
			/* not used all bufs. If i am the last one
			 * i can recover the slots, otherwise must
			 * fill them with 0 to mark empty packets.
			 */
			ND("leftover %d bufs", howmany);
			if (nm_next(lease_idx, lim) == kring->nkr_lease_idx) {
			    /* yes i am the last one */
			    ND("roll back nkr_hwlease to %d", j);
			    kring->nkr_hwlease = j;
			} else {
			    while (howmany-- > 0) {
				ring->slot[j].len = 0;
				ring->slot[j].flags = 0;
				j = nm_next(j, lim);
			    }
			}
		    }
		    p[lease_idx] = j; /* report I am done */

		    update_pos = is_vp ? nm_kr_rxpos(kring) : ring->cur;

		    if (my_start == update_pos) {
			/* all slots before my_start have been reported,
			 * so scan subsequent leases to see if other ranges
			 * have been completed, and to a selwakeup or txsync.
		         */
			while (lease_idx != kring->nkr_lease_idx &&
				p[lease_idx] != NR_NOSLOT) {
			    j = p[lease_idx];
			    p[lease_idx] = NR_NOSLOT;
			    lease_idx = nm_next(lease_idx, lim); 
			}
			/* j is the new 'write' position. j != my_start
			 * means there are new buffers to report
			 */
			if (likely(j != my_start)) {
			    if (is_vp) {
				uint32_t old_avail = kring->nr_hwavail;

				kring->nr_hwavail = (j >= kring->nr_hwcur) ?
					j - kring->nr_hwcur :
					j + lim + 1 - kring->nr_hwcur;
				if (kring->nr_hwavail < old_avail) {
					D("avail shrink %d -> %d",
						old_avail, kring->nr_hwavail);
				}
				still_locked = 0;
				mtx_unlock(&kring->q_lock);
				selwakeuppri(&kring->si, PI_NET);
			    } else {
				ring->cur = j;
				/* XXX update avail ? */
				still_locked = 0;
				dst_na->nm_txsync(dst_ifp, dst_nr, 0);
				mtx_unlock(&kring->q_lock);

				/* retry to send more packets */
				if (nma_is_hw(dst_na) && retry--)
					goto retry;
			    }
			}
		    }
		    if (still_locked)
			mtx_unlock(&kring->q_lock);
		}
cleanup:
		d->bq_head = d->bq_tail = NM_FT_NULL; /* cleanup */
		d->bq_len = 0;
	}
	brddst->bq_head = brddst->bq_tail = NM_FT_NULL; /* cleanup */
	brddst->bq_len = 0;
	return 0;
}


/*
 * main dispatch routine for the bridge.
 * We already know that only one thread is running this.
 * we must run nm_bdg_preflush without lock.
 */
static int
bdg_netmap_txsync(struct ifnet *ifp, u_int ring_nr, int flags)
{
	struct netmap_adapter *na = NA(ifp);
	struct netmap_kring *kring = &na->tx_rings[ring_nr];
	struct netmap_ring *ring = kring->ring;
	u_int j, k, lim = kring->nkr_num_slots - 1;

	k = ring->cur;
	if (k > lim)
		return netmap_ring_reinit(kring);

	if (bridge_batch <= 0) { /* testing only */
		j = k; // used all
		goto done;
	}
	if (bridge_batch > NM_BDG_BATCH)
		bridge_batch = NM_BDG_BATCH;

	j = nm_bdg_preflush(na, ring_nr, kring, k);
	if (j != k)
		D("early break at %d/ %d, avail %d", j, k, kring->nr_hwavail);
	/* k-j modulo ring size is the number of slots processed */
	if (k < j)
		k += kring->nkr_num_slots;
	kring->nr_hwavail = lim - (k - j);

done:
	kring->nr_hwcur = j;
	ring->avail = kring->nr_hwavail;
	if (netmap_verbose)
		D("%s ring %d flags %d", ifp->if_xname, ring_nr, flags);
	return 0;
}


/*
 * user process reading from a VALE switch.
 * Already protected against concurrent calls from userspace,
 * but we must acquire the queue's lock to protect against
 * writers on the same queue.
 */
static int
bdg_netmap_rxsync(struct ifnet *ifp, u_int ring_nr, int flags)
{
	struct netmap_adapter *na = NA(ifp);
	struct netmap_kring *kring = &na->rx_rings[ring_nr];
	struct netmap_ring *ring = kring->ring;
	u_int j, lim = kring->nkr_num_slots - 1;
	u_int k = ring->cur, resvd = ring->reserved;
	int n;

	mtx_lock(&kring->q_lock);
	if (k > lim) {
		D("ouch dangerous reset!!!");
		n = netmap_ring_reinit(kring);
		goto done;
	}

	/* skip past packets that userspace has released */
	j = kring->nr_hwcur;    /* netmap ring index */
	if (resvd > 0) {
		if (resvd + ring->avail >= lim + 1) {
			D("XXX invalid reserve/avail %d %d", resvd, ring->avail);
			ring->reserved = resvd = 0; // XXX panic...
		}
		k = (k >= resvd) ? k - resvd : k + lim + 1 - resvd;
	}

	if (j != k) { /* userspace has released some packets. */
		n = k - j;
		if (n < 0)
			n += kring->nkr_num_slots;
		ND("userspace releases %d packets", n);
                for (n = 0; likely(j != k); n++) {
                        struct netmap_slot *slot = &ring->slot[j];
                        void *addr = BDG_NMB(na->nm_mem, slot);

                        if (addr == netmap_buffer_base) { /* bad buf */
				D("bad buffer index %d, ignore ?",
					slot->buf_idx);
                        }
			slot->flags &= ~NS_BUF_CHANGED;
                        j = nm_next(j, lim);
                }
                kring->nr_hwavail -= n;
                kring->nr_hwcur = k;
        }
        /* tell userspace that there are new packets */
        ring->avail = kring->nr_hwavail - resvd;
	n = 0;
done:
	mtx_unlock(&kring->q_lock);
	return n;
}


static int
bdg_netmap_attach(struct netmap_adapter *arg)
{
	struct netmap_adapter na;

	ND("attaching virtual bridge");
	bzero(&na, sizeof(na));

	na.ifp = arg->ifp;
	na.na_flags = NAF_BDG_MAYSLEEP | NAF_MEM_OWNER;
	na.num_tx_rings = arg->num_tx_rings;
	na.num_rx_rings = arg->num_rx_rings;
	na.num_tx_desc = arg->num_tx_desc;
	na.num_rx_desc = arg->num_rx_desc;
	na.nm_txsync = bdg_netmap_txsync;
	na.nm_rxsync = bdg_netmap_rxsync;
	na.nm_register = bdg_netmap_reg;
	na.nm_mem = netmap_mem_private_new(arg->ifp->if_xname,
			na.num_tx_rings, na.num_tx_desc,
			na.num_rx_rings, na.num_rx_desc);
	return netmap_attach(&na, na.num_tx_rings);
}


static struct cdev *netmap_dev; /* /dev/netmap character device. */


/*
 * Module loader.
 *
 * Create the /dev/netmap device and initialize all global
 * variables.
 *
 * Return 0 on success, errno on failure.
 */
static int
netmap_init(void)
{
	int i, error;

	NMG_LOCK_INIT();

	error = netmap_mem_init();
	if (error != 0) {
		printf("netmap: unable to initialize the memory allocator.\n");
		return (error);
	}
	printf("netmap: loaded module\n");
	netmap_dev = make_dev(&netmap_cdevsw, 0, UID_ROOT, GID_WHEEL, 0660,
			      "netmap");

	bzero(nm_bridges, sizeof(struct nm_bridge) * NM_BRIDGES); /* safety */
	for (i = 0; i < NM_BRIDGES; i++)
		BDG_RWINIT(&nm_bridges[i]);
	return (error);
}


/*
 * Module unloader.
 *
 * Free all the memory, and destroy the ``/dev/netmap`` device.
 */
static void
netmap_fini(void)
{
	destroy_dev(netmap_dev);
	netmap_mem_fini();
	NMG_LOCK_DESTROY();
	printf("netmap: unloaded module.\n");
}


#ifdef __FreeBSD__
/*
 * Kernel entry point.
 *
 * Initialize/finalize the module and return.
 *
 * Return 0 on success, errno on failure.
 */
static int
netmap_loader(__unused struct module *module, int event, __unused void *arg)
{
	int error = 0;

	switch (event) {
	case MOD_LOAD:
		error = netmap_init();
		break;

	case MOD_UNLOAD:
		netmap_fini();
		break;

	default:
		error = EOPNOTSUPP;
		break;
	}

	return (error);
}


DEV_MODULE(netmap, netmap_loader, NULL);
#endif /* __FreeBSD__ */