xref: /freebsd-14.2/sys/dev/netmap/netmap_vale.c (revision 0c7ba37e)

/*
 * Copyright (C) 2013-2014 Universita` di Pisa. 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 implements the VALE switch for netmap

--- 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/errno.h>
#include <sys/param.h>	/* defines used in kernel.h */
#include <sys/kernel.h>	/* types used in module initialization */
#include <sys/conf.h>	/* cdevsw struct, UID, GID */
#include <sys/sockio.h>
#include <sys/socketvar.h>	/* struct socket */
#include <sys/malloc.h>
#include <sys/poll.h>
#include <sys/rwlock.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 <machine/bus.h>	/* bus_dmamap_* */
#include <sys/endian.h>
#include <sys/refcount.h>


#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)


#elif defined(linux)

#include "bsd_glue.h"

#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>

#ifdef WITH_VALE

/*
 * 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_DECL(_dev_netmap);
SYSCTL_INT(_dev_netmap, OID_AUTO, bridge_batch, CTLFLAG_RW, &bridge_batch, 0 , "");


static int bdg_netmap_attach(struct nmreq *nmr, struct ifnet *ifp);
static int bdg_netmap_reg(struct netmap_adapter *na, int onoff);
static int netmap_bwrap_attach(struct ifnet *, struct ifnet *);
static int netmap_bwrap_register(struct netmap_adapter *, 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_vp_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];


/*
 * 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 = na->num_tx_rings;
	kring = na->tx_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 */
		}
	}
}


/*
 * 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 = na->num_tx_rings + 1;
	kring = na->tx_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;
	}
	return 0;
}


static void
netmap_bdg_detach_common(struct nm_bridge *b, int hw, int sw)
{
	int s_hw = hw, s_sw = sw;
	int i, lim =b->bdg_active_ports;
	uint8_t tmp[NM_BDG_MAXPORTS];

	/*
	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.
	 */

	D("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);
	}

	BDG_WLOCK(b);
	b->bdg_ports[s_hw] = NULL;
	if (s_sw >= 0) {
		b->bdg_ports[s_sw] = 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;
	}
}


static void
netmap_adapter_vp_dtor(struct netmap_adapter *na)
{
	struct netmap_vp_adapter *vpna = (struct netmap_vp_adapter*)na;
	struct nm_bridge *b = vpna->na_bdg;
	struct ifnet *ifp = na->ifp;

	ND("%s has %d references", NM_IFPNAME(ifp), na->na_refcount);

	if (b) {
		netmap_bdg_detach_common(b, vpna->bdg_port, -1);
	}

	bzero(ifp, sizeof(*ifp));
	free(ifp, M_DEVBUF);
	na->ifp = NULL;
}


/* Try to get a reference to a netmap adapter attached to a VALE switch.
 * If the adapter is found (or is created), this function returns 0, a
 * non NULL pointer is returned into *na, and the caller holds a
 * reference to the adapter.
 * If an adapter is not found, then no reference is grabbed and the
 * function returns an error code, or 0 if there is just a VALE prefix
 * mismatch. Therefore the caller holds a reference when
 * (*na != NULL && return == 0).
 */
int
netmap_get_bdg_na(struct nmreq *nmr, struct netmap_adapter **na, int create)
{
	const char *name = nmr->nr_name;
	struct ifnet *ifp;
	int error = 0;
	struct netmap_adapter *ret;
	struct netmap_vp_adapter *vpna;
	struct nm_bridge *b;
	int i, j, cand = -1, cand2 = -1;
	int needed;

	*na = NULL;     /* default return value */

	/* first try to see if this is a bridge port. */
	NMG_LOCK_ASSERT();
	if (strncmp(name, NM_NAME, sizeof(NM_NAME) - 1)) {
		return 0;  /* no error, but no VALE prefix */
	}

	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];
		vpna = b->bdg_ports[i];
		// KASSERT(na != NULL);
		ifp = vpna->up.ifp;
		/* XXX make sure the name only contains one : */
		if (!strcmp(NM_IFPNAME(ifp), name)) {
			netmap_adapter_get(&vpna->up);
			ND("found existing if %s refs %d", name,
				vpna->na_bdg_refcount);
			*na = (struct netmap_adapter *)vpna;
			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)
	 */
	ifp = ifunit_ref(name + b->bdg_namelen + 1);
	if (!ifp) { /* this is a virtual port */
		if (nmr->nr_cmd) {
			/* nr_cmd must be 0 for a virtual port */
			return EINVAL;
		}

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

		strcpy(ifp->if_xname, name);
		/* bdg_netmap_attach creates a struct netmap_adapter */
		error = bdg_netmap_attach(nmr, ifp);
		if (error) {
			D("error %d", error);
			free(ifp, M_DEVBUF);
			return error;
		}
		ret = NA(ifp);
		cand2 = -1;	/* only need one port */
	} else {  /* this is a NIC */
		struct ifnet *fake_ifp;

		error = netmap_get_hw_na(ifp, &ret);
		if (error || ret == NULL)
			goto out;

		/* make sure the NIC is not already in use */
		if (NETMAP_OWNED_BY_ANY(ret)) {
			D("NIC %s busy, cannot attach to bridge",
				NM_IFPNAME(ifp));
			error = EINVAL;
			goto out;
		}
		/* create a fake interface */
		fake_ifp = malloc(sizeof(*ifp), M_DEVBUF, M_NOWAIT | M_ZERO);
		if (!fake_ifp) {
			error = ENOMEM;
			goto out;
		}
		strcpy(fake_ifp->if_xname, name);
		error = netmap_bwrap_attach(fake_ifp, ifp);
		if (error) {
			free(fake_ifp, M_DEVBUF);
			goto out;
		}
		ret = NA(fake_ifp);
		if (nmr->nr_arg1 != NETMAP_BDG_HOST)
			cand2 = -1; /* only need one port */
		if_rele(ifp);
	}
	vpna = (struct netmap_vp_adapter *)ret;

	BDG_WLOCK(b);
	vpna->bdg_port = cand;
	ND("NIC  %p to bridge port %d", vpna, cand);
	/* bind the port to the bridge (virtual ports are not active) */
	b->bdg_ports[cand] = vpna;
	vpna->na_bdg = b;
	b->bdg_active_ports++;
	if (cand2 >= 0) {
		struct netmap_vp_adapter *hostna = vpna + 1;
		/* also bind the host stack to the bridge */
		b->bdg_ports[cand2] = hostna;
		hostna->bdg_port = cand2;
		hostna->na_bdg = b;
		b->bdg_active_ports++;
		ND("host %p to bridge port %d", hostna, cand2);
	}
	ND("if %s refs %d", name, vpna->up.na_refcount);
	BDG_WUNLOCK(b);
	*na = ret;
	netmap_adapter_get(ret);
	return 0;

out:
	if_rele(ifp);

	return error;
}


/* Process NETMAP_BDG_ATTACH and NETMAP_BDG_DETACH */
static int
nm_bdg_attach(struct nmreq *nmr)
{
	struct netmap_adapter *na;
	struct netmap_if *nifp;
	struct netmap_priv_d *npriv;
	struct netmap_bwrap_adapter *bna;
	int error;

	npriv = malloc(sizeof(*npriv), M_DEVBUF, M_NOWAIT|M_ZERO);
	if (npriv == NULL)
		return ENOMEM;
	NMG_LOCK();
	/* XXX probably netmap_get_bdg_na() */
	error = netmap_get_bdg_na(nmr, &na, 1 /* create if not exists */);
	if (error) /* no device, or another bridge or user owns the device */
		goto unlock_exit;
	if (na == NULL) { /* VALE prefix missing */
		error = EINVAL;
		goto unlock_exit;
	}

	if (na->active_fds > 0) { /* already registered */
		error = EBUSY;
		goto unref_exit;
	}

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

	bna = (struct netmap_bwrap_adapter*)na;
	bna->na_kpriv = npriv;
	NMG_UNLOCK();
	ND("registered %s to netmap-mode", NM_IFPNAME(na->ifp));
	return 0;

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


static int
nm_bdg_detach(struct nmreq *nmr)
{
	struct netmap_adapter *na;
	int error;
	struct netmap_bwrap_adapter *bna;
	int last_instance;

	NMG_LOCK();
	error = netmap_get_bdg_na(nmr, &na, 0 /* don't create */);
	if (error) { /* no device, or another bridge or user owns the device */
		goto unlock_exit;
	}
	if (na == NULL) { /* VALE prefix missing */
		error = EINVAL;
		goto unlock_exit;
	}

	bna = (struct netmap_bwrap_adapter *)na;

	if (na->active_fds == 0) { /* not registered */
		error = EINVAL;
		goto unref_exit;
	}

	last_instance = netmap_dtor_locked(bna->na_kpriv); /* unregister */
	if (!last_instance) {
		D("--- error, trying to detach an entry with active mmaps");
		error = EINVAL;
	} else {
		struct netmap_priv_d *npriv = bna->na_kpriv;

		bna->na_kpriv = NULL;
		D("deleting priv");

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

unref_exit:
	netmap_adapter_put(na);
unlock_exit:
	NMG_UNLOCK();
	return error;

}


/* 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 netmap_vp_adapter *vpna;
	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];
				vpna = b->bdg_ports[i];
				if (vpna == NULL) {
					D("---AAAAAAAAARGH-------");
					continue;
				}
				iter = vpna->up.ifp;
				/* the former and the latter identify a
				 * virtual port and a NIC, respectively
				 */
				if (!strcmp(iter->if_xname, name)) {
					/* 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];
				vpna = b->bdg_ports[j];
				iter = vpna->up.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;

	case NETMAP_BDG_OFFSET:
		NMG_LOCK();
		error = netmap_get_bdg_na(nmr, &na, 0);
		if (na && !error) {
			vpna = (struct netmap_vp_adapter *)na;
			if (nmr->nr_arg1 > NETMAP_BDG_MAX_OFFSET)
				nmr->nr_arg1 = NETMAP_BDG_MAX_OFFSET;
			vpna->offset = nmr->nr_arg1;
			D("Using offset %d for %p", vpna->offset, vpna);
			netmap_adapter_put(na);
		}
		NMG_UNLOCK();
		break;

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


static int
netmap_vp_krings_create(struct netmap_adapter *na)
{
	u_int ntx, nrx, tailroom;
	int error, i;
	uint32_t *leases;

	/* XXX vps do not need host rings,
	 * but we crash if we don't have one
	 */
	ntx = na->num_tx_rings + 1;
	nrx = na->num_rx_rings + 1;

	/*
	 * Leases are attached to RX rings on vale ports
	 */
	tailroom = sizeof(uint32_t) * na->num_rx_desc * nrx;

	error = netmap_krings_create(na, ntx, nrx, tailroom);
	if (error)
		return error;

	leases = na->tailroom;

	for (i = 0; i < nrx; i++) { /* Receive rings */
		na->rx_rings[i].nkr_leases = leases;
		leases += na->num_rx_desc;
	}

	error = nm_alloc_bdgfwd(na);
	if (error) {
		netmap_krings_delete(na);
		return error;
	}

	return 0;
}


static void
netmap_vp_krings_delete(struct netmap_adapter *na)
{
	nm_free_bdgfwd(na);
	netmap_krings_delete(na);
}


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


/*
 * 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_vp_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->up.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->up, slot);
		__builtin_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;
}


/* ----- 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 netmap_adapter *na, int onoff)
{
	struct netmap_vp_adapter *vpna =
		(struct netmap_vp_adapter*)na;
	struct ifnet *ifp = na->ifp;

	/* the interface is already attached to the bridge,
	 * so we only need to toggle IFCAP_NETMAP.
	 */
	BDG_WLOCK(vpna->na_bdg);
	if (onoff) {
		ifp->if_capenable |= IFCAP_NETMAP;
	} else {
		ifp->if_capenable &= ~IFCAP_NETMAP;
	}
	BDG_WUNLOCK(vpna->na_bdg);
	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_vp_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;
}


/*
 * Available space in the ring. Only used in VALE code
 * and only with is_rx = 1
 */
static inline uint32_t
nm_kr_space(struct netmap_kring *k, int is_rx)
{
	int space;

	if (is_rx) {
		int busy = k->nkr_hwlease - k->nr_hwcur;
		if (busy < 0)
			busy += k->nkr_num_slots;
		space = k->nkr_num_slots - 1 - busy;
	} else {
		/* XXX never used in this branch */
		space = k->nr_hwtail - k->nkr_hwlease;
		if (space < 0)
			space += k->nkr_num_slots;
	}
#if 0
	// sanity check
	if (k->nkr_hwlease >= k->nkr_num_slots ||
		k->nr_hwcur >= k->nkr_num_slots ||
		k->nr_tail >= k->nkr_num_slots ||
		busy < 0 ||
		busy >= k->nkr_num_slots) {
		D("invalid kring, cur %d tail %d lease %d lease_idx %d lim %d",			k->nr_hwcur, k->nr_hwtail, k->nkr_hwlease,
			k->nkr_lease_idx, k->nkr_num_slots);
	}
#endif
	return space;
}




/* make a lease on the kring for N positions. return the
 * lease index
 * XXX only used in VALE code and with is_rx = 1
 */
static inline uint32_t
nm_kr_lease(struct netmap_kring *k, u_int n, int is_rx)
{
	uint32_t lim = k->nkr_num_slots - 1;
	uint32_t lease_idx = k->nkr_lease_idx;

	k->nkr_leases[lease_idx] = NR_NOSLOT;
	k->nkr_lease_idx = nm_next(lease_idx, lim);

	if (n > nm_kr_space(k, is_rx)) {
		D("invalid request for %d slots", n);
		panic("x");
	}
	/* XXX verify that there are n slots */
	k->nkr_hwlease += n;
	if (k->nkr_hwlease > lim)
		k->nkr_hwlease -= lim + 1;

	if (k->nkr_hwlease >= k->nkr_num_slots ||
		k->nr_hwcur >= k->nkr_num_slots ||
		k->nr_hwtail >= k->nkr_num_slots ||
		k->nkr_lease_idx >= k->nkr_num_slots) {
		D("invalid kring %s, cur %d tail %d lease %d lease_idx %d lim %d",
			k->na->ifp->if_xname,
			k->nr_hwcur, k->nr_hwtail, k->nkr_hwlease,
			k->nkr_lease_idx, k->nkr_num_slots);
	}
	return lease_idx;
}

/*
 * 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_vp_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;
		uint8_t *buf = ft[i].ft_buf;
		u_int len = ft[i].ft_len;

		ND("slot %d frags %d", i, ft[i].ft_frags);
		/* Drop the packet if the offset is not into the first
		   fragment nor at the very beginning of the second. */
		if (unlikely(na->offset > len))
			continue;
		if (len == na->offset) {
			buf = ft[i+1].ft_buf;
			len = ft[i+1].ft_len;
		} else {
			buf += na->offset;
			len -= na->offset;
		}
		dst_port = b->nm_bdg_lookup(buf, 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_vp_adapter *dst_na;
		struct netmap_kring *kring;
		struct netmap_ring *ring;
		u_int dst_nr, 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;
		int offset_mismatch;

		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->up.na_flags & NAF_SW_ONLY)
			goto cleanup;
		dst_ifp = dst_na->up.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;
		}

		offset_mismatch = (dst_na->offset != na->offset);

		/* 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;

		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);
		nrings = dst_na->up.num_rx_rings;
		if (dst_nr >= nrings)
			dst_nr = dst_nr % nrings;
		kring = &dst_na->up.rx_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;
		}
		if (dst_na->retry) {
			dst_na->up.nm_notify(&dst_na->up, dst_nr, NR_RX, 0);
		}
		my_start = j = kring->nkr_hwlease;
		howmany = nm_kr_space(kring, 1);
		if (needed < howmany)
			howmany = needed;
		lease_idx = nm_kr_lease(kring, howmany, 1);
		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;
			int fix_mismatch = offset_mismatch;

			/* 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 {
			    char *dst, *src = ft_p->ft_buf;
			    size_t copy_len = ft_p->ft_len, dst_len = copy_len;

			    slot = &ring->slot[j];
			    dst = BDG_NMB(&dst_na->up, slot);

			    if (unlikely(fix_mismatch)) {
				    /* We are processing the first fragment
				     * and there is a mismatch between source
				     * and destination offsets. Create a zeroed
				     * header for the destination, independently
				     * of the source header length and content.
				     */
				    src += na->offset;
				    copy_len -= na->offset;
				    bzero(dst, dst_na->offset);
				    dst += dst_na->offset;
				    dst_len = dst_na->offset + copy_len;
				    /* fix the first fragment only */
				    fix_mismatch = 0;
				    /* Here it could be copy_len == dst_len == 0,
				     * and so a zero length fragment is passed.
				     */
			    }

			    ND("send [%d] %d(%d) bytes at %s:%d",
				i, (int)copy_len, (int)dst_len,
				NM_IFPNAME(dst_ifp), j);
			    /* round to a multiple of 64 */
			    copy_len = (copy_len + 63) & ~63;

			    if (ft_p->ft_flags & NS_INDIRECT) {
				if (copyin(src, dst, copy_len)) {
					// invalid user pointer, pretend len is 0
					dst_len = 0;
				}
			    } else {
				//memcpy(dst, src, copy_len);
				pkt_copy(src, dst, (int)copy_len);
			    }
			    slot->len = dst_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 = kring->nr_hwtail;

		    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)) {
				kring->nr_hwtail = j;
				dst_na->up.nm_notify(&dst_na->up, dst_nr, NR_RX, 0);
				still_locked = 0;
				mtx_unlock(&kring->q_lock);
				if (dst_na->retry && 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;
}


static int
netmap_vp_txsync(struct netmap_vp_adapter *na, u_int ring_nr, int flags)
{
	struct netmap_kring *kring = &na->up.tx_rings[ring_nr];
	u_int done;
	u_int const lim = kring->nkr_num_slots - 1;
	u_int const cur = kring->rcur;

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

	done = nm_bdg_preflush(na, ring_nr, kring, cur);
done:
	if (done != cur)
		D("early break at %d/ %d, tail %d", done, cur, kring->nr_hwtail);
	/*
	 * packets between 'done' and 'cur' are left unsent.
	 */
	kring->nr_hwcur = done;
	kring->nr_hwtail = nm_prev(done, lim);
	nm_txsync_finalize(kring);
	if (netmap_verbose)
		D("%s ring %d flags %d", NM_IFPNAME(na->up.ifp), ring_nr, flags);
	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 netmap_adapter *na, u_int ring_nr, int flags)
{
	struct netmap_vp_adapter *vpna = (struct netmap_vp_adapter*)na;
	return netmap_vp_txsync(vpna, ring_nr, flags);
}

static int
netmap_vp_rxsync(struct netmap_adapter *na, u_int ring_nr, int flags)
{
	struct netmap_kring *kring = &na->rx_rings[ring_nr];
	struct netmap_ring *ring = kring->ring;
	u_int nm_i, lim = kring->nkr_num_slots - 1;
	u_int head = nm_rxsync_prologue(kring);
	int n;

	if (head > lim) {
		D("ouch dangerous reset!!!");
		n = netmap_ring_reinit(kring);
		goto done;
	}

	/* First part, import newly received packets. */
	/* actually nothing to do here, they are already in the kring */

	/* Second part, skip past packets that userspace has released. */
	nm_i = kring->nr_hwcur;
	if (nm_i != head) {
		/* consistency check, but nothing really important here */
		for (n = 0; likely(nm_i != head); n++) {
			struct netmap_slot *slot = &ring->slot[nm_i];
			void *addr = BDG_NMB(na, slot);

			if (addr == netmap_buffer_base) { /* bad buf */
				D("bad buffer index %d, ignore ?",
					slot->buf_idx);
			}
			slot->flags &= ~NS_BUF_CHANGED;
			nm_i = nm_next(nm_i, lim);
		}
		kring->nr_hwcur = head;
	}

	/* tell userspace that there are new packets */
	nm_rxsync_finalize(kring);
	n = 0;
done:
	return n;
}

/*
 * 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 netmap_adapter *na, u_int ring_nr, int flags)
{
	struct netmap_kring *kring = &na->rx_rings[ring_nr];
	int n;

	mtx_lock(&kring->q_lock);
	n = netmap_vp_rxsync(na, ring_nr, flags);
	mtx_unlock(&kring->q_lock);
	return n;
}


static int
bdg_netmap_attach(struct nmreq *nmr, struct ifnet *ifp)
{
	struct netmap_vp_adapter *vpna;
	struct netmap_adapter *na;
	int error;

	vpna = malloc(sizeof(*vpna), M_DEVBUF, M_NOWAIT | M_ZERO);
	if (vpna == NULL)
		return ENOMEM;

 	na = &vpna->up;

	na->ifp = ifp;

	/* bound checking */
	na->num_tx_rings = nmr->nr_tx_rings;
	nm_bound_var(&na->num_tx_rings, 1, 1, NM_BDG_MAXRINGS, NULL);
	nmr->nr_tx_rings = na->num_tx_rings; // write back
	na->num_rx_rings = nmr->nr_rx_rings;
	nm_bound_var(&na->num_rx_rings, 1, 1, NM_BDG_MAXRINGS, NULL);
	nmr->nr_rx_rings = na->num_rx_rings; // write back
	nm_bound_var(&nmr->nr_tx_slots, NM_BRIDGE_RINGSIZE,
			1, NM_BDG_MAXSLOTS, NULL);
	na->num_tx_desc = nmr->nr_tx_slots;
	nm_bound_var(&nmr->nr_rx_slots, NM_BRIDGE_RINGSIZE,
			1, NM_BDG_MAXSLOTS, NULL);
	na->num_rx_desc = nmr->nr_rx_slots;
	vpna->offset = 0;

	na->na_flags |= NAF_BDG_MAYSLEEP | NAF_MEM_OWNER;
	na->nm_txsync = bdg_netmap_txsync;
	na->nm_rxsync = bdg_netmap_rxsync;
	na->nm_register = bdg_netmap_reg;
	na->nm_dtor = netmap_adapter_vp_dtor;
	na->nm_krings_create = netmap_vp_krings_create;
	na->nm_krings_delete = netmap_vp_krings_delete;
	na->nm_mem = netmap_mem_private_new(NM_IFPNAME(na->ifp),
			na->num_tx_rings, na->num_tx_desc,
			na->num_rx_rings, na->num_rx_desc);
	/* other nmd fields are set in the common routine */
	error = netmap_attach_common(na);
	if (error) {
		free(vpna, M_DEVBUF);
		return error;
	}
	return 0;
}


static void
netmap_bwrap_dtor(struct netmap_adapter *na)
{
	struct netmap_bwrap_adapter *bna = (struct netmap_bwrap_adapter*)na;
	struct netmap_adapter *hwna = bna->hwna;
	struct nm_bridge *b = bna->up.na_bdg,
		*bh = bna->host.na_bdg;
	struct ifnet *ifp = na->ifp;

	ND("na %p", na);

	if (b) {
		netmap_bdg_detach_common(b, bna->up.bdg_port,
			(bh ? bna->host.bdg_port : -1));
	}

	hwna->na_private = NULL;
	netmap_adapter_put(hwna);

	bzero(ifp, sizeof(*ifp));
	free(ifp, M_DEVBUF);
	na->ifp = NULL;

}


/*
 * Intr callback for NICs connected to a bridge.
 * Simply ignore tx interrupts (maybe we could try to recover space ?)
 * and pass received 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 or the host stack.
 * The only part of the ring that is significant are the slots,
 * and head/cur/tail are set from the kring as needed
 * (part as a receive ring, part as a transmit ring).
 *
 * callback that overwrites the hwna notify callback.
 * Packets come from the outside or from the host stack and are put on an hwna rx ring.
 * The bridge wrapper then sends the packets through the bridge.
 */
static int
netmap_bwrap_intr_notify(struct netmap_adapter *na, u_int ring_nr, enum txrx tx, int flags)
{
	struct ifnet *ifp = na->ifp;
	struct netmap_bwrap_adapter *bna = na->na_private;
	struct netmap_vp_adapter *hostna = &bna->host;
	struct netmap_kring *kring, *bkring;
	struct netmap_ring *ring;
	int is_host_ring = ring_nr == na->num_rx_rings;
	struct netmap_vp_adapter *vpna = &bna->up;
	int error = 0;

	if (netmap_verbose)
	    D("%s %s%d 0x%x", NM_IFPNAME(ifp),
		(tx == NR_TX ? "TX" : "RX"), ring_nr, flags);

	if (flags & NAF_DISABLE_NOTIFY) {
		kring = tx == NR_TX ? na->tx_rings : na->rx_rings;
		bkring = tx == NR_TX ? vpna->up.rx_rings : vpna->up.tx_rings;
		if (kring[ring_nr].nkr_stopped)
			netmap_disable_ring(&bkring[ring_nr]);
		else
			bkring[ring_nr].nkr_stopped = 0;
		return 0;
	}

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

	/* we only care about receive interrupts */
	if (tx == NR_TX)
		return 0;

	kring = &na->rx_rings[ring_nr];
	ring = kring->ring;

	/* make sure the ring is not disabled */
	if (nm_kr_tryget(kring))
		return 0;

	if (is_host_ring && hostna->na_bdg == NULL) {
		error = bna->save_notify(na, ring_nr, tx, flags);
		goto put_out;
	}

	/* Here we expect ring->head = ring->cur = ring->tail
	 * because everything has been released from the previous round.
	 * However the ring is shared and we might have info from
	 * the wrong side (the tx ring). Hence we overwrite with
	 * the info from the rx kring.
	 */
	if (netmap_verbose)
	    D("%s head %d cur %d tail %d (kring %d %d %d)",  NM_IFPNAME(ifp),
		ring->head, ring->cur, ring->tail,
		kring->rhead, kring->rcur, kring->rtail);

	ring->head = kring->rhead;
	ring->cur = kring->rcur;
	ring->tail = kring->rtail;

	/* simulate a user wakeup on the rx ring */
	if (is_host_ring) {
		netmap_rxsync_from_host(na, NULL, NULL);
		vpna = hostna;
		ring_nr = 0;
	} else {
		/* fetch packets that have arrived.
		 * XXX maybe do this in a loop ?
		 */
		error = na->nm_rxsync(na, ring_nr, 0);
		if (error)
			goto put_out;
	}
	if (kring->nr_hwcur == kring->nr_hwtail && netmap_verbose) {
		D("how strange, interrupt with no packets on %s",
			NM_IFPNAME(ifp));
		goto put_out;
	}

	/* new packets are ring->cur to ring->tail, and the bkring
	 * had hwcur == ring->cur. So advance ring->cur to ring->tail
	 * to push all packets out.
	 */
	ring->head = ring->cur = ring->tail;

	/* also set tail to what the bwrap expects */
	bkring = &vpna->up.tx_rings[ring_nr];
	ring->tail = bkring->nr_hwtail; // rtail too ?

	/* pass packets to the switch */
	nm_txsync_prologue(bkring); // XXX error checking ?
	netmap_vp_txsync(vpna, ring_nr, flags);

	/* mark all buffers as released on this ring */
	ring->head = ring->cur = kring->nr_hwtail;
	ring->tail = kring->rtail;
	/* another call to actually release the buffers */
	if (!is_host_ring) {
		error = na->nm_rxsync(na, ring_nr, 0);
	} else {
		/* mark all packets as released, as in the
		 * second part of netmap_rxsync_from_host()
		 */
		kring->nr_hwcur = kring->nr_hwtail;
		nm_rxsync_finalize(kring);
	}

put_out:
	nm_kr_put(kring);
	return error;
}


static int
netmap_bwrap_register(struct netmap_adapter *na, int onoff)
{
	struct netmap_bwrap_adapter *bna =
		(struct netmap_bwrap_adapter *)na;
	struct netmap_adapter *hwna = bna->hwna;
	struct netmap_vp_adapter *hostna = &bna->host;
	int error;

	ND("%s %s", NM_IFPNAME(na->ifp), onoff ? "on" : "off");

	if (onoff) {
		int i;

		hwna->na_lut = na->na_lut;
		hwna->na_lut_objtotal = na->na_lut_objtotal;

		if (hostna->na_bdg) {
			hostna->up.na_lut = na->na_lut;
			hostna->up.na_lut_objtotal = na->na_lut_objtotal;
		}

		/* cross-link the netmap rings
		 * The original number of rings comes from hwna,
		 * rx rings on one side equals tx rings on the other.
		 */
		for (i = 0; i <= na->num_rx_rings; i++) {
			hwna->tx_rings[i].nkr_num_slots = na->rx_rings[i].nkr_num_slots;
			hwna->tx_rings[i].ring = na->rx_rings[i].ring;
		}
		for (i = 0; i <= na->num_tx_rings; i++) {
			hwna->rx_rings[i].nkr_num_slots = na->tx_rings[i].nkr_num_slots;
			hwna->rx_rings[i].ring = na->tx_rings[i].ring;
		}
	}

	if (hwna->ifp) {
		error = hwna->nm_register(hwna, onoff);
		if (error)
			return error;
	}

	bdg_netmap_reg(na, onoff);

	if (onoff) {
		bna->save_notify = hwna->nm_notify;
		hwna->nm_notify = netmap_bwrap_intr_notify;
	} else {
		hwna->nm_notify = bna->save_notify;
		hwna->na_lut = NULL;
		hwna->na_lut_objtotal = 0;
	}

	return 0;
}


static int
netmap_bwrap_config(struct netmap_adapter *na, u_int *txr, u_int *txd,
				    u_int *rxr, u_int *rxd)
{
	struct netmap_bwrap_adapter *bna =
		(struct netmap_bwrap_adapter *)na;
	struct netmap_adapter *hwna = bna->hwna;

	/* forward the request */
	netmap_update_config(hwna);
	/* swap the results */
	*txr = hwna->num_rx_rings;
	*txd = hwna->num_rx_desc;
	*rxr = hwna->num_tx_rings;
	*rxd = hwna->num_rx_desc;

	return 0;
}


static int
netmap_bwrap_krings_create(struct netmap_adapter *na)
{
	struct netmap_bwrap_adapter *bna =
		(struct netmap_bwrap_adapter *)na;
	struct netmap_adapter *hwna = bna->hwna;
	struct netmap_adapter *hostna = &bna->host.up;
	int error;

	ND("%s", NM_IFPNAME(na->ifp));

	error = netmap_vp_krings_create(na);
	if (error)
		return error;

	error = hwna->nm_krings_create(hwna);
	if (error) {
		netmap_vp_krings_delete(na);
		return error;
	}

	hostna->tx_rings = na->tx_rings + na->num_tx_rings;
	hostna->rx_rings = na->rx_rings + na->num_rx_rings;

	return 0;
}


static void
netmap_bwrap_krings_delete(struct netmap_adapter *na)
{
	struct netmap_bwrap_adapter *bna =
		(struct netmap_bwrap_adapter *)na;
	struct netmap_adapter *hwna = bna->hwna;

	ND("%s", NM_IFPNAME(na->ifp));

	hwna->nm_krings_delete(hwna);
	netmap_vp_krings_delete(na);
}


/* notify method for the bridge-->hwna direction */
static int
netmap_bwrap_notify(struct netmap_adapter *na, u_int ring_n, enum txrx tx, int flags)
{
	struct netmap_bwrap_adapter *bna =
		(struct netmap_bwrap_adapter *)na;
	struct netmap_adapter *hwna = bna->hwna;
	struct netmap_kring *kring, *hw_kring;
	struct netmap_ring *ring;
	u_int lim;
	int error = 0;

	if (tx == NR_TX)
	        return ENXIO;

	kring = &na->rx_rings[ring_n];
	hw_kring = &hwna->tx_rings[ring_n];
	ring = kring->ring;
	lim = kring->nkr_num_slots - 1;

	if (hwna->ifp == NULL || !(hwna->ifp->if_capenable & IFCAP_NETMAP))
		return 0;
	/* first step: simulate a user wakeup on the rx ring */
	netmap_vp_rxsync(na, ring_n, flags);
	ND("%s[%d] PRE rx(c%3d t%3d l%3d) ring(h%3d c%3d t%3d) tx(c%3d ht%3d t%3d)",
		NM_IFPNAME(na->ifp), ring_n,
		kring->nr_hwcur, kring->nr_hwtail, kring->nkr_hwlease,
		ring->head, ring->cur, ring->tail,
		hw_kring->nr_hwcur, hw_kring->nr_hwtail, hw_ring->rtail);
	/* second step: the simulated user consumes all new packets */
	ring->head = ring->cur = ring->tail;

	/* third step: the new packets are sent on the tx ring
	 * (which is actually the same ring)
	 */
	/* set tail to what the hw expects */
	ring->tail = hw_kring->rtail;
	if (ring_n == na->num_rx_rings) {
		netmap_txsync_to_host(hwna);
	} else {
		nm_txsync_prologue(&hwna->tx_rings[ring_n]); // XXX error checking ?
		error = hwna->nm_txsync(hwna, ring_n, flags);
	}

	/* fourth step: now we are back the rx ring */
	/* claim ownership on all hw owned bufs */
	ring->head = nm_next(ring->tail, lim); /* skip past reserved slot */
	ring->tail = kring->rtail; /* restore saved value of tail, for safety */

	/* fifth step: the user goes to sleep again, causing another rxsync */
	netmap_vp_rxsync(na, ring_n, flags);
	ND("%s[%d] PST rx(c%3d t%3d l%3d) ring(h%3d c%3d t%3d) tx(c%3d ht%3d t%3d)",
		NM_IFPNAME(na->ifp), ring_n,
		kring->nr_hwcur, kring->nr_hwtail, kring->nkr_hwlease,
		ring->head, ring->cur, ring->tail,
		hw_kring->nr_hwcur, hw_kring->nr_hwtail, hw_kring->rtail);

	return error;
}


static int
netmap_bwrap_host_notify(struct netmap_adapter *na, u_int ring_n, enum txrx tx, int flags)
{
	struct netmap_bwrap_adapter *bna = na->na_private;
	struct netmap_adapter *port_na = &bna->up.up;
	if (tx == NR_TX || ring_n != 0)
		return ENXIO;
	return netmap_bwrap_notify(port_na, port_na->num_rx_rings, NR_RX, flags);
}


/* attach a bridge wrapper to the 'real' device */
static int
netmap_bwrap_attach(struct ifnet *fake, struct ifnet *real)
{
	struct netmap_bwrap_adapter *bna;
	struct netmap_adapter *na;
	struct netmap_adapter *hwna = NA(real);
	struct netmap_adapter *hostna;
	int error;


	bna = malloc(sizeof(*bna), M_DEVBUF, M_NOWAIT | M_ZERO);
	if (bna == NULL)
		return ENOMEM;

	na = &bna->up.up;
	na->ifp = fake;
	/* fill the ring data for the bwrap adapter with rx/tx meanings
	 * swapped. The real cross-linking will be done during register,
	 * when all the krings will have been created.
	 */
	na->num_rx_rings = hwna->num_tx_rings;
	na->num_tx_rings = hwna->num_rx_rings;
	na->num_tx_desc = hwna->num_rx_desc;
	na->num_rx_desc = hwna->num_tx_desc;
	na->nm_dtor = netmap_bwrap_dtor;
	na->nm_register = netmap_bwrap_register;
	// na->nm_txsync = netmap_bwrap_txsync;
	// na->nm_rxsync = netmap_bwrap_rxsync;
	na->nm_config = netmap_bwrap_config;
	na->nm_krings_create = netmap_bwrap_krings_create;
	na->nm_krings_delete = netmap_bwrap_krings_delete;
	na->nm_notify = netmap_bwrap_notify;
	na->nm_mem = hwna->nm_mem;
	na->na_private = na; /* prevent NIOCREGIF */
	bna->up.retry = 1; /* XXX maybe this should depend on the hwna */

	bna->hwna = hwna;
	netmap_adapter_get(hwna);
	hwna->na_private = bna; /* weak reference */

	hostna = &bna->host.up;
	hostna->ifp = hwna->ifp;
	hostna->num_tx_rings = 1;
	hostna->num_tx_desc = hwna->num_rx_desc;
	hostna->num_rx_rings = 1;
	hostna->num_rx_desc = hwna->num_tx_desc;
	// hostna->nm_txsync = netmap_bwrap_host_txsync;
	// hostna->nm_rxsync = netmap_bwrap_host_rxsync;
	hostna->nm_notify = netmap_bwrap_host_notify;
	hostna->nm_mem = na->nm_mem;
	hostna->na_private = bna;

	ND("%s<->%s txr %d txd %d rxr %d rxd %d",
		fake->if_xname, real->if_xname,
		na->num_tx_rings, na->num_tx_desc,
		na->num_rx_rings, na->num_rx_desc);

	error = netmap_attach_common(na);
	if (error) {
		netmap_adapter_put(hwna);
		free(bna, M_DEVBUF);
		return error;
	}
	return 0;
}


void
netmap_init_bridges(void)
{
	int i;
	bzero(nm_bridges, sizeof(struct nm_bridge) * NM_BRIDGES); /* safety */
	for (i = 0; i < NM_BRIDGES; i++)
		BDG_RWINIT(&nm_bridges[i]);
}
#endif /* WITH_VALE */