Vendor import of netgraph from FreeBSD-current 20080626

[dragonfly.git] / sys / netgraph7 / netflow / netflow.c

/*-
 * Copyright (c) 2004-2005 Gleb Smirnoff <glebius@FreeBSD.org>
 * Copyright (c) 2001-2003 Roman V. Palagin <romanp@unshadow.net>
 * 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.
 *
 * $SourceForge: netflow.c,v 1.41 2004/09/05 11:41:10 glebius Exp $
 */

static const char rcs_id[] =
    "@(#) $FreeBSD: src/sys/netgraph/netflow/netflow.c,v 1.29 2008/05/09 23:02:57 julian Exp $";

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/mbuf.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <sys/socket.h>

#include <machine/atomic.h>

#include <net/if.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>

#include <netgraph/ng_message.h>
#include <netgraph/netgraph.h>

#include <netgraph/netflow/netflow.h>
#include <netgraph/netflow/ng_netflow.h>

#define NBUCKETS        (65536)         /* must be power of 2 */

/* This hash is for TCP or UDP packets. */
#define FULL_HASH(addr1, addr2, port1, port2)   \
        (((addr1 ^ (addr1 >> 16) ^              \
        htons(addr2 ^ (addr2 >> 16))) ^         \
        port1 ^ htons(port2)) &                 \
        (NBUCKETS - 1))

/* This hash is for all other IP packets. */
#define ADDR_HASH(addr1, addr2)                 \
        ((addr1 ^ (addr1 >> 16) ^               \
        htons(addr2 ^ (addr2 >> 16))) &         \
        (NBUCKETS - 1))

/* Macros to shorten logical constructions */
/* XXX: priv must exist in namespace */
#define INACTIVE(fle)   (time_uptime - fle->f.last > priv->info.nfinfo_inact_t)
#define AGED(fle)       (time_uptime - fle->f.first > priv->info.nfinfo_act_t)
#define ISFREE(fle)     (fle->f.packets == 0)

/*
 * 4 is a magical number: statistically number of 4-packet flows is
 * bigger than 5,6,7...-packet flows by an order of magnitude. Most UDP/ICMP
 * scans are 1 packet (~ 90% of flow cache). TCP scans are 2-packet in case
 * of reachable host and 4-packet otherwise.
 */
#define SMALL(fle)      (fle->f.packets <= 4)

/*
 * Cisco uses milliseconds for uptime. Bad idea, since it overflows
 * every 48+ days. But we will do same to keep compatibility. This macro
 * does overflowable multiplication to 1000.
 */
#define MILLIUPTIME(t)  (((t) << 9) +   /* 512 */       \
                         ((t) << 8) +   /* 256 */       \
                         ((t) << 7) +   /* 128 */       \
                         ((t) << 6) +   /* 64  */       \
                         ((t) << 5) +   /* 32  */       \
                         ((t) << 3))    /* 8   */

MALLOC_DECLARE(M_NETFLOW_HASH);
MALLOC_DEFINE(M_NETFLOW_HASH, "netflow_hash", "NetFlow hash");

static int export_add(item_p, struct flow_entry *);
static int export_send(priv_p, item_p, int flags);

/* Generate hash for a given flow record. */
static __inline uint32_t
ip_hash(struct flow_rec *r)
{
        switch (r->r_ip_p) {
        case IPPROTO_TCP:
        case IPPROTO_UDP:
                return FULL_HASH(r->r_src.s_addr, r->r_dst.s_addr,
                    r->r_sport, r->r_dport);
        default:
                return ADDR_HASH(r->r_src.s_addr, r->r_dst.s_addr);
        }
}

/* This is callback from uma(9), called on alloc. */
static int
uma_ctor_flow(void *mem, int size, void *arg, int how)
{
        priv_p priv = (priv_p )arg;

        if (atomic_load_acq_32(&priv->info.nfinfo_used) >= CACHESIZE)
                return (ENOMEM);

        atomic_add_32(&priv->info.nfinfo_used, 1);

        return (0);
}

/* This is callback from uma(9), called on free. */
static void
uma_dtor_flow(void *mem, int size, void *arg)
{
        priv_p priv = (priv_p )arg;

        atomic_subtract_32(&priv->info.nfinfo_used, 1);
}

/*
 * Detach export datagram from priv, if there is any.
 * If there is no, allocate a new one.
 */
static item_p
get_export_dgram(priv_p priv)
{
        item_p  item = NULL;

        mtx_lock(&priv->export_mtx);
        if (priv->export_item != NULL) {
                item = priv->export_item;
                priv->export_item = NULL;
        }
        mtx_unlock(&priv->export_mtx);

        if (item == NULL) {
                struct netflow_v5_export_dgram *dgram;
                struct mbuf *m;

                m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
                if (m == NULL)
                        return (NULL);
                item = ng_package_data(m, NG_NOFLAGS);
                if (item == NULL)
                        return (NULL);
                dgram = mtod(m, struct netflow_v5_export_dgram *);
                dgram->header.count = 0;
                dgram->header.version = htons(NETFLOW_V5);

        }

        return (item);
}

/*
 * Re-attach incomplete datagram back to priv.
 * If there is already another one, then send incomplete. */
static void
return_export_dgram(priv_p priv, item_p item, int flags)
{
        /*
         * It may happen on SMP, that some thread has already
         * put its item there, in this case we bail out and
         * send what we have to collector.
         */
        mtx_lock(&priv->export_mtx);
        if (priv->export_item == NULL) {
                priv->export_item = item;
                mtx_unlock(&priv->export_mtx);
        } else {
                mtx_unlock(&priv->export_mtx);
                export_send(priv, item, flags);
        }
}

/*
 * The flow is over. Call export_add() and free it. If datagram is
 * full, then call export_send().
 */
static __inline void
expire_flow(priv_p priv, item_p *item, struct flow_entry *fle, int flags)
{
        if (*item == NULL)
                *item = get_export_dgram(priv);
        if (*item == NULL) {
                atomic_add_32(&priv->info.nfinfo_export_failed, 1);
                uma_zfree_arg(priv->zone, fle, priv);
                return;
        }
        if (export_add(*item, fle) > 0) {
                export_send(priv, *item, flags);
                *item = NULL;
        }
        uma_zfree_arg(priv->zone, fle, priv);
}

/* Get a snapshot of node statistics */
void
ng_netflow_copyinfo(priv_p priv, struct ng_netflow_info *i)
{
        /* XXX: atomic */
        memcpy((void *)i, (void *)&priv->info, sizeof(priv->info));
}

/*
 * Insert a record into defined slot.
 *
 * First we get for us a free flow entry, then fill in all
 * possible fields in it.
 *
 * TODO: consider dropping hash mutex while filling in datagram,
 * as this was done in previous version. Need to test & profile
 * to be sure.
 */
static __inline int
hash_insert(priv_p priv, struct flow_hash_entry  *hsh, struct flow_rec *r,
        int plen, uint8_t tcp_flags)
{
        struct flow_entry *fle;
        struct sockaddr_in sin;
        struct rtentry *rt;

        mtx_assert(&hsh->mtx, MA_OWNED);

        fle = uma_zalloc_arg(priv->zone, priv, M_NOWAIT);
        if (fle == NULL) {
                atomic_add_32(&priv->info.nfinfo_alloc_failed, 1);
                return (ENOMEM);
        }

        /*
         * Now fle is totally ours. It is detached from all lists,
         * we can safely edit it.
         */

        bcopy(r, &fle->f.r, sizeof(struct flow_rec));
        fle->f.bytes = plen;
        fle->f.packets = 1;
        fle->f.tcp_flags = tcp_flags;

        fle->f.first = fle->f.last = time_uptime;

        /*
         * First we do route table lookup on destination address. So we can
         * fill in out_ifx, dst_mask, nexthop, and dst_as in future releases.
         */
        bzero(&sin, sizeof(sin));
        sin.sin_len = sizeof(struct sockaddr_in);
        sin.sin_family = AF_INET;
        sin.sin_addr = fle->f.r.r_dst;
        /* XXX MRT 0 as a default.. need the m here to get fib */
        rt = rtalloc1_fib((struct sockaddr *)&sin, 0, RTF_CLONING, 0);
        if (rt != NULL) {
                fle->f.fle_o_ifx = rt->rt_ifp->if_index;

                if (rt->rt_flags & RTF_GATEWAY &&
                    rt->rt_gateway->sa_family == AF_INET)
                        fle->f.next_hop =
                            ((struct sockaddr_in *)(rt->rt_gateway))->sin_addr;

                if (rt_mask(rt))
                        fle->f.dst_mask = bitcount32(((struct sockaddr_in *)
                            rt_mask(rt))->sin_addr.s_addr);
                else if (rt->rt_flags & RTF_HOST)
                        /* Give up. We can't determine mask :( */
                        fle->f.dst_mask = 32;

                RTFREE_LOCKED(rt);
        }

        /* Do route lookup on source address, to fill in src_mask. */
        bzero(&sin, sizeof(sin));
        sin.sin_len = sizeof(struct sockaddr_in);
        sin.sin_family = AF_INET;
        sin.sin_addr = fle->f.r.r_src;
        /* XXX MRT 0 as a default  revisit.  need the mbuf for fib*/
        rt = rtalloc1_fib((struct sockaddr *)&sin, 0, RTF_CLONING, 0);
        if (rt != NULL) {
                if (rt_mask(rt))
                        fle->f.src_mask = bitcount32(((struct sockaddr_in *)
                            rt_mask(rt))->sin_addr.s_addr);
                else if (rt->rt_flags & RTF_HOST)
                        /* Give up. We can't determine mask :( */
                        fle->f.src_mask = 32;

                RTFREE_LOCKED(rt);
        }

        /* Push new flow at the and of hash. */
        TAILQ_INSERT_TAIL(&hsh->head, fle, fle_hash);

        return (0);
}


/*
 * Non-static functions called from ng_netflow.c
 */

/* Allocate memory and set up flow cache */
int
ng_netflow_cache_init(priv_p priv)
{
        struct flow_hash_entry  *hsh;
        int i;

        /* Initialize cache UMA zone. */
        priv->zone = uma_zcreate("NetFlow cache", sizeof(struct flow_entry),
            uma_ctor_flow, uma_dtor_flow, NULL, NULL, UMA_ALIGN_CACHE, 0);
        uma_zone_set_max(priv->zone, CACHESIZE);

        /* Allocate hash. */
        MALLOC(priv->hash, struct flow_hash_entry *,
            NBUCKETS * sizeof(struct flow_hash_entry),
            M_NETFLOW_HASH, M_WAITOK | M_ZERO);

        if (priv->hash == NULL) {
                uma_zdestroy(priv->zone);
                return (ENOMEM);
        }

        /* Initialize hash. */
        for (i = 0, hsh = priv->hash; i < NBUCKETS; i++, hsh++) {
                mtx_init(&hsh->mtx, "hash mutex", NULL, MTX_DEF);
                TAILQ_INIT(&hsh->head);
        }

        mtx_init(&priv->export_mtx, "export dgram lock", NULL, MTX_DEF);

        return (0);
}

/* Free all flow cache memory. Called from node close method. */
void
ng_netflow_cache_flush(priv_p priv)
{
        struct flow_entry       *fle, *fle1;
        struct flow_hash_entry  *hsh;
        item_p                  item = NULL;
        int i;

        /*
         * We are going to free probably billable data.
         * Expire everything before freeing it.
         * No locking is required since callout is already drained.
         */
        for (hsh = priv->hash, i = 0; i < NBUCKETS; hsh++, i++)
                TAILQ_FOREACH_SAFE(fle, &hsh->head, fle_hash, fle1) {
                        TAILQ_REMOVE(&hsh->head, fle, fle_hash);
                        expire_flow(priv, &item, fle, NG_QUEUE);
                }

        if (item != NULL)
                export_send(priv, item, NG_QUEUE);

        uma_zdestroy(priv->zone);

        /* Destroy hash mutexes. */
        for (i = 0, hsh = priv->hash; i < NBUCKETS; i++, hsh++)
                mtx_destroy(&hsh->mtx);

        /* Free hash memory. */
        if (priv->hash)
                FREE(priv->hash, M_NETFLOW_HASH);

        mtx_destroy(&priv->export_mtx);
}

/* Insert packet from into flow cache. */
int
ng_netflow_flow_add(priv_p priv, struct ip *ip, iface_p iface,
        struct ifnet *ifp)
{
        register struct flow_entry      *fle, *fle1;
        struct flow_hash_entry          *hsh;
        struct flow_rec         r;
        item_p                  item = NULL;
        int                     hlen, plen;
        int                     error = 0;
        uint8_t                 tcp_flags = 0;

        /* Try to fill flow_rec r */
        bzero(&r, sizeof(r));
        /* check version */
        if (ip->ip_v != IPVERSION)
                return (EINVAL);

        /* verify min header length */
        hlen = ip->ip_hl << 2;

        if (hlen < sizeof(struct ip))
                return (EINVAL);

        r.r_src = ip->ip_src;
        r.r_dst = ip->ip_dst;

        /* save packet length */
        plen = ntohs(ip->ip_len);

        r.r_ip_p = ip->ip_p;
        r.r_tos = ip->ip_tos;

        /* Configured in_ifx overrides mbuf's */
        if (iface->info.ifinfo_index == 0) {
                if (ifp != NULL)
                        r.r_i_ifx = ifp->if_index;
        } else
                r.r_i_ifx = iface->info.ifinfo_index;

        /*
         * XXX NOTE: only first fragment of fragmented TCP, UDP and
         * ICMP packet will be recorded with proper s_port and d_port.
         * Following fragments will be recorded simply as IP packet with
         * ip_proto = ip->ip_p and s_port, d_port set to zero.
         * I know, it looks like bug. But I don't want to re-implement
         * ip packet assebmling here. Anyway, (in)famous trafd works this way -
         * and nobody complains yet :)
         */
        if ((ip->ip_off & htons(IP_OFFMASK)) == 0)
                switch(r.r_ip_p) {
                case IPPROTO_TCP:
                {
                        register struct tcphdr *tcp;

                        tcp = (struct tcphdr *)((caddr_t )ip + hlen);
                        r.r_sport = tcp->th_sport;
                        r.r_dport = tcp->th_dport;
                        tcp_flags = tcp->th_flags;
                        break;
                }
                        case IPPROTO_UDP:
                        r.r_ports = *(uint32_t *)((caddr_t )ip + hlen);
                        break;
                }

        /* Update node statistics. XXX: race... */
        priv->info.nfinfo_packets ++;
        priv->info.nfinfo_bytes += plen;

        /* Find hash slot. */
        hsh = &priv->hash[ip_hash(&r)];

        mtx_lock(&hsh->mtx);

        /*
         * Go through hash and find our entry. If we encounter an
         * entry, that should be expired, purge it. We do a reverse
         * search since most active entries are first, and most
         * searches are done on most active entries.
         */
        TAILQ_FOREACH_REVERSE_SAFE(fle, &hsh->head, fhead, fle_hash, fle1) {
                if (bcmp(&r, &fle->f.r, sizeof(struct flow_rec)) == 0)
                        break;
                if ((INACTIVE(fle) && SMALL(fle)) || AGED(fle)) {
                        TAILQ_REMOVE(&hsh->head, fle, fle_hash);
                        expire_flow(priv, &item, fle, NG_QUEUE);
                        atomic_add_32(&priv->info.nfinfo_act_exp, 1);
                }
        }

        if (fle) {                      /* An existent entry. */

                fle->f.bytes += plen;
                fle->f.packets ++;
                fle->f.tcp_flags |= tcp_flags;
                fle->f.last = time_uptime;

                /*
                 * We have the following reasons to expire flow in active way:
                 * - it hit active timeout
                 * - a TCP connection closed
                 * - it is going to overflow counter
                 */
                if (tcp_flags & TH_FIN || tcp_flags & TH_RST || AGED(fle) ||
                    (fle->f.bytes >= (UINT_MAX - IF_MAXMTU)) ) {
                        TAILQ_REMOVE(&hsh->head, fle, fle_hash);
                        expire_flow(priv, &item, fle, NG_QUEUE);
                        atomic_add_32(&priv->info.nfinfo_act_exp, 1);
                } else {
                        /*
                         * It is the newest, move it to the tail,
                         * if it isn't there already. Next search will
                         * locate it quicker.
                         */
                        if (fle != TAILQ_LAST(&hsh->head, fhead)) {
                                TAILQ_REMOVE(&hsh->head, fle, fle_hash);
                                TAILQ_INSERT_TAIL(&hsh->head, fle, fle_hash);
                        }
                }
        } else                          /* A new flow entry. */
                error = hash_insert(priv, hsh, &r, plen, tcp_flags);

        mtx_unlock(&hsh->mtx);

        if (item != NULL)
                return_export_dgram(priv, item, NG_QUEUE);

        return (error);
}

/*
 * Return records from cache to userland.
 *
 * TODO: matching particular IP should be done in kernel, here.
 */
int
ng_netflow_flow_show(priv_p priv, uint32_t last, struct ng_mesg *resp)
{
        struct flow_hash_entry *hsh;
        struct flow_entry *fle;
        struct ngnf_flows *data;
        int i;

        data = (struct ngnf_flows *)resp->data;
        data->last = 0;
        data->nentries = 0;

        /* Check if this is a first run */
        if (last == 0) {
                hsh = priv->hash;
                i = 0;
        } else {
                if (last > NBUCKETS-1)
                        return (EINVAL);
                hsh = priv->hash + last;
                i = last;
        }

        /*
         * We will transfer not more than NREC_AT_ONCE. More data
         * will come in next message.
         * We send current hash index to userland, and userland should
         * return it back to us. Then, we will restart with new entry.
         *
         * The resulting cache snapshot is inaccurate for the
         * following reasons:
         *  - we skip locked hash entries
         *  - we bail out, if someone wants our entry
         *  - we skip rest of entry, when hit NREC_AT_ONCE
         */
        for (; i < NBUCKETS; hsh++, i++) {
                if (mtx_trylock(&hsh->mtx) == 0)
                        continue;

                TAILQ_FOREACH(fle, &hsh->head, fle_hash) {
                        if (hsh->mtx.mtx_lock & MTX_CONTESTED)
                                break;

                        bcopy(&fle->f, &(data->entries[data->nentries]),
                            sizeof(fle->f));
                        data->nentries++;
                        if (data->nentries == NREC_AT_ONCE) {
                                mtx_unlock(&hsh->mtx);
                                if (++i < NBUCKETS)
                                        data->last = i;
                                return (0);
                        }
                }
                mtx_unlock(&hsh->mtx);
        }

        return (0);
}

/* We have full datagram in privdata. Send it to export hook. */
static int
export_send(priv_p priv, item_p item, int flags)
{
        struct mbuf *m = NGI_M(item);
        struct netflow_v5_export_dgram *dgram = mtod(m,
                                        struct netflow_v5_export_dgram *);
        struct netflow_v5_header *header = &dgram->header;
        struct timespec ts;
        int error = 0;

        /* Fill mbuf header. */
        m->m_len = m->m_pkthdr.len = sizeof(struct netflow_v5_record) *
           header->count + sizeof(struct netflow_v5_header);

        /* Fill export header. */
        header->sys_uptime = htonl(MILLIUPTIME(time_uptime));
        getnanotime(&ts);
        header->unix_secs  = htonl(ts.tv_sec);
        header->unix_nsecs = htonl(ts.tv_nsec);
        header->engine_type = 0;
        header->engine_id = 0;
        header->pad = 0;
        header->flow_seq = htonl(atomic_fetchadd_32(&priv->flow_seq,
            header->count));
        header->count = htons(header->count);

        if (priv->export != NULL)
                NG_FWD_ITEM_HOOK_FLAGS(error, item, priv->export, flags);
        else
                NG_FREE_ITEM(item);

        return (error);
}


/* Add export record to dgram. */
static int
export_add(item_p item, struct flow_entry *fle)
{
        struct netflow_v5_export_dgram *dgram = mtod(NGI_M(item),
                                        struct netflow_v5_export_dgram *);
        struct netflow_v5_header *header = &dgram->header;
        struct netflow_v5_record *rec;

        rec = &dgram->r[header->count];
        header->count ++;

        KASSERT(header->count <= NETFLOW_V5_MAX_RECORDS,
            ("ng_netflow: export too big"));

        /* Fill in export record. */
        rec->src_addr = fle->f.r.r_src.s_addr;
        rec->dst_addr = fle->f.r.r_dst.s_addr;
        rec->next_hop = fle->f.next_hop.s_addr;
        rec->i_ifx    = htons(fle->f.fle_i_ifx);
        rec->o_ifx    = htons(fle->f.fle_o_ifx);
        rec->packets  = htonl(fle->f.packets);
        rec->octets   = htonl(fle->f.bytes);
        rec->first    = htonl(MILLIUPTIME(fle->f.first));
        rec->last     = htonl(MILLIUPTIME(fle->f.last));
        rec->s_port   = fle->f.r.r_sport;
        rec->d_port   = fle->f.r.r_dport;
        rec->flags    = fle->f.tcp_flags;
        rec->prot     = fle->f.r.r_ip_p;
        rec->tos      = fle->f.r.r_tos;
        rec->dst_mask = fle->f.dst_mask;
        rec->src_mask = fle->f.src_mask;

        /* Not supported fields. */
        rec->src_as = rec->dst_as = 0;

        if (header->count == NETFLOW_V5_MAX_RECORDS)
                return (1); /* end of datagram */
        else
                return (0);     
}

/* Periodic flow expiry run. */
void
ng_netflow_expire(void *arg)
{
        struct flow_entry       *fle, *fle1;
        struct flow_hash_entry  *hsh;
        priv_p                  priv = (priv_p )arg;
        item_p                  item = NULL;
        uint32_t                used;
        int                     i;

        /*
         * Going through all the cache.
         */
        for (hsh = priv->hash, i = 0; i < NBUCKETS; hsh++, i++) {
                /*
                 * Skip entries, that are already being worked on.
                 */
                if (mtx_trylock(&hsh->mtx) == 0)
                        continue;

                used = atomic_load_acq_32(&priv->info.nfinfo_used);
                TAILQ_FOREACH_SAFE(fle, &hsh->head, fle_hash, fle1) {
                        /*
                         * Interrupt thread wants this entry!
                         * Quick! Quick! Bail out!
                         */
                        if (hsh->mtx.mtx_lock & MTX_CONTESTED)
                                break;

                        /*
                         * Don't expire aggressively while hash collision
                         * ratio is predicted small.
                         */
                        if (used <= (NBUCKETS*2) && !INACTIVE(fle))
                                break;

                        if ((INACTIVE(fle) && (SMALL(fle) ||
                            (used > (NBUCKETS*2)))) || AGED(fle)) {
                                TAILQ_REMOVE(&hsh->head, fle, fle_hash);
                                expire_flow(priv, &item, fle, NG_NOFLAGS);
                                used--;
                                atomic_add_32(&priv->info.nfinfo_inact_exp, 1);
                        }
                }
                mtx_unlock(&hsh->mtx);
        }

        if (item != NULL)
                return_export_dgram(priv, item, NG_NOFLAGS);

        /* Schedule next expire. */
        callout_reset(&priv->exp_callout, (1*hz), &ng_netflow_expire,
            (void *)priv);
}