Merge remote-tracking branch 'origin/master'

[unleashed/lotheac.git] / usr / src / uts / common / io / dls / dls_link.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright 2017 Joyent, Inc.
 */

/*
 * Data-Link Services Module
 */

#include        <sys/sysmacros.h>
#include        <sys/strsubr.h>
#include        <sys/strsun.h>
#include        <sys/vlan.h>
#include        <sys/dld_impl.h>
#include        <sys/sdt.h>
#include        <sys/atomic.h>

static kmem_cache_t     *i_dls_link_cachep;
mod_hash_t              *i_dls_link_hash;
static uint_t           i_dls_link_count;

#define         LINK_HASHSZ     67      /* prime */
#define         IMPL_HASHSZ     67      /* prime */

/*
 * Construct a hash key from the DLSAP value.
 */
#define MAKE_KEY(_sap)                                          \
        ((mod_hash_key_t)(uintptr_t)((_sap) << VLAN_ID_SIZE))

#define DLS_STRIP_PADDING(pktsize, p) {                 \
        if (pktsize != 0) {                             \
                ssize_t delta = pktsize - msgdsize(p);  \
                                                        \
                if (delta < 0)                          \
                        (void) adjmsg(p, delta);        \
        }                                               \
}

/*
 * Private functions.
 */

/*ARGSUSED*/
static int
i_dls_link_constructor(void *buf, void *arg, int kmflag)
{
        dls_link_t      *dlp = buf;
        char            name[MAXNAMELEN];

        bzero(buf, sizeof (dls_link_t));

        (void) snprintf(name, MAXNAMELEN, "dls_link_t_%p_hash", buf);
        dlp->dl_str_hash = mod_hash_create_idhash(name, IMPL_HASHSZ,
            mod_hash_null_valdtor);

        return (0);
}

/*ARGSUSED*/
static void
i_dls_link_destructor(void *buf, void *arg)
{
        dls_link_t      *dlp = buf;

        ASSERT(dlp->dl_ref == 0);
        ASSERT(dlp->dl_mh == NULL);
        ASSERT(dlp->dl_mah == NULL);
        ASSERT(dlp->dl_unknowns == 0);

        mod_hash_destroy_idhash(dlp->dl_str_hash);
        dlp->dl_str_hash = NULL;

}

/*
 * - Parse the mac header information of the given packet.
 * - Strip the padding and skip over the header. Note that because some
 *   DLS consumers only check the db_ref count of the first mblk, we
 *   pullup the message into a single mblk. Because the original message
 *   is freed as the result of message pulling up, mac_vlan_header_info()
 *   is called again to update the mhi_saddr and mhi_daddr pointers in the
 *   mhip. Further, the mac_vlan_header_info() function ensures that the
 *   size of the pulled message is greater than the MAC header size,
 *   therefore we can directly advance b_rptr to point at the payload.
 *
 * We choose to use a macro for performance reasons.
 */
#define DLS_PREPARE_PKT(mh, mp, mhip, err) {                            \
        mblk_t *nextp = (mp)->b_next;                                   \
        if (((err) = mac_vlan_header_info((mh), (mp), (mhip))) == 0) {  \
                DLS_STRIP_PADDING((mhip)->mhi_pktsize, (mp));           \
                if (MBLKL((mp)) < (mhip)->mhi_hdrsize) {                \
                        mblk_t *newmp;                                  \
                        if ((newmp = msgpullup((mp), -1)) == NULL) {    \
                                (err) = EINVAL;                         \
                        } else {                                        \
                                (mp)->b_next = NULL;                    \
                                freemsg((mp));                          \
                                (mp) = newmp;                           \
                                VERIFY(mac_vlan_header_info((mh),       \
                                    (mp), (mhip)) == 0);                \
                                (mp)->b_next = nextp;                   \
                                (mp)->b_rptr += (mhip)->mhi_hdrsize;    \
                        }                                               \
                } else {                                                \
                        (mp)->b_rptr += (mhip)->mhi_hdrsize;            \
                }                                                       \
        }                                                               \
}

/*
 * Truncate the chain starting at mp such that all packets in the chain
 * have identical source and destination addresses, saps, and tag types
 * (see below).  It returns a pointer to the mblk following the chain,
 * NULL if there is no further packet following the processed chain.
 * The countp argument is set to the number of valid packets in the chain.
 * Note that the whole MAC header (including the VLAN tag if any) in each
 * packet will be stripped.
 */
static mblk_t *
i_dls_link_subchain(dls_link_t *dlp, mblk_t *mp, const mac_header_info_t *mhip,
    uint_t *countp)
{
        mblk_t          *prevp;
        uint_t          npacket = 1;
        size_t          addr_size = dlp->dl_mip->mi_addr_length;
        uint16_t        vid = VLAN_ID(mhip->mhi_tci);
        uint16_t        pri = VLAN_PRI(mhip->mhi_tci);

        /*
         * Compare with subsequent headers until we find one that has
         * differing header information. After checking each packet
         * strip padding and skip over the header.
         */
        for (prevp = mp; (mp = mp->b_next) != NULL; prevp = mp) {
                mac_header_info_t cmhi;
                uint16_t cvid, cpri;
                int err;

                DLS_PREPARE_PKT(dlp->dl_mh, mp, &cmhi, err);
                if (err != 0)
                        break;

                prevp->b_next = mp;

                /*
                 * The source, destination, sap, vlan tag must all match in
                 * a given subchain.
                 */
                if (mhip->mhi_saddr == NULL || cmhi.mhi_saddr == NULL ||
                    memcmp(mhip->mhi_daddr, cmhi.mhi_daddr, addr_size) != 0 ||
                    memcmp(mhip->mhi_saddr, cmhi.mhi_saddr, addr_size) != 0 ||
                    mhip->mhi_bindsap != cmhi.mhi_bindsap) {
                        /*
                         * Note that we don't need to restore the padding.
                         */
                        mp->b_rptr -= cmhi.mhi_hdrsize;
                        break;
                }

                cvid = VLAN_ID(cmhi.mhi_tci);
                cpri = VLAN_PRI(cmhi.mhi_tci);

                /*
                 * There are several types of packets. Packets don't match
                 * if they are classified to different type or if they are
                 * VLAN packets but belong to different VLANs:
                 *
                 * packet type          tagged          vid             pri
                 * ---------------------------------------------------------
                 * untagged             No              zero            zero
                 * VLAN packets         Yes             non-zero        -
                 * priority tagged      Yes             zero            non-zero
                 * 0 tagged             Yes             zero            zero
                 */
                if ((mhip->mhi_istagged != cmhi.mhi_istagged) ||
                    (vid != cvid) || ((vid == VLAN_ID_NONE) &&
                    (((pri == 0) && (cpri != 0)) ||
                    ((pri != 0) && (cpri == 0))))) {
                        mp->b_rptr -= cmhi.mhi_hdrsize;
                        break;
                }

                npacket++;
        }

        /*
         * Break the chain at this point and return a pointer to the next
         * sub-chain.
         */
        prevp->b_next = NULL;
        *countp = npacket;
        return (mp);
}

/* ARGSUSED */
static int
i_dls_head_hold(mod_hash_key_t key, mod_hash_val_t val)
{
        dls_head_t *dhp = (dls_head_t *)val;

        /*
         * The lock order is  mod_hash's internal lock -> dh_lock as in the
         * call to i_dls_link_rx -> mod_hash_find_cb_rval -> i_dls_head_hold
         */
        mutex_enter(&dhp->dh_lock);
        if (dhp->dh_removing) {
                mutex_exit(&dhp->dh_lock);
                return (-1);
        }
        dhp->dh_ref++;
        mutex_exit(&dhp->dh_lock);
        return (0);
}

void
i_dls_head_rele(dls_head_t *dhp)
{
        mutex_enter(&dhp->dh_lock);
        dhp->dh_ref--;
        if (dhp->dh_ref == 0 && dhp->dh_removing != 0)
                cv_broadcast(&dhp->dh_cv);
        mutex_exit(&dhp->dh_lock);
}

static dls_head_t *
i_dls_head_alloc(mod_hash_key_t key)
{
        dls_head_t      *dhp;

        dhp = kmem_zalloc(sizeof (dls_head_t), KM_SLEEP);
        dhp->dh_key = key;
        return (dhp);
}

static void
i_dls_head_free(dls_head_t *dhp)
{
        ASSERT(dhp->dh_ref == 0);
        kmem_free(dhp, sizeof (dls_head_t));
}

/*
 * Try to send mp up to the streams of the given sap. Return the
 * number of streams which accepted this message, or 0 if no streams
 * accepted the message.
 *
 * Note that this function copies the message chain and the original
 * mp remains valid after this function returns.
 */
static uint_t
i_dls_link_rx_func(dls_link_t *dlp, mac_resource_handle_t mrh,
    mac_header_info_t *mhip, mblk_t *mp, uint32_t sap,
    boolean_t (*acceptfunc)())
{
        mod_hash_t      *hash = dlp->dl_str_hash;
        mod_hash_key_t  key;
        dls_head_t      *dhp;
        dld_str_t       *dsp;
        mblk_t          *nmp;
        dls_rx_t        ds_rx;
        void            *ds_rx_arg;
        uint_t          naccepted = 0;
        int             rval;

        /*
         * Construct a hash key from the DLSAP.
         */
        key = MAKE_KEY(sap);

        /*
         * Search the hash table for a dld_str_t eligible to receive a
         * packet chain for this DLSAP. The mod hash's internal lock
         * serializes find/insert/remove from the mod hash list.
         * Incrementing the dh_ref (while holding the mod hash lock)
         * ensures dls_link_remove will wait for the upcall to finish.
         */
        if (mod_hash_find_cb_rval(hash, key, (mod_hash_val_t *)&dhp,
            i_dls_head_hold, &rval) != 0 || (rval != 0)) {
                return (0);
        }

        /*
         * Find all dld_str_t that will accept the sub-chain.
         */
        for (dsp = dhp->dh_list; dsp != NULL; dsp = dsp->ds_next) {
                if (!acceptfunc(dsp, mhip, &ds_rx, &ds_rx_arg))
                        continue;

                /*
                 * We have at least one acceptor.
                 */
                naccepted++;

                /*
                 * There will normally be at least one more dld_str_t
                 * (since we've yet to check for non-promiscuous
                 * dld_str_t) so dup the sub-chain.
                 */
                if ((nmp = copymsgchain(mp)) != NULL)
                        ds_rx(ds_rx_arg, mrh, nmp, mhip);
        }

        /*
         * Release the hold on the dld_str_t chain now that we have
         * finished walking it.
         */
        i_dls_head_rele(dhp);
        return (naccepted);
}

/* ARGSUSED */
void
i_dls_link_rx(void *arg, mac_resource_handle_t mrh, mblk_t *mp,
    boolean_t loopback)
{
        dls_link_t                      *dlp = arg;
        mod_hash_t                      *hash = dlp->dl_str_hash;
        mblk_t                          *nextp;
        mac_header_info_t               mhi;
        dls_head_t                      *dhp;
        dld_str_t                       *dsp;
        dld_str_t                       *ndsp;
        mblk_t                          *nmp;
        mod_hash_key_t                  key;
        uint_t                          npacket;
        boolean_t                       accepted;
        dls_rx_t                        ds_rx, nds_rx;
        void                            *ds_rx_arg, *nds_rx_arg;
        uint16_t                        vid;
        int                             err, rval;

        /*
         * Walk the packet chain.
         */
        for (; mp != NULL; mp = nextp) {
                /*
                 * Wipe the accepted state.
                 */
                accepted = B_FALSE;

                DLS_PREPARE_PKT(dlp->dl_mh, mp, &mhi, err);
                if (err != 0) {
                        atomic_inc_32(&(dlp->dl_unknowns));
                        nextp = mp->b_next;
                        mp->b_next = NULL;
                        freemsg(mp);
                        continue;
                }

                /*
                 * Grab the longest sub-chain we can process as a single
                 * unit.
                 */
                nextp = i_dls_link_subchain(dlp, mp, &mhi, &npacket);
                ASSERT(npacket != 0);

                vid = VLAN_ID(mhi.mhi_tci);

                if (mhi.mhi_istagged) {
                        /*
                         * If it is tagged traffic, send it upstream to
                         * all dld_str_t which are attached to the physical
                         * link and bound to SAP 0x8100.
                         */
                        if (i_dls_link_rx_func(dlp, mrh, &mhi, mp,
                            ETHERTYPE_VLAN, dls_accept) > 0) {
                                accepted = B_TRUE;
                        }

                        /*
                         * Don't pass the packets up if they are tagged
                         * packets and:
                         *  - their VID and priority are both zero and the
                         *    original packet isn't using the PVID (invalid
                         *    packets).
                         *  - their sap is ETHERTYPE_VLAN and their VID is
                         *    zero as they have already been sent upstreams.
                         */
                        if ((vid == VLAN_ID_NONE && !mhi.mhi_ispvid &&
                            VLAN_PRI(mhi.mhi_tci) == 0) ||
                            (mhi.mhi_bindsap == ETHERTYPE_VLAN &&
                            vid == VLAN_ID_NONE)) {
                                freemsgchain(mp);
                                goto loop;
                        }
                }

                /*
                 * Construct a hash key from the DLSAP.
                 */
                key = MAKE_KEY(mhi.mhi_bindsap);

                /*
                 * Search the hash table for dld_str_t eligible to receive
                 * a packet chain for this DLSAP.
                 */
                if (mod_hash_find_cb_rval(hash, key, (mod_hash_val_t *)&dhp,
                    i_dls_head_hold, &rval) != 0 || (rval != 0)) {
                        freemsgchain(mp);
                        goto loop;
                }

                /*
                 * Find the first dld_str_t that will accept the sub-chain.
                 */
                for (dsp = dhp->dh_list; dsp != NULL; dsp = dsp->ds_next)
                        if (dls_accept(dsp, &mhi, &ds_rx, &ds_rx_arg))
                                break;

                /*
                 * If we did not find any dld_str_t willing to accept the
                 * sub-chain then throw it away.
                 */
                if (dsp == NULL) {
                        i_dls_head_rele(dhp);
                        freemsgchain(mp);
                        goto loop;
                }

                /*
                 * We have at least one acceptor.
                 */
                accepted = B_TRUE;
                for (;;) {
                        /*
                         * Find the next dld_str_t that will accept the
                         * sub-chain.
                         */
                        for (ndsp = dsp->ds_next; ndsp != NULL;
                            ndsp = ndsp->ds_next)
                                if (dls_accept(ndsp, &mhi, &nds_rx,
                                    &nds_rx_arg))
                                        break;

                        /*
                         * If there are no more dld_str_t that are willing
                         * to accept the sub-chain then we don't need to dup
                         * it before handing it to the current one.
                         */
                        if (ndsp == NULL) {
                                ds_rx(ds_rx_arg, mrh, mp, &mhi);

                                /*
                                 * Since there are no more dld_str_t, we're
                                 * done.
                                 */
                                break;
                        }

                        /*
                         * There are more dld_str_t so dup the sub-chain.
                         */
                        if ((nmp = copymsgchain(mp)) != NULL)
                                ds_rx(ds_rx_arg, mrh, nmp, &mhi);

                        dsp = ndsp;
                        ds_rx = nds_rx;
                        ds_rx_arg = nds_rx_arg;
                }

                /*
                 * Release the hold on the dld_str_t chain now that we have
                 * finished walking it.
                 */
                i_dls_head_rele(dhp);

loop:
                /*
                 * If there were no acceptors then add the packet count to the
                 * 'unknown' count.
                 */
                if (!accepted)
                        atomic_add_32(&(dlp->dl_unknowns), npacket);
        }
}

/* ARGSUSED */
void
dls_rx_vlan_promisc(void *arg, mac_resource_handle_t mrh, mblk_t *mp,
    boolean_t loopback)
{
        dld_str_t                       *dsp = arg;
        dls_link_t                      *dlp = dsp->ds_dlp;
        mac_header_info_t               mhi;
        dls_rx_t                        ds_rx;
        void                            *ds_rx_arg;
        int                             err;

        DLS_PREPARE_PKT(dlp->dl_mh, mp, &mhi, err);
        if (err != 0)
                goto drop;

        /*
         * If there is promiscuous handle for vlan, we filter out the untagged
         * pkts and pkts that are not for the primary unicast address.
         */
        if (dsp->ds_vlan_mph != NULL) {
                uint8_t prim_addr[MAXMACADDRLEN];
                size_t  addr_length = dsp->ds_mip->mi_addr_length;

                if (!(mhi.mhi_istagged))
                        goto drop;
                ASSERT(dsp->ds_mh != NULL);
                mac_unicast_primary_get(dsp->ds_mh, (uint8_t *)prim_addr);
                if (memcmp(mhi.mhi_daddr, prim_addr, addr_length) != 0)
                        goto drop;

                if (!dls_accept(dsp, &mhi, &ds_rx, &ds_rx_arg))
                        goto drop;

                ds_rx(ds_rx_arg, NULL, mp, &mhi);
                return;
        }

drop:
        atomic_inc_32(&dlp->dl_unknowns);
        freemsg(mp);
}

/* ARGSUSED */
void
dls_rx_promisc(void *arg, mac_resource_handle_t mrh, mblk_t *mp,
    boolean_t loopback)
{
        dld_str_t                       *dsp = arg;
        dls_link_t                      *dlp = dsp->ds_dlp;
        mac_header_info_t               mhi;
        dls_rx_t                        ds_rx;
        void                            *ds_rx_arg;
        int                             err;
        dls_head_t                      *dhp;
        mod_hash_key_t                  key;

        DLS_PREPARE_PKT(dlp->dl_mh, mp, &mhi, err);
        if (err != 0)
                goto drop;

        /*
         * In order to filter out sap pkt that no dls channel listens, search
         * the hash table trying to find a dld_str_t eligible to receive the pkt
         */
        if ((dsp->ds_promisc & DLS_PROMISC_SAP) == 0) {
                key = MAKE_KEY(mhi.mhi_bindsap);
                if (mod_hash_find(dsp->ds_dlp->dl_str_hash, key,
                    (mod_hash_val_t *)&dhp) != 0)
                        goto drop;
        }

        if (!dls_accept_promisc(dsp, &mhi, &ds_rx, &ds_rx_arg, loopback))
                goto drop;

        ds_rx(ds_rx_arg, NULL, mp, &mhi);
        return;

drop:
        atomic_inc_32(&dlp->dl_unknowns);
        freemsg(mp);
}

static void
i_dls_link_destroy(dls_link_t *dlp)
{
        ASSERT(dlp->dl_nactive == 0);
        ASSERT(dlp->dl_impl_count == 0);
        ASSERT(dlp->dl_zone_ref == 0);

        /*
         * Free the structure back to the cache.
         */
        if (dlp->dl_mch != NULL)
                mac_client_close(dlp->dl_mch, 0);

        if (dlp->dl_mh != NULL) {
                ASSERT(MAC_PERIM_HELD(dlp->dl_mh));
                mac_close(dlp->dl_mh);
        }

        dlp->dl_mh = NULL;
        dlp->dl_mch = NULL;
        dlp->dl_mip = NULL;
        dlp->dl_unknowns = 0;
        dlp->dl_nonip_cnt = 0;
        kmem_cache_free(i_dls_link_cachep, dlp);
}

static int
i_dls_link_create(const char *name, dls_link_t **dlpp)
{
        dls_link_t              *dlp;
        int                     err;

        /*
         * Allocate a new dls_link_t structure.
         */
        dlp = kmem_cache_alloc(i_dls_link_cachep, KM_SLEEP);

        /*
         * Name the dls_link_t after the MAC interface it represents.
         */
        (void) strlcpy(dlp->dl_name, name, sizeof (dlp->dl_name));

        /*
         * First reference; hold open the MAC interface.
         */
        ASSERT(dlp->dl_mh == NULL);
        err = mac_open(dlp->dl_name, &dlp->dl_mh);
        if (err != 0)
                goto bail;

        ASSERT(MAC_PERIM_HELD(dlp->dl_mh));
        dlp->dl_mip = mac_info(dlp->dl_mh);

        /* DLS is the "primary" MAC client */
        ASSERT(dlp->dl_mch == NULL);

        err = mac_client_open(dlp->dl_mh, &dlp->dl_mch, NULL,
            MAC_OPEN_FLAGS_USE_DATALINK_NAME);
        if (err != 0)
                goto bail;

        DTRACE_PROBE2(dls__primary__client, char *, dlp->dl_name, void *,
            dlp->dl_mch);

        *dlpp = dlp;
        return (0);

bail:
        i_dls_link_destroy(dlp);
        return (err);
}

/*
 * Module initialization functions.
 */

void
dls_link_init(void)
{
        /*
         * Create a kmem_cache of dls_link_t structures.
         */
        i_dls_link_cachep = kmem_cache_create("dls_link_cache",
            sizeof (dls_link_t), 0, i_dls_link_constructor,
            i_dls_link_destructor, NULL, NULL, NULL, 0);
        ASSERT(i_dls_link_cachep != NULL);

        /*
         * Create a dls_link_t hash table and associated lock.
         */
        i_dls_link_hash = mod_hash_create_extended("dls_link_hash",
            IMPL_HASHSZ, mod_hash_null_keydtor, mod_hash_null_valdtor,
            mod_hash_bystr, NULL, mod_hash_strkey_cmp, KM_SLEEP);
        i_dls_link_count = 0;
}

int
dls_link_fini(void)
{
        if (i_dls_link_count > 0)
                return (EBUSY);

        /*
         * Destroy the kmem_cache.
         */
        kmem_cache_destroy(i_dls_link_cachep);

        /*
         * Destroy the hash table and associated lock.
         */
        mod_hash_destroy_hash(i_dls_link_hash);
        return (0);
}

/*
 * Exported functions.
 */

static int
dls_link_hold_common(const char *name, dls_link_t **dlpp, boolean_t create)
{
        dls_link_t              *dlp;
        int                     err;

        /*
         * Look up a dls_link_t corresponding to the given macname in the
         * global hash table. The i_dls_link_hash itself is protected by the
         * mod_hash package's internal lock which synchronizes
         * find/insert/remove into the global mod_hash list. Assumes that
         * inserts and removes are single threaded on a per mac end point
         * by the mac perimeter.
         */
        if ((err = mod_hash_find(i_dls_link_hash, (mod_hash_key_t)name,
            (mod_hash_val_t *)&dlp)) == 0)
                goto done;

        ASSERT(err == MH_ERR_NOTFOUND);
        if (!create)
                return (ENOENT);

        /*
         * We didn't find anything so we need to create one.
         */
        if ((err = i_dls_link_create(name, &dlp)) != 0)
                return (err);

        /*
         * Insert the dls_link_t.
         */
        err = mod_hash_insert(i_dls_link_hash, (mod_hash_key_t)dlp->dl_name,
            (mod_hash_val_t)dlp);
        ASSERT(err == 0);

        atomic_inc_32(&i_dls_link_count);
        ASSERT(i_dls_link_count != 0);

done:
        ASSERT(MAC_PERIM_HELD(dlp->dl_mh));
        /*
         * Bump the reference count and hand back the reference.
         */
        dlp->dl_ref++;
        *dlpp = dlp;
        return (0);
}

int
dls_link_hold_create(const char *name, dls_link_t **dlpp)
{
        return (dls_link_hold_common(name, dlpp, B_TRUE));
}

int
dls_link_hold(const char *name, dls_link_t **dlpp)
{
        return (dls_link_hold_common(name, dlpp, B_FALSE));
}

dev_info_t *
dls_link_devinfo(dev_t dev)
{
        dls_link_t      *dlp;
        dev_info_t      *dip;
        char    macname[MAXNAMELEN];
        char    *drv;
        mac_perim_handle_t      mph;

        if ((drv = ddi_major_to_name(getmajor(dev))) == NULL)
                return (NULL);
        (void) snprintf(macname, MAXNAMELEN, "%s%d", drv,
            DLS_MINOR2INST(getminor(dev)));

        /*
         * The code below assumes that the name constructed above is the
         * macname. This is not the case for legacy devices. Currently this
         * is ok because this function is only called in the getinfo(9e) path,
         * which for a legacy device would directly end up in the driver's
         * getinfo, rather than here
         */
        if (mac_perim_enter_by_macname(macname, &mph) != 0)
                return (NULL);

        if (dls_link_hold(macname, &dlp) != 0) {
                mac_perim_exit(mph);
                return (NULL);
        }

        dip = mac_devinfo_get(dlp->dl_mh);
        dls_link_rele(dlp);
        mac_perim_exit(mph);

        return (dip);
}

dev_t
dls_link_dev(dls_link_t *dlp)
{
        return (makedevice(ddi_driver_major(mac_devinfo_get(dlp->dl_mh)),
            mac_minor(dlp->dl_mh)));
}

void
dls_link_rele(dls_link_t *dlp)
{
        mod_hash_val_t  val;

        ASSERT(MAC_PERIM_HELD(dlp->dl_mh));
        /*
         * Check if there are any more references.
         */
        if (--dlp->dl_ref == 0) {
                (void) mod_hash_remove(i_dls_link_hash,
                    (mod_hash_key_t)dlp->dl_name, &val);
                ASSERT(dlp == (dls_link_t *)val);

                /*
                 * Destroy the dls_link_t.
                 */
                i_dls_link_destroy(dlp);
                ASSERT(i_dls_link_count > 0);
                atomic_dec_32(&i_dls_link_count);
        }
}

int
dls_link_rele_by_name(const char *name)
{
        dls_link_t              *dlp;

        if (mod_hash_find(i_dls_link_hash, (mod_hash_key_t)name,
            (mod_hash_val_t *)&dlp) != 0)
                return (ENOENT);

        ASSERT(MAC_PERIM_HELD(dlp->dl_mh));

        /*
         * Must fail detach if mac client is busy.
         */
        ASSERT(dlp->dl_ref > 0 && dlp->dl_mch != NULL);
        if (mac_link_has_flows(dlp->dl_mch))
                return (ENOTEMPTY);

        dls_link_rele(dlp);
        return (0);
}

int
dls_link_setzid(const char *name, zoneid_t zid)
{
        dls_link_t      *dlp;
        int             err = 0;
        zoneid_t        old_zid;

        if ((err = dls_link_hold_create(name, &dlp)) != 0)
                return (err);

        ASSERT(MAC_PERIM_HELD(dlp->dl_mh));

        if ((old_zid = dlp->dl_zid) == zid)
                goto done;

        /*
         * Check whether this dlp is used by its own zone.  If yes, we cannot
         * change its zoneid.
         */
        if (dlp->dl_zone_ref != 0) {
                err = EBUSY;
                goto done;
        }

        dlp->dl_zid = zid;

        if (zid == GLOBAL_ZONEID) {
                /*
                 * The link is moving from a non-global zone to the global
                 * zone, so we need to release the reference that was held
                 * when the link was originally assigned to the non-global
                 * zone.
                 */
                dls_link_rele(dlp);
        }

done:
        /*
         * We only keep the reference to this link open if the link has
         * successfully moved from the global zone to a non-global zone.
         */
        if (err != 0 || old_zid != GLOBAL_ZONEID)
                dls_link_rele(dlp);
        return (err);
}

int
dls_link_getzid(const char *name, zoneid_t *zidp)
{
        dls_link_t      *dlp;
        int             err = 0;

        if ((err = dls_link_hold(name, &dlp)) != 0)
                return (err);

        ASSERT(MAC_PERIM_HELD(dlp->dl_mh));

        *zidp = dlp->dl_zid;

        dls_link_rele(dlp);
        return (0);
}

void
dls_link_add(dls_link_t *dlp, uint32_t sap, dld_str_t *dsp)
{
        mod_hash_t      *hash = dlp->dl_str_hash;
        mod_hash_key_t  key;
        dls_head_t      *dhp;
        dld_str_t       *p;
        int             err;

        ASSERT(MAC_PERIM_HELD(dlp->dl_mh));

        /*
         * Generate a hash key based on the sap.
         */
        key = MAKE_KEY(sap);

        /*
         * Search the table for a list head with this key.
         */
        if ((err = mod_hash_find(hash, key, (mod_hash_val_t *)&dhp)) != 0) {
                ASSERT(err == MH_ERR_NOTFOUND);

                dhp = i_dls_head_alloc(key);
                err = mod_hash_insert(hash, key, (mod_hash_val_t)dhp);
                ASSERT(err == 0);
        }

        /*
         * Add the dld_str_t to the head of the list. List walkers in
         * i_dls_link_rx_* bump up dh_ref to ensure the list does not change
         * while they walk the list. The membar below ensures that list walkers
         * see exactly the old list or the new list.
         */
        ASSERT(dsp->ds_next == NULL);
        p = dhp->dh_list;
        dsp->ds_next = p;

        membar_producer();

        dhp->dh_list = dsp;

        /*
         * Save a pointer to the list head.
         */
        dsp->ds_head = dhp;
        dlp->dl_impl_count++;
}

void
dls_link_remove(dls_link_t *dlp, dld_str_t *dsp)
{
        mod_hash_t      *hash = dlp->dl_str_hash;
        dld_str_t       **pp;
        dld_str_t       *p;
        dls_head_t      *dhp;

        ASSERT(MAC_PERIM_HELD(dlp->dl_mh));

        /*
         * We set dh_removing here to tell the receive callbacks not to pass
         * up packets anymore. Then wait till the current callbacks are done.
         * This happens either in the close path or in processing the
         * DL_UNBIND_REQ via a taskq thread, and it is ok to cv_wait in either.
         * The dh_ref ensures there aren't and there won't be any upcalls
         * walking or using the dh_list. The mod hash internal lock ensures
         * that the insert/remove of the dls_head_t itself synchronizes with
         * any i_dls_link_rx trying to locate it. The perimeter ensures that
         * there isn't another simultaneous dls_link_add/remove.
         */
        dhp = dsp->ds_head;

        mutex_enter(&dhp->dh_lock);
        dhp->dh_removing = B_TRUE;
        while (dhp->dh_ref != 0)
                cv_wait(&dhp->dh_cv, &dhp->dh_lock);
        mutex_exit(&dhp->dh_lock);

        /*
         * Walk the list and remove the dld_str_t.
         */
        for (pp = &dhp->dh_list; (p = *pp) != NULL; pp = &(p->ds_next)) {
                if (p == dsp)
                        break;
        }
        ASSERT(p != NULL);
        *pp = p->ds_next;
        p->ds_next = NULL;
        p->ds_head = NULL;

        ASSERT(dlp->dl_impl_count != 0);
        dlp->dl_impl_count--;

        if (dhp->dh_list == NULL) {
                mod_hash_val_t  val = NULL;

                /*
                 * The list is empty so remove the hash table entry.
                 */
                (void) mod_hash_remove(hash, dhp->dh_key, &val);
                ASSERT(dhp == (dls_head_t *)val);
                i_dls_head_free(dhp);
        } else {
                mutex_enter(&dhp->dh_lock);
                dhp->dh_removing = B_FALSE;
                mutex_exit(&dhp->dh_lock);
        }
}