efivar.{3,8}: Fix some mdoc issues.

[dragonfly.git] / sys / net / netisr.c

/*
 * Copyright (c) 2003, 2004 Matthew Dillon. All rights reserved.
 * Copyright (c) 2003, 2004 Jeffrey M. Hsu.  All rights reserved.
 * Copyright (c) 2003 Jonathan Lemon.  All rights reserved.
 * Copyright (c) 2003, 2004 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Jonathan Lemon, Jeffrey M. Hsu, and Matthew Dillon.
 *
 * Jonathan Lemon gave Jeffrey Hsu permission to combine his copyright
 * into this one around July 8 2004.
 *
 * 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.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/msgport.h>
#include <sys/proc.h>
#include <sys/interrupt.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/socketvar.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/netisr2.h>
#include <machine/cpufunc.h>
#include <machine/smp.h>

#include <sys/thread2.h>
#include <sys/msgport2.h>
#include <net/netmsg2.h>
#include <sys/mplock2.h>

static void netmsg_service_loop(void *arg);
static void netisr_hashfn0(struct mbuf **mp, int hoff);
static void netisr_nohashck(struct mbuf *, const struct pktinfo *);

struct netmsg_port_registration {
        TAILQ_ENTRY(netmsg_port_registration) npr_entry;
        lwkt_port_t     npr_port;
};

struct netmsg_rollup {
        TAILQ_ENTRY(netmsg_rollup) ru_entry;
        netisr_ru_t     ru_func;
        int             ru_prio;
};

struct netmsg_barrier {
        struct netmsg_base      base;
        volatile cpumask_t      *br_cpumask;
        volatile uint32_t       br_done;
};

#define NETISR_BR_NOTDONE       0x1
#define NETISR_BR_WAITDONE      0x80000000

struct netisr_barrier {
        struct netmsg_barrier   *br_msgs[MAXCPU];
        int                     br_isset;
};

void *netlastfunc[MAXCPU];
static struct netisr netisrs[NETISR_MAX];
static TAILQ_HEAD(,netmsg_port_registration) netreglist;
static TAILQ_HEAD(,netmsg_rollup) netrulist;

/* Per-CPU thread to handle any protocol.  */
struct thread *netisr_cpu[MAXCPU];
lwkt_port netisr_afree_rport;
lwkt_port netisr_afree_free_so_rport;
lwkt_port netisr_adone_rport;
lwkt_port netisr_apanic_rport;
lwkt_port netisr_sync_port;

static int (*netmsg_fwd_port_fn)(lwkt_port_t, lwkt_msg_t);

SYSCTL_NODE(_net, OID_AUTO, netisr, CTLFLAG_RW, 0, "netisr");
static int netisr_rollup_limit = 32;
SYSCTL_INT(_net_netisr, OID_AUTO, rollup_limit, CTLFLAG_RW,
        &netisr_rollup_limit, 0, "Message to process before rollup");


/*
 * netisr_afree_rport replymsg function, only used to handle async
 * messages which the sender has abandoned to their fate.
 */
static void
netisr_autofree_reply(lwkt_port_t port, lwkt_msg_t msg)
{
        kfree(msg, M_LWKTMSG);
}

static void
netisr_autofree_free_so_reply(lwkt_port_t port, lwkt_msg_t msg)
{
        sofree(((netmsg_t)msg)->base.nm_so);
        kfree(msg, M_LWKTMSG);
}

/*
 * We need a custom putport function to handle the case where the
 * message target is the current thread's message port.  This case
 * can occur when the TCP or UDP stack does a direct callback to NFS and NFS
 * then turns around and executes a network operation synchronously.
 *
 * To prevent deadlocking, we must execute these self-referential messages
 * synchronously, effectively turning the message into a glorified direct
 * procedure call back into the protocol stack.  The operation must be
 * complete on return or we will deadlock, so panic if it isn't.
 *
 * However, the target function is under no obligation to immediately
 * reply the message.  It may forward it elsewhere.
 */
static int
netmsg_put_port(lwkt_port_t port, lwkt_msg_t lmsg)
{
        netmsg_base_t nmsg = (void *)lmsg;

        if ((lmsg->ms_flags & MSGF_SYNC) && port == &curthread->td_msgport) {
                nmsg->nm_dispatch((netmsg_t)nmsg);
                return(EASYNC);
        } else {
                return(netmsg_fwd_port_fn(port, lmsg));
        }
}

/*
 * UNIX DOMAIN sockets still have to run their uipc functions synchronously,
 * because they depend on the user proc context for a number of things 
 * (like creds) which we have not yet incorporated into the message structure.
 *
 * However, we maintain or message/port abstraction.  Having a special 
 * synchronous port which runs the commands synchronously gives us the
 * ability to serialize operations in one place later on when we start
 * removing the BGL.
 */
static int
netmsg_sync_putport(lwkt_port_t port, lwkt_msg_t lmsg)
{
        netmsg_base_t nmsg = (void *)lmsg;

        KKASSERT((lmsg->ms_flags & MSGF_DONE) == 0);

        lmsg->ms_target_port = port;    /* required for abort */
        nmsg->nm_dispatch((netmsg_t)nmsg);
        return(EASYNC);
}

static void
netisr_init(void)
{
        int i;

        TAILQ_INIT(&netreglist);
        TAILQ_INIT(&netrulist);

        /*
         * Create default per-cpu threads for generic protocol handling.
         */
        for (i = 0; i < ncpus; ++i) {
                lwkt_create(netmsg_service_loop, NULL, &netisr_cpu[i],
                            NULL,
                            TDF_NOSTART|TDF_FORCE_SPINPORT|TDF_FIXEDCPU,
                            i, "netisr_cpu %d", i);
                netmsg_service_port_init(&netisr_cpu[i]->td_msgport);
                lwkt_schedule(netisr_cpu[i]);
        }

        /*
         * The netisr_afree_rport is a special reply port which automatically
         * frees the replied message.  The netisr_adone_rport simply marks
         * the message as being done.  The netisr_apanic_rport panics if
         * the message is replied to.
         */
        lwkt_initport_replyonly(&netisr_afree_rport, netisr_autofree_reply);
        lwkt_initport_replyonly(&netisr_afree_free_so_rport,
                                netisr_autofree_free_so_reply);
        lwkt_initport_replyonly_null(&netisr_adone_rport);
        lwkt_initport_panic(&netisr_apanic_rport);

        /*
         * The netisr_syncport is a special port which executes the message
         * synchronously and waits for it if EASYNC is returned.
         */
        lwkt_initport_putonly(&netisr_sync_port, netmsg_sync_putport);
}

SYSINIT(netisr, SI_SUB_PRE_DRIVERS, SI_ORDER_FIRST, netisr_init, NULL);

/*
 * Finish initializing the message port for a netmsg service.  This also
 * registers the port for synchronous cleanup operations such as when an
 * ifnet is being destroyed.  There is no deregistration API yet.
 */
void
netmsg_service_port_init(lwkt_port_t port)
{
        struct netmsg_port_registration *reg;

        /*
         * Override the putport function.  Our custom function checks for
         * self-references and executes such commands synchronously.
         */
        if (netmsg_fwd_port_fn == NULL)
                netmsg_fwd_port_fn = port->mp_putport;
        KKASSERT(netmsg_fwd_port_fn == port->mp_putport);
        port->mp_putport = netmsg_put_port;

        /*
         * Keep track of ports using the netmsg API so we can synchronize
         * certain operations (such as freeing an ifnet structure) across all
         * consumers.
         */
        reg = kmalloc(sizeof(*reg), M_TEMP, M_WAITOK|M_ZERO);
        reg->npr_port = port;
        TAILQ_INSERT_TAIL(&netreglist, reg, npr_entry);
}

/*
 * This function synchronizes the caller with all netmsg services.  For
 * example, if an interface is being removed we must make sure that all
 * packets related to that interface complete processing before the structure
 * can actually be freed.  This sort of synchronization is an alternative to
 * ref-counting the netif, removing the ref counting overhead in favor of
 * placing additional overhead in the netif freeing sequence (where it is
 * inconsequential).
 */
void
netmsg_service_sync(void)
{
        struct netmsg_port_registration *reg;
        struct netmsg_base smsg;

        netmsg_init(&smsg, NULL, &curthread->td_msgport, 0, netmsg_sync_handler);

        TAILQ_FOREACH(reg, &netreglist, npr_entry) {
                lwkt_domsg(reg->npr_port, &smsg.lmsg, 0);
        }
}

/*
 * The netmsg function simply replies the message.  API semantics require
 * EASYNC to be returned if the netmsg function disposes of the message.
 */
void
netmsg_sync_handler(netmsg_t msg)
{
        lwkt_replymsg(&msg->lmsg, 0);
}

/*
 * Generic netmsg service loop.  Some protocols may roll their own but all
 * must do the basic command dispatch function call done here.
 */
static void
netmsg_service_loop(void *arg)
{
        struct netmsg_rollup *ru;
        netmsg_base_t msg;
        thread_t td = curthread;
        int limit;

        td->td_type = TD_TYPE_NETISR;

        while ((msg = lwkt_waitport(&td->td_msgport, 0))) {
                /*
                 * Run up to 512 pending netmsgs.
                 */
                limit = netisr_rollup_limit;
                do {
                        KASSERT(msg->nm_dispatch != NULL,
                                ("netmsg_service isr %d badmsg",
                                msg->lmsg.u.ms_result));
                        /*
                         * Don't match so_port, if the msg explicitly
                         * asks us to ignore its so_port.
                         */
                        if ((msg->lmsg.ms_flags & MSGF_IGNSOPORT) == 0 &&
                            msg->nm_so &&
                            msg->nm_so->so_port != &td->td_msgport) {
                                /*
                                 * Sockets undergoing connect or disconnect
                                 * ops can change ports on us.  Chase the
                                 * port.
                                 */
#ifdef foo
                                /*
                                 * This could be quite common for protocols
                                 * which support asynchronous pru_connect,
                                 * e.g. TCP, so kprintf socket port chasing
                                 * could be too verbose for the console.
                                 */
                                kprintf("%s: Warning, port changed so=%p\n",
                                        __func__, msg->nm_so);
#endif
                                lwkt_forwardmsg(msg->nm_so->so_port,
                                                &msg->lmsg);
                        } else {
                                /*
                                 * We are on the correct port, dispatch it.
                                 */
                                netlastfunc[mycpuid] = msg->nm_dispatch;
                                msg->nm_dispatch((netmsg_t)msg);
                        }
                        if (--limit == 0)
                                break;
                } while ((msg = lwkt_getport(&td->td_msgport)) != NULL);

                /*
                 * Run all registered rollup functions for this cpu
                 * (e.g. tcp_willblock()).
                 */
                TAILQ_FOREACH(ru, &netrulist, ru_entry)
                        ru->ru_func();
        }
}

/*
 * Forward a packet to a netisr service function.
 *
 * If the packet has not been assigned to a protocol thread we call
 * the port characterization function to assign it.  The caller must
 * clear M_HASH (or not have set it in the first place) if the caller
 * wishes the packet to be recharacterized.
 */
int
netisr_queue(int num, struct mbuf *m)
{
        struct netisr *ni;
        struct netmsg_packet *pmsg;
        lwkt_port_t port;

        KASSERT((num > 0 && num <= NELEM(netisrs)),
                ("Bad isr %d", num));

        ni = &netisrs[num];
        if (ni->ni_handler == NULL) {
                kprintf("%s: Unregistered isr %d\n", __func__, num);
                m_freem(m);
                return (EIO);
        }

        /*
         * Figure out which protocol thread to send to.  This does not
         * have to be perfect but performance will be really good if it
         * is correct.  Major protocol inputs such as ip_input() will
         * re-characterize the packet as necessary.
         */
        if ((m->m_flags & M_HASH) == 0) {
                ni->ni_hashfn(&m, 0);
                if (m == NULL)
                        return (EIO);
                if ((m->m_flags & M_HASH) == 0) {
                        kprintf("%s(%d): packet hash failed\n",
                                __func__, num);
                        m_freem(m);
                        return (EIO);
                }
        }

        /*
         * Get the protocol port based on the packet hash, initialize
         * the netmsg, and send it off.
         */
        port = netisr_hashport(m->m_pkthdr.hash);
        pmsg = &m->m_hdr.mh_netmsg;
        netmsg_init(&pmsg->base, NULL, &netisr_apanic_rport,
                    0, ni->ni_handler);
        pmsg->nm_packet = m;
        pmsg->base.lmsg.u.ms_result = num;
        lwkt_sendmsg(port, &pmsg->base.lmsg);

        return (0);
}

/*
 * Run a netisr service function on the packet.
 *
 * The packet must have been correctly characterized!
 */
int
netisr_handle(int num, struct mbuf *m)
{
        struct netisr *ni;
        struct netmsg_packet *pmsg;
        lwkt_port_t port;

        /*
         * Get the protocol port based on the packet hash
         */
        KASSERT((m->m_flags & M_HASH), ("packet not characterized"));
        port = netisr_hashport(m->m_pkthdr.hash);
        KASSERT(&curthread->td_msgport == port, ("wrong msgport"));

        KASSERT((num > 0 && num <= NELEM(netisrs)), ("bad isr %d", num));
        ni = &netisrs[num];
        if (ni->ni_handler == NULL) {
                kprintf("%s: unregistered isr %d\n", __func__, num);
                m_freem(m);
                return EIO;
        }

        /*
         * Initialize the netmsg, and run the handler directly.
         */
        pmsg = &m->m_hdr.mh_netmsg;
        netmsg_init(&pmsg->base, NULL, &netisr_apanic_rport,
                    0, ni->ni_handler);
        pmsg->nm_packet = m;
        pmsg->base.lmsg.u.ms_result = num;
        ni->ni_handler((netmsg_t)&pmsg->base);

        return 0;
}

/*
 * Pre-characterization of a deeper portion of the packet for the
 * requested isr.
 *
 * The base of the ISR type (e.g. IP) that we want to characterize is
 * at (hoff) relative to the beginning of the mbuf.  This allows
 * e.g. ether_characterize() to not have to adjust the m_data/m_len.
 */
void
netisr_characterize(int num, struct mbuf **mp, int hoff)
{
        struct netisr *ni;
        struct mbuf *m;

        /*
         * Validation
         */
        m = *mp;
        KKASSERT(m != NULL);

        if (num < 0 || num >= NETISR_MAX) {
                if (num == NETISR_MAX) {
                        m->m_flags |= M_HASH;
                        m->m_pkthdr.hash = 0;
                        return;
                }
                panic("Bad isr %d", num);
        }

        /*
         * Valid netisr?
         */
        ni = &netisrs[num];
        if (ni->ni_handler == NULL) {
                kprintf("%s: Unregistered isr %d\n", __func__, num);
                m_freem(m);
                *mp = NULL;
        }

        /*
         * Characterize the packet
         */
        if ((m->m_flags & M_HASH) == 0) {
                ni->ni_hashfn(mp, hoff);
                m = *mp;
                if (m && (m->m_flags & M_HASH) == 0) {
                        kprintf("%s(%d): packet hash failed\n",
                                __func__, num);
                }
        }
}

void
netisr_register(int num, netisr_fn_t handler, netisr_hashfn_t hashfn)
{
        struct netisr *ni;

        KASSERT((num > 0 && num <= NELEM(netisrs)),
                ("netisr_register: bad isr %d", num));
        KKASSERT(handler != NULL);

        if (hashfn == NULL)
                hashfn = netisr_hashfn0;

        ni = &netisrs[num];

        ni->ni_handler = handler;
        ni->ni_hashck = netisr_nohashck;
        ni->ni_hashfn = hashfn;
        netmsg_init(&ni->ni_netmsg, NULL, &netisr_adone_rport, 0, NULL);
}

void
netisr_register_hashcheck(int num, netisr_hashck_t hashck)
{
        struct netisr *ni;

        KASSERT((num > 0 && num <= NELEM(netisrs)),
                ("netisr_register: bad isr %d", num));

        ni = &netisrs[num];
        ni->ni_hashck = hashck;
}

void
netisr_register_rollup(netisr_ru_t ru_func, int prio)
{
        struct netmsg_rollup *new_ru, *ru;

        new_ru = kmalloc(sizeof(*new_ru), M_TEMP, M_WAITOK|M_ZERO);
        new_ru->ru_func = ru_func;
        new_ru->ru_prio = prio;

        /*
         * Higher priority "rollup" appears first
         */
        TAILQ_FOREACH(ru, &netrulist, ru_entry) {
                if (ru->ru_prio < new_ru->ru_prio) {
                        TAILQ_INSERT_BEFORE(ru, new_ru, ru_entry);
                        return;
                }
        }
        TAILQ_INSERT_TAIL(&netrulist, new_ru, ru_entry);
}

/*
 * Return a default protocol control message processing thread port
 */
lwkt_port_t
cpu0_ctlport(int cmd __unused, struct sockaddr *sa __unused,
    void *extra __unused, int *cpuid)
{
        *cpuid = 0;
        return netisr_cpuport(*cpuid);
}

/*
 * This is a default netisr packet characterization function which
 * sets M_HASH.  If a netisr is registered with a NULL hashfn function
 * this one is assigned.
 *
 * This function makes no attempt to validate the packet.
 */
static void
netisr_hashfn0(struct mbuf **mp, int hoff __unused)
{
        struct mbuf *m = *mp;

        m->m_flags |= M_HASH;
        m->m_pkthdr.hash = 0;
}

/*
 * schednetisr() is used to call the netisr handler from the appropriate
 * netisr thread for polling and other purposes.
 *
 * This function may be called from a hard interrupt or IPI and must be
 * MP SAFE and non-blocking.  We use a fixed per-cpu message instead of
 * trying to allocate one.  We must get ourselves onto the target cpu
 * to safely check the MSGF_DONE bit on the message but since the message
 * will be sent to that cpu anyway this does not add any extra work beyond
 * what lwkt_sendmsg() would have already had to do to schedule the target
 * thread.
 */
static void
schednetisr_remote(void *data)
{
        int num = (int)(intptr_t)data;
        struct netisr *ni = &netisrs[num];
        lwkt_port_t port = &netisr_cpu[0]->td_msgport;
        netmsg_base_t pmsg;

        pmsg = &netisrs[num].ni_netmsg;
        if (pmsg->lmsg.ms_flags & MSGF_DONE) {
                netmsg_init(pmsg, NULL, &netisr_adone_rport, 0, ni->ni_handler);
                pmsg->lmsg.u.ms_result = num;
                lwkt_sendmsg(port, &pmsg->lmsg);
        }
}

void
schednetisr(int num)
{
        KASSERT((num > 0 && num <= NELEM(netisrs)),
                ("schednetisr: bad isr %d", num));
        KKASSERT(netisrs[num].ni_handler != NULL);
        if (mycpu->gd_cpuid != 0) {
                lwkt_send_ipiq(globaldata_find(0),
                               schednetisr_remote, (void *)(intptr_t)num);
        } else {
                crit_enter();
                schednetisr_remote((void *)(intptr_t)num);
                crit_exit();
        }
}

static void
netisr_barrier_dispatch(netmsg_t nmsg)
{
        struct netmsg_barrier *msg = (struct netmsg_barrier *)nmsg;

        ATOMIC_CPUMASK_NANDBIT(*msg->br_cpumask, mycpu->gd_cpuid);
        if (CPUMASK_TESTZERO(*msg->br_cpumask))
                wakeup(msg->br_cpumask);

        for (;;) {
                uint32_t done = msg->br_done;

                cpu_ccfence();
                if ((done & NETISR_BR_NOTDONE) == 0)
                        break;

                tsleep_interlock(&msg->br_done, 0);
                if (atomic_cmpset_int(&msg->br_done,
                    done, done | NETISR_BR_WAITDONE))
                        tsleep(&msg->br_done, PINTERLOCKED, "nbrdsp", 0);
        }

        lwkt_replymsg(&nmsg->lmsg, 0);
}

struct netisr_barrier *
netisr_barrier_create(void)
{
        struct netisr_barrier *br;

        br = kmalloc(sizeof(*br), M_LWKTMSG, M_WAITOK | M_ZERO);
        return br;
}

void
netisr_barrier_set(struct netisr_barrier *br)
{
        volatile cpumask_t other_cpumask;
        int i, cur_cpuid;

        ASSERT_IN_NETISR(0);
        KKASSERT(!br->br_isset);

        other_cpumask = mycpu->gd_other_cpus;
        CPUMASK_ANDMASK(other_cpumask, smp_active_mask);
        cur_cpuid = mycpuid;

        for (i = 0; i < ncpus; ++i) {
                struct netmsg_barrier *msg;

                if (i == cur_cpuid)
                        continue;

                msg = kmalloc(sizeof(struct netmsg_barrier),
                              M_LWKTMSG, M_WAITOK);

                /*
                 * Don't use priority message here; mainly to keep
                 * it ordered w/ the previous data packets sent by
                 * the caller.
                 */
                netmsg_init(&msg->base, NULL, &netisr_afree_rport, 0,
                            netisr_barrier_dispatch);
                msg->br_cpumask = &other_cpumask;
                msg->br_done = NETISR_BR_NOTDONE;

                KKASSERT(br->br_msgs[i] == NULL);
                br->br_msgs[i] = msg;
        }

        for (i = 0; i < ncpus; ++i) {
                if (i == cur_cpuid)
                        continue;
                lwkt_sendmsg(netisr_cpuport(i), &br->br_msgs[i]->base.lmsg);
        }

        while (CPUMASK_TESTNZERO(other_cpumask)) {
                tsleep_interlock(&other_cpumask, 0);
                if (CPUMASK_TESTNZERO(other_cpumask))
                        tsleep(&other_cpumask, PINTERLOCKED, "nbrset", 0);
        }
        br->br_isset = 1;
}

void
netisr_barrier_rem(struct netisr_barrier *br)
{
        int i, cur_cpuid;

        ASSERT_IN_NETISR(0);
        KKASSERT(br->br_isset);

        cur_cpuid = mycpuid;
        for (i = 0; i < ncpus; ++i) {
                struct netmsg_barrier *msg = br->br_msgs[i];
                uint32_t done;

                msg = br->br_msgs[i];
                br->br_msgs[i] = NULL;

                if (i == cur_cpuid)
                        continue;

                done = atomic_swap_int(&msg->br_done, 0);
                if (done & NETISR_BR_WAITDONE)
                        wakeup(&msg->br_done);
        }
        br->br_isset = 0;
}

static void
netisr_nohashck(struct mbuf *m, const struct pktinfo *pi __unused)
{
        m->m_flags &= ~M_HASH;
}

void
netisr_hashcheck(int num, struct mbuf *m, const struct pktinfo *pi)
{
        struct netisr *ni;

        if (num < 0 || num >= NETISR_MAX)
                panic("Bad isr %d", num);

        /*
         * Valid netisr?
         */
        ni = &netisrs[num];
        if (ni->ni_handler == NULL)
                panic("Unregistered isr %d", num);

        ni->ni_hashck(m, pi);
}