/*
 * ng_ppp.c
 *
 * Copyright (c) 1996-2000 Whistle Communications, Inc.
 * All rights reserved.
 * 
 * Subject to the following obligations and disclaimer of warranty, use and
 * redistribution of this software, in source or object code forms, with or
 * without modifications are expressly permitted by Whistle Communications;
 * provided, however, that:
 * 1. Any and all reproductions of the source or object code must include the
 *    copyright notice above and the following disclaimer of warranties; and
 * 2. No rights are granted, in any manner or form, to use Whistle
 *    Communications, Inc. trademarks, including the mark "WHISTLE
 *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
 *    such appears in the above copyright notice or in the software.
 * 
 * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
 * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
 * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
 * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
 * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
 * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
 * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
 * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
 * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
 * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER 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 WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * Author: Archie Cobbs <archie@freebsd.org>
 *
 * $FreeBSD: src/sys/netgraph/ng_ppp.c,v 1.15.2.10 2003/03/10 17:55:48 archie Exp $
 * $Whistle: ng_ppp.c,v 1.24 1999/11/01 09:24:52 julian Exp $
 */

/*
 * PPP node type.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/time.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/errno.h>
#include <sys/ctype.h>
#include <sys/thread2.h>

#include <machine/limits.h>

#include <netgraph/ng_message.h>
#include <netgraph/netgraph.h>
#include <netgraph/ng_parse.h>
#include "ng_ppp.h"
#include <netgraph/vjc/ng_vjc.h>

#define PROT_VALID(p)           (((p) & 0x0101) == 0x0001)
#define PROT_COMPRESSABLE(p)    (((p) & 0xff00) == 0x0000)

/* Some PPP protocol numbers we're interested in */
#define PROT_APPLETALK          0x0029
#define PROT_COMPD              0x00fd
#define PROT_CRYPTD             0x0053
#define PROT_IP                 0x0021
#define PROT_IPV6               0x0057
#define PROT_IPX                0x002b
#define PROT_LCP                0xc021
#define PROT_MP                 0x003d
#define PROT_VJCOMP             0x002d
#define PROT_VJUNCOMP           0x002f

/* Multilink PPP definitions */
#define MP_MIN_MRRU             1500            /* per RFC 1990 */
#define MP_INITIAL_SEQ          0               /* per RFC 1990 */
#define MP_MIN_LINK_MRU         32

#define MP_SHORT_SEQ_MASK       0x00000fff      /* short seq # mask */
#define MP_SHORT_SEQ_HIBIT      0x00000800      /* short seq # high bit */
#define MP_SHORT_FIRST_FLAG     0x00008000      /* first fragment in frame */
#define MP_SHORT_LAST_FLAG      0x00004000      /* last fragment in frame */

#define MP_LONG_SEQ_MASK        0x00ffffff      /* long seq # mask */
#define MP_LONG_SEQ_HIBIT       0x00800000      /* long seq # high bit */
#define MP_LONG_FIRST_FLAG      0x80000000      /* first fragment in frame */
#define MP_LONG_LAST_FLAG       0x40000000      /* last fragment in frame */

#define MP_NOSEQ                0x7fffffff      /* impossible sequence number */

/* Sign extension of MP sequence numbers */
#define MP_SHORT_EXTEND(s)      (((s) & MP_SHORT_SEQ_HIBIT) ?           \
                                    ((s) | ~MP_SHORT_SEQ_MASK)          \
                                    : ((s) & MP_SHORT_SEQ_MASK))
#define MP_LONG_EXTEND(s)       (((s) & MP_LONG_SEQ_HIBIT) ?            \
                                    ((s) | ~MP_LONG_SEQ_MASK)           \
                                    : ((s) & MP_LONG_SEQ_MASK))

/* Comparision of MP sequence numbers. Note: all sequence numbers
   except priv->xseq are stored with the sign bit extended. */
#define MP_SHORT_SEQ_DIFF(x,y)  MP_SHORT_EXTEND((x) - (y))
#define MP_LONG_SEQ_DIFF(x,y)   MP_LONG_EXTEND((x) - (y))

#define MP_RECV_SEQ_DIFF(priv,x,y)                                      \
                                ((priv)->conf.recvShortSeq ?            \
                                    MP_SHORT_SEQ_DIFF((x), (y)) :       \
                                    MP_LONG_SEQ_DIFF((x), (y)))

/* Increment receive sequence number */
#define MP_NEXT_RECV_SEQ(priv,seq)                                      \
                                ((priv)->conf.recvShortSeq ?            \
                                    MP_SHORT_EXTEND((seq) + 1) :        \
                                    MP_LONG_EXTEND((seq) + 1))

/* Don't fragment transmitted packets smaller than this */
#define MP_MIN_FRAG_LEN         6

/* Maximum fragment reasssembly queue length */
#define MP_MAX_QUEUE_LEN        128

/* Fragment queue scanner period */
#define MP_FRAGTIMER_INTERVAL   (hz/2)

/* We store incoming fragments this way */
struct ng_ppp_frag {
        int                             seq;            /* fragment seq# */
        u_char                          first;          /* First in packet? */
        u_char                          last;           /* Last in packet? */
        struct timeval                  timestamp;      /* time of reception */
        struct mbuf                     *data;          /* Fragment data */
        meta_p                          meta;           /* Fragment meta */
        TAILQ_ENTRY(ng_ppp_frag)        f_qent;         /* Fragment queue */
};

/* We use integer indicies to refer to the non-link hooks */
static const char *const ng_ppp_hook_names[] = {
        NG_PPP_HOOK_ATALK,
#define HOOK_INDEX_ATALK                0
        NG_PPP_HOOK_BYPASS,
#define HOOK_INDEX_BYPASS               1
        NG_PPP_HOOK_COMPRESS,
#define HOOK_INDEX_COMPRESS             2
        NG_PPP_HOOK_ENCRYPT,
#define HOOK_INDEX_ENCRYPT              3
        NG_PPP_HOOK_DECOMPRESS,
#define HOOK_INDEX_DECOMPRESS           4
        NG_PPP_HOOK_DECRYPT,
#define HOOK_INDEX_DECRYPT              5
        NG_PPP_HOOK_INET,
#define HOOK_INDEX_INET                 6
        NG_PPP_HOOK_IPX,
#define HOOK_INDEX_IPX                  7
        NG_PPP_HOOK_VJC_COMP,
#define HOOK_INDEX_VJC_COMP             8
        NG_PPP_HOOK_VJC_IP,
#define HOOK_INDEX_VJC_IP               9
        NG_PPP_HOOK_VJC_UNCOMP,
#define HOOK_INDEX_VJC_UNCOMP           10
        NG_PPP_HOOK_VJC_VJIP,
#define HOOK_INDEX_VJC_VJIP             11
        NG_PPP_HOOK_IPV6,
#define HOOK_INDEX_IPV6                 12
        NULL
#define HOOK_INDEX_MAX                  13
};

/* We store index numbers in the hook private pointer. The HOOK_INDEX()
   for a hook is either the index (above) for normal hooks, or the ones
   complement of the link number for link hooks. */
#define HOOK_INDEX(hook)        (*((int16_t *) &(hook)->private))

/* Per-link private information */
struct ng_ppp_link {
        struct ng_ppp_link_conf conf;           /* link configuration */
        hook_p                  hook;           /* connection to link data */
        int32_t                 seq;            /* highest rec'd seq# - MSEQ */
        struct timeval          lastWrite;      /* time of last write */
        int                     bytesInQueue;   /* bytes in the output queue */
        struct ng_ppp_link_stat stats;          /* Link stats */
};

/* Total per-node private information */
struct ng_ppp_private {
        struct ng_ppp_bund_conf conf;                   /* bundle config */
        struct ng_ppp_link_stat bundleStats;            /* bundle stats */
        struct ng_ppp_link      links[NG_PPP_MAX_LINKS];/* per-link info */
        int32_t                 xseq;                   /* next out MP seq # */
        int32_t                 mseq;                   /* min links[i].seq */
        u_char                  vjCompHooked;           /* VJ comp hooked up? */
        u_char                  allLinksEqual;          /* all xmit the same? */
        u_char                  timerActive;            /* frag timer active? */
        u_int                   numActiveLinks;         /* how many links up */
        int                     activeLinks[NG_PPP_MAX_LINKS];  /* indicies */
        u_int                   lastLink;               /* for round robin */
        hook_p                  hooks[HOOK_INDEX_MAX];  /* non-link hooks */
        TAILQ_HEAD(ng_ppp_fraglist, ng_ppp_frag)        /* fragment queue */
                                frags;
        int                     qlen;                   /* fraq queue length */
        struct callout          fragTimer;              /* fraq queue check */
};
typedef struct ng_ppp_private *priv_p;

/* Netgraph node methods */
static ng_constructor_t ng_ppp_constructor;
static ng_rcvmsg_t      ng_ppp_rcvmsg;
static ng_shutdown_t    ng_ppp_rmnode;
static ng_newhook_t     ng_ppp_newhook;
static ng_rcvdata_t     ng_ppp_rcvdata;
static ng_disconnect_t  ng_ppp_disconnect;

/* Helper functions */
static int      ng_ppp_input(node_p node, int bypass,
                        int linkNum, struct mbuf *m, meta_p meta);
static int      ng_ppp_output(node_p node, int bypass, int proto,
                        int linkNum, struct mbuf *m, meta_p meta);
static int      ng_ppp_mp_input(node_p node, int linkNum,
                        struct mbuf *m, meta_p meta);
static int      ng_ppp_check_packet(node_p node);
static void     ng_ppp_get_packet(node_p node, struct mbuf **mp, meta_p *metap);
static int      ng_ppp_frag_process(node_p node);
static int      ng_ppp_frag_trim(node_p node);
static void     ng_ppp_frag_timeout(void *arg);
static void     ng_ppp_frag_checkstale(node_p node);
static void     ng_ppp_frag_reset(node_p node);
static int      ng_ppp_mp_output(node_p node, struct mbuf *m, meta_p meta);
static void     ng_ppp_mp_strategy(node_p node, int len, int *distrib);
static int      ng_ppp_intcmp(const void *v1, const void *v2);
static struct   mbuf *ng_ppp_addproto(struct mbuf *m, int proto, int compOK);
static struct   mbuf *ng_ppp_prepend(struct mbuf *m, const void *buf, int len);
static int      ng_ppp_config_valid(node_p node,
                        const struct ng_ppp_node_conf *newConf);
static void     ng_ppp_update(node_p node, int newConf);
static void     ng_ppp_start_frag_timer(node_p node);
static void     ng_ppp_stop_frag_timer(node_p node);

/* Parse type for struct ng_ppp_mp_state_type */
static const struct ng_parse_fixedarray_info ng_ppp_rseq_array_info = {
        &ng_parse_hint32_type,
        NG_PPP_MAX_LINKS
};
static const struct ng_parse_type ng_ppp_rseq_array_type = {
        &ng_parse_fixedarray_type,
        &ng_ppp_rseq_array_info,
};
static const struct ng_parse_struct_field ng_ppp_mp_state_type_fields[]
        = NG_PPP_MP_STATE_TYPE_INFO(&ng_ppp_rseq_array_type);
static const struct ng_parse_type ng_ppp_mp_state_type = {
        &ng_parse_struct_type,
        &ng_ppp_mp_state_type_fields
};

/* Parse type for struct ng_ppp_link_conf */
static const struct ng_parse_struct_field ng_ppp_link_type_fields[]
        = NG_PPP_LINK_TYPE_INFO;
static const struct ng_parse_type ng_ppp_link_type = {
        &ng_parse_struct_type,
        &ng_ppp_link_type_fields
};

/* Parse type for struct ng_ppp_bund_conf */
static const struct ng_parse_struct_field ng_ppp_bund_type_fields[]
        = NG_PPP_BUND_TYPE_INFO;
static const struct ng_parse_type ng_ppp_bund_type = {
        &ng_parse_struct_type,
        &ng_ppp_bund_type_fields
};

/* Parse type for struct ng_ppp_node_conf */
static const struct ng_parse_fixedarray_info ng_ppp_array_info = {
        &ng_ppp_link_type,
        NG_PPP_MAX_LINKS
};
static const struct ng_parse_type ng_ppp_link_array_type = {
        &ng_parse_fixedarray_type,
        &ng_ppp_array_info,
};
static const struct ng_parse_struct_field ng_ppp_conf_type_fields[]
        = NG_PPP_CONFIG_TYPE_INFO(&ng_ppp_bund_type, &ng_ppp_link_array_type);
static const struct ng_parse_type ng_ppp_conf_type = {
        &ng_parse_struct_type,
        &ng_ppp_conf_type_fields
};

/* Parse type for struct ng_ppp_link_stat */
static const struct ng_parse_struct_field ng_ppp_stats_type_fields[]
        = NG_PPP_STATS_TYPE_INFO;
static const struct ng_parse_type ng_ppp_stats_type = {
        &ng_parse_struct_type,
        &ng_ppp_stats_type_fields
};

/* List of commands and how to convert arguments to/from ASCII */
static const struct ng_cmdlist ng_ppp_cmds[] = {
        {
          NGM_PPP_COOKIE,
          NGM_PPP_SET_CONFIG,
          "setconfig",
          &ng_ppp_conf_type,
          NULL
        },
        {
          NGM_PPP_COOKIE,
          NGM_PPP_GET_CONFIG,
          "getconfig",
          NULL,
          &ng_ppp_conf_type
        },
        {
          NGM_PPP_COOKIE,
          NGM_PPP_GET_MP_STATE,
          "getmpstate",
          NULL,
          &ng_ppp_mp_state_type
        },
        {
          NGM_PPP_COOKIE,
          NGM_PPP_GET_LINK_STATS,
          "getstats",
          &ng_parse_int16_type,
          &ng_ppp_stats_type
        },
        {
          NGM_PPP_COOKIE,
          NGM_PPP_CLR_LINK_STATS,
          "clrstats",
          &ng_parse_int16_type,
          NULL
        },
        {
          NGM_PPP_COOKIE,
          NGM_PPP_GETCLR_LINK_STATS,
          "getclrstats",
          &ng_parse_int16_type,
          &ng_ppp_stats_type
        },
        { 0 }
};

/* Node type descriptor */
static struct ng_type ng_ppp_typestruct = {
        NG_VERSION,
        NG_PPP_NODE_TYPE,
        NULL,
        ng_ppp_constructor,
        ng_ppp_rcvmsg,
        ng_ppp_rmnode,
        ng_ppp_newhook,
        NULL,
        NULL,
        ng_ppp_rcvdata,
        ng_ppp_rcvdata,
        ng_ppp_disconnect,
        ng_ppp_cmds
};
NETGRAPH_INIT(ppp, &ng_ppp_typestruct);

static int *compareLatencies;                   /* hack for ng_ppp_intcmp() */

/* Address and control field header */
static const u_char ng_ppp_acf[2] = { 0xff, 0x03 };

/* Maximum time we'll let a complete incoming packet sit in the queue */
static const struct timeval ng_ppp_max_staleness = { 2, 0 };    /* 2 seconds */

#define ERROUT(x)       do { error = (x); goto done; } while (0)

/************************************************************************
                        NETGRAPH NODE STUFF
 ************************************************************************/

/*
 * Node type constructor
 */
static int
ng_ppp_constructor(node_p *nodep)
{
        priv_p priv;
        int i, error;

        /* Allocate private structure */
        priv = kmalloc(sizeof(*priv), M_NETGRAPH, M_NOWAIT | M_ZERO);
        if (priv == NULL)
                return (ENOMEM);

        /* Call generic node constructor */
        if ((error = ng_make_node_common(&ng_ppp_typestruct, nodep))) {
                kfree(priv, M_NETGRAPH);
                return (error);
        }
        (*nodep)->private = priv;

        /* Initialize state */
        TAILQ_INIT(&priv->frags);
        for (i = 0; i < NG_PPP_MAX_LINKS; i++)
                priv->links[i].seq = MP_NOSEQ;
        callout_init(&priv->fragTimer);

        /* Done */
        return (0);
}

/*
 * Give our OK for a hook to be added
 */
static int
ng_ppp_newhook(node_p node, hook_p hook, const char *name)
{
        const priv_p priv = node->private;
        int linkNum = -1;
        hook_p *hookPtr = NULL;
        int hookIndex = -1;

        /* Figure out which hook it is */
        if (strncmp(name, NG_PPP_HOOK_LINK_PREFIX,      /* a link hook? */
            strlen(NG_PPP_HOOK_LINK_PREFIX)) == 0) {
                const char *cp;
                char *eptr;

                cp = name + strlen(NG_PPP_HOOK_LINK_PREFIX);
                if (!isdigit(*cp) || (cp[0] == '0' && cp[1] != '\0'))
                        return (EINVAL);
                linkNum = (int)strtoul(cp, &eptr, 10);
                if (*eptr != '\0' || linkNum < 0 || linkNum >= NG_PPP_MAX_LINKS)
                        return (EINVAL);
                hookPtr = &priv->links[linkNum].hook;
                hookIndex = ~linkNum;
        } else {                                /* must be a non-link hook */
                int i;

                for (i = 0; ng_ppp_hook_names[i] != NULL; i++) {
                        if (strcmp(name, ng_ppp_hook_names[i]) == 0) {
                                hookPtr = &priv->hooks[i];
                                hookIndex = i;
                                break;
                        }
                }
                if (ng_ppp_hook_names[i] == NULL)
                        return (EINVAL);        /* no such hook */
        }

        /* See if hook is already connected */
        if (*hookPtr != NULL)
                return (EISCONN);

        /* Disallow more than one link unless multilink is enabled */
        if (linkNum != -1 && priv->links[linkNum].conf.enableLink
            && !priv->conf.enableMultilink && priv->numActiveLinks >= 1)
                return (ENODEV);

        /* OK */
        *hookPtr = hook;
        HOOK_INDEX(hook) = hookIndex;
        ng_ppp_update(node, 0);
        return (0);
}

/*
 * Receive a control message
 */
static int
ng_ppp_rcvmsg(node_p node, struct ng_mesg *msg,
              const char *raddr, struct ng_mesg **rptr)
{
        const priv_p priv = node->private;
        struct ng_mesg *resp = NULL;
        int error = 0;

        switch (msg->header.typecookie) {
        case NGM_PPP_COOKIE:
                switch (msg->header.cmd) {
                case NGM_PPP_SET_CONFIG:
                    {
                        struct ng_ppp_node_conf *const conf =
                            (struct ng_ppp_node_conf *)msg->data;
                        int i;

                        /* Check for invalid or illegal config */
                        if (msg->header.arglen != sizeof(*conf))
                                ERROUT(EINVAL);
                        if (!ng_ppp_config_valid(node, conf))
                                ERROUT(EINVAL);

                        /* Copy config */
                        priv->conf = conf->bund;
                        for (i = 0; i < NG_PPP_MAX_LINKS; i++)
                                priv->links[i].conf = conf->links[i];
                        ng_ppp_update(node, 1);
                        break;
                    }
                case NGM_PPP_GET_CONFIG:
                    {
                        struct ng_ppp_node_conf *conf;
                        int i;

                        NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
                        if (resp == NULL)
                                ERROUT(ENOMEM);
                        conf = (struct ng_ppp_node_conf *)resp->data;
                        conf->bund = priv->conf;
                        for (i = 0; i < NG_PPP_MAX_LINKS; i++)
                                conf->links[i] = priv->links[i].conf;
                        break;
                    }
                case NGM_PPP_GET_MP_STATE:
                    {
                        struct ng_ppp_mp_state *info;
                        int i;

                        NG_MKRESPONSE(resp, msg, sizeof(*info), M_NOWAIT);
                        if (resp == NULL)
                                ERROUT(ENOMEM);
                        info = (struct ng_ppp_mp_state *)resp->data;
                        bzero(info, sizeof(*info));
                        for (i = 0; i < NG_PPP_MAX_LINKS; i++) {
                                if (priv->links[i].seq != MP_NOSEQ)
                                        info->rseq[i] = priv->links[i].seq;
                        }
                        info->mseq = priv->mseq;
                        info->xseq = priv->xseq;
                        break;
                    }
                case NGM_PPP_GET_LINK_STATS:
                case NGM_PPP_CLR_LINK_STATS:
                case NGM_PPP_GETCLR_LINK_STATS:
                    {
                        struct ng_ppp_link_stat *stats;
                        u_int16_t linkNum;

                        if (msg->header.arglen != sizeof(u_int16_t))
                                ERROUT(EINVAL);
                        linkNum = *((u_int16_t *) msg->data);
                        if (linkNum >= NG_PPP_MAX_LINKS
                            && linkNum != NG_PPP_BUNDLE_LINKNUM)
                                ERROUT(EINVAL);
                        stats = (linkNum == NG_PPP_BUNDLE_LINKNUM) ?
                            &priv->bundleStats : &priv->links[linkNum].stats;
                        if (msg->header.cmd != NGM_PPP_CLR_LINK_STATS) {
                                NG_MKRESPONSE(resp, msg,
                                    sizeof(struct ng_ppp_link_stat), M_NOWAIT);
                                if (resp == NULL)
                                        ERROUT(ENOMEM);
                                bcopy(stats, resp->data, sizeof(*stats));
                        }
                        if (msg->header.cmd != NGM_PPP_GET_LINK_STATS)
                                bzero(stats, sizeof(*stats));
                        break;
                    }
                default:
                        error = EINVAL;
                        break;
                }
                break;
        case NGM_VJC_COOKIE:
            {
                char path[NG_PATHSIZ];
                node_p origNode;

                if ((error = ng_path2node(node, raddr, &origNode, NULL)) != 0)
                        ERROUT(error);
                ksnprintf(path, sizeof(path), "[%lx]:%s",
                    (long)node, NG_PPP_HOOK_VJC_IP);
                return ng_send_msg(origNode, msg, path, rptr);
            }
        default:
                error = EINVAL;
                break;
        }
        if (rptr)
                *rptr = resp;
        else if (resp)
                kfree(resp, M_NETGRAPH);

done:
        kfree(msg, M_NETGRAPH);
        return (error);
}

/*
 * Receive data on a hook
 */
static int
ng_ppp_rcvdata(hook_p hook, struct mbuf *m, meta_p meta)
{
        const node_p node = hook->node;
        const priv_p priv = node->private;
        const int index = HOOK_INDEX(hook);
        u_int16_t linkNum = NG_PPP_BUNDLE_LINKNUM;
        hook_p outHook = NULL;
        int proto = 0, error;

        /* Did it come from a link hook? */
        if (index < 0) {
                struct ng_ppp_link *link;

                /* Convert index into a link number */
                linkNum = (u_int16_t)~index;
                KASSERT(linkNum < NG_PPP_MAX_LINKS,
                    ("%s: bogus index 0x%x", __func__, index));
                link = &priv->links[linkNum];

                /* Stats */
                link->stats.recvFrames++;
                link->stats.recvOctets += m->m_pkthdr.len;

                /* Strip address and control fields, if present */
                if (m->m_pkthdr.len >= 2) {
                        if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
                                NG_FREE_DATA(m, meta);
                                return (ENOBUFS);
                        }
                        if (bcmp(mtod(m, u_char *), &ng_ppp_acf, 2) == 0)
                                m_adj(m, 2);
                }

                /* Dispatch incoming frame (if not enabled, to bypass) */
                return ng_ppp_input(node,
                    !link->conf.enableLink, linkNum, m, meta);
        }

        /* Get protocol & check if data allowed from this hook */
        switch (index) {

        /* Outgoing data */
        case HOOK_INDEX_ATALK:
                if (!priv->conf.enableAtalk) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                proto = PROT_APPLETALK;
                break;
        case HOOK_INDEX_IPX:
                if (!priv->conf.enableIPX) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                proto = PROT_IPX;
                break;
        case HOOK_INDEX_IPV6:
                if (!priv->conf.enableIPv6) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                proto = PROT_IPV6;
                break;
        case HOOK_INDEX_INET:
        case HOOK_INDEX_VJC_VJIP:
                if (!priv->conf.enableIP) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                proto = PROT_IP;
                break;
        case HOOK_INDEX_VJC_COMP:
                if (!priv->conf.enableVJCompression) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                proto = PROT_VJCOMP;
                break;
        case HOOK_INDEX_VJC_UNCOMP:
                if (!priv->conf.enableVJCompression) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                proto = PROT_VJUNCOMP;
                break;
        case HOOK_INDEX_COMPRESS:
                if (!priv->conf.enableCompression) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                proto = PROT_COMPD;
                break;
        case HOOK_INDEX_ENCRYPT:
                if (!priv->conf.enableEncryption) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                proto = PROT_CRYPTD;
                break;
        case HOOK_INDEX_BYPASS:
                if (m->m_pkthdr.len < 4) {
                        NG_FREE_DATA(m, meta);
                        return (EINVAL);
                }
                if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
                        NG_FREE_META(meta);
                        return (ENOBUFS);
                }
                linkNum = ntohs(mtod(m, u_int16_t *)[0]);
                proto = ntohs(mtod(m, u_int16_t *)[1]);
                m_adj(m, 4);
                if (linkNum >= NG_PPP_MAX_LINKS
                    && linkNum != NG_PPP_BUNDLE_LINKNUM) {
                        NG_FREE_DATA(m, meta);
                        return (EINVAL);
                }
                break;

        /* Incoming data */
        case HOOK_INDEX_VJC_IP:
                if (!priv->conf.enableIP || !priv->conf.enableVJDecompression) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                break;
        case HOOK_INDEX_DECOMPRESS:
                if (!priv->conf.enableDecompression) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                break;
        case HOOK_INDEX_DECRYPT:
                if (!priv->conf.enableDecryption) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                break;
        default:
                panic("%s: bogus index 0x%x", __func__, index);
        }

        /* Now figure out what to do with the frame */
        switch (index) {

        /* Outgoing data */
        case HOOK_INDEX_INET:
                if (priv->conf.enableVJCompression && priv->vjCompHooked) {
                        outHook = priv->hooks[HOOK_INDEX_VJC_IP];
                        break;
                }
                /* FALLTHROUGH */
        case HOOK_INDEX_ATALK:
        case HOOK_INDEX_IPV6:
        case HOOK_INDEX_IPX:
        case HOOK_INDEX_VJC_COMP:
        case HOOK_INDEX_VJC_UNCOMP:
        case HOOK_INDEX_VJC_VJIP:
                if (priv->conf.enableCompression
                    && priv->hooks[HOOK_INDEX_COMPRESS] != NULL) {
                        if ((m = ng_ppp_addproto(m, proto, 1)) == NULL) {
                                NG_FREE_META(meta);
                                return (ENOBUFS);
                        }
                        outHook = priv->hooks[HOOK_INDEX_COMPRESS];
                        break;
                }
                /* FALLTHROUGH */
        case HOOK_INDEX_COMPRESS:
                if (priv->conf.enableEncryption
                    && priv->hooks[HOOK_INDEX_ENCRYPT] != NULL) {
                        if ((m = ng_ppp_addproto(m, proto, 1)) == NULL) {
                                NG_FREE_META(meta);
                                return (ENOBUFS);
                        }
                        outHook = priv->hooks[HOOK_INDEX_ENCRYPT];
                        break;
                }
                /* FALLTHROUGH */
        case HOOK_INDEX_ENCRYPT:
                return ng_ppp_output(node, 0,
                    proto, NG_PPP_BUNDLE_LINKNUM, m, meta);

        case HOOK_INDEX_BYPASS:
                return ng_ppp_output(node, 1, proto, linkNum, m, meta);

        /* Incoming data */
        case HOOK_INDEX_DECRYPT:
        case HOOK_INDEX_DECOMPRESS:
                return ng_ppp_input(node, 0, NG_PPP_BUNDLE_LINKNUM, m, meta);

        case HOOK_INDEX_VJC_IP:
                outHook = priv->hooks[HOOK_INDEX_INET];
                break;
        }

        /* Send packet out hook */
        NG_SEND_DATA(error, outHook, m, meta);
        return (error);
}

/*
 * Destroy node
 */
static int
ng_ppp_rmnode(node_p node)
{
        const priv_p priv = node->private;

        /* Stop fragment queue timer */
        ng_ppp_stop_frag_timer(node);

        /* Take down netgraph node */
        node->flags |= NG_INVALID;
        ng_cutlinks(node);
        ng_unname(node);
        ng_ppp_frag_reset(node);
        bzero(priv, sizeof(*priv));
        kfree(priv, M_NETGRAPH);
        node->private = NULL;
        ng_unref(node);         /* let the node escape */
        return (0);
}

/*
 * Hook disconnection
 */
static int
ng_ppp_disconnect(hook_p hook)
{
        const node_p node = hook->node;
        const priv_p priv = node->private;
        const int index = HOOK_INDEX(hook);

        /* Zero out hook pointer */
        if (index < 0)
                priv->links[~index].hook = NULL;
        else
                priv->hooks[index] = NULL;

        /* Update derived info (or go away if no hooks left) */
        if (node->numhooks > 0)
                ng_ppp_update(node, 0);
        else
                ng_rmnode(node);
        return (0);
}

/************************************************************************
                        HELPER STUFF
 ************************************************************************/

/*
 * Handle an incoming frame.  Extract the PPP protocol number
 * and dispatch accordingly.
 */
static int
ng_ppp_input(node_p node, int bypass, int linkNum, struct mbuf *m, meta_p meta)
{
        const priv_p priv = node->private;
        hook_p outHook = NULL;
        int proto, error;

        /* Extract protocol number */
        for (proto = 0; !PROT_VALID(proto) && m->m_pkthdr.len > 0; ) {
                if (m->m_len < 1 && (m = m_pullup(m, 1)) == NULL) {
                        NG_FREE_META(meta);
                        return (ENOBUFS);
                }
                proto = (proto << 8) + *mtod(m, u_char *);
                m_adj(m, 1);
        }
        if (!PROT_VALID(proto)) {
                if (linkNum == NG_PPP_BUNDLE_LINKNUM)
                        priv->bundleStats.badProtos++;
                else
                        priv->links[linkNum].stats.badProtos++;
                NG_FREE_DATA(m, meta);
                return (EINVAL);
        }

        /* Bypass frame? */
        if (bypass)
                goto bypass;

        /* Check protocol */
        switch (proto) {
        case PROT_COMPD:
                if (priv->conf.enableDecompression)
                        outHook = priv->hooks[HOOK_INDEX_DECOMPRESS];
                break;
        case PROT_CRYPTD:
                if (priv->conf.enableDecryption)
                        outHook = priv->hooks[HOOK_INDEX_DECRYPT];
                break;
        case PROT_VJCOMP:
                if (priv->conf.enableVJDecompression && priv->vjCompHooked)
                        outHook = priv->hooks[HOOK_INDEX_VJC_COMP];
                break;
        case PROT_VJUNCOMP:
                if (priv->conf.enableVJDecompression && priv->vjCompHooked)
                        outHook = priv->hooks[HOOK_INDEX_VJC_UNCOMP];
                break;
        case PROT_MP:
                if (priv->conf.enableMultilink
                    && linkNum != NG_PPP_BUNDLE_LINKNUM)
                        return ng_ppp_mp_input(node, linkNum, m, meta);
                break;
        case PROT_APPLETALK:
                if (priv->conf.enableAtalk)
                        outHook = priv->hooks[HOOK_INDEX_ATALK];
                break;
        case PROT_IPX:
                if (priv->conf.enableIPX)
                        outHook = priv->hooks[HOOK_INDEX_IPX];
                break;
        case PROT_IP:
                if (priv->conf.enableIP)
                        outHook = priv->hooks[HOOK_INDEX_INET];
                break;
        case PROT_IPV6:
                if (priv->conf.enableIPv6)
                        outHook = priv->hooks[HOOK_INDEX_IPV6];
                break;
        }

bypass:
        /* For unknown/inactive protocols, forward out the bypass hook */
        if (outHook == NULL) {
                u_int16_t hdr[2];

                hdr[0] = htons(linkNum);
                hdr[1] = htons((u_int16_t)proto);
                if ((m = ng_ppp_prepend(m, &hdr, 4)) == NULL) {
                        NG_FREE_META(meta);
                        return (ENOBUFS);
                }
                outHook = priv->hooks[HOOK_INDEX_BYPASS];
        }

        /* Forward frame */
        NG_SEND_DATA(error, outHook, m, meta);
        return (error);
}

/*
 * Deliver a frame out a link, either a real one or NG_PPP_BUNDLE_LINKNUM.
 * If the link is not enabled then ENXIO is returned, unless "bypass" is != 0.
 *
 * If the frame is too big for the particular link, return EMSGSIZE.
 */
static int
ng_ppp_output(node_p node, int bypass,
        int proto, int linkNum, struct mbuf *m, meta_p meta)
{
        const priv_p priv = node->private;
        struct ng_ppp_link *link;
        int len, error;
        u_int16_t mru;

        /* If not doing MP, map bundle virtual link to (the only) link */
        if (linkNum == NG_PPP_BUNDLE_LINKNUM && !priv->conf.enableMultilink)
                linkNum = priv->activeLinks[0];

        /* Get link pointer (optimization) */
        link = (linkNum != NG_PPP_BUNDLE_LINKNUM) ?
            &priv->links[linkNum] : NULL;

        /* Check link status (if real) */
        if (linkNum != NG_PPP_BUNDLE_LINKNUM) {
                if (!bypass && !link->conf.enableLink) {
                        NG_FREE_DATA(m, meta);
                        return (ENXIO);
                }
                if (link->hook == NULL) {
                        NG_FREE_DATA(m, meta);
                        return (ENETDOWN);
                }
        }

        /* Check peer's MRU for this link */
        mru = (link != NULL) ? link->conf.mru : priv->conf.mrru;
        if (mru != 0 && m->m_pkthdr.len > mru) {
                NG_FREE_DATA(m, meta);
                return (EMSGSIZE);
        }

        /* Prepend protocol number, possibly compressed */
        if ((m = ng_ppp_addproto(m, proto,
            linkNum == NG_PPP_BUNDLE_LINKNUM
              || link->conf.enableProtoComp)) == NULL) {
                NG_FREE_META(meta);
                return (ENOBUFS);
        }

        /* Special handling for the MP virtual link */
        if (linkNum == NG_PPP_BUNDLE_LINKNUM)
                return ng_ppp_mp_output(node, m, meta);

        /* Prepend address and control field (unless compressed) */
        if (proto == PROT_LCP || !link->conf.enableACFComp) {
                if ((m = ng_ppp_prepend(m, &ng_ppp_acf, 2)) == NULL) {
                        NG_FREE_META(meta);
                        return (ENOBUFS);
                }
        }

        /* Deliver frame */
        len = m->m_pkthdr.len;
        NG_SEND_DATA(error, link->hook, m, meta);

        /* Update stats and 'bytes in queue' counter */
        if (error == 0) {
                link->stats.xmitFrames++;
                link->stats.xmitOctets += len;
                link->bytesInQueue += len;
                getmicrouptime(&link->lastWrite);
        }
        return error;
}

/*
 * Handle an incoming multi-link fragment
 *
 * The fragment reassembly algorithm is somewhat complex. This is mainly
 * because we are required not to reorder the reconstructed packets, yet
 * fragments are only guaranteed to arrive in order on a per-link basis.
 * In other words, when we have a complete packet ready, but the previous
 * packet is still incomplete, we have to decide between delivering the
 * complete packet and throwing away the incomplete one, or waiting to
 * see if the remainder of the incomplete one arrives, at which time we
 * can deliver both packets, in order.
 *
 * This problem is exacerbated by "sequence number slew", which is when
 * the sequence numbers coming in from different links are far apart from
 * each other. In particular, certain unnamed equipment (*cough* Ascend)
 * has been seen to generate sequence number slew of up to 10 on an ISDN
 * 2B-channel MP link. There is nothing invalid about sequence number slew
 * but it makes the reasssembly process have to work harder.
 *
 * However, the peer is required to transmit fragments in order on each
 * link. That means if we define MSEQ as the minimum over all links of
 * the highest sequence number received on that link, then we can always
 * give up any hope of receiving a fragment with sequence number < MSEQ in
 * the future (all of this using 'wraparound' sequence number space).
 * Therefore we can always immediately throw away incomplete packets
 * missing fragments with sequence numbers < MSEQ.
 *
 * Here is an overview of our algorithm:
 *
 *    o Received fragments are inserted into a queue, for which we
 *      maintain these invariants between calls to this function:
 *
 *      - Fragments are ordered in the queue by sequence number
 *      - If a complete packet is at the head of the queue, then
 *        the first fragment in the packet has seq# > MSEQ + 1
 *        (otherwise, we could deliver it immediately)
 *      - If any fragments have seq# < MSEQ, then they are necessarily
 *        part of a packet whose missing seq#'s are all > MSEQ (otherwise,
 *        we can throw them away because they'll never be completed)
 *      - The queue contains at most MP_MAX_QUEUE_LEN fragments
 *
 *    o We have a periodic timer that checks the queue for the first
 *      complete packet that has been sitting in the queue "too long".
 *      When one is detected, all previous (incomplete) fragments are
 *      discarded, their missing fragments are declared lost and MSEQ
 *      is increased.
 *
 *    o If we recieve a fragment with seq# < MSEQ, we throw it away
 *      because we've already delcared it lost.
 *
 * This assumes linkNum != NG_PPP_BUNDLE_LINKNUM.
 */
static int
ng_ppp_mp_input(node_p node, int linkNum, struct mbuf *m, meta_p meta)
{
        const priv_p priv = node->private;
        struct ng_ppp_link *const link = &priv->links[linkNum];
        struct ng_ppp_frag frag0, *frag = &frag0;
        struct ng_ppp_frag *qent;
        int i, diff, inserted;

        /* Stats */
        priv->bundleStats.recvFrames++;
        priv->bundleStats.recvOctets += m->m_pkthdr.len;

        /* Extract fragment information from MP header */
        if (priv->conf.recvShortSeq) {
                u_int16_t shdr;

                if (m->m_pkthdr.len < 2) {
                        link->stats.runts++;
                        NG_FREE_DATA(m, meta);
                        return (EINVAL);
                }
                if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
                        NG_FREE_META(meta);
                        return (ENOBUFS);
                }
                shdr = ntohs(*mtod(m, u_int16_t *));
                frag->seq = MP_SHORT_EXTEND(shdr);
                frag->first = (shdr & MP_SHORT_FIRST_FLAG) != 0;
                frag->last = (shdr & MP_SHORT_LAST_FLAG) != 0;
                diff = MP_SHORT_SEQ_DIFF(frag->seq, priv->mseq);
                m_adj(m, 2);
        } else {
                u_int32_t lhdr;

                if (m->m_pkthdr.len < 4) {
                        link->stats.runts++;
                        NG_FREE_DATA(m, meta);
                        return (EINVAL);
                }
                if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
                        NG_FREE_META(meta);
                        return (ENOBUFS);
                }
                lhdr = ntohl(*mtod(m, u_int32_t *));
                frag->seq = MP_LONG_EXTEND(lhdr);
                frag->first = (lhdr & MP_LONG_FIRST_FLAG) != 0;
                frag->last = (lhdr & MP_LONG_LAST_FLAG) != 0;
                diff = MP_LONG_SEQ_DIFF(frag->seq, priv->mseq);
                m_adj(m, 4);
        }
        frag->data = m;
        frag->meta = meta;
        getmicrouptime(&frag->timestamp);

        /* If sequence number is < MSEQ, we've already declared this
           fragment as lost, so we have no choice now but to drop it */
        if (diff < 0) {
                link->stats.dropFragments++;
                NG_FREE_DATA(m, meta);
                return (0);
        }

        /* Update highest received sequence number on this link and MSEQ */
        priv->mseq = link->seq = frag->seq;
        for (i = 0; i < priv->numActiveLinks; i++) {
                struct ng_ppp_link *const alink =
                    &priv->links[priv->activeLinks[i]];

                if (MP_RECV_SEQ_DIFF(priv, alink->seq, priv->mseq) < 0)
                        priv->mseq = alink->seq;
        }

        /* Allocate a new frag struct for the queue */
        frag = kmalloc(sizeof(*frag), M_NETGRAPH, M_NOWAIT);
        if (frag == NULL) {
                NG_FREE_DATA(m, meta);
                ng_ppp_frag_process(node);
                return (ENOMEM);
        }
        *frag = frag0;

        /* Add fragment to queue, which is sorted by sequence number */
        inserted = 0;
        TAILQ_FOREACH_REVERSE(qent, &priv->frags, ng_ppp_fraglist, f_qent) {
                diff = MP_RECV_SEQ_DIFF(priv, frag->seq, qent->seq);
                if (diff > 0) {
                        TAILQ_INSERT_AFTER(&priv->frags, qent, frag, f_qent);
                        inserted = 1;
                        break;
                } else if (diff == 0) {      /* should never happen! */
                        link->stats.dupFragments++;
                        NG_FREE_DATA(frag->data, frag->meta);
                        kfree(frag, M_NETGRAPH);
                        return (EINVAL);
                }
        }
        if (!inserted)
                TAILQ_INSERT_HEAD(&priv->frags, frag, f_qent);
        priv->qlen++;

        /* Process the queue */
        return ng_ppp_frag_process(node);
}

/*
 * Examine our list of fragments, and determine if there is a
 * complete and deliverable packet at the head of the list.
 * Return 1 if so, zero otherwise.
 */
static int
ng_ppp_check_packet(node_p node)
{
        const priv_p priv = node->private;
        struct ng_ppp_frag *qent, *qnext;

        /* Check for empty queue */
        if (TAILQ_EMPTY(&priv->frags))
                return (0);

        /* Check first fragment is the start of a deliverable packet */
        qent = TAILQ_FIRST(&priv->frags);
        if (!qent->first || MP_RECV_SEQ_DIFF(priv, qent->seq, priv->mseq) > 1)
                return (0);

        /* Check that all the fragments are there */
        while (!qent->last) {
                qnext = TAILQ_NEXT(qent, f_qent);
                if (qnext == NULL)      /* end of queue */
                        return (0);
                if (qnext->seq != MP_NEXT_RECV_SEQ(priv, qent->seq))
                        return (0);
                qent = qnext;
        }

        /* Got one */
        return (1);
}

/*
 * Pull a completed packet off the head of the incoming fragment queue.
 * This assumes there is a completed packet there to pull off.
 */
static void
ng_ppp_get_packet(node_p node, struct mbuf **mp, meta_p *metap)
{
        const priv_p priv = node->private;
        struct ng_ppp_frag *qent, *qnext;
        struct mbuf *m = NULL, *tail;

        qent = TAILQ_FIRST(&priv->frags);
        KASSERT(!TAILQ_EMPTY(&priv->frags) && qent->first,
            ("%s: no packet", __func__));
        for (tail = NULL; qent != NULL; qent = qnext) {
                qnext = TAILQ_NEXT(qent, f_qent);
                KASSERT(!TAILQ_EMPTY(&priv->frags),
                    ("%s: empty q", __func__));
                TAILQ_REMOVE(&priv->frags, qent, f_qent);
                if (tail == NULL) {
                        tail = m = qent->data;
                        *metap = qent->meta;    /* inherit first frag's meta */
                } else {
                        m->m_pkthdr.len += qent->data->m_pkthdr.len;
                        tail->m_next = qent->data;
                        NG_FREE_META(qent->meta); /* drop other frags' metas */
                }
                while (tail->m_next != NULL)
                        tail = tail->m_next;
                if (qent->last)
                        qnext = NULL;
                kfree(qent, M_NETGRAPH);
                priv->qlen--;
        }
        *mp = m;
}

/*
 * Trim fragments from the queue whose packets can never be completed.
 * This assumes a complete packet is NOT at the beginning of the queue.
 * Returns 1 if fragments were removed, zero otherwise.
 */
static int
ng_ppp_frag_trim(node_p node)
{
        const priv_p priv = node->private;
        struct ng_ppp_frag *qent, *qnext = NULL;
        int removed = 0;

        /* Scan for "dead" fragments and remove them */
        while (1) {
                int dead = 0;

                /* If queue is empty, we're done */
                if (TAILQ_EMPTY(&priv->frags))
                        break;

                /* Determine whether first fragment can ever be completed */
                TAILQ_FOREACH(qent, &priv->frags, f_qent) {
                        if (MP_RECV_SEQ_DIFF(priv, qent->seq, priv->mseq) >= 0)
                                break;
                        qnext = TAILQ_NEXT(qent, f_qent);
                        KASSERT(qnext != NULL,
                            ("%s: last frag < MSEQ?", __func__));
                        if (qnext->seq != MP_NEXT_RECV_SEQ(priv, qent->seq)
                            || qent->last || qnext->first) {
                                dead = 1;
                                break;
                        }
                }
                if (!dead)
                        break;

                /* Remove fragment and all others in the same packet */
                while ((qent = TAILQ_FIRST(&priv->frags)) != qnext) {
                        KASSERT(!TAILQ_EMPTY(&priv->frags),
                            ("%s: empty q", __func__));
                        priv->bundleStats.dropFragments++;
                        TAILQ_REMOVE(&priv->frags, qent, f_qent);
                        NG_FREE_DATA(qent->data, qent->meta);
                        kfree(qent, M_NETGRAPH);
                        priv->qlen--;
                        removed = 1;
                }
        }
        return (removed);
}

/*
 * Run the queue, restoring the queue invariants
 */
static int
ng_ppp_frag_process(node_p node)
{
        const priv_p priv = node->private;
        struct mbuf *m;
        meta_p meta;

        /* Deliver any deliverable packets */
        while (ng_ppp_check_packet(node)) {
                ng_ppp_get_packet(node, &m, &meta);
                ng_ppp_input(node, 0, NG_PPP_BUNDLE_LINKNUM, m, meta);
        }

        /* Delete dead fragments and try again */
        if (ng_ppp_frag_trim(node)) {
                while (ng_ppp_check_packet(node)) {
                        ng_ppp_get_packet(node, &m, &meta);
                        ng_ppp_input(node, 0, NG_PPP_BUNDLE_LINKNUM, m, meta);
                }
        }

        /* Check for stale fragments while we're here */
        ng_ppp_frag_checkstale(node);

        /* Check queue length */
        if (priv->qlen > MP_MAX_QUEUE_LEN) {
                struct ng_ppp_frag *qent;
                int i;

                /* Get oldest fragment */
                KASSERT(!TAILQ_EMPTY(&priv->frags),
                    ("%s: empty q", __func__));
                qent = TAILQ_FIRST(&priv->frags);

                /* Bump MSEQ if necessary */
                if (MP_RECV_SEQ_DIFF(priv, priv->mseq, qent->seq) < 0) {
                        priv->mseq = qent->seq;
                        for (i = 0; i < priv->numActiveLinks; i++) {
                                struct ng_ppp_link *const alink =
                                    &priv->links[priv->activeLinks[i]];

                                if (MP_RECV_SEQ_DIFF(priv,
                                    alink->seq, priv->mseq) < 0)
                                        alink->seq = priv->mseq;
                        }
                }

                /* Drop it */
                priv->bundleStats.dropFragments++;
                TAILQ_REMOVE(&priv->frags, qent, f_qent);
                NG_FREE_DATA(qent->data, qent->meta);
                kfree(qent, M_NETGRAPH);
                priv->qlen--;

                /* Process queue again */
                return ng_ppp_frag_process(node);
        }

        /* Done */
        return (0);
}

/*
 * Check for 'stale' completed packets that need to be delivered
 *
 * If a link goes down or has a temporary failure, MSEQ can get
 * "stuck", because no new incoming fragments appear on that link.
 * This can cause completed packets to never get delivered if
 * their sequence numbers are all > MSEQ + 1.
 *
 * This routine checks how long all of the completed packets have
 * been sitting in the queue, and if too long, removes fragments
 * from the queue and increments MSEQ to allow them to be delivered.
 */
static void
ng_ppp_frag_checkstale(node_p node)
{
        const priv_p priv = node->private;
        struct ng_ppp_frag *qent, *beg, *end;
        struct timeval now, age;
        struct mbuf *m;
        meta_p meta;
        int i, seq;
        int endseq;

        now.tv_sec = 0;                 /* uninitialized state */
        while (1) {

                /* If queue is empty, we're done */
                if (TAILQ_EMPTY(&priv->frags))
                        break;

                /* Find the first complete packet in the queue */
                beg = end = NULL;
                seq = TAILQ_FIRST(&priv->frags)->seq;
                TAILQ_FOREACH(qent, &priv->frags, f_qent) {
                        if (qent->first)
                                beg = qent;
                        else if (qent->seq != seq)
                                beg = NULL;
                        if (beg != NULL && qent->last) {
                                end = qent;
                                break;
                        }
                        seq = MP_NEXT_RECV_SEQ(priv, seq);
                }

                /* If none found, exit */
                if (end == NULL)
                        break;

                /* Get current time (we assume we've been up for >= 1 second) */
                if (now.tv_sec == 0)
                        getmicrouptime(&now);

                /* Check if packet has been queued too long */
                age = now;
                timevalsub(&age, &beg->timestamp);
                if (timevalcmp(&age, &ng_ppp_max_staleness, < ))
                        break;

                /* Throw away junk fragments in front of the completed packet */
                while ((qent = TAILQ_FIRST(&priv->frags)) != beg) {
                        KASSERT(!TAILQ_EMPTY(&priv->frags),
                            ("%s: empty q", __func__));
                        priv->bundleStats.dropFragments++;
                        TAILQ_REMOVE(&priv->frags, qent, f_qent);
                        NG_FREE_DATA(qent->data, qent->meta);
                        kfree(qent, M_NETGRAPH);
                        priv->qlen--;
                }

                /* Extract completed packet */
                endseq = end->seq;
                ng_ppp_get_packet(node, &m, &meta);

                /* Bump MSEQ if necessary */
                if (MP_RECV_SEQ_DIFF(priv, priv->mseq, endseq) < 0) {
                        priv->mseq = endseq;
                        for (i = 0; i < priv->numActiveLinks; i++) {
                                struct ng_ppp_link *const alink =
                                    &priv->links[priv->activeLinks[i]];

                                if (MP_RECV_SEQ_DIFF(priv,
                                    alink->seq, priv->mseq) < 0)
                                        alink->seq = priv->mseq;
                        }
                }

                /* Deliver packet */
                ng_ppp_input(node, 0, NG_PPP_BUNDLE_LINKNUM, m, meta);
        }
}

/*
 * Periodically call ng_ppp_frag_checkstale()
 */
static void
ng_ppp_frag_timeout(void *arg)
{
        const node_p node = arg;
        const priv_p priv = node->private;

        crit_enter();
        /* Handle the race where shutdown happens just before splnet() above */
        if ((node->flags & NG_INVALID) != 0) {
                ng_unref(node);
                crit_exit();
                return;
        }

        /* Reset timer state after timeout */
        KASSERT(priv->timerActive, ("%s: !timerActive", __func__));
        priv->timerActive = 0;
        KASSERT(node->refs > 1, ("%s: refs=%d", __func__, node->refs));
        ng_unref(node);

        /* Start timer again */
        ng_ppp_start_frag_timer(node);

        /* Scan the fragment queue */
        ng_ppp_frag_checkstale(node);
        crit_exit();
}

/*
 * Deliver a frame out on the bundle, i.e., figure out how to fragment
 * the frame across the individual PPP links and do so.
 */
static int
ng_ppp_mp_output(node_p node, struct mbuf *m, meta_p meta)
{
        const priv_p priv = node->private;
        const int hdr_len = priv->conf.xmitShortSeq ? 2 : 4;
        int distrib[NG_PPP_MAX_LINKS];
        int firstFragment;
        int activeLinkNum;

        /* At least one link must be active */
        if (priv->numActiveLinks == 0) {
                NG_FREE_DATA(m, meta);
                return (ENETDOWN);
        }

        /* Round-robin strategy */
        if (priv->conf.enableRoundRobin || m->m_pkthdr.len < MP_MIN_FRAG_LEN) {
                activeLinkNum = priv->lastLink++ % priv->numActiveLinks;
                bzero(&distrib, priv->numActiveLinks * sizeof(distrib[0]));
                distrib[activeLinkNum] = m->m_pkthdr.len;
                goto deliver;
        }

        /* Strategy when all links are equivalent (optimize the common case) */
        if (priv->allLinksEqual) {
                const int fraction = m->m_pkthdr.len / priv->numActiveLinks;
                int i, remain;

                for (i = 0; i < priv->numActiveLinks; i++)
                        distrib[priv->lastLink++ % priv->numActiveLinks]
                            = fraction;
                remain = m->m_pkthdr.len - (fraction * priv->numActiveLinks);
                while (remain > 0) {
                        distrib[priv->lastLink++ % priv->numActiveLinks]++;
                        remain--;
                }
                goto deliver;
        }

        /* Strategy when all links are not equivalent */
        ng_ppp_mp_strategy(node, m->m_pkthdr.len, distrib);

deliver:
        /* Update stats */
        priv->bundleStats.xmitFrames++;
        priv->bundleStats.xmitOctets += m->m_pkthdr.len;

        /* Send alloted portions of frame out on the link(s) */
        for (firstFragment = 1, activeLinkNum = priv->numActiveLinks - 1;
            activeLinkNum >= 0; activeLinkNum--) {
                const int linkNum = priv->activeLinks[activeLinkNum];
                struct ng_ppp_link *const link = &priv->links[linkNum];

                /* Deliver fragment(s) out the next link */
                for ( ; distrib[activeLinkNum] > 0; firstFragment = 0) {
                        int len, lastFragment, error;
                        struct mbuf *m2;
                        meta_p meta2;

                        /* Calculate fragment length; don't exceed link MTU */
                        len = distrib[activeLinkNum];
                        if (len > link->conf.mru - hdr_len)
                                len = link->conf.mru - hdr_len;
                        distrib[activeLinkNum] -= len;
                        lastFragment = (len == m->m_pkthdr.len);

                        /* Split off next fragment as "m2" */
                        m2 = m;
                        if (!lastFragment) {
                                struct mbuf *n = m_split(m, len, M_NOWAIT);

                                if (n == NULL) {
                                        NG_FREE_DATA(m, meta);
                                        return (ENOMEM);
                                }
                                m = n;
                        }

                        /* Prepend MP header */
                        if (priv->conf.xmitShortSeq) {
                                u_int16_t shdr;

                                shdr = priv->xseq;
                                priv->xseq =
                                    (priv->xseq + 1) & MP_SHORT_SEQ_MASK;
                                if (firstFragment)
                                        shdr |= MP_SHORT_FIRST_FLAG;
                                if (lastFragment)
                                        shdr |= MP_SHORT_LAST_FLAG;
                                shdr = htons(shdr);
                                m2 = ng_ppp_prepend(m2, &shdr, 2);
                        } else {
                                u_int32_t lhdr;

                                lhdr = priv->xseq;
                                priv->xseq =
                                    (priv->xseq + 1) & MP_LONG_SEQ_MASK;
                                if (firstFragment)
                                        lhdr |= MP_LONG_FIRST_FLAG;
                                if (lastFragment)
                                        lhdr |= MP_LONG_LAST_FLAG;
                                lhdr = htonl(lhdr);
                                m2 = ng_ppp_prepend(m2, &lhdr, 4);
                        }
                        if (m2 == NULL) {
                                if (!lastFragment)
                                        m_freem(m);
                                NG_FREE_META(meta);
                                return (ENOBUFS);
                        }

                        /* Copy the meta information, if any */
                        meta2 = lastFragment ? meta : ng_copy_meta(meta);

                        /* Send fragment */
                        error = ng_ppp_output(node, 0,
                            PROT_MP, linkNum, m2, meta2);
                        if (error != 0) {
                                if (!lastFragment)
                                        NG_FREE_DATA(m, meta);
                                return (error);
                        }
                }
        }

        /* Done */
        return (0);
}

/*
 * Computing the optimal fragmentation
 * -----------------------------------
 *
 * This routine tries to compute the optimal fragmentation pattern based
 * on each link's latency, bandwidth, and calculated additional latency.
 * The latter quantity is the additional latency caused by previously
 * written data that has not been transmitted yet.
 *
 * This algorithm is only useful when not all of the links have the
 * same latency and bandwidth values.
 *
 * The essential idea is to make the last bit of each fragment of the
 * frame arrive at the opposite end at the exact same time. This greedy
 * algorithm is optimal, in that no other scheduling could result in any
 * packet arriving any sooner unless packets are delivered out of order.
 *
 * Suppose link i has bandwidth b_i (in tens of bytes per milisecond) and
 * latency l_i (in miliseconds). Consider the function function f_i(t)
 * which is equal to the number of bytes that will have arrived at
 * the peer after t miliseconds if we start writing continuously at
 * time t = 0. Then f_i(t) = b_i * (t - l_i) = ((b_i * t) - (l_i * b_i).
 * That is, f_i(t) is a line with slope b_i and y-intersect -(l_i * b_i).
 * Note that the y-intersect is always <= zero because latency can't be
 * negative.  Note also that really the function is f_i(t) except when
 * f_i(t) is negative, in which case the function is zero.  To take
 * care of this, let Q_i(t) = { if (f_i(t) > 0) return 1; else return 0; }.
 * So the actual number of bytes that will have arrived at the peer after
 * t miliseconds is f_i(t) * Q_i(t).
 *
 * At any given time, each link has some additional latency a_i >= 0
 * due to previously written fragment(s) which are still in the queue.
 * This value is easily computed from the time since last transmission,
 * the previous latency value, the number of bytes written, and the
 * link's bandwidth.
 *
 * Assume that l_i includes any a_i already, and that the links are
 * sorted by latency, so that l_i <= l_{i+1}.
 *
 * Let N be the total number of bytes in the current frame we are sending.
 *
 * Suppose we were to start writing bytes at time t = 0 on all links
 * simultaneously, which is the most we can possibly do.  Then let
 * F(t) be equal to the total number of bytes received by the peer
 * after t miliseconds. Then F(t) = Sum_i (f_i(t) * Q_i(t)).
 *
 * Our goal is simply this: fragment the frame across the links such
 * that the peer is able to reconstruct the completed frame as soon as
 * possible, i.e., at the least possible value of t. Call this value t_0.
 *
 * Then it follows that F(t_0) = N. Our strategy is first to find the value
 * of t_0, and then deduce how many bytes to write to each link.
 *
 * Rewriting F(t_0):
 *
 *   t_0 = ( N + Sum_i ( l_i * b_i * Q_i(t_0) ) ) / Sum_i ( b_i * Q_i(t_0) )
 *
 * Now, we note that Q_i(t) is constant for l_i <= t <= l_{i+1}. t_0 will
 * lie in one of these ranges.  To find it, we just need to find the i such
 * that F(l_i) <= N <= F(l_{i+1}).  Then we compute all the constant values
 * for Q_i() in this range, plug in the remaining values, solving for t_0.
 *
 * Once t_0 is known, then the number of bytes to send on link i is
 * just f_i(t_0) * Q_i(t_0).
 *
 * In other words, we start allocating bytes to the links one at a time.
 * We keep adding links until the frame is completely sent.  Some links
 * may not get any bytes because their latency is too high.
 *
 * Is all this work really worth the trouble?  Depends on the situation.
 * The bigger the ratio of computer speed to link speed, and the more
 * important total bundle latency is (e.g., for interactive response time),
 * the more it's worth it.  There is however the cost of calling this
 * function for every frame.  The running time is O(n^2) where n is the
 * number of links that receive a non-zero number of bytes.
 *
 * Since latency is measured in miliseconds, the "resolution" of this
 * algorithm is one milisecond.
 *
 * To avoid this algorithm altogether, configure all links to have the
 * same latency and bandwidth.
 */
static void
ng_ppp_mp_strategy(node_p node, int len, int *distrib)
{
        const priv_p priv = node->private;
        int latency[NG_PPP_MAX_LINKS];
        int sortByLatency[NG_PPP_MAX_LINKS];
        int activeLinkNum;
        int t0, total, topSum, botSum;
        struct timeval now;
        int i, numFragments;

        /* If only one link, this gets real easy */
        if (priv->numActiveLinks == 1) {
                distrib[0] = len;
                return;
        }

        /* Get current time */
        getmicrouptime(&now);

        /* Compute latencies for each link at this point in time */
        for (activeLinkNum = 0;
            activeLinkNum < priv->numActiveLinks; activeLinkNum++) {
                struct ng_ppp_link *alink;
                struct timeval diff;
                int xmitBytes;

                /* Start with base latency value */
                alink = &priv->links[priv->activeLinks[activeLinkNum]];
                latency[activeLinkNum] = alink->conf.latency;
                sortByLatency[activeLinkNum] = activeLinkNum;   /* see below */

                /* Any additional latency? */
                if (alink->bytesInQueue == 0)
                        continue;

                /* Compute time delta since last write */
                diff = now;
                timevalsub(&diff, &alink->lastWrite);
                if (now.tv_sec < 0 || diff.tv_sec >= 10) {      /* sanity */
                        alink->bytesInQueue = 0;
                        continue;
                }

                /* How many bytes could have transmitted since last write? */
                xmitBytes = (alink->conf.bandwidth * diff.tv_sec)
                    + (alink->conf.bandwidth * (diff.tv_usec / 1000)) / 100;
                alink->bytesInQueue -= xmitBytes;
                if (alink->bytesInQueue < 0)
                        alink->bytesInQueue = 0;
                else
                        latency[activeLinkNum] +=
                            (100 * alink->bytesInQueue) / alink->conf.bandwidth;
        }

        /* Sort active links by latency */
        compareLatencies = latency;
        kqsort(sortByLatency,
            priv->numActiveLinks, sizeof(*sortByLatency), ng_ppp_intcmp);
        compareLatencies = NULL;

        /* Find the interval we need (add links in sortByLatency[] order) */
        for (numFragments = 1;
            numFragments < priv->numActiveLinks; numFragments++) {
                for (total = i = 0; i < numFragments; i++) {
                        int flowTime;

                        flowTime = latency[sortByLatency[numFragments]]
                            - latency[sortByLatency[i]];
                        total += ((flowTime * priv->links[
                            priv->activeLinks[sortByLatency[i]]].conf.bandwidth)
                                + 99) / 100;
                }
                if (total >= len)
                        break;
        }

        /* Solve for t_0 in that interval */
        for (topSum = botSum = i = 0; i < numFragments; i++) {
                int bw = priv->links[
                    priv->activeLinks[sortByLatency[i]]].conf.bandwidth;

                topSum += latency[sortByLatency[i]] * bw;       /* / 100 */
                botSum += bw;                                   /* / 100 */
        }
        t0 = ((len * 100) + topSum + botSum / 2) / botSum;

        /* Compute f_i(t_0) all i */
        bzero(distrib, priv->numActiveLinks * sizeof(*distrib));
        for (total = i = 0; i < numFragments; i++) {
                int bw = priv->links[
                    priv->activeLinks[sortByLatency[i]]].conf.bandwidth;

                distrib[sortByLatency[i]] =
                    (bw * (t0 - latency[sortByLatency[i]]) + 50) / 100;
                total += distrib[sortByLatency[i]];
        }

        /* Deal with any rounding error */
        if (total < len) {
                struct ng_ppp_link *fastLink =
                    &priv->links[priv->activeLinks[sortByLatency[0]]];
                int fast = 0;

                /* Find the fastest link */
                for (i = 1; i < numFragments; i++) {
                        struct ng_ppp_link *const link =
                            &priv->links[priv->activeLinks[sortByLatency[i]]];

                        if (link->conf.bandwidth > fastLink->conf.bandwidth) {
                                fast = i;
                                fastLink = link;
                        }
                }
                distrib[sortByLatency[fast]] += len - total;
        } else while (total > len) {
                struct ng_ppp_link *slowLink =
                    &priv->links[priv->activeLinks[sortByLatency[0]]];
                int delta, slow = 0;

                /* Find the slowest link that still has bytes to remove */
                for (i = 1; i < numFragments; i++) {
                        struct ng_ppp_link *const link =
                            &priv->links[priv->activeLinks[sortByLatency[i]]];

                        if (distrib[sortByLatency[slow]] == 0
                          || (distrib[sortByLatency[i]] > 0
                            && link->conf.bandwidth <
                              slowLink->conf.bandwidth)) {
                                slow = i;
                                slowLink = link;
                        }
                }
                delta = total - len;
                if (delta > distrib[sortByLatency[slow]])
                        delta = distrib[sortByLatency[slow]];
                distrib[sortByLatency[slow]] -= delta;
                total -= delta;
        }
}

/*
 * Compare two integers
 */
static int
ng_ppp_intcmp(const void *v1, const void *v2)
{
        const int index1 = *((const int *) v1);
        const int index2 = *((const int *) v2);

        return compareLatencies[index1] - compareLatencies[index2];
}

/*
 * Prepend a possibly compressed PPP protocol number in front of a frame
 */
static struct mbuf *
ng_ppp_addproto(struct mbuf *m, int proto, int compOK)
{
        if (compOK && PROT_COMPRESSABLE(proto)) {
                u_char pbyte = (u_char)proto;

                return ng_ppp_prepend(m, &pbyte, 1);
        } else {
                u_int16_t pword = htons((u_int16_t)proto);

                return ng_ppp_prepend(m, &pword, 2);
        }
}

/*
 * Prepend some bytes to an mbuf
 */
static struct mbuf *
ng_ppp_prepend(struct mbuf *m, const void *buf, int len)
{
        M_PREPEND(m, len, M_NOWAIT);
        if (m == NULL || (m->m_len < len && (m = m_pullup(m, len)) == NULL))
                return (NULL);
        bcopy(buf, mtod(m, u_char *), len);
        return (m);
}

/*
 * Update private information that is derived from other private information
 */
static void
ng_ppp_update(node_p node, int newConf)
{
        const priv_p priv = node->private;
        int i;

        /* Update active status for VJ Compression */
        priv->vjCompHooked = priv->hooks[HOOK_INDEX_VJC_IP] != NULL
            && priv->hooks[HOOK_INDEX_VJC_COMP] != NULL
            && priv->hooks[HOOK_INDEX_VJC_UNCOMP] != NULL
            && priv->hooks[HOOK_INDEX_VJC_VJIP] != NULL;

        /* Increase latency for each link an amount equal to one MP header */
        if (newConf) {
                for (i = 0; i < NG_PPP_MAX_LINKS; i++) {
                        int hdrBytes;

                        hdrBytes = (priv->links[i].conf.enableACFComp ? 0 : 2)
                            + (priv->links[i].conf.enableProtoComp ? 1 : 2)
                            + (priv->conf.xmitShortSeq ? 2 : 4);
                        priv->links[i].conf.latency +=
                            ((hdrBytes * priv->links[i].conf.bandwidth) + 50)
                                / 100;
                }
        }

        /* Update list of active links */
        bzero(&priv->activeLinks, sizeof(priv->activeLinks));
        priv->numActiveLinks = 0;
        priv->allLinksEqual = 1;
        for (i = 0; i < NG_PPP_MAX_LINKS; i++) {
                struct ng_ppp_link *const link = &priv->links[i];

                /* Is link active? */
                if (link->conf.enableLink && link->hook != NULL) {
                        struct ng_ppp_link *link0;

                        /* Add link to list of active links */
                        priv->activeLinks[priv->numActiveLinks++] = i;
                        link0 = &priv->links[priv->activeLinks[0]];

                        /* Determine if all links are still equal */
                        if (link->conf.latency != link0->conf.latency
                          || link->conf.bandwidth != link0->conf.bandwidth)
                                priv->allLinksEqual = 0;

                        /* Initialize rec'd sequence number */
                        if (link->seq == MP_NOSEQ) {
                                link->seq = (link == link0) ?
                                    MP_INITIAL_SEQ : link0->seq;
                        }
                } else
                        link->seq = MP_NOSEQ;
        }

        /* Update MP state as multi-link is active or not */
        if (priv->conf.enableMultilink && priv->numActiveLinks > 0)
                ng_ppp_start_frag_timer(node);
        else {
                ng_ppp_stop_frag_timer(node);
                ng_ppp_frag_reset(node);
                priv->xseq = MP_INITIAL_SEQ;
                priv->mseq = MP_INITIAL_SEQ;
                for (i = 0; i < NG_PPP_MAX_LINKS; i++) {
                        struct ng_ppp_link *const link = &priv->links[i];

                        bzero(&link->lastWrite, sizeof(link->lastWrite));
                        link->bytesInQueue = 0;
                        link->seq = MP_NOSEQ;
                }
        }
}

/*
 * Determine if a new configuration would represent a valid change
 * from the current configuration and link activity status.
 */
static int
ng_ppp_config_valid(node_p node, const struct ng_ppp_node_conf *newConf)
{
        const priv_p priv = node->private;
        int i, newNumLinksActive;

        /* Check per-link config and count how many links would be active */
        for (newNumLinksActive = i = 0; i < NG_PPP_MAX_LINKS; i++) {
                if (newConf->links[i].enableLink && priv->links[i].hook != NULL)
                        newNumLinksActive++;
                if (!newConf->links[i].enableLink)
                        continue;
                if (newConf->links[i].mru < MP_MIN_LINK_MRU)
                        return (0);
                if (newConf->links[i].bandwidth == 0)
                        return (0);
                if (newConf->links[i].bandwidth > NG_PPP_MAX_BANDWIDTH)
                        return (0);
                if (newConf->links[i].latency > NG_PPP_MAX_LATENCY)
                        return (0);
        }

        /* Check bundle parameters */
        if (newConf->bund.enableMultilink && newConf->bund.mrru < MP_MIN_MRRU)
                return (0);

        /* Disallow changes to multi-link configuration while MP is active */
        if (priv->numActiveLinks > 0 && newNumLinksActive > 0) {
                if (!priv->conf.enableMultilink
                                != !newConf->bund.enableMultilink
                    || !priv->conf.xmitShortSeq != !newConf->bund.xmitShortSeq
                    || !priv->conf.recvShortSeq != !newConf->bund.recvShortSeq)
                        return (0);
        }

        /* At most one link can be active unless multi-link is enabled */
        if (!newConf->bund.enableMultilink && newNumLinksActive > 1)
                return (0);

        /* Configuration change would be valid */
        return (1);
}

/*
 * Free all entries in the fragment queue
 */
static void
ng_ppp_frag_reset(node_p node)
{
        const priv_p priv = node->private;
        struct ng_ppp_frag *qent, *qnext;

        for (qent = TAILQ_FIRST(&priv->frags); qent; qent = qnext) {
                qnext = TAILQ_NEXT(qent, f_qent);
                NG_FREE_DATA(qent->data, qent->meta);
                kfree(qent, M_NETGRAPH);
        }
        TAILQ_INIT(&priv->frags);
        priv->qlen = 0;
}

/*
 * Start fragment queue timer
 */
static void
ng_ppp_start_frag_timer(node_p node)
{
        const priv_p priv = node->private;

        if (!priv->timerActive) {
                callout_reset(&priv->fragTimer, MP_FRAGTIMER_INTERVAL,
                                ng_ppp_frag_timeout, node);
                priv->timerActive = 1;
                node->refs++;
        }
}

/*
 * Stop fragment queue timer
 */
static void
ng_ppp_stop_frag_timer(node_p node)
{
        const priv_p priv = node->private;

        if (priv->timerActive) {
                callout_stop(&priv->fragTimer);
                priv->timerActive = 0;
                KASSERT(node->refs > 1,
                    ("%s: refs=%d", __func__, node->refs));
                ng_unref(node);
        }
}