/*
 * ng_frame_relay.c
 */

/*-
 * Copyright (c) 1996-1999 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: Julian Elischer <julian@freebsd.org>
 * $Whistle: ng_frame_relay.c,v 1.20 1999/11/01 09:24:51 julian Exp $
 */

/*
 * This node implements the frame relay protocol, not including
 * the LMI line management. This means basically keeping track
 * of which DLCI's are active, doing frame (de)multiplexing, etc.
 *
 * It has a 'downstream' hook that goes to the line, and a
 * hook for each DLCI (eg, 'dlci16').
 */

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

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

/*
 * Line info, and status per channel.
 */
struct ctxinfo {                /* one per active hook */
        u_int   flags;
#define CHAN_VALID      0x01    /* assigned to a channel */
#define CHAN_ACTIVE     0x02    /* bottom level active */
        int     dlci;           /* the dlci assigned to this context */
        hook_p  hook;           /* if there's a hook assigned.. */
};

#define MAX_CT 16               /* # of dlci's active at a time (POWER OF 2!) */
struct frmrel_softc {
        int     unit;           /* which card are we? */
        int     datahooks;      /* number of data hooks attached */
        node_p  node;           /* netgraph node */
        int     addrlen;        /* address header length */
        int     flags;          /* state */
        int     mtu;            /* guess */
        u_char  remote_seq;     /* sequence number the remote sent */
        u_char  local_seq;      /* sequence number the remote rcvd */
        u_short ALT[1024];      /* map DLCIs to CTX */
#define CTX_VALID       0x8000          /* this bit means it's a valid CTX */
#define CTX_VALUE       (MAX_CT - 1)    /* mask for context part */
        struct  ctxinfo channel[MAX_CT];
        struct  ctxinfo downstream;
};
typedef struct frmrel_softc *sc_p;

#define BYTEX_EA        0x01    /* End Address. Always 0 on byte1 */
#define BYTE1_C_R       0x02
#define BYTE2_FECN      0x08    /* forwards congestion notification */
#define BYTE2_BECN      0x04    /* Backward congestion notification */
#define BYTE2_DE        0x02    /* Discard elligability */
#define LASTBYTE_D_C    0x02    /* last byte is dl_core or dlci info */

/* Used to do headers */
const static struct segment {
        u_char  mask;
        u_char  shift;
        u_char  width;
} makeup[] = {
        { 0xfc, 2, 6 },
        { 0xf0, 4, 4 },
        { 0xfe, 1, 7 },
        { 0xfc, 2, 6 }
};

#define SHIFTIN(segment, byte, dlci)                                         \
        {                                                                    \
                (dlci) <<= (segment)->width;                                 \
                (dlci) |=                                                    \
                        (((byte) & (segment)->mask) >> (segment)->shift);    \
        }

#define SHIFTOUT(segment, byte, dlci)                                        \
        {                                                                    \
                (byte) |= (((dlci) << (segment)->shift) & (segment)->mask);  \
                (dlci) >>= (segment)->width;                                 \
        }

/* Netgraph methods */
static ng_constructor_t ngfrm_constructor;
static ng_shutdown_t    ngfrm_shutdown;
static ng_newhook_t     ngfrm_newhook;
static ng_rcvdata_t     ngfrm_rcvdata;
static ng_disconnect_t  ngfrm_disconnect;

/* Other internal functions */
static int ngfrm_decode(node_p node, item_p item);
static int ngfrm_addrlen(char *hdr);
static int ngfrm_allocate_CTX(sc_p sc, int dlci);

/* Netgraph type */
static struct ng_type typestruct = {
        .version =      NG_ABI_VERSION,
        .name =         NG_FRAMERELAY_NODE_TYPE,
        .constructor =  ngfrm_constructor,
        .shutdown =     ngfrm_shutdown,
        .newhook =      ngfrm_newhook,
        .rcvdata =      ngfrm_rcvdata,
        .disconnect =   ngfrm_disconnect,
};
NETGRAPH_INIT(framerelay, &typestruct);

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

/*
 * Given a DLCI, return the index of the  context table entry for it,
 * Allocating a new one if needs be, or -1 if none available.
 */
static int
ngfrm_allocate_CTX(sc_p sc, int dlci)
{
        u_int   ctxnum = -1;    /* what ctx number we are using */
        volatile struct ctxinfo *CTXp = NULL;

        /* Sanity check the dlci value */
        if (dlci > 1023)
                return (-1);

        /* Check to see if we already have an entry for this DLCI */
        if (sc->ALT[dlci]) {
                if ((ctxnum = sc->ALT[dlci] & CTX_VALUE) < MAX_CT) {
                        CTXp = sc->channel + ctxnum;
                } else {
                        ctxnum = -1;
                        sc->ALT[dlci] = 0;      /* paranoid but... */
                }
        }

        /*
         * If the index has no valid entry yet, then we need to allocate a
         * CTX number to it
         */
        if (CTXp == NULL) {
                for (ctxnum = 0; ctxnum < MAX_CT; ctxnum++) {
                        /*
                         * If the VALID flag is empty it is unused
                         */
                        if ((sc->channel[ctxnum].flags & CHAN_VALID) == 0) {
                                bzero(sc->channel + ctxnum,
                                      sizeof(struct ctxinfo));
                                CTXp = sc->channel + ctxnum;
                                sc->ALT[dlci] = ctxnum | CTX_VALID;
                                sc->channel[ctxnum].dlci = dlci;
                                sc->channel[ctxnum].flags = CHAN_VALID;
                                break;
                        }
                }
        }

        /*
         * If we still don't have a CTX pointer, then we never found a free
         * spot so give up now..
         */
        if (!CTXp) {
                log(LOG_ERR, "No CTX available for dlci %d\n", dlci);
                return (-1);
        }
        return (ctxnum);
}

/*
 * Node constructor
 */
static int
ngfrm_constructor(node_p node)
{
        sc_p sc;

        sc = malloc(sizeof(*sc), M_NETGRAPH, M_WAITOK | M_ZERO);
        sc->addrlen = 2;        /* default */

        /* Link the node and our private info */
        NG_NODE_SET_PRIVATE(node, sc);
        sc->node = node;
        return (0);
}

/*
 * Add a new hook
 *
 * We allow hooks called "debug", "downstream" and dlci[0-1023]
 * The hook's private info points to our stash of info about that
 * channel. A NULL pointer is debug and a DLCI of -1 means downstream.
 */
static int
ngfrm_newhook(node_p node, hook_p hook, const char *name)
{
        const sc_p sc = NG_NODE_PRIVATE(node);
        const char *cp;
        char *eptr;
        int dlci = 0;
        int ctxnum;

        /* Check if it's our friend the control hook */
        if (strcmp(name, NG_FRAMERELAY_HOOK_DEBUG) == 0) {
                NG_HOOK_SET_PRIVATE(hook, NULL);        /* paranoid */
                return (0);
        }

        /*
         * All other hooks either start with 'dlci' and have a decimal
         * trailing channel number up to 4 digits, or are the downstream
         * hook.
         */
        if (strncmp(name, NG_FRAMERELAY_HOOK_DLCI,
            strlen(NG_FRAMERELAY_HOOK_DLCI)) != 0) {
                /* It must be the downstream connection */
                if (strcmp(name, NG_FRAMERELAY_HOOK_DOWNSTREAM) != 0)
                        return EINVAL;

                /* Make sure we haven't already got one (paranoid) */
                if (sc->downstream.hook)
                        return (EADDRINUSE);

                /* OK add it */
                NG_HOOK_SET_PRIVATE(hook, &sc->downstream);
                sc->downstream.hook = hook;
                sc->downstream.dlci = -1;
                sc->downstream.flags |= CHAN_ACTIVE;
                sc->datahooks++;
                return (0);
        }

        /* Must be a dlci hook at this point */
        cp = name + strlen(NG_FRAMERELAY_HOOK_DLCI);
        if (!isdigit(*cp) || (cp[0] == '0' && cp[1] != '\0'))
                return (EINVAL);
        dlci = (int)strtoul(cp, &eptr, 10);
        if (*eptr != '\0' || dlci < 0 || dlci > 1023)
                return (EINVAL);

        /*
         * We have a dlci, now either find it, or allocate it. It's possible
         * that we might have seen packets for it already and made an entry
         * for it.
         */
        ctxnum = ngfrm_allocate_CTX(sc, dlci);
        if (ctxnum == -1)
                return (ENOBUFS);

        /*
         * Be paranoid: if it's got a hook already, that dlci is in use .
         * Generic code can not catch all the synonyms (e.g. dlci016 vs
         * dlci16)
         */
        if (sc->channel[ctxnum].hook != NULL)
                return (EADDRINUSE);

        /*
         * Put our hooks into it (pun not intended)
         */
        sc->channel[ctxnum].flags |= CHAN_ACTIVE;
        NG_HOOK_SET_PRIVATE(hook, sc->channel + ctxnum);
        sc->channel[ctxnum].hook = hook;
        sc->datahooks++;
        return (0);
}

/*
 * Count up the size of the address header if we don't already know
 */
int
ngfrm_addrlen(char *hdr)
{
        if (hdr[0] & BYTEX_EA)
                return 0;
        if (hdr[1] & BYTEX_EA)
                return 2;
        if (hdr[2] & BYTEX_EA)
                return 3;
        if (hdr[3] & BYTEX_EA)
                return 4;
        return 0;
}

/*
 * Receive data packet
 */
static int
ngfrm_rcvdata(hook_p hook, item_p item)
{
        struct  ctxinfo *const ctxp = NG_HOOK_PRIVATE(hook);
        struct  mbuf *m = NULL;
        int     error = 0;
        int     dlci;
        sc_p    sc;
        int     alen;
        char   *data;

        /* Data doesn't come in from just anywhere (e.g debug hook) */
        if (ctxp == NULL)
                ERROUT(ENETDOWN);

        /* If coming from downstream, decode it to a channel */
        dlci = ctxp->dlci;
        if (dlci == -1)
                return (ngfrm_decode(NG_HOOK_NODE(hook), item));

        NGI_GET_M(item, m);
        /* Derive the softc we will need */
        sc = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));

        /* If there is no live channel, throw it away */
        if ((sc->downstream.hook == NULL)
            || ((ctxp->flags & CHAN_ACTIVE) == 0))
                ERROUT(ENETDOWN);

        /* Store the DLCI on the front of the packet */
        alen = sc->addrlen;
        if (alen == 0)
                alen = 2;       /* default value for transmit */
        M_PREPEND(m, alen, M_NOWAIT);
        if (m == NULL)
                ERROUT(ENOBUFS);
        data = mtod(m, char *);

        /*
         * Shift the lowest bits into the address field until we are done.
         * First byte is MSBits of addr so work backwards.
         */
        switch (alen) {
        case 2:
                data[0] = data[1] = '\0';
                SHIFTOUT(makeup + 1, data[1], dlci);
                SHIFTOUT(makeup + 0, data[0], dlci);
                data[1] |= BYTEX_EA;
                break;
        case 3:
                data[0] = data[1] = data[2] = '\0';
                SHIFTOUT(makeup + 3, data[2], dlci);    /* 3 and 2 is correct */
                SHIFTOUT(makeup + 1, data[1], dlci);
                SHIFTOUT(makeup + 0, data[0], dlci);
                data[2] |= BYTEX_EA;
                break;
        case 4:
                data[0] = data[1] = data[2] = data[3] = '\0';
                SHIFTOUT(makeup + 3, data[3], dlci);
                SHIFTOUT(makeup + 2, data[2], dlci);
                SHIFTOUT(makeup + 1, data[1], dlci);
                SHIFTOUT(makeup + 0, data[0], dlci);
                data[3] |= BYTEX_EA;
                break;
        default:
                panic("%s", __func__);
        }

        /* Send it */
        NG_FWD_NEW_DATA(error, item, sc->downstream.hook, m);
        return (error);

done:
        NG_FREE_ITEM(item);
        NG_FREE_M(m);
        return (error);
}

/*
 * Decode an incoming frame coming from the switch
 */
static int
ngfrm_decode(node_p node, item_p item)
{
        const sc_p  sc = NG_NODE_PRIVATE(node);
        char       *data;
        int         alen;
        u_int       dlci = 0;
        int         error = 0;
        int         ctxnum;
        struct mbuf *m;

        NGI_GET_M(item, m);
        if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL)
                ERROUT(ENOBUFS);
        data = mtod(m, char *);
        if ((alen = sc->addrlen) == 0) {
                sc->addrlen = alen = ngfrm_addrlen(data);
        }
        switch (alen) {
        case 2:
                SHIFTIN(makeup + 0, data[0], dlci);
                SHIFTIN(makeup + 1, data[1], dlci);
                break;
        case 3:
                SHIFTIN(makeup + 0, data[0], dlci);
                SHIFTIN(makeup + 1, data[1], dlci);
                SHIFTIN(makeup + 3, data[2], dlci);     /* 3 and 2 is correct */
                break;
        case 4:
                SHIFTIN(makeup + 0, data[0], dlci);
                SHIFTIN(makeup + 1, data[1], dlci);
                SHIFTIN(makeup + 2, data[2], dlci);
                SHIFTIN(makeup + 3, data[3], dlci);
                break;
        default:
                ERROUT(EINVAL);
        }

        if (dlci > 1023)
                ERROUT(EINVAL);
        ctxnum = sc->ALT[dlci];
        if ((ctxnum & CTX_VALID) && sc->channel[ctxnum &= CTX_VALUE].hook) {
                /* Send it */
                m_adj(m, alen);
                NG_FWD_NEW_DATA(error, item, sc->channel[ctxnum].hook, m);
                return (error);
        } else {
                error = ENETDOWN;
        }
done:
        NG_FREE_ITEM(item);
        NG_FREE_M(m);
        return (error);
}

/*
 * Shutdown node
 */
static int
ngfrm_shutdown(node_p node)
{
        const sc_p sc = NG_NODE_PRIVATE(node);

        NG_NODE_SET_PRIVATE(node, NULL);
        free(sc, M_NETGRAPH);
        NG_NODE_UNREF(node);
        return (0);
}

/*
 * Hook disconnection
 *
 * Invalidate the private data associated with this dlci.
 * For this type, removal of the last link resets tries to destroy the node.
 */
static int
ngfrm_disconnect(hook_p hook)
{
        const sc_p sc = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
        struct ctxinfo *const cp = NG_HOOK_PRIVATE(hook);
        int dlci;

        /* If it's a regular dlci hook, then free resources etc.. */
        if (cp != NULL) {
                cp->hook = NULL;
                dlci = cp->dlci;
                if (dlci != -1)
                        sc->ALT[dlci] = 0;
                cp->flags = 0;
                sc->datahooks--;
        }
        if ((NG_NODE_NUMHOOKS(NG_HOOK_NODE(hook)) == 0)
        && (NG_NODE_IS_VALID(NG_HOOK_NODE(hook))))
                ng_rmnode_self(NG_HOOK_NODE(hook));
        return (0);
}