rfc1201.c

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/*
 * Linux ARCnet driver - RFC1201 (standard) packet encapsulation
 * 
 * Written 1994-1999 by Avery Pennarun.
 * Derived from skeleton.c by Donald Becker.
 *
 * Special thanks to Contemporary Controls, Inc. (www.ccontrols.com)
 *  for sponsoring the further development of this driver.
 *
 * **********************
 *
 * The original copyright of skeleton.c was as follows:
 *
 * skeleton.c Written 1993 by Donald Becker.
 * Copyright 1993 United States Government as represented by the
 * Director, National Security Agency.  This software may only be used
 * and distributed according to the terms of the GNU General Public License as
 * modified by SRC, incorporated herein by reference.
 *
 * **********************
 *
 * For more details, see drivers/net/arcnet.c
 *
 * **********************
 */
#include <linux/gfp.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/if_arp.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/arcdevice.h>

MODULE_LICENSE("GPL");
#define VERSION "arcnet: RFC1201 \"standard\" (`a') encapsulation support loaded.\n"


static __be16 type_trans(struct sk_buff *skb, struct net_device *dev);
static void rx(struct net_device *dev, int bufnum,
           struct archdr *pkthdr, int length);
static int build_header(struct sk_buff *skb, struct net_device *dev,
            unsigned short type, uint8_t daddr);
static int prepare_tx(struct net_device *dev, struct archdr *pkt, int length,
              int bufnum);
static int continue_tx(struct net_device *dev, int bufnum);

static struct ArcProto rfc1201_proto =
{
    .suffix     = 'a',
    .mtu        = 1500, /* could be more, but some receivers can't handle it... */
    .is_ip          = 1,    /* This is for sending IP and ARP packages */
    .rx     = rx,
    .build_header   = build_header,
    .prepare_tx = prepare_tx,
    .continue_tx    = continue_tx,
    .ack_tx         = NULL
};


static int __init arcnet_rfc1201_init(void)
{
    printk(VERSION);

    arc_proto_map[ARC_P_IP]
        = arc_proto_map[ARC_P_IPV6]
        = arc_proto_map[ARC_P_ARP]
        = arc_proto_map[ARC_P_RARP]
        = arc_proto_map[ARC_P_IPX]
        = arc_proto_map[ARC_P_NOVELL_EC]
        = &rfc1201_proto;

    /* if someone else already owns the broadcast, we won't take it */
    if (arc_bcast_proto == arc_proto_default)
        arc_bcast_proto = &rfc1201_proto;

    return 0;
}

static void __exit arcnet_rfc1201_exit(void)
{
    arcnet_unregister_proto(&rfc1201_proto);
}

module_init(arcnet_rfc1201_init);
module_exit(arcnet_rfc1201_exit);

/*
 * Determine a packet's protocol ID.
 * 
 * With ARCnet we have to convert everything to Ethernet-style stuff.
 */
static __be16 type_trans(struct sk_buff *skb, struct net_device *dev)
{
    struct archdr *pkt = (struct archdr *) skb->data;
    struct arc_rfc1201 *soft = &pkt->soft.rfc1201;
    int hdr_size = ARC_HDR_SIZE + RFC1201_HDR_SIZE;

    /* Pull off the arcnet header. */
    skb_reset_mac_header(skb);
    skb_pull(skb, hdr_size);

    if (pkt->hard.dest == 0)
        skb->pkt_type = PACKET_BROADCAST;
    else if (dev->flags & IFF_PROMISC) {
        /* if we're not sending to ourselves :) */
        if (pkt->hard.dest != dev->dev_addr[0])
            skb->pkt_type = PACKET_OTHERHOST;
    }
    /* now return the protocol number */
    switch (soft->proto) {
    case ARC_P_IP:
        return htons(ETH_P_IP);
    case ARC_P_IPV6:
        return htons(ETH_P_IPV6);
    case ARC_P_ARP:
        return htons(ETH_P_ARP);
    case ARC_P_RARP:
        return htons(ETH_P_RARP);

    case ARC_P_IPX:
    case ARC_P_NOVELL_EC:
        return htons(ETH_P_802_3);
    default:
        dev->stats.rx_errors++;
        dev->stats.rx_crc_errors++;
        return 0;
    }

    return htons(ETH_P_IP);
}


/* packet receiver */
static void rx(struct net_device *dev, int bufnum,
           struct archdr *pkthdr, int length)
{
    struct arcnet_local *lp = netdev_priv(dev);
    struct sk_buff *skb;
    struct archdr *pkt = pkthdr;
    struct arc_rfc1201 *soft = &pkthdr->soft.rfc1201;
    int saddr = pkt->hard.source, ofs;
    struct Incoming *in = &lp->rfc1201.incoming[saddr];

    BUGMSG(D_DURING, "it's an RFC1201 packet (length=%d)\n", length);

    if (length >= MinTU)
        ofs = 512 - length;
    else
        ofs = 256 - length;

    if (soft->split_flag == 0xFF) {     /* Exception Packet */
        if (length >= 4 + RFC1201_HDR_SIZE)
            BUGMSG(D_DURING, "compensating for exception packet\n");
        else {
            BUGMSG(D_EXTRA, "short RFC1201 exception packet from %02Xh",
                   saddr);
            return;
        }

        /* skip over 4-byte junkola */
        length -= 4;
        ofs += 4;
        lp->hw.copy_from_card(dev, bufnum, 512 - length,
                      soft, sizeof(pkt->soft));
    }
    if (!soft->split_flag) {    /* not split */
        BUGMSG(D_RX, "incoming is not split (splitflag=%d)\n",
               soft->split_flag);

        if (in->skb) {  /* already assembling one! */
            BUGMSG(D_EXTRA, "aborting assembly (seq=%d) for unsplit packet (splitflag=%d, seq=%d)\n",
             in->sequence, soft->split_flag, soft->sequence);
            lp->rfc1201.aborted_seq = soft->sequence;
            dev_kfree_skb_irq(in->skb);
            dev->stats.rx_errors++;
            dev->stats.rx_missed_errors++;
            in->skb = NULL;
        }
        in->sequence = soft->sequence;

        skb = alloc_skb(length + ARC_HDR_SIZE, GFP_ATOMIC);
        if (skb == NULL) {
            BUGMSG(D_NORMAL, "Memory squeeze, dropping packet.\n");
            dev->stats.rx_dropped++;
            return;
        }
        skb_put(skb, length + ARC_HDR_SIZE);
        skb->dev = dev;

        pkt = (struct archdr *) skb->data;
        soft = &pkt->soft.rfc1201;

        /* up to sizeof(pkt->soft) has already been copied from the card */
        memcpy(pkt, pkthdr, sizeof(struct archdr));
        if (length > sizeof(pkt->soft))
            lp->hw.copy_from_card(dev, bufnum, ofs + sizeof(pkt->soft),
                       pkt->soft.raw + sizeof(pkt->soft),
                          length - sizeof(pkt->soft));

        /*
         * ARP packets have problems when sent from some DOS systems: the
         * source address is always 0!  So we take the hardware source addr
         * (which is impossible to fumble) and insert it ourselves.
         */
        if (soft->proto == ARC_P_ARP) {
            struct arphdr *arp = (struct arphdr *) soft->payload;

            /* make sure addresses are the right length */
            if (arp->ar_hln == 1 && arp->ar_pln == 4) {
                uint8_t *cptr = (uint8_t *) arp + sizeof(struct arphdr);

                if (!*cptr) {   /* is saddr = 00? */
                    BUGMSG(D_EXTRA,
                           "ARP source address was 00h, set to %02Xh.\n",
                           saddr);
                    dev->stats.rx_crc_errors++;
                    *cptr = saddr;
                } else {
                    BUGMSG(D_DURING, "ARP source address (%Xh) is fine.\n",
                           *cptr);
                }
            } else {
                BUGMSG(D_NORMAL, "funny-shaped ARP packet. (%Xh, %Xh)\n",
                       arp->ar_hln, arp->ar_pln);
                dev->stats.rx_errors++;
                dev->stats.rx_crc_errors++;
            }
        }
        BUGLVL(D_SKB) arcnet_dump_skb(dev, skb, "rx");

        skb->protocol = type_trans(skb, dev);
        netif_rx(skb);
    } else {        /* split packet */
        /*
         * NOTE: MSDOS ARP packet correction should only need to apply to
         * unsplit packets, since ARP packets are so short.
         *
         * My interpretation of the RFC1201 document is that if a packet is
         * received out of order, the entire assembly process should be
         * aborted.
         *
         * The RFC also mentions "it is possible for successfully received
         * packets to be retransmitted." As of 0.40 all previously received
         * packets are allowed, not just the most recent one.
         *
         * We allow multiple assembly processes, one for each ARCnet card
         * possible on the network.  Seems rather like a waste of memory,
         * but there's no other way to be reliable.
         */

        BUGMSG(D_RX, "packet is split (splitflag=%d, seq=%d)\n",
               soft->split_flag, in->sequence);

        if (in->skb && in->sequence != soft->sequence) {
            BUGMSG(D_EXTRA, "wrong seq number (saddr=%d, expected=%d, seq=%d, splitflag=%d)\n",
                   saddr, in->sequence, soft->sequence,
                   soft->split_flag);
            dev_kfree_skb_irq(in->skb);
            in->skb = NULL;
            dev->stats.rx_errors++;
            dev->stats.rx_missed_errors++;
            in->lastpacket = in->numpackets = 0;
        }
        if (soft->split_flag & 1) { /* first packet in split */
            BUGMSG(D_RX, "brand new splitpacket (splitflag=%d)\n",
                   soft->split_flag);
            if (in->skb) {  /* already assembling one! */
                BUGMSG(D_EXTRA, "aborting previous (seq=%d) assembly "
                       "(splitflag=%d, seq=%d)\n",
                       in->sequence, soft->split_flag,
                       soft->sequence);
                dev->stats.rx_errors++;
                dev->stats.rx_missed_errors++;
                dev_kfree_skb_irq(in->skb);
            }
            in->sequence = soft->sequence;
            in->numpackets = ((unsigned) soft->split_flag >> 1) + 2;
            in->lastpacket = 1;

            if (in->numpackets > 16) {
                BUGMSG(D_EXTRA, "incoming packet more than 16 segments; dropping. (splitflag=%d)\n",
                       soft->split_flag);
                lp->rfc1201.aborted_seq = soft->sequence;
                dev->stats.rx_errors++;
                dev->stats.rx_length_errors++;
                return;
            }
            in->skb = skb = alloc_skb(508 * in->numpackets + ARC_HDR_SIZE,
                          GFP_ATOMIC);
            if (skb == NULL) {
                BUGMSG(D_NORMAL, "(split) memory squeeze, dropping packet.\n");
                lp->rfc1201.aborted_seq = soft->sequence;
                dev->stats.rx_dropped++;
                return;
            }
            skb->dev = dev;
            pkt = (struct archdr *) skb->data;
            soft = &pkt->soft.rfc1201;

            memcpy(pkt, pkthdr, ARC_HDR_SIZE + RFC1201_HDR_SIZE);
            skb_put(skb, ARC_HDR_SIZE + RFC1201_HDR_SIZE);

            soft->split_flag = 0;   /* end result won't be split */
        } else {    /* not first packet */
            int packetnum = ((unsigned) soft->split_flag >> 1) + 1;

            /*
             * if we're not assembling, there's no point trying to
             * continue.
             */
            if (!in->skb) {
                if (lp->rfc1201.aborted_seq != soft->sequence) {
                    BUGMSG(D_EXTRA, "can't continue split without starting "
                           "first! (splitflag=%d, seq=%d, aborted=%d)\n",
                    soft->split_flag, soft->sequence,
                           lp->rfc1201.aborted_seq);
                    dev->stats.rx_errors++;
                    dev->stats.rx_missed_errors++;
                }
                return;
            }
            in->lastpacket++;
            if (packetnum != in->lastpacket) {  /* not the right flag! */
                /* harmless duplicate? ignore. */
                if (packetnum <= in->lastpacket - 1) {
                    BUGMSG(D_EXTRA, "duplicate splitpacket ignored! (splitflag=%d)\n",
                           soft->split_flag);
                    dev->stats.rx_errors++;
                    dev->stats.rx_frame_errors++;
                    return;
                }
                /* "bad" duplicate, kill reassembly */
                BUGMSG(D_EXTRA, "out-of-order splitpacket, reassembly "
                       "(seq=%d) aborted (splitflag=%d, seq=%d)\n",
                       in->sequence, soft->split_flag, soft->sequence);
                lp->rfc1201.aborted_seq = soft->sequence;
                dev_kfree_skb_irq(in->skb);
                in->skb = NULL;
                dev->stats.rx_errors++;
                dev->stats.rx_missed_errors++;
                in->lastpacket = in->numpackets = 0;
                return;
            }
            pkt = (struct archdr *) in->skb->data;
            soft = &pkt->soft.rfc1201;
        }

        skb = in->skb;

        lp->hw.copy_from_card(dev, bufnum, ofs + RFC1201_HDR_SIZE,
                      skb->data + skb->len,
                      length - RFC1201_HDR_SIZE);
        skb_put(skb, length - RFC1201_HDR_SIZE);

        /* are we done? */
        if (in->lastpacket == in->numpackets) {
            in->skb = NULL;
            in->lastpacket = in->numpackets = 0;

        BUGMSG(D_SKB_SIZE, "skb: received %d bytes from %02X (unsplit)\n",
            skb->len, pkt->hard.source);
        BUGMSG(D_SKB_SIZE, "skb: received %d bytes from %02X (split)\n",
            skb->len, pkt->hard.source);
            BUGLVL(D_SKB) arcnet_dump_skb(dev, skb, "rx");

            skb->protocol = type_trans(skb, dev);
            netif_rx(skb);
        }
    }
}


/* Create the ARCnet hard/soft headers for RFC1201. */
static int build_header(struct sk_buff *skb, struct net_device *dev,
            unsigned short type, uint8_t daddr)
{
    struct arcnet_local *lp = netdev_priv(dev);
    int hdr_size = ARC_HDR_SIZE + RFC1201_HDR_SIZE;
    struct archdr *pkt = (struct archdr *) skb_push(skb, hdr_size);
    struct arc_rfc1201 *soft = &pkt->soft.rfc1201;

    /* set the protocol ID according to RFC1201 */
    switch (type) {
    case ETH_P_IP:
        soft->proto = ARC_P_IP;
        break;
    case ETH_P_IPV6:
        soft->proto = ARC_P_IPV6;
        break;
    case ETH_P_ARP:
        soft->proto = ARC_P_ARP;
        break;
    case ETH_P_RARP:
        soft->proto = ARC_P_RARP;
        break;
    case ETH_P_IPX:
    case ETH_P_802_3:
    case ETH_P_802_2:
        soft->proto = ARC_P_IPX;
        break;
    case ETH_P_ATALK:
        soft->proto = ARC_P_ATALK;
        break;
    default:
        BUGMSG(D_NORMAL, "RFC1201: I don't understand protocol %d (%Xh)\n",
               type, type);
        dev->stats.tx_errors++;
        dev->stats.tx_aborted_errors++;
        return 0;
    }

    /*
     * Set the source hardware address.
     *
     * This is pretty pointless for most purposes, but it can help in
     * debugging.  ARCnet does not allow us to change the source address in
     * the actual packet sent)
     */
    pkt->hard.source = *dev->dev_addr;

    soft->sequence = htons(lp->rfc1201.sequence++);
    soft->split_flag = 0;   /* split packets are done elsewhere */

    /* see linux/net/ethernet/eth.c to see where I got the following */

    if (dev->flags & (IFF_LOOPBACK | IFF_NOARP)) {
        /* 
         * FIXME: fill in the last byte of the dest ipaddr here to better
         * comply with RFC1051 in "noarp" mode.  For now, always broadcasting
         * will probably at least get packets sent out :)
         */
        pkt->hard.dest = 0;
        return hdr_size;
    }
    /* otherwise, drop in the dest address */
    pkt->hard.dest = daddr;
    return hdr_size;
}


static void load_pkt(struct net_device *dev, struct arc_hardware *hard,
             struct arc_rfc1201 *soft, int softlen, int bufnum)
{
    struct arcnet_local *lp = netdev_priv(dev);
    int ofs;

    /* assume length <= XMTU: someone should have handled that by now. */

    if (softlen > MinTU) {
        hard->offset[0] = 0;
        hard->offset[1] = ofs = 512 - softlen;
    } else if (softlen > MTU) { /* exception packet - add an extra header */
        struct arc_rfc1201 excsoft;

        excsoft.proto = soft->proto;
        excsoft.split_flag = 0xff;
        excsoft.sequence = htons(0xffff);

        hard->offset[0] = 0;
        ofs = 512 - softlen;
        hard->offset[1] = ofs - RFC1201_HDR_SIZE;
        lp->hw.copy_to_card(dev, bufnum, ofs - RFC1201_HDR_SIZE,
                    &excsoft, RFC1201_HDR_SIZE);
    } else
        hard->offset[0] = ofs = 256 - softlen;

    lp->hw.copy_to_card(dev, bufnum, 0, hard, ARC_HDR_SIZE);
    lp->hw.copy_to_card(dev, bufnum, ofs, soft, softlen);

    lp->lastload_dest = hard->dest;
}


static int prepare_tx(struct net_device *dev, struct archdr *pkt, int length,
              int bufnum)
{
    struct arcnet_local *lp = netdev_priv(dev);
    const int maxsegsize = XMTU - RFC1201_HDR_SIZE;
    struct Outgoing *out;


    BUGMSG(D_DURING, "prepare_tx: txbufs=%d/%d/%d\n",
           lp->next_tx, lp->cur_tx, bufnum);

    length -= ARC_HDR_SIZE; /* hard header is not included in packet length */
    pkt->soft.rfc1201.split_flag = 0;

    /* need to do a split packet? */
    if (length > XMTU) {
        out = &lp->outgoing;

        out->length = length - RFC1201_HDR_SIZE;
        out->dataleft = lp->outgoing.length;
        out->numsegs = (out->dataleft + maxsegsize - 1) / maxsegsize;
        out->segnum = 0;

        BUGMSG(D_DURING, "rfc1201 prep_tx: ready for %d-segment split "
               "(%d bytes, seq=%d)\n", out->numsegs, out->length,
               pkt->soft.rfc1201.sequence);

        return 0;   /* not done */
    }
    /* just load the packet into the buffers and send it off */
    load_pkt(dev, &pkt->hard, &pkt->soft.rfc1201, length, bufnum);

    return 1;       /* done */
}


static int continue_tx(struct net_device *dev, int bufnum)
{
    struct arcnet_local *lp = netdev_priv(dev);
    struct Outgoing *out = &lp->outgoing;
    struct arc_hardware *hard = &out->pkt->hard;
    struct arc_rfc1201 *soft = &out->pkt->soft.rfc1201, *newsoft;
    int maxsegsize = XMTU - RFC1201_HDR_SIZE;
    int seglen;

    BUGMSG(D_DURING,
      "rfc1201 continue_tx: loading segment %d(+1) of %d (seq=%d)\n",
           out->segnum, out->numsegs, soft->sequence);

    /* the "new" soft header comes right before the data chunk */
    newsoft = (struct arc_rfc1201 *)
        (out->pkt->soft.raw + out->length - out->dataleft);

    if (!out->segnum)   /* first packet; newsoft == soft */
        newsoft->split_flag = ((out->numsegs - 2) << 1) | 1;
    else {
        newsoft->split_flag = out->segnum << 1;
        newsoft->proto = soft->proto;
        newsoft->sequence = soft->sequence;
    }

    seglen = maxsegsize;
    if (seglen > out->dataleft)
        seglen = out->dataleft;
    out->dataleft -= seglen;

    load_pkt(dev, hard, newsoft, seglen + RFC1201_HDR_SIZE, bufnum);

    out->segnum++;
    if (out->segnum >= out->numsegs)
        return 1;
    else
        return 0;
}