rfc1051.c

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/*
 * Linux ARCnet driver - RFC1051 ("simple" 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/module.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/if_arp.h>
#include <net/arp.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/arcdevice.h>

#define VERSION "arcnet: RFC1051 \"simple standard\" (`s') 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 struct ArcProto rfc1051_proto =
{
    .suffix     = 's',
    .mtu        = XMTU - RFC1051_HDR_SIZE,
    .is_ip          = 1,
    .rx     = rx,
    .build_header   = build_header,
    .prepare_tx = prepare_tx,
    .continue_tx    = NULL,
    .ack_tx         = NULL
};


static int __init arcnet_rfc1051_init(void)
{
    printk(VERSION);

    arc_proto_map[ARC_P_IP_RFC1051]
        = arc_proto_map[ARC_P_ARP_RFC1051]
        = &rfc1051_proto;

    /* if someone else already owns the broadcast, we won't take it */
    if (arc_bcast_proto == arc_proto_default)
        arc_bcast_proto = &rfc1051_proto;

    return 0;
}

static void __exit arcnet_rfc1051_exit(void)
{
    arcnet_unregister_proto(&rfc1051_proto);
}

module_init(arcnet_rfc1051_init);
module_exit(arcnet_rfc1051_exit);

MODULE_LICENSE("GPL");

/*
 * 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_rfc1051 *soft = &pkt->soft.rfc1051;
    int hdr_size = ARC_HDR_SIZE + RFC1051_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_RFC1051:
        return htons(ETH_P_IP);
    case ARC_P_ARP_RFC1051:
        return htons(ETH_P_ARP);

    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;
    int ofs;

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

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

    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;

    /* 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));

    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 RFC1051.
 */
static int build_header(struct sk_buff *skb, struct net_device *dev,
            unsigned short type, uint8_t daddr)
{
    int hdr_size = ARC_HDR_SIZE + RFC1051_HDR_SIZE;
    struct archdr *pkt = (struct archdr *) skb_push(skb, hdr_size);
    struct arc_rfc1051 *soft = &pkt->soft.rfc1051;

    /* set the protocol ID according to RFC1051 */
    switch (type) {
    case ETH_P_IP:
        soft->proto = ARC_P_IP_RFC1051;
        break;
    case ETH_P_ARP:
        soft->proto = ARC_P_ARP_RFC1051;
        break;
    default:
        BUGMSG(D_NORMAL, "RFC1051: 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;

    /* 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.
         */
        pkt->hard.dest = 0;
        return hdr_size;
    }
    /* otherwise, just fill it in and go! */
    pkt->hard.dest = daddr;

    return hdr_size;    /* success */
}


static int prepare_tx(struct net_device *dev, struct archdr *pkt, int length,
              int bufnum)
{
    struct arcnet_local *lp = netdev_priv(dev);
    struct arc_hardware *hard = &pkt->hard;
    int ofs;

    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 */

    if (length > XMTU) {
        /* should never happen! other people already check for this. */
        BUGMSG(D_NORMAL, "Bug!  prepare_tx with size %d (> %d)\n",
               length, XMTU);
        length = XMTU;
    }
    if (length > MinTU) {
        hard->offset[0] = 0;
        hard->offset[1] = ofs = 512 - length;
    } else if (length > MTU) {
        hard->offset[0] = 0;
        hard->offset[1] = ofs = 512 - length - 3;
    } else
        hard->offset[0] = ofs = 256 - length;

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

    lp->lastload_dest = hard->dest;

    return 1;       /* done */
}