capmode.c

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/*
 * Linux ARCnet driver - "cap mode" packet encapsulation.
 * It adds sequence numbers to packets for communicating between a user space
 * application and the driver. After a transmit it sends a packet with protocol
 * byte 0 back up to the userspace containing the sequence number of the packet
 * plus the transmit-status on the ArcNet.
 *
 * Written 2002-4 by Esben Nielsen, Vestas Wind Systems A/S
 * Derived from arc-rawmode.c by Avery Pennarun.
 * arc-rawmode was in turned based on skeleton.c, see below.
 *
 * **********************
 *
 * 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: cap mode (`c') encapsulation support loaded.\n"

/* 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;
    char *pktbuf, *pkthdrbuf;
    int ofs;

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

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

    skb = alloc_skb(length + ARC_HDR_SIZE + sizeof(int), 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 + sizeof(int));
    skb->dev = dev;
    skb_reset_mac_header(skb);
    pkt = (struct archdr *)skb_mac_header(skb);
    skb_pull(skb, ARC_HDR_SIZE);

    /* up to sizeof(pkt->soft) has already been copied from the card */
    /* squeeze in an int for the cap encapsulation */

    /* use these variables to be sure we count in bytes, not in
       sizeof(struct archdr) */
    pktbuf=(char*)pkt;
    pkthdrbuf=(char*)pkthdr;
    memcpy(pktbuf, pkthdrbuf, ARC_HDR_SIZE+sizeof(pkt->soft.cap.proto));
    memcpy(pktbuf+ARC_HDR_SIZE+sizeof(pkt->soft.cap.proto)+sizeof(int),
           pkthdrbuf+ARC_HDR_SIZE+sizeof(pkt->soft.cap.proto),
           sizeof(struct archdr)-ARC_HDR_SIZE-sizeof(pkt->soft.cap.proto));

    if (length > sizeof(pkt->soft))
        lp->hw.copy_from_card(dev, bufnum, ofs + sizeof(pkt->soft),
                      pkt->soft.raw + sizeof(pkt->soft)
                      + sizeof(int),
                      length - sizeof(pkt->soft));

    BUGLVL(D_SKB) arcnet_dump_skb(dev, skb, "rx");

    skb->protocol = cpu_to_be16(ETH_P_ARCNET);
    netif_rx(skb);
}


/*
 * Create the ARCnet hard/soft headers for cap mode.
 * There aren't any soft headers in cap mode - not even the protocol id.
 */
static int build_header(struct sk_buff *skb,
            struct net_device *dev,
            unsigned short type,
            uint8_t daddr)
{
    int hdr_size = ARC_HDR_SIZE;
    struct archdr *pkt = (struct archdr *) skb_push(skb, hdr_size);

    BUGMSG(D_PROTO, "Preparing header for cap packet %x.\n",
           *((int*)&pkt->soft.cap.cookie[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;


    /* hard header is not included in packet length */
    length -= ARC_HDR_SIZE;
    /* And neither is the cookie field */
    length -= sizeof(int);

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

    BUGMSG(D_PROTO, "Sending for cap packet %x.\n",
           *((int*)&pkt->soft.cap.cookie[0]));

    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;

    BUGMSG(D_DURING, "prepare_tx: length=%d ofs=%d\n",
           length,ofs);

    /* Copy the arcnet-header + the protocol byte down: */
    lp->hw.copy_to_card(dev, bufnum, 0, hard, ARC_HDR_SIZE);
    lp->hw.copy_to_card(dev, bufnum, ofs, &pkt->soft.cap.proto,
                sizeof(pkt->soft.cap.proto));

    /* Skip the extra integer we have written into it as a cookie
       but write the rest of the message: */
    lp->hw.copy_to_card(dev, bufnum, ofs+1,
                ((unsigned char*)&pkt->soft.cap.mes),length-1);

    lp->lastload_dest = hard->dest;

    return 1;   /* done */
}

static int ack_tx(struct net_device *dev, int acked)
{
    struct arcnet_local *lp = netdev_priv(dev);
    struct sk_buff *ackskb;
    struct archdr *ackpkt;
    int length=sizeof(struct arc_cap);

    BUGMSG(D_DURING, "capmode: ack_tx: protocol: %x: result: %d\n",
        lp->outgoing.skb->protocol, acked);

    BUGLVL(D_SKB) arcnet_dump_skb(dev, lp->outgoing.skb, "ack_tx");

    /* Now alloc a skb to send back up through the layers: */
    ackskb = alloc_skb(length + ARC_HDR_SIZE , GFP_ATOMIC);
    if (ackskb == NULL) {
        BUGMSG(D_NORMAL, "Memory squeeze, can't acknowledge.\n");
        goto free_outskb;
    }

    skb_put(ackskb, length + ARC_HDR_SIZE );
    ackskb->dev = dev;

    skb_reset_mac_header(ackskb);
    ackpkt = (struct archdr *)skb_mac_header(ackskb);
    /* skb_pull(ackskb, ARC_HDR_SIZE); */

    skb_copy_from_linear_data(lp->outgoing.skb, ackpkt,
                  ARC_HDR_SIZE + sizeof(struct arc_cap));
    ackpkt->soft.cap.proto = 0; /* using protocol 0 for acknowledge */
    ackpkt->soft.cap.mes.ack=acked;

    BUGMSG(D_PROTO, "Ackknowledge for cap packet %x.\n",
            *((int*)&ackpkt->soft.cap.cookie[0]));

    ackskb->protocol = cpu_to_be16(ETH_P_ARCNET);

    BUGLVL(D_SKB) arcnet_dump_skb(dev, ackskb, "ack_tx_recv");
    netif_rx(ackskb);

free_outskb:
    dev_kfree_skb_irq(lp->outgoing.skb);
    lp->outgoing.proto = NULL; /* We are always finished when in this protocol */

    return 0;
}

static struct ArcProto capmode_proto =
{
    'r',
    XMTU,
    0,
    rx,
    build_header,
    prepare_tx,
    NULL,
    ack_tx
};

static void arcnet_cap_init(void)
{
    int count;

    for (count = 1; count <= 8; count++)
        if (arc_proto_map[count] == arc_proto_default)
            arc_proto_map[count] = &capmode_proto;

    /* for cap mode, we only set the bcast proto if there's no better one */
    if (arc_bcast_proto == arc_proto_default)
        arc_bcast_proto = &capmode_proto;

    arc_proto_default = &capmode_proto;
    arc_raw_proto = &capmode_proto;
}

static int __init capmode_module_init(void)
{
    printk(VERSION);
    arcnet_cap_init();
    return 0;
}

static void __exit capmode_module_exit(void)
{
    arcnet_unregister_proto(&capmode_proto);
}
module_init(capmode_module_init);
module_exit(capmode_module_exit);

MODULE_LICENSE("GPL");