/*
 * 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
 *
 * **********************
 */

#define pr_fmt(fmt) "arcnet:" KBUILD_MODNAME ": " fmt

#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 "arcdevice.h"

MODULE_DESCRIPTION("ARCNet packet format (RFC 1201) module");
MODULE_LICENSE("GPL");

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)
{
        pr_info("%s\n", "RFC1201 \"standard\" (`a') encapsulation support loaded");

        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];

        arc_printk(D_DURING, dev, "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) {
                        arc_printk(D_DURING, dev, "compensating for exception packet\n");
                } else {
                        arc_printk(D_EXTRA, dev, "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 */
                arc_printk(D_RX, dev, "incoming is not split (splitflag=%d)\n",
                           soft->split_flag);

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

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

                if (in->skb && in->sequence != soft->sequence) {
                        arc_printk(D_EXTRA, dev, "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 */
                        arc_printk(D_RX, dev, "brand new splitpacket (splitflag=%d)\n",
                                   soft->split_flag);
                        if (in->skb) {  /* already assembling one! */
                                arc_printk(D_EXTRA, dev, "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) {
                                arc_printk(D_EXTRA, dev, "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) {
                                arc_printk(D_NORMAL, dev, "(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) {
                                        arc_printk(D_EXTRA, dev, "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 not the right flag */
                        if (packetnum != in->lastpacket) {
                                /* harmless duplicate? ignore. */
                                if (packetnum <= in->lastpacket - 1) {
                                        arc_printk(D_EXTRA, dev, "duplicate splitpacket ignored! (splitflag=%d)\n",
                                                   soft->split_flag);
                                        dev->stats.rx_errors++;
                                        dev->stats.rx_frame_errors++;
                                        return;
                                }
                                /* "bad" duplicate, kill reassembly */
                                arc_printk(D_EXTRA, dev, "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;

                        arc_printk(D_SKB_SIZE, dev, "skb: received %d bytes from %02X (unsplit)\n",
                                   skb->len, pkt->hard.source);
                        arc_printk(D_SKB_SIZE, dev, "skb: received %d bytes from %02X (split)\n",
                                   skb->len, pkt->hard.source);
                        if (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 = 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:
                arc_printk(D_NORMAL, dev, "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;

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

        /* hard header is not included in packet length */
        length -= ARC_HDR_SIZE;
        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;

                arc_printk(D_DURING, dev, "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;

        arc_printk(D_DURING, dev,
                   "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;
}