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/*

 *      SNAP data link layer. Derived from 802.2

 *

 *              Alan Cox <Alan.Cox@linux.org>, from the 802.2 layer by Greg Page.

 *              Merged in additions from Greg Page's psnap.c.

 *

 *              This program is free software; you can redistribute it and/or

 *              modify it under the terms of the GNU General Public License

 *              as published by the Free Software Foundation; either version

 *              2 of the License, or (at your option) any later version.

 */

#include <linux/module.h>

#include <linux/netdevice.h>

#include <linux/skbuff.h>

#include <net/datalink.h>

#include <net/p8022.h>

#include <net/psnap.h>

#include <linux/mm.h>

#include <linux/in.h>

#include <linux/init.h>

static struct datalink_proto *snap_list = NULL;

static struct datalink_proto *snap_dl = NULL;           /* 802.2 DL for SNAP */

/*

 *      Find a snap client by matching the 5 bytes.

 */

static struct datalink_proto *find_snap_client(unsigned char *desc)

{

        struct datalink_proto   *proto;

        for (proto = snap_list; proto != NULL && memcmp(proto->type, desc, 5) ; proto = proto->next);

        return proto;

}

/*

 *      A SNAP packet has arrived

 */

int snap_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)

{

        static struct packet_type psnap_packet_type =

        {

                0,

                NULL,           /* All Devices */

                snap_rcv,

                NULL,

                NULL,

        };

        struct datalink_proto   *proto;

        proto = find_snap_client(skb->h.raw);

        if (proto != NULL)

        {

                /*

                 *      Pass the frame on.

                 */

                skb->h.raw += 5;

                skb->nh.raw += 5;

                skb_pull(skb,5);

                if (psnap_packet_type.type == 0)

                        psnap_packet_type.type=htons(ETH_P_SNAP);

                return proto->rcvfunc(skb, dev, &psnap_packet_type);

        }

        skb->sk = NULL;

        kfree_skb(skb);

        return 0;

}

/*

 *      Put a SNAP header on a frame and pass to 802.2

 */

static void snap_datalink_header(struct datalink_proto *dl, struct sk_buff *skb, unsigned char *dest_node)

{

        memcpy(skb_push(skb,5),dl->type,5);

        snap_dl->datalink_header(snap_dl, skb, dest_node);

}

/*

 *      Set up the SNAP layer

 */

EXPORT_SYMBOL(register_snap_client);

EXPORT_SYMBOL(unregister_snap_client);

static int __init snap_init(void)

{

        snap_dl=register_8022_client(0xAA, snap_rcv);

        if(snap_dl==NULL)

                printk("SNAP - unable to register with 802.2\n");

        return 0;

}

module_init(snap_init);

/*

 *      Register SNAP clients. We don't yet use this for IP.

 */

struct datalink_proto *register_snap_client(unsigned char *desc, int (*rcvfunc)(struct sk_buff *, struct net_device *, struct packet_type *))

{

        struct datalink_proto   *proto;

        if (find_snap_client(desc) != NULL)

                return NULL;

        proto = (struct datalink_proto *) kmalloc(sizeof(*proto), GFP_ATOMIC);

        if (proto != NULL)

        {

                memcpy(proto->type, desc,5);

                proto->type_len = 5;

                proto->rcvfunc = rcvfunc;

                proto->header_length = 5+snap_dl->header_length;

                proto->datalink_header = snap_datalink_header;

                proto->string_name = "SNAP";

                proto->next = snap_list;

                snap_list = proto;

        }

        return proto;

}

/*

 *      Unregister SNAP clients. Protocols no longer want to play with us ...

 */

void unregister_snap_client(unsigned char *desc)

{

        struct datalink_proto **clients = &snap_list;

        struct datalink_proto *tmp;

        unsigned long flags;

        save_flags(flags);

        cli();

        while ((tmp = *clients) != NULL)

        {

                if (memcmp(tmp->type,desc,5) == 0)

                {

                        *clients = tmp->next;

                        kfree(tmp);

                        break;

                }

                else

                        clients = &tmp->next;

        }

        restore_flags(flags);

}