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/*

 * SKIPLINK     An implementation of a loadable kernel mode driver providing

 *              multiple kernel/user space bidirectional communications links.

 *

 *              Author:         Alan Cox <alan@cymru.net>

 *

 *              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/errno.h>

#include <linux/kernel.h>

#include <linux/major.h>

#include <linux/sched.h>

#include <linux/lp.h>

#include <linux/malloc.h>

#include <linux/ioport.h>

#include <linux/fcntl.h>

#include <linux/delay.h>

#include <linux/skbuff.h>

#include <net/netlink.h>

#include <asm/io.h>

#include <asm/segment.h>

#include <asm/system.h>

static int (*netlink_handler[MAX_LINKS])(struct sk_buff *skb);

static struct sk_buff_head skb_queue_rd[MAX_LINKS];

static int rdq_size[MAX_LINKS];

static struct wait_queue *read_space_wait[MAX_LINKS];

static int active_map = 0;

static int open_map = 0;

/*

 *      Device operations

 */

/*

 *      Default write handler.

 */

static int netlink_err(struct sk_buff *skb)

{

        kfree_skb(skb, FREE_READ);

        return -EUNATCH;

}

/*

 *      Exported do nothing receiver for one way

 *      interfaces.

 */

int netlink_donothing(struct sk_buff *skb)

{

        kfree_skb(skb, FREE_READ);

        return -EINVAL;

}

static int netlink_select(struct inode *inode, struct file *file, int sel_type, select_table * wait)

{

        unsigned int minor = MINOR(inode->i_rdev);

        switch (sel_type) {

        case SEL_IN:

                if (skb_peek(&skb_queue_rd[minor])!=NULL)

                        return 1;

                select_wait(&read_space_wait[minor], wait);

                break;

        case SEL_OUT:

                return 1;

        }

        return 0;

}

/*

 *      Write a message to the kernel side of a communication link

 */

static int netlink_write(struct inode * inode, struct file * file, const char * buf, int count)

{

        unsigned int minor = MINOR(inode->i_rdev);

        struct sk_buff *skb;

        skb=alloc_skb(count, GFP_KERNEL);

        if (!skb)

                return -ENOBUFS;

        skb->free=1;

        memcpy_fromfs(skb_put(skb,count),buf, count);

        return (netlink_handler[minor])(skb);

}

/*

 *      Read a message from the kernel side of the communication link

 */

static int netlink_read(struct inode * inode, struct file * file, char * buf, int count)

{

        unsigned int minor = MINOR(inode->i_rdev);

        struct sk_buff *skb;

        cli();

        while((skb=skb_dequeue(&skb_queue_rd[minor]))==NULL)

        {

                if(file->f_flags&O_NONBLOCK)

                {

                        sti();

                        return -EAGAIN;

                }

                interruptible_sleep_on(&read_space_wait[minor]);

                if(current->signal & ~current->blocked)

                {

                        sti();

                        return -ERESTARTSYS;

                }

        }

        rdq_size[minor]-=skb->len;

        sti();

        if(skb->len<count)

                count=skb->len;

        memcpy_tofs(buf,skb->data,count);

        kfree_skb(skb, FREE_READ);

        return count;

}

static int netlink_lseek(struct inode * inode, struct file * file,

                    off_t offset, int origin)

{

        return -ESPIPE;

}

static int netlink_open(struct inode * inode, struct file * file)

{

        unsigned int minor = MINOR(inode->i_rdev);

        if(minor>=MAX_LINKS)

                return -ENODEV;

        if(open_map&(1<<minor))

                return -EBUSY;

        if(active_map&(1<<minor))

        {

                open_map|=(1<<minor);

                MOD_INC_USE_COUNT;

                return 0;

        }

        return -EUNATCH;

}

static void netlink_release(struct inode * inode, struct file * file)

{

        unsigned int minor = MINOR(inode->i_rdev);

        open_map&=~(1<<minor);

        MOD_DEC_USE_COUNT;

}

static int netlink_ioctl(struct inode *inode, struct file *file,

                    unsigned int cmd, unsigned long arg)

{

        unsigned int minor = MINOR(inode->i_rdev);

        int retval = 0;

        if (minor >= MAX_LINKS)

                return -ENODEV;

        switch ( cmd ) {

                default:

                        retval = -EINVAL;

        }

        return retval;

}

static struct file_operations netlink_fops = {

        netlink_lseek,

        netlink_read,

        netlink_write,

        NULL,           /* netlink_readdir */

        netlink_select,

        netlink_ioctl,

        NULL,           /* netlink_mmap */

        netlink_open,

        netlink_release

};

/*

 *      We export these functions to other modules. They provide a

 *      complete set of kernel non-blocking support for message

 *      queueing.

 */

int netlink_attach(int unit, int (*function)(struct sk_buff *skb))

{

        if(unit>=MAX_LINKS)

                return -ENODEV;

        if(active_map&(1<<unit))

                return -EBUSY;

        active_map|=(1<<unit);

        open_map&=~(1<<unit);

        netlink_handler[unit]=function;

        return 0;

}

void netlink_detach(int unit)

{

        active_map&=~(1<<unit);

        netlink_handler[unit]=netlink_err;

        open_map&=~(1<<unit);

}

int netlink_post(int unit, struct sk_buff *skb)

{

        unsigned long flags;

        int ret=-EUNATCH;

        if(open_map&(1<<unit))

        {

                save_flags(flags);

                cli();

                if(rdq_size[unit]+skb->len>MAX_QBYTES)

                        ret=-EAGAIN;

                else

                {

                        skb_queue_tail(&skb_queue_rd[unit], skb);

                        rdq_size[unit]+=skb->len;

                        ret=0;

                        wake_up_interruptible(&read_space_wait[unit]);

                }

                restore_flags(flags);

        }

        return ret;

}

int init_netlink(void)

{

        int ct;

        if(register_chrdev(NETLINK_MAJOR,"netlink", &netlink_fops)) {

                printk(KERN_ERR "netlink: unable to get major %d\n", NETLINK_MAJOR);

                return -EIO;

        }

        for(ct=0;ct<MAX_LINKS;ct++)

        {

                skb_queue_head_init(&skb_queue_rd[ct]);

                netlink_handler[ct]=netlink_err;

        }

        return 0;

}

#ifdef MODULE

int init_module(void)

{

        printk(KERN_INFO "Network Kernel/User communications module 0.03\n");

        return init_netlink();

}

void cleanup_module(void)

{

        unregister_chrdev(NET_MAJOR,"netlink");

}

#endif