Linux/NetDriver/sheep_net.c

/*
 *  sheep_net.c - Linux driver for SheepShaver/Basilisk II networking (access to raw Ethernet packets)
 *
 *  sheep_net (C) 1999-2002 Mar"c" Hellwig and Christian Bauer
 *
 *  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.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/version.h>
#include <linux/miscdevice.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <net/arp.h>
#include <net/ip.h>
#include <linux/in.h>
#include <linux/wait.h>

MODULE_AUTHOR("Christian Bauer");
MODULE_DESCRIPTION("Pseudo ethernet device for emulators");

/* Compatibility glue */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,4,0)
#define LINUX_24
#else
#define net_device device
typedef struct wait_queue *wait_queue_head_t;
#define init_waitqueue_head(x) *(x)=NULL
#endif

#define DEBUG 0

#define bug printk
#if DEBUG
#define D(x) (x);
#else
#define D(x) ;
#endif


/* Constants */
#define SHEEP_NET_MINOR 198             /* Driver minor number */
#define MAX_QUEUE 32                    /* Maximum number of packets in queue */
#define PROT_MAGIC 1520                 /* Our "magic" protocol type */

#define ETH_ADDR_MULTICAST 0x1
#define ETH_ADDR_LOCALLY_DEFINED 0x02

#define SIOC_MOL_GET_IPFILTER SIOCDEVPRIVATE
#define SIOC_MOL_SET_IPFILTER (SIOCDEVPRIVATE + 1)

/* Prototypes */
static int sheep_net_open(struct inode *inode, struct file *f);
static int sheep_net_release(struct inode *inode, struct file *f);
static ssize_t sheep_net_read(struct file *f, char *buf, size_t count, loff_t *off);
static ssize_t sheep_net_write(struct file *f, const char *buf, size_t count, loff_t *off);
static unsigned int sheep_net_poll(struct file *f, struct poll_table_struct *wait);
static int sheep_net_ioctl(struct inode *inode, struct file *f, unsigned int code, unsigned long arg);
static int sheep_net_receiver(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt);


/*
 *  Driver private variables
 */

struct SheepVars {
        struct net_device *ether;       /* The Ethernet device we're attached to */
        struct sock *skt;                       /* Socket for communication with Ethernet card */
        struct sk_buff_head queue;      /* Receiver packet queue */
        struct packet_type pt;          /* Receiver packet type */
        wait_queue_head_t wait;         /* Wait queue for blocking read operations */
        u32 ipfilter;                           /* Only receive IP packets destined for this address (host byte order) */
        char eth_addr[6];                       /* Hardware address of the Ethernet card */
        char fake_addr[6];                      /* Local faked hardware address (what SheepShaver sees) */
};


/*
 *  file_operations structure - has function pointers to the
 *  various entry points for device operations
 */

static struct file_operations sheep_net_fops = {
        read:           sheep_net_read,
        write:          sheep_net_write,
        poll:           sheep_net_poll,
        ioctl:          sheep_net_ioctl,
        open:           sheep_net_open,
        release:        sheep_net_release,
};


/*
 *  miscdevice structure for driver initialization
 */

static struct miscdevice sheep_net_device = {
        SHEEP_NET_MINOR,        /* minor number */
        "sheep_net",            /* name */
        &sheep_net_fops,
        NULL,
        NULL
};


/*
 *  Initialize module
 */

int init_module(void)
{
        int ret;

        /* Register driver */
        ret = misc_register(&sheep_net_device);
        D(bug("Sheep net driver installed\n"));
        return ret;
}


/*
 *  Deinitialize module
 */

int cleanup_module(void)
{
        int ret;

        /* Unregister driver */
        ret = misc_deregister(&sheep_net_device);
        D(bug("Sheep net driver removed\n"));
        return ret;
}


/*
 *  Driver open() function
 */

static int sheep_net_open(struct inode *inode, struct file *f)
{
        struct SheepVars *v;
        D(bug("sheep_net: open\n"));

        /* Must be opened with read permissions */
        if ((f->f_flags & O_ACCMODE) == O_WRONLY)
                return -EPERM;

        /* Allocate private variables */
        v = (struct SheepVars *)f->private_data = kmalloc(sizeof(struct SheepVars), GFP_USER);
        if (v == NULL)
                return -ENOMEM;
        memset(v, 0, sizeof(struct SheepVars));
        skb_queue_head_init(&v->queue);
        init_waitqueue_head(&v->wait);
        v->fake_addr[0] = 0xfe;
        v->fake_addr[1] = 0xfd;
        v->fake_addr[2] = 0xde;
        v->fake_addr[3] = 0xad;
        v->fake_addr[4] = 0xbe;
        v->fake_addr[5] = 0xef;

        /* Yes, we're open */
        MOD_INC_USE_COUNT;
        return 0;
}


/*
 *  Driver release() function
 */

static int sheep_net_release(struct inode *inode, struct file *f)
{
        struct SheepVars *v = (struct SheepVars *)f->private_data;
        struct sk_buff *skb;
        D(bug("sheep_net: close\n"));

        /* Detach from Ethernet card */
        if (v->ether) {
                dev_remove_pack(&v->pt);
                sk_free(v->skt);
                v->skt = NULL;
#ifdef LINUX_24
                dev_put( v->ether );
#endif
                v->ether = NULL;
        }

        /* Empty packet queue */
        while ((skb = skb_dequeue(&v->queue)) != NULL)
                dev_kfree_skb(skb);

        /* Free private variables */
        kfree(v);

        /* Sorry, we're closed */
        MOD_DEC_USE_COUNT;
        return 0;
}


/*
 *  Check whether an Ethernet address is the local (attached) one or
 *  the fake one
 */

static inline int is_local_addr(struct SheepVars *v, void *a)
{
        return memcmp(a, v->eth_addr, 6) == 0;
}

static inline int is_fake_addr(struct SheepVars *v, void *a)
{
        return memcmp(a, v->fake_addr, 6) == 0;
}


/* 
 * Outgoing packet. Replace the fake enet addr with the real local one.
 */

static inline void do_demasq(struct SheepVars *v, u8 *p)
{
        memcpy(p, v->eth_addr, 6);
}

static void demasquerade(struct SheepVars *v, struct sk_buff *skb)
{
        u8 *p = skb->mac.raw;
        int proto = (p[12] << 8) | p[13];
        
        do_demasq(v, p + 6); /* source address */

        /* Need to fix ARP packets */
        if (proto == ETH_P_ARP) {
                if (is_fake_addr(v, p + 14 + 8)) /* sender HW-addr */
                        do_demasq(v, p + 14 + 8);
        }

        /* ...and AARPs (snap code: 0x00,0x00,0x00,0x80,0xF3) */
        if (p[17] == 0 && p[18] == 0 && p[19] == 0 && p[20] == 0x80 && p[21] == 0xf3) {
                /* XXX: we should perhaps look for the 802 frame too */
                if (is_fake_addr(v, p + 30))
                        do_demasq(v, p + 30); /* sender HW-addr */
        }
}


/*
 * Incoming packet. Replace the local enet addr with the fake one.
 */

static inline void do_masq(struct SheepVars *v, u8 *p)
{
        memcpy(p, v->fake_addr, 6);
}

static void masquerade(struct SheepVars *v, struct sk_buff *skb)
{
        u8 *p = skb->mac.raw;
        if (!(p[0] & ETH_ADDR_MULTICAST))
                do_masq(v, p); /* destination address */

        /* XXX: reverse ARP might need to be fixed */
}


/*
 *  Driver read() function
 */

static ssize_t sheep_net_read(struct file *f, char *buf, size_t count, loff_t *off)
{
        struct SheepVars *v = (struct SheepVars *)f->private_data;
        struct sk_buff *skb;

        D(bug("sheep_net: read\n"));

        for (;;) {

                /* Get next packet from queue */
                skb = skb_dequeue(&v->queue);
                if (skb != NULL || (f->f_flags & O_NONBLOCK))
                        break;

                /* No packet in queue and in blocking mode, so block */
                interruptible_sleep_on(&v->wait);

                /* Signal received? Then bail out */
                if (signal_pending(current))
                        return -EINTR;
        }
        if (skb == NULL)
                return -EAGAIN;

        /* Pass packet to caller */
        if (count > skb->len)
                count = skb->len;
        if (copy_to_user(buf, skb->data, count))
                count = -EFAULT;
        dev_kfree_skb(skb);
        return count;
}


/*
 *  Driver write() function
 */

static ssize_t sheep_net_write(struct file *f, const char *buf, size_t count, loff_t *off)
{
        struct SheepVars *v = (struct SheepVars *)f->private_data;
        struct sk_buff *skb;
        char *p;
        D(bug("sheep_net: write\n"));

        /* Check packet size */
        if (count < sizeof(struct ethhdr))
                return -EINVAL;
        if (count > 1514) {
                printk("sheep_net_write: packet size > 1514\n");
                count = 1514;
        }

        /* Interface active? */
        if (v->ether == NULL)
                return count;

        /* Allocate buffer for packet */
        skb = dev_alloc_skb(count);
        if (skb == NULL)
                return -ENOBUFS;

        /* Stuff packet in buffer */
        p = skb_put(skb, count);
        if (copy_from_user(p, buf, count)) {
                kfree_skb(skb);
                return -EFAULT;
        }

        /* Transmit packet */
        atomic_add(skb->truesize, &v->skt->wmem_alloc);
        skb->sk = v->skt;
        skb->dev = v->ether;
        skb->priority = 0;
        skb->nh.raw = skb->h.raw = skb->data + v->ether->hard_header_len;
        skb->mac.raw = skb->data;

        /* Base the IP-filtering on the IP address in any outgoing ARP packets */
        if (skb->mac.ethernet->h_proto == htons(ETH_P_ARP)) {
                u8 *p = &skb->data[14+14];      /* source IP address */
                u32 ip = (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
                if (ip != v->ipfilter) {
                        v->ipfilter = ip;
                        printk("sheep_net: ipfilter set to %d.%d.%d.%d\n", (ip >> 24) & 0xff, (ip >> 16) & 0xff, (ip >> 8) & 0xff, ip & 0xff);
                }
        }

        /* Is this packet addressed solely to the local host? */
        if (is_local_addr(v, skb->data) && !(skb->data[0] & ETH_ADDR_MULTICAST)) {
                skb->protocol = eth_type_trans(skb, v->ether);
                netif_rx(skb);
                return count;
        }
        if (skb->data[0] & ETH_ADDR_MULTICAST) {
                /* We can't clone the skb since we will manipulate the data below */
                struct sk_buff *lskb = skb_copy(skb, GFP_ATOMIC);
                if (lskb) {
                        lskb->protocol = eth_type_trans(lskb, v->ether);
                        netif_rx(lskb);
                }
        }

        /* Outgoing packet (will be on the net) */
        demasquerade(v, skb);

        skb->protocol = PROT_MAGIC;     /* Magic value (we can recognize the packet in sheep_net_receiver) */
        dev_queue_xmit(skb);
        return count;
}


/*
 *  Driver poll() function
 */

static unsigned int sheep_net_poll(struct file *f, struct poll_table_struct *wait)
{
        struct SheepVars *v = (struct SheepVars *)f->private_data;
        D(bug("sheep_net: poll\n"));

        /* Packets in queue? Then return */
        if (!skb_queue_empty(&v->queue))
                return POLLIN | POLLRDNORM;

        /* Otherwise wait for packet */
        poll_wait(f, &v->wait, wait);
        if (!skb_queue_empty(&v->queue))
                return POLLIN | POLLRDNORM;
        else
                return 0;
}


/*
 *  Driver ioctl() function
 */

static int sheep_net_ioctl(struct inode *inode, struct file *f, unsigned int code, unsigned long arg)
{
        struct SheepVars *v = (struct SheepVars *)f->private_data;
        D(bug("sheep_net: ioctl %04x\n", code));

        switch (code) {

                /* Attach to Ethernet card
                   arg: pointer to name of Ethernet device (char[20]) */
                case SIOCSIFLINK: {
                        char name[20];
                        int err;

                        /* Already attached? */
                        if (v->ether)
                                return -EBUSY;

                        /* Get Ethernet card name */
                        if (copy_from_user(name, (void *)arg, 20))
                                return -EFAULT;
                        name[19] = 0;

                        /* Find card */
#ifdef LINUX_24
                        v->ether = dev_get_by_name(name);
#else
                        dev_lock_list();
                        v->ether = dev_get(name);
#endif
                        if (v->ether == NULL) {
                                err = -ENODEV;
                                goto error;
                        }

                        /* Is it Ethernet? */
                        if (v->ether->type != ARPHRD_ETHER) {
                                err = -EINVAL;
                                goto error;
                        }

                        /* Remember the card's hardware address */
                        memcpy(v->eth_addr, v->ether->dev_addr, 6);

                        /* Allocate socket */
                        v->skt = sk_alloc(0, GFP_USER, 1);
                        if (v->skt == NULL) {
                                err = -ENOMEM;
                                goto error;
                        }
                        v->skt->dead = 1;

                        /* Attach packet handler */
                        v->pt.type = htons(ETH_P_ALL);
                        v->pt.dev = v->ether;
                        v->pt.func = sheep_net_receiver;
                        v->pt.data = v;
                        dev_add_pack(&v->pt);
#ifndef LINUX_24
                        dev_unlock_list();
#endif
                        return 0;

error:
#ifdef LINUX_24
                        if (v->ether)
                                dev_put(v->ether);
#else
                        dev_unlock_list();
#endif
                        v->ether = NULL;
                        return err;
                }

                /* Get hardware address of the sheep_net module
                   arg: pointer to buffer (6 bytes) to store address */
                case SIOCGIFADDR:
                        if (copy_to_user((void *)arg, v->fake_addr, 6))
                                return -EFAULT;
                        return 0;

                /* Set the hardware address of the sheep_net module
                   arg: pointer to new address (6 bytes) */
                case SIOCSIFADDR:
                        if (copy_from_user(v->fake_addr, (void*)arg, 6))
                                return -EFAULT;
                        return 0;

                /* Add multicast address
                   arg: pointer to address (6 bytes) */
                case SIOCADDMULTI: {
                        char addr[6];
                        if (v->ether == NULL)
                                return -ENODEV;
                        if (copy_from_user(addr, (void *)arg, 6))
                                return -EFAULT;
                        return dev_mc_add(v->ether, addr, 6, 0);
                }

                /* Remove multicast address
                   arg: pointer to address (6 bytes) */
                case SIOCDELMULTI: {
                        char addr[6];
                        if (v->ether == NULL)
                                return -ENODEV;
                        if (copy_from_user(addr, (void *)arg, 6))
                                return -EFAULT;
                        return dev_mc_delete(v->ether, addr, 6, 0);
                }

                /* Return size of first packet in queue */
                case FIONREAD: {
                        int count = 0;
                        struct sk_buff *skb;
#ifdef LINUX_24
                        long flags;
                        spin_lock_irqsave(&v->queue.lock, flags);
#else
                        cli();
#endif
                        skb = skb_peek(&v->queue);
                        if (skb)
                                count = skb->len;
#ifdef LINUX_24
                        spin_unlock_irqrestore(&v->queue.lock, flags);
#else
                        sti();
#endif
                        return put_user(count, (int *)arg);
                }

                case SIOC_MOL_GET_IPFILTER:
                        return put_user(v->ipfilter, (int *)arg);

                case SIOC_MOL_SET_IPFILTER:
                        v->ipfilter = arg;
                        return 0;

                default:
                        return -ENOIOCTLCMD;
        }
}


/*
 *  Packet receiver function
 */

static int sheep_net_receiver(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
{
        struct SheepVars *v = (struct SheepVars *)pt->data;
        struct sk_buff *skb2;
        int fake;
        int multicast;
        D(bug("sheep_net: packet received\n"));

        multicast = (skb->mac.ethernet->h_dest[0] & ETH_ADDR_MULTICAST);
        fake = is_fake_addr(v, &skb->mac.ethernet->h_dest);

        /* Packet sent by us? Then discard */
        if (is_fake_addr(v, &skb->mac.ethernet->h_source) || skb->protocol == PROT_MAGIC)
                goto drop;

        /* If the packet is not meant for this host, discard it */
        if (!is_local_addr(v, &skb->mac.ethernet->h_dest) && !multicast && !fake)
                goto drop;

        /* Discard packets if queue gets too full */
        if (skb_queue_len(&v->queue) > MAX_QUEUE)
                goto drop;

        /* Apply any filters here (if fake is true, then we *know* we want this packet) */
        if (!fake) {
                if ((skb->protocol == htons(ETH_P_IP))
                 && (!v->ipfilter || (ntohl(skb->h.ipiph->daddr) != v->ipfilter && !multicast)))
                        goto drop;
        }

        /* Masquerade (we are typically a clone - best to make a real copy) */
        skb2 = skb_copy(skb, GFP_ATOMIC);
        if (!skb2)
                goto drop;
        kfree_skb(skb);
        skb = skb2;
        masquerade(v, skb);

        /* We also want the Ethernet header */
        skb_push(skb, skb->data - skb->mac.raw);

        /* Enqueue packet */
        skb_queue_tail(&v->queue, skb);

        /* Unblock blocked read */
        wake_up(&v->wait);
        return 0;

drop:
        kfree_skb(skb);
        return 0;
}
Revision:	1.8
Committed:	2002-01-15T14:58:39Z (22 years, 10 months ago) by cebix
Content type:	text/plain
Branch:	MAIN
CVS Tags:	snapshot-15012002
Changes since 1.7:	+1 -1 lines
Log Message:	- documentation updates - 2001 -> 2002 - version 0.9 -> 1.0
#	Content
1	/*
2	* sheep_net.c - Linux driver for SheepShaver/Basilisk II networking (access to raw Ethernet packets)
3	*
4	* sheep_net (C) 1999-2002 Mar"c" Hellwig and Christian Bauer
5	*
6	* This program is free software; you can redistribute it and/or modify
7	* it under the terms of the GNU General Public License as published by
8	* the Free Software Foundation; either version 2 of the License, or
9	* (at your option) any later version.
10	*
11	* This program is distributed in the hope that it will be useful,
12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14	* GNU General Public License for more details.
15	*
16	* You should have received a copy of the GNU General Public License
17	* along with this program; if not, write to the Free Software
18	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19	*/
20
21	#include <linux/kernel.h>
22	#include <linux/module.h>
23	#include <linux/version.h>
24	#include <linux/miscdevice.h>
25	#include <linux/netdevice.h>
26	#include <linux/etherdevice.h>
27	#include <linux/if_ether.h>
28	#include <linux/if_arp.h>
29	#include <linux/fs.h>
30	#include <linux/poll.h>
31	#include <linux/init.h>
32	#include <net/sock.h>
33	#include <asm/uaccess.h>
34	#include <net/arp.h>
35	#include <net/ip.h>
36	#include <linux/in.h>
37	#include <linux/wait.h>
38
39	MODULE_AUTHOR("Christian Bauer");
40	MODULE_DESCRIPTION("Pseudo ethernet device for emulators");
41
42	/* Compatibility glue */
43	#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,4,0)
44	#define LINUX_24
45	#else
46	#define net_device device
47	typedef struct wait_queue *wait_queue_head_t;
48	#define init_waitqueue_head(x) *(x)=NULL
49	#endif
50
51	#define DEBUG 0
52
53	#define bug printk
54	#if DEBUG
55	#define D(x) (x);
56	#else
57	#define D(x) ;
58	#endif
59
60
61	/* Constants */
62	#define SHEEP_NET_MINOR 198 /* Driver minor number */
63	#define MAX_QUEUE 32 /* Maximum number of packets in queue */
64	#define PROT_MAGIC 1520 /* Our "magic" protocol type */
65
66	#define ETH_ADDR_MULTICAST 0x1
67	#define ETH_ADDR_LOCALLY_DEFINED 0x02
68
69	#define SIOC_MOL_GET_IPFILTER SIOCDEVPRIVATE
70	#define SIOC_MOL_SET_IPFILTER (SIOCDEVPRIVATE + 1)
71
72	/* Prototypes */
73	static int sheep_net_open(struct inode inode, struct file f);
74	static int sheep_net_release(struct inode inode, struct file f);
75	static ssize_t sheep_net_read(struct file f, char buf, size_t count, loff_t *off);
76	static ssize_t sheep_net_write(struct file f, const char buf, size_t count, loff_t *off);
77	static unsigned int sheep_net_poll(struct file f, struct poll_table_struct wait);
78	static int sheep_net_ioctl(struct inode inode, struct file f, unsigned int code, unsigned long arg);
79	static int sheep_net_receiver(struct sk_buff skb, struct net_device dev, struct packet_type *pt);
80
81
82	/*
83	* Driver private variables
84	*/
85
86	struct SheepVars {
87	struct net_device ether; / The Ethernet device we're attached to */
88	struct sock skt; / Socket for communication with Ethernet card */
89	struct sk_buff_head queue; /* Receiver packet queue */
90	struct packet_type pt; /* Receiver packet type */
91	wait_queue_head_t wait; /* Wait queue for blocking read operations */
92	u32 ipfilter; /* Only receive IP packets destined for this address (host byte order) */
93	char eth_addr[6]; /* Hardware address of the Ethernet card */
94	char fake_addr[6]; /* Local faked hardware address (what SheepShaver sees) */
95	};
96
97
98	/*
99	* file_operations structure - has function pointers to the
100	* various entry points for device operations
101	*/
102
103	static struct file_operations sheep_net_fops = {
104	read: sheep_net_read,
105	write: sheep_net_write,
106	poll: sheep_net_poll,
107	ioctl: sheep_net_ioctl,
108	open: sheep_net_open,
109	release: sheep_net_release,
110	};
111
112
113	/*
114	* miscdevice structure for driver initialization
115	*/
116
117	static struct miscdevice sheep_net_device = {
118	SHEEP_NET_MINOR, /* minor number */
119	"sheep_net", /* name */
120	&sheep_net_fops,
121	NULL,
122	NULL
123	};
124
125
126	/*
127	* Initialize module
128	*/
129
130	int init_module(void)
131	{
132	int ret;
133
134	/* Register driver */
135	ret = misc_register(&sheep_net_device);
136	D(bug("Sheep net driver installed\n"));
137	return ret;
138	}
139
140
141	/*
142	* Deinitialize module
143	*/
144
145	int cleanup_module(void)
146	{
147	int ret;
148
149	/* Unregister driver */
150	ret = misc_deregister(&sheep_net_device);
151	D(bug("Sheep net driver removed\n"));
152	return ret;
153	}
154
155
156	/*
157	* Driver open() function
158	*/
159
160	static int sheep_net_open(struct inode inode, struct file f)
161	{
162	struct SheepVars *v;
163	D(bug("sheep_net: open\n"));
164
165	/* Must be opened with read permissions */
166	if ((f->f_flags & O_ACCMODE) == O_WRONLY)
167	return -EPERM;
168
169	/* Allocate private variables */
170	v = (struct SheepVars *)f->private_data = kmalloc(sizeof(struct SheepVars), GFP_USER);
171	if (v == NULL)
172	return -ENOMEM;
173	memset(v, 0, sizeof(struct SheepVars));
174	skb_queue_head_init(&v->queue);
175	init_waitqueue_head(&v->wait);
176	v->fake_addr[0] = 0xfe;
177	v->fake_addr[1] = 0xfd;
178	v->fake_addr[2] = 0xde;
179	v->fake_addr[3] = 0xad;
180	v->fake_addr[4] = 0xbe;
181	v->fake_addr[5] = 0xef;
182
183	/* Yes, we're open */
184	MOD_INC_USE_COUNT;
185	return 0;
186	}
187
188
189	/*
190	* Driver release() function
191	*/
192
193	static int sheep_net_release(struct inode inode, struct file f)
194	{
195	struct SheepVars v = (struct SheepVars )f->private_data;
196	struct sk_buff *skb;
197	D(bug("sheep_net: close\n"));
198
199	/* Detach from Ethernet card */
200	if (v->ether) {
201	dev_remove_pack(&v->pt);
202	sk_free(v->skt);
203	v->skt = NULL;
204	#ifdef LINUX_24
205	dev_put( v->ether );
206	#endif
207	v->ether = NULL;
208	}
209
210	/* Empty packet queue */
211	while ((skb = skb_dequeue(&v->queue)) != NULL)
212	dev_kfree_skb(skb);
213
214	/* Free private variables */
215	kfree(v);
216
217	/* Sorry, we're closed */
218	MOD_DEC_USE_COUNT;
219	return 0;
220	}
221
222
223	/*
224	* Check whether an Ethernet address is the local (attached) one or
225	* the fake one
226	*/
227
228	static inline int is_local_addr(struct SheepVars v, void a)
229	{
230	return memcmp(a, v->eth_addr, 6) == 0;
231	}
232
233	static inline int is_fake_addr(struct SheepVars v, void a)
234	{
235	return memcmp(a, v->fake_addr, 6) == 0;
236	}
237
238
239	/*
240	* Outgoing packet. Replace the fake enet addr with the real local one.
241	*/
242
243	static inline void do_demasq(struct SheepVars v, u8 p)
244	{
245	memcpy(p, v->eth_addr, 6);
246	}
247
248	static void demasquerade(struct SheepVars v, struct sk_buff skb)
249	{
250	u8 *p = skb->mac.raw;
251	int proto = (p[12] << 8) \| p[13];
252
253	do_demasq(v, p + 6); /* source address */
254
255	/* Need to fix ARP packets */
256	if (proto == ETH_P_ARP) {
257	if (is_fake_addr(v, p + 14 + 8)) /* sender HW-addr */
258	do_demasq(v, p + 14 + 8);
259	}
260
261	/* ...and AARPs (snap code: 0x00,0x00,0x00,0x80,0xF3) */
262	if (p[17] == 0 && p[18] == 0 && p[19] == 0 && p[20] == 0x80 && p[21] == 0xf3) {
263	/* XXX: we should perhaps look for the 802 frame too */
264	if (is_fake_addr(v, p + 30))
265	do_demasq(v, p + 30); /* sender HW-addr */
266	}
267	}
268
269
270	/*
271	* Incoming packet. Replace the local enet addr with the fake one.
272	*/
273
274	static inline void do_masq(struct SheepVars v, u8 p)
275	{
276	memcpy(p, v->fake_addr, 6);
277	}
278
279	static void masquerade(struct SheepVars v, struct sk_buff skb)
280	{
281	u8 *p = skb->mac.raw;
282	if (!(p[0] & ETH_ADDR_MULTICAST))
283	do_masq(v, p); /* destination address */
284
285	/* XXX: reverse ARP might need to be fixed */
286	}
287
288
289	/*
290	* Driver read() function
291	*/
292
293	static ssize_t sheep_net_read(struct file f, char buf, size_t count, loff_t *off)
294	{
295	struct SheepVars v = (struct SheepVars )f->private_data;
296	struct sk_buff *skb;
297
298	D(bug("sheep_net: read\n"));
299
300	for (;;) {
301
302	/* Get next packet from queue */
303	skb = skb_dequeue(&v->queue);
304	if (skb != NULL \|\| (f->f_flags & O_NONBLOCK))
305	break;
306
307	/* No packet in queue and in blocking mode, so block */
308	interruptible_sleep_on(&v->wait);
309
310	/* Signal received? Then bail out */
311	if (signal_pending(current))
312	return -EINTR;
313	}
314	if (skb == NULL)
315	return -EAGAIN;
316
317	/* Pass packet to caller */
318	if (count > skb->len)
319	count = skb->len;
320	if (copy_to_user(buf, skb->data, count))
321	count = -EFAULT;
322	dev_kfree_skb(skb);
323	return count;
324	}
325
326
327	/*
328	* Driver write() function
329	*/
330
331	static ssize_t sheep_net_write(struct file f, const char buf, size_t count, loff_t *off)
332	{
333	struct SheepVars v = (struct SheepVars )f->private_data;
334	struct sk_buff *skb;
335	char *p;
336	D(bug("sheep_net: write\n"));
337
338	/* Check packet size */
339	if (count < sizeof(struct ethhdr))
340	return -EINVAL;
341	if (count > 1514) {
342	printk("sheep_net_write: packet size > 1514\n");
343	count = 1514;
344	}
345
346	/* Interface active? */
347	if (v->ether == NULL)
348	return count;
349
350	/* Allocate buffer for packet */
351	skb = dev_alloc_skb(count);
352	if (skb == NULL)
353	return -ENOBUFS;
354
355	/* Stuff packet in buffer */
356	p = skb_put(skb, count);
357	if (copy_from_user(p, buf, count)) {
358	kfree_skb(skb);
359	return -EFAULT;
360	}
361
362	/* Transmit packet */
363	atomic_add(skb->truesize, &v->skt->wmem_alloc);
364	skb->sk = v->skt;
365	skb->dev = v->ether;
366	skb->priority = 0;
367	skb->nh.raw = skb->h.raw = skb->data + v->ether->hard_header_len;
368	skb->mac.raw = skb->data;
369
370	/* Base the IP-filtering on the IP address in any outgoing ARP packets */
371	if (skb->mac.ethernet->h_proto == htons(ETH_P_ARP)) {
372	u8 p = &skb->data[14+14]; / source IP address */
373	u32 ip = (p[0] << 24) \| (p[1] << 16) \| (p[2] << 8) \| p[3];
374	if (ip != v->ipfilter) {
375	v->ipfilter = ip;
376	printk("sheep_net: ipfilter set to %d.%d.%d.%d\n", (ip >> 24) & 0xff, (ip >> 16) & 0xff, (ip >> 8) & 0xff, ip & 0xff);
377	}
378	}
379
380	/* Is this packet addressed solely to the local host? */
381	if (is_local_addr(v, skb->data) && !(skb->data[0] & ETH_ADDR_MULTICAST)) {
382	skb->protocol = eth_type_trans(skb, v->ether);
383	netif_rx(skb);
384	return count;
385	}
386	if (skb->data[0] & ETH_ADDR_MULTICAST) {
387	/* We can't clone the skb since we will manipulate the data below */
388	struct sk_buff *lskb = skb_copy(skb, GFP_ATOMIC);
389	if (lskb) {
390	lskb->protocol = eth_type_trans(lskb, v->ether);
391	netif_rx(lskb);
392	}
393	}
394
395	/* Outgoing packet (will be on the net) */
396	demasquerade(v, skb);
397
398	skb->protocol = PROT_MAGIC; /* Magic value (we can recognize the packet in sheep_net_receiver) */
399	dev_queue_xmit(skb);
400	return count;
401	}
402
403
404	/*
405	* Driver poll() function
406	*/
407
408	static unsigned int sheep_net_poll(struct file f, struct poll_table_struct wait)
409	{
410	struct SheepVars v = (struct SheepVars )f->private_data;
411	D(bug("sheep_net: poll\n"));
412
413	/* Packets in queue? Then return */
414	if (!skb_queue_empty(&v->queue))
415	return POLLIN \| POLLRDNORM;
416
417	/* Otherwise wait for packet */
418	poll_wait(f, &v->wait, wait);
419	if (!skb_queue_empty(&v->queue))
420	return POLLIN \| POLLRDNORM;
421	else
422	return 0;
423	}
424
425
426	/*
427	* Driver ioctl() function
428	*/
429
430	static int sheep_net_ioctl(struct inode inode, struct file f, unsigned int code, unsigned long arg)
431	{
432	struct SheepVars v = (struct SheepVars )f->private_data;
433	D(bug("sheep_net: ioctl %04x\n", code));
434
435	switch (code) {
436
437	/* Attach to Ethernet card
438	arg: pointer to name of Ethernet device (char[20]) */
439	case SIOCSIFLINK: {
440	char name[20];
441	int err;
442
443	/* Already attached? */
444	if (v->ether)
445	return -EBUSY;
446
447	/* Get Ethernet card name */
448	if (copy_from_user(name, (void *)arg, 20))
449	return -EFAULT;
450	name[19] = 0;
451
452	/* Find card */
453	#ifdef LINUX_24
454	v->ether = dev_get_by_name(name);
455	#else
456	dev_lock_list();
457	v->ether = dev_get(name);
458	#endif
459	if (v->ether == NULL) {
460	err = -ENODEV;
461	goto error;
462	}
463
464	/* Is it Ethernet? */
465	if (v->ether->type != ARPHRD_ETHER) {
466	err = -EINVAL;
467	goto error;
468	}
469
470	/* Remember the card's hardware address */
471	memcpy(v->eth_addr, v->ether->dev_addr, 6);
472
473	/* Allocate socket */
474	v->skt = sk_alloc(0, GFP_USER, 1);
475	if (v->skt == NULL) {
476	err = -ENOMEM;
477	goto error;
478	}
479	v->skt->dead = 1;
480
481	/* Attach packet handler */
482	v->pt.type = htons(ETH_P_ALL);
483	v->pt.dev = v->ether;
484	v->pt.func = sheep_net_receiver;
485	v->pt.data = v;
486	dev_add_pack(&v->pt);
487	#ifndef LINUX_24
488	dev_unlock_list();
489	#endif
490	return 0;
491
492	error:
493	#ifdef LINUX_24
494	if (v->ether)
495	dev_put(v->ether);
496	#else
497	dev_unlock_list();
498	#endif
499	v->ether = NULL;
500	return err;
501	}
502
503	/* Get hardware address of the sheep_net module
504	arg: pointer to buffer (6 bytes) to store address */
505	case SIOCGIFADDR:
506	if (copy_to_user((void *)arg, v->fake_addr, 6))
507	return -EFAULT;
508	return 0;
509
510	/* Set the hardware address of the sheep_net module
511	arg: pointer to new address (6 bytes) */
512	case SIOCSIFADDR:
513	if (copy_from_user(v->fake_addr, (void*)arg, 6))
514	return -EFAULT;
515	return 0;
516
517	/* Add multicast address
518	arg: pointer to address (6 bytes) */
519	case SIOCADDMULTI: {
520	char addr[6];
521	if (v->ether == NULL)
522	return -ENODEV;
523	if (copy_from_user(addr, (void *)arg, 6))
524	return -EFAULT;
525	return dev_mc_add(v->ether, addr, 6, 0);
526	}
527
528	/* Remove multicast address
529	arg: pointer to address (6 bytes) */
530	case SIOCDELMULTI: {
531	char addr[6];
532	if (v->ether == NULL)
533	return -ENODEV;
534	if (copy_from_user(addr, (void *)arg, 6))
535	return -EFAULT;
536	return dev_mc_delete(v->ether, addr, 6, 0);
537	}
538
539	/* Return size of first packet in queue */
540	case FIONREAD: {
541	int count = 0;
542	struct sk_buff *skb;
543	#ifdef LINUX_24
544	long flags;
545	spin_lock_irqsave(&v->queue.lock, flags);
546	#else
547	cli();
548	#endif
549	skb = skb_peek(&v->queue);
550	if (skb)
551	count = skb->len;
552	#ifdef LINUX_24
553	spin_unlock_irqrestore(&v->queue.lock, flags);
554	#else
555	sti();
556	#endif
557	return put_user(count, (int *)arg);
558	}
559
560	case SIOC_MOL_GET_IPFILTER:
561	return put_user(v->ipfilter, (int *)arg);
562
563	case SIOC_MOL_SET_IPFILTER:
564	v->ipfilter = arg;
565	return 0;
566
567	default:
568	return -ENOIOCTLCMD;
569	}
570	}
571
572
573	/*
574	* Packet receiver function
575	*/
576
577	static int sheep_net_receiver(struct sk_buff skb, struct net_device dev, struct packet_type *pt)
578	{
579	struct SheepVars v = (struct SheepVars )pt->data;
580	struct sk_buff *skb2;
581	int fake;
582	int multicast;
583	D(bug("sheep_net: packet received\n"));
584
585	multicast = (skb->mac.ethernet->h_dest[0] & ETH_ADDR_MULTICAST);
586	fake = is_fake_addr(v, &skb->mac.ethernet->h_dest);
587
588	/* Packet sent by us? Then discard */
589	if (is_fake_addr(v, &skb->mac.ethernet->h_source) \|\| skb->protocol == PROT_MAGIC)
590	goto drop;
591
592	/* If the packet is not meant for this host, discard it */
593	if (!is_local_addr(v, &skb->mac.ethernet->h_dest) && !multicast && !fake)
594	goto drop;
595
596	/* Discard packets if queue gets too full */
597	if (skb_queue_len(&v->queue) > MAX_QUEUE)
598	goto drop;
599
600	/* Apply any filters here (if fake is true, then we know we want this packet) */
601	if (!fake) {
602	if ((skb->protocol == htons(ETH_P_IP))
603	&& (!v->ipfilter \|\| (ntohl(skb->h.ipiph->daddr) != v->ipfilter && !multicast)))
604	goto drop;
605	}
606
607	/* Masquerade (we are typically a clone - best to make a real copy) */
608	skb2 = skb_copy(skb, GFP_ATOMIC);
609	if (!skb2)
610	goto drop;
611	kfree_skb(skb);
612	skb = skb2;
613	masquerade(v, skb);
614
615	/* We also want the Ethernet header */
616	skb_push(skb, skb->data - skb->mac.raw);
617
618	/* Enqueue packet */
619	skb_queue_tail(&v->queue, skb);
620
621	/* Unblock blocked read */
622	wake_up(&v->wait);
623	return 0;
624
625	drop:
626	kfree_skb(skb);
627	return 0;
628	}