Linux/NetDriver/sheep_net.c

/*
 *  sheep_net.c - Linux driver for SheepShaver/Basilisk II networking (access to raw Ethernet packets)
 *
 *  sheep_net (C) 1999-2001 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/module.h>
#include <linux/version.h>

#ifdef CONFIG_MODVERSIONS
#define MODVERSIONS
#include <linux/modversions.h>
#endif

#ifdef CONFIG_SMP
#define __SMP__
#endif

#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 <linux/in.h>
#include <linux/wait.h>
#include <net/sock.h>
#include <net/arp.h>
#include <net/ip.h>
#include <asm/uaccess.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 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
 */

void cleanup_module(void)
{
        /* Unregister driver */
        misc_deregister(&sheep_net_device);
        D(bug("Sheep net driver removed\n"));
}


/*
 *  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)
                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[8]) */
                case SIOCSIFLINK: {
                        char name[8];
                        int err;

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

                        /* Get Ethernet card name */
                        if (copy_from_user(name, (void *)arg, 8))
                                return -EFAULT;
                        name[7] = 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:	1.5
Committed:	2001-03-28T14:18:58Z (23 years, 8 months ago) by cebix
Content type:	text/plain
Branch:	MAIN
CVS Tags:	snapshot-29052001, release-0_9-1
Changes since 1.4:	+15 -6 lines
Log Message:	cleaned up a little
#	Content
1	/*
2	* sheep_net.c - Linux driver for SheepShaver/Basilisk II networking (access to raw Ethernet packets)
3	*
4	* sheep_net (C) 1999-2001 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/module.h>
22	#include <linux/version.h>
23
24	#ifdef CONFIG_MODVERSIONS
25	#define MODVERSIONS
26	#include <linux/modversions.h>
27	#endif
28
29	#ifdef CONFIG_SMP
30	#define __SMP__
31	#endif
32
33	#include <linux/miscdevice.h>
34	#include <linux/netdevice.h>
35	#include <linux/etherdevice.h>
36	#include <linux/if_ether.h>
37	#include <linux/if_arp.h>
38	#include <linux/fs.h>
39	#include <linux/poll.h>
40	#include <linux/init.h>
41	#include <linux/in.h>
42	#include <linux/wait.h>
43	#include <net/sock.h>
44	#include <net/arp.h>
45	#include <net/ip.h>
46	#include <asm/uaccess.h>
47
48	MODULE_AUTHOR("Christian Bauer");
49	MODULE_DESCRIPTION("Pseudo ethernet device for emulators");
50
51	/* Compatibility glue */
52	#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,4,0)
53	#define LINUX_24
54	#else
55	#define net_device device
56	typedef struct wait_queue *wait_queue_head_t;
57	#define init_waitqueue_head(x) *(x)=NULL
58	#endif
59
60	#define DEBUG 0
61
62	#define bug printk
63	#if DEBUG
64	#define D(x) (x);
65	#else
66	#define D(x) ;
67	#endif
68
69
70	/* Constants */
71	#define SHEEP_NET_MINOR 198 /* Driver minor number */
72	#define MAX_QUEUE 32 /* Maximum number of packets in queue */
73	#define PROT_MAGIC 1520 /* Our "magic" protocol type */
74
75	#define ETH_ADDR_MULTICAST 0x1
76
77	#define SIOC_MOL_GET_IPFILTER SIOCDEVPRIVATE
78	#define SIOC_MOL_SET_IPFILTER (SIOCDEVPRIVATE + 1)
79
80	/* Prototypes */
81	static int sheep_net_open(struct inode inode, struct file f);
82	static int sheep_net_release(struct inode inode, struct file f);
83	static ssize_t sheep_net_read(struct file f, char buf, size_t count, loff_t *off);
84	static ssize_t sheep_net_write(struct file f, const char buf, size_t count, loff_t *off);
85	static unsigned int sheep_net_poll(struct file f, struct poll_table_struct wait);
86	static int sheep_net_ioctl(struct inode inode, struct file f, unsigned int code, unsigned long arg);
87	static int sheep_net_receiver(struct sk_buff skb, struct net_device dev, struct packet_type *pt);
88
89
90	/*
91	* Driver private variables
92	*/
93
94	struct SheepVars {
95	struct net_device ether; / The Ethernet device we're attached to */
96	struct sock skt; / Socket for communication with Ethernet card */
97	struct sk_buff_head queue; /* Receiver packet queue */
98	struct packet_type pt; /* Receiver packet type */
99	wait_queue_head_t wait; /* Wait queue for blocking read operations */
100	u32 ipfilter; /* Only receive IP packets destined for this address (host byte order) */
101	char eth_addr[6]; /* Hardware address of the Ethernet card */
102	char fake_addr[6]; /* Local faked hardware address (what SheepShaver sees) */
103	};
104
105
106	/*
107	* file_operations structure - has function pointers to the
108	* various entry points for device operations
109	*/
110
111	static struct file_operations sheep_net_fops = {
112	read: sheep_net_read,
113	write: sheep_net_write,
114	poll: sheep_net_poll,
115	ioctl: sheep_net_ioctl,
116	open: sheep_net_open,
117	release: sheep_net_release,
118	};
119
120
121	/*
122	* miscdevice structure for driver initialization
123	*/
124
125	static struct miscdevice sheep_net_device = {
126	SHEEP_NET_MINOR, /* minor number */
127	"sheep_net", /* name */
128	&sheep_net_fops,
129	NULL,
130	NULL
131	};
132
133
134	/*
135	* Initialize module
136	*/
137
138	int init_module(void)
139	{
140	int ret;
141
142	/* Register driver */
143	ret = misc_register(&sheep_net_device);
144	D(bug("Sheep net driver installed\n"));
145	return ret;
146	}
147
148
149	/*
150	* Deinitialize module
151	*/
152
153	void cleanup_module(void)
154	{
155	/* Unregister driver */
156	misc_deregister(&sheep_net_device);
157	D(bug("Sheep net driver removed\n"));
158	}
159
160
161	/*
162	* Driver open() function
163	*/
164
165	static int sheep_net_open(struct inode inode, struct file f)
166	{
167	struct SheepVars *v;
168	D(bug("sheep_net: open\n"));
169
170	/* Must be opened with read permissions */
171	if ((f->f_flags & O_ACCMODE) == O_WRONLY)
172	return -EPERM;
173
174	/* Allocate private variables */
175	v = (struct SheepVars *)f->private_data = kmalloc(sizeof(struct SheepVars), GFP_USER);
176	if (v == NULL)
177	return -ENOMEM;
178	memset(v, 0, sizeof(struct SheepVars));
179	skb_queue_head_init(&v->queue);
180	init_waitqueue_head(&v->wait);
181	v->fake_addr[0] = 0xfe;
182	v->fake_addr[1] = 0xfd;
183	v->fake_addr[2] = 0xde;
184	v->fake_addr[3] = 0xad;
185	v->fake_addr[4] = 0xbe;
186	v->fake_addr[5] = 0xef;
187
188	/* Yes, we're open */
189	MOD_INC_USE_COUNT;
190	return 0;
191	}
192
193
194	/*
195	* Driver release() function
196	*/
197
198	static int sheep_net_release(struct inode inode, struct file f)
199	{
200	struct SheepVars v = (struct SheepVars )f->private_data;
201	struct sk_buff *skb;
202	D(bug("sheep_net: close\n"));
203
204	/* Detach from Ethernet card */
205	if (v->ether) {
206	dev_remove_pack(&v->pt);
207	sk_free(v->skt);
208	v->skt = NULL;
209	#ifdef LINUX_24
210	dev_put( v->ether );
211	#endif
212	v->ether = NULL;
213	}
214
215	/* Empty packet queue */
216	while ((skb = skb_dequeue(&v->queue)) != NULL)
217	dev_kfree_skb(skb);
218
219	/* Free private variables */
220	kfree(v);
221
222	/* Sorry, we're closed */
223	MOD_DEC_USE_COUNT;
224	return 0;
225	}
226
227
228	/*
229	* Check whether an Ethernet address is the local (attached) one or
230	* the fake one
231	*/
232
233	static inline int is_local_addr(struct SheepVars v, void a)
234	{
235	return memcmp(a, v->eth_addr, 6) == 0;
236	}
237
238	static inline int is_fake_addr(struct SheepVars v, void a)
239	{
240	return memcmp(a, v->fake_addr, 6) == 0;
241	}
242
243
244	/*
245	* Outgoing packet. Replace the fake enet addr with the real local one.
246	*/
247
248	static inline void do_demasq(struct SheepVars v, u8 p)
249	{
250	memcpy(p, v->eth_addr, 6);
251	}
252
253	static void demasquerade(struct SheepVars v, struct sk_buff skb)
254	{
255	u8 *p = skb->mac.raw;
256	int proto = (p[12] << 8) \| p[13];
257
258	do_demasq(v, p + 6); /* source address */
259
260	/* Need to fix ARP packets */
261	if (proto == ETH_P_ARP) {
262	if (is_fake_addr(v, p + 14 + 8)) /* sender HW-addr */
263	do_demasq(v, p + 14 + 8);
264	}
265
266	/* ...and AARPs (snap code: 0x00,0x00,0x00,0x80,0xF3) */
267	if (p[17] == 0 && p[18] == 0 && p[19] == 0 && p[20] == 0x80 && p[21] == 0xf3) {
268	/* XXX: we should perhaps look for the 802 frame too */
269	if (is_fake_addr(v, p + 30))
270	do_demasq(v, p + 30); /* sender HW-addr */
271	}
272	}
273
274
275	/*
276	* Incoming packet. Replace the local enet addr with the fake one.
277	*/
278
279	static inline void do_masq(struct SheepVars v, u8 p)
280	{
281	memcpy(p, v->fake_addr, 6);
282	}
283
284	static void masquerade(struct SheepVars v, struct sk_buff skb)
285	{
286	u8 *p = skb->mac.raw;
287	if (!(p[0] & ETH_ADDR_MULTICAST))
288	do_masq(v, p); /* destination address */
289
290	/* XXX: reverse ARP might need to be fixed */
291	}
292
293
294	/*
295	* Driver read() function
296	*/
297
298	static ssize_t sheep_net_read(struct file f, char buf, size_t count, loff_t *off)
299	{
300	struct SheepVars v = (struct SheepVars )f->private_data;
301	struct sk_buff *skb;
302
303	D(bug("sheep_net: read\n"));
304
305	for (;;) {
306
307	/* Get next packet from queue */
308	skb = skb_dequeue(&v->queue);
309	if (skb != NULL \|\| (f->f_flags & O_NONBLOCK))
310	break;
311
312	/* No packet in queue and in blocking mode, so block */
313	interruptible_sleep_on(&v->wait);
314
315	/* Signal received? Then bail out */
316	if (signal_pending(current))
317	return -EINTR;
318	}
319	if (skb == NULL)
320	return -EAGAIN;
321
322	/* Pass packet to caller */
323	if (count > skb->len)
324	count = skb->len;
325	if (copy_to_user(buf, skb->data, count))
326	count = -EFAULT;
327	dev_kfree_skb(skb);
328	return count;
329	}
330
331
332	/*
333	* Driver write() function
334	*/
335
336	static ssize_t sheep_net_write(struct file f, const char buf, size_t count, loff_t *off)
337	{
338	struct SheepVars v = (struct SheepVars )f->private_data;
339	struct sk_buff *skb;
340	char *p;
341	D(bug("sheep_net: write\n"));
342
343	/* Check packet size */
344	if (count < sizeof(struct ethhdr))
345	return -EINVAL;
346	if (count > 1514)
347	count = 1514;
348
349	/* Interface active? */
350	if (v->ether == NULL)
351	return count;
352
353	/* Allocate buffer for packet */
354	skb = dev_alloc_skb(count);
355	if (skb == NULL)
356	return -ENOBUFS;
357
358	/* Stuff packet in buffer */
359	p = skb_put(skb, count);
360	if (copy_from_user(p, buf, count)) {
361	kfree_skb(skb);
362	return -EFAULT;
363	}
364
365	/* Transmit packet */
366	atomic_add(skb->truesize, &v->skt->wmem_alloc);
367	skb->sk = v->skt;
368	skb->dev = v->ether;
369	skb->priority = 0;
370	skb->nh.raw = skb->h.raw = skb->data + v->ether->hard_header_len;
371	skb->mac.raw = skb->data;
372
373	/* Base the IP-filtering on the IP address in any outgoing ARP packets */
374	if (skb->mac.ethernet->h_proto == htons(ETH_P_ARP)) {
375	u8 p = &skb->data[14+14]; / source IP address */
376	u32 ip = (p[0] << 24) \| (p[1] << 16) \| (p[2] << 8) \| p[3];
377	if (ip != v->ipfilter) {
378	v->ipfilter = ip;
379	printk("sheep_net: ipfilter set to %d.%d.%d.%d\n", (ip >> 24) & 0xff, (ip >> 16) & 0xff, (ip >> 8) & 0xff, ip & 0xff);
380	}
381	}
382
383	/* Is this packet addressed solely to the local host? */
384	if (is_local_addr(v, skb->data) && !(skb->data[0] & ETH_ADDR_MULTICAST)) {
385	skb->protocol = eth_type_trans(skb, v->ether);
386	netif_rx(skb);
387	return count;
388	}
389	if (skb->data[0] & ETH_ADDR_MULTICAST) {
390	/* We can't clone the skb since we will manipulate the data below */
391	struct sk_buff *lskb = skb_copy(skb, GFP_ATOMIC);
392	if (lskb) {
393	lskb->protocol = eth_type_trans(lskb, v->ether);
394	netif_rx(lskb);
395	}
396	}
397
398	/* Outgoing packet (will be on the net) */
399	demasquerade(v, skb);
400
401	skb->protocol = PROT_MAGIC; /* Magic value (we can recognize the packet in sheep_net_receiver) */
402	dev_queue_xmit(skb);
403	return count;
404	}
405
406
407	/*
408	* Driver poll() function
409	*/
410
411	static unsigned int sheep_net_poll(struct file f, struct poll_table_struct wait)
412	{
413	struct SheepVars v = (struct SheepVars )f->private_data;
414	D(bug("sheep_net: poll\n"));
415
416	/* Packets in queue? Then return */
417	if (!skb_queue_empty(&v->queue))
418	return POLLIN \| POLLRDNORM;
419
420	/* Otherwise wait for packet */
421	poll_wait(f, &v->wait, wait);
422	if (!skb_queue_empty(&v->queue))
423	return POLLIN \| POLLRDNORM;
424	else
425	return 0;
426	}
427
428
429	/*
430	* Driver ioctl() function
431	*/
432
433	static int sheep_net_ioctl(struct inode inode, struct file f, unsigned int code, unsigned long arg)
434	{
435	struct SheepVars v = (struct SheepVars )f->private_data;
436	D(bug("sheep_net: ioctl %04x\n", code));
437
438	switch (code) {
439
440	/* Attach to Ethernet card
441	arg: pointer to name of Ethernet device (char[8]) */
442	case SIOCSIFLINK: {
443	char name[8];
444	int err;
445
446	/* Already attached? */
447	if (v->ether)
448	return -EBUSY;
449
450	/* Get Ethernet card name */
451	if (copy_from_user(name, (void *)arg, 8))
452	return -EFAULT;
453	name[7] = 0;
454
455	/* Find card */
456	#ifdef LINUX_24
457	v->ether = dev_get_by_name(name);
458	#else
459	dev_lock_list();
460	v->ether = dev_get(name);
461	#endif
462	if (v->ether == NULL) {
463	err = -ENODEV;
464	goto error;
465	}
466
467	/* Is it Ethernet? */
468	if (v->ether->type != ARPHRD_ETHER) {
469	err = -EINVAL;
470	goto error;
471	}
472
473	/* Remember the card's hardware address */
474	memcpy(v->eth_addr, v->ether->dev_addr, 6);
475
476	/* Allocate socket */
477	v->skt = sk_alloc(0, GFP_USER, 1);
478	if (v->skt == NULL) {
479	err = -ENOMEM;
480	goto error;
481	}
482	v->skt->dead = 1;
483
484	/* Attach packet handler */
485	v->pt.type = htons(ETH_P_ALL);
486	v->pt.dev = v->ether;
487	v->pt.func = sheep_net_receiver;
488	v->pt.data = v;
489	dev_add_pack(&v->pt);
490	#ifndef LINUX_24
491	dev_unlock_list();
492	#endif
493	return 0;
494
495	error:
496	#ifdef LINUX_24
497	if (v->ether)
498	dev_put(v->ether);
499	#else
500	dev_unlock_list();
501	#endif
502	v->ether = NULL;
503	return err;
504	}
505
506	/* Get hardware address of the sheep_net module
507	arg: pointer to buffer (6 bytes) to store address */
508	case SIOCGIFADDR:
509	if (copy_to_user((void *)arg, v->fake_addr, 6))
510	return -EFAULT;
511	return 0;
512
513	/* Set the hardware address of the sheep_net module
514	arg: pointer to new address (6 bytes) */
515	case SIOCSIFADDR:
516	if (copy_from_user(v->fake_addr, (void*)arg, 6))
517	return -EFAULT;
518	return 0;
519
520	/* Add multicast address
521	arg: pointer to address (6 bytes) */
522	case SIOCADDMULTI: {
523	char addr[6];
524	if (v->ether == NULL)
525	return -ENODEV;
526	if (copy_from_user(addr, (void *)arg, 6))
527	return -EFAULT;
528	return dev_mc_add(v->ether, addr, 6, 0);
529	}
530
531	/* Remove multicast address
532	arg: pointer to address (6 bytes) */
533	case SIOCDELMULTI: {
534	char addr[6];
535	if (v->ether == NULL)
536	return -ENODEV;
537	if (copy_from_user(addr, (void *)arg, 6))
538	return -EFAULT;
539	return dev_mc_delete(v->ether, addr, 6, 0);
540	}
541
542	/* Return size of first packet in queue */
543	case FIONREAD: {
544	int count = 0;
545	struct sk_buff *skb;
546	#ifdef LINUX_24
547	long flags;
548	spin_lock_irqsave(&v->queue.lock, flags);
549	#else
550	cli();
551	#endif
552	skb = skb_peek(&v->queue);
553	if (skb)
554	count = skb->len;
555	#ifdef LINUX_24
556	spin_unlock_irqrestore(&v->queue.lock, flags);
557	#else
558	sti();
559	#endif
560	return put_user(count, (int *)arg);
561	}
562
563	case SIOC_MOL_GET_IPFILTER:
564	return put_user(v->ipfilter, (int *)arg);
565
566	case SIOC_MOL_SET_IPFILTER:
567	v->ipfilter = arg;
568	return 0;
569
570	default:
571	return -ENOIOCTLCMD;
572	}
573	}
574
575
576	/*
577	* Packet receiver function
578	*/
579
580	static int sheep_net_receiver(struct sk_buff skb, struct net_device dev, struct packet_type *pt)
581	{
582	struct SheepVars v = (struct SheepVars )pt->data;
583	struct sk_buff *skb2;
584	int fake;
585	int multicast;
586	D(bug("sheep_net: packet received\n"));
587
588	multicast = (skb->mac.ethernet->h_dest[0] & ETH_ADDR_MULTICAST);
589	fake = is_fake_addr(v, &skb->mac.ethernet->h_dest);
590
591	/* Packet sent by us? Then discard */
592	if (is_fake_addr(v, &skb->mac.ethernet->h_source) \|\| skb->protocol == PROT_MAGIC)
593	goto drop;
594
595	/* If the packet is not meant for this host, discard it */
596	if (!is_local_addr(v, &skb->mac.ethernet->h_dest) && !multicast && !fake)
597	goto drop;
598
599	/* Discard packets if queue gets too full */
600	if (skb_queue_len(&v->queue) > MAX_QUEUE)
601	goto drop;
602
603	/* Apply any filters here (if fake is true, then we know we want this packet) */
604	if (!fake) {
605	if ((skb->protocol == htons(ETH_P_IP))
606	&& (!v->ipfilter \|\| (ntohl(skb->h.ipiph->daddr) != v->ipfilter && !multicast)))
607	goto drop;
608	}
609
610	/* Masquerade (we are typically a clone - best to make a real copy) */
611	skb2 = skb_copy(skb, GFP_ATOMIC);
612	if (!skb2)
613	goto drop;
614	kfree_skb(skb);
615	skb = skb2;
616	masquerade(v, skb);
617
618	/* We also want the Ethernet header */
619	skb_push(skb, skb->data - skb->mac.raw);
620
621	/* Enqueue packet */
622	skb_queue_tail(&v->queue, skb);
623
624	/* Unblock blocked read */
625	wake_up(&v->wait);
626	return 0;
627
628	drop:
629	kfree_skb(skb);
630	return 0;
631	}