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hook.c
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hook.c
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#include <linux/etherdevice.h>
#include <linux/fs.h>
#include <linux/ip.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/tcp.h>
#include <linux/version.h>
#include <linux/wait.h>
#include <asm/uaccess.h>
#include "hook.h"
#define NH_MINOR 214
static LIST_HEAD(current_skbs);
static DEFINE_SPINLOCK(skb_list_lock);
struct skb_entry {
struct list_head list;
struct sk_buff *skb;
};
#if defined(__DEBUG__)
static unsigned int list_size(struct list_head *head)
{
unsigned int count = 0;
struct list_head *pos;
list_for_each(pos, head)
count++;
return count;
}
#endif
/*
* Must hold skb_list_lock
*/
static struct skb_entry *is_hooked(struct sk_buff *skb)
{
struct skb_entry *e;
int found = 0;
list_for_each_entry(e, ¤t_skbs, list) {
if(e->skb == skb) {
found = 1;
break;
}
}
return found ? e : NULL;
}
static LIST_HEAD(nh_privs);
static DEFINE_SPINLOCK(nh_privs_lock);
struct nh_private {
struct list_head list;
struct nh_filter *filter;
struct nh_writer *writer;
struct sk_buff_head skb_queue ;
wait_queue_head_t wq;
};
static struct nf_hook_ops *cb_in_use[NF_IP_NUMHOOKS + 1];
enum {
CHECK_PROTO = (1 << 0),
CHECK_OUT = (1 << 1),
CHECK_IN = (1 << 2),
CHECK_SADDR = (1 << 3),
CHECK_DADDR = (1 << 4),
CHECK_SPORT = (1 << 5),
CHECK_DPORT = (1 << 6),
};
/*
* Must hold the nh_privs_lock
*/
static struct nh_private *pass(struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int hooknum)
{
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,22)
struct iphdr *iph = (struct iphdr *)skb_network_header(skb);
struct tcphdr *tph = (struct tcphdr *)skb_transport_header(skb);
#else
struct iphdr *iph = skb->nh.iph;
struct tcphdr *tph = skb->h.th;
#endif
struct nh_private *e;
list_for_each_entry(e, &nh_privs, list) {
if (e->filter->hooknum != hooknum) {
continue;
}
if ((e->filter->flags & CHECK_OUT) && e->filter->out != out) {
continue;
}
if ((e->filter->flags & CHECK_IN) && e->filter->in != in) {
continue;
}
if (iph) {
if ((e->filter->flags & CHECK_PROTO) && e->filter->proto != iph->protocol) {
continue;
}
if ((e->filter->flags & CHECK_SADDR) && e->filter->saddr != iph->saddr) {
continue;
}
if ((e->filter->flags & CHECK_DADDR) && e->filter->daddr != iph->daddr) {
continue;
}
}
if (tph) {
if ((e->filter->flags & CHECK_SPORT) && e->filter->sport != tph->source) {
continue;
}
if ((e->filter->flags & CHECK_DPORT) && e->filter->dport != tph->dest) {
continue;
}
}
return e;
}
return NULL;
}
static unsigned int nf_cb(
unsigned int hooknum,
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
struct sk_buff *skb,
#else
struct sk_buff **pskb,
#endif
const struct net_device *in, const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct nh_private *p;
struct skb_entry *e;
unsigned long flags;
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
struct sk_buff **pskb = &skb;
#endif
/* if the packet was hooked once, don't send it back to user space */
spin_lock_irqsave(&skb_list_lock, flags);
e = is_hooked(*pskb);
if (e) {
list_del(&e->list);
spin_unlock_irqrestore(&skb_list_lock, flags);
kfree(e);
return NF_ACCEPT;
}
spin_unlock_irqrestore(&skb_list_lock, flags);
spin_lock_irqsave(&nh_privs_lock, flags);
p = pass(*pskb, in, out, hooknum);
if (p) {
skb_queue_tail(&p->skb_queue, *pskb);
spin_unlock_irqrestore(&nh_privs_lock, flags);
wake_up_interruptible(&p->wq);
return NF_STOLEN;
}
spin_unlock_irqrestore(&nh_privs_lock, flags);
return NF_ACCEPT;
}
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
#define NET_NAMESPACE
#else
#define NET_NAMESPACE &init_net,
#endif
static int setup_filter(struct nh_private *p)
{
struct nh_filter *f = p->filter;
struct nf_hook_ops *nf_hook;
int ret = 0;
if (f->hooknum < 0 || f->hooknum > (NF_IP_NUMHOOKS - 1))
return -EINVAL;
nf_hook = kzalloc(sizeof(*nf_hook), GFP_KERNEL);
if (!nf_hook)
return -ENOMEM;
f->in = dev_get_by_name(NET_NAMESPACE f->in_dev);
if (f->in)
f->flags |= CHECK_IN;
f->out = dev_get_by_name(NET_NAMESPACE f->out_dev);
if (f->out)
f->flags |= CHECK_OUT;
if (f->saddr)
f->flags |= CHECK_SADDR;
if (f->daddr)
f->flags |= CHECK_DADDR;
if (f->dport)
f->flags |= CHECK_DPORT;
if (f->sport)
f->flags |= CHECK_SPORT;
if (f->proto)
f->flags |= CHECK_PROTO;
if (!cb_in_use[f->hooknum]) {
nf_hook->hook = nf_cb;
nf_hook->owner = THIS_MODULE;
nf_hook->pf = PF_INET;
nf_hook->hooknum = f->hooknum;
nf_hook->priority = f->priority;
ret = nf_register_hook(nf_hook);
if (ret < 0) {
printk("nf_hook: can't register netfilter hook.\n");
kfree(nf_hook);
goto err;
}
cb_in_use[f->hooknum] = nf_hook;
}
return 0;
err:
kfree(nf_hook);
return ret;
}
static int nh_open(struct inode *inode, struct file *file)
{
struct nh_private *p;
p = kzalloc(sizeof(*p), GFP_KERNEL);
if (!p)
return -ENOMEM;
init_waitqueue_head(&p->wq);
skb_queue_head_init(&p->skb_queue);
file->private_data = p;
return 0;
}
static int nh_release(struct inode *inode, struct file *file)
{
struct nh_private *p = file->private_data;
unsigned long flags;
spin_lock_irqsave(&nh_privs_lock, flags);
if (p->filter) {
list_del(&p->list);
if (p->filter->in)
dev_put(p->filter->in);
if (p->filter->out)
dev_put(p->filter->out);
kfree(p->filter);
}
while (!skb_queue_empty(&p->skb_queue)) {
struct sk_buff *skb;
skb = skb_dequeue(&p->skb_queue);
kfree_skb(skb);
}
if (p->writer) {
if (p->writer->dest_dev)
dev_put(p->writer->dest_dev);
kfree(p->writer);
}
spin_unlock_irqrestore(&nh_privs_lock, flags);
kfree(p);
return 0;
}
static ssize_t nh_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
struct nh_private *p;
struct sk_buff *skb;
int ret;
unsigned long flags;
p = file->private_data;
if (!p->writer) {
return -EBADF;
}
skb = dev_alloc_skb(count + 2);
if (!skb)
return -ENOMEM;
skb_reserve(skb, 2);
if (copy_from_user(skb_put(skb, count), buf, count)) {
kfree_skb(skb);
printk("nh_write: failed copy_from_user %d\n", count);
return -EFAULT;
}
if (p->writer->mode == TO_ROUTING_STACK) {
struct skb_entry *e;
e = kmalloc(sizeof(*e), GFP_ATOMIC);
if (!e) {
kfree_skb(skb);
return -ENOMEM;
}
e->skb = skb;
/* mark this skb as 'ours' */
spin_lock_irqsave(&skb_list_lock, flags);
list_add(&e->list, ¤t_skbs);
spin_unlock_irqrestore(&skb_list_lock, flags);
skb->dev = p->writer->dest_dev; /* needed for <= 2.6.18 */
skb->protocol = eth_type_trans(skb, p->writer->dest_dev);
ret = netif_rx_ni(skb);
} else {
struct net_device *dev;
skb->dev = p->writer->dest_dev;
skb->protocol = be16_to_cpu(0x0800);
skb_pull(skb, sizeof(struct ethhdr));
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,22)
skb_reset_network_header(skb);
#endif
skb->protocol = __constant_htons(ETH_P_IP);
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
if (skb->dev->hard_header)
skb->dev->hard_header(skb, skb->dev, be16_to_cpu(skb->protocol), NULL, skb->dev->dev_addr, skb->len);
#else
dev_hard_header(skb, skb->dev, be16_to_cpu(skb->protocol), NULL, skb->dev->dev_addr, skb->len);
#endif
switch (p->writer->mode) {
case TO_INTERFACE:
dev = skb->dev;
spin_lock_irqsave(&dev->_tx->_xmit_lock, flags);
dev->_tx->xmit_lock_owner = smp_processor_id();
if (!netif_queue_stopped(skb->dev)
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,18)
&& !netif_subqueue_stopped(skb->dev, skb)
#endif
) {
ret = skb->dev->netdev_ops->ndo_start_xmit(skb, skb->dev);
}
dev->_tx->xmit_lock_owner = -1;
spin_unlock_irqrestore(&dev->_tx->_xmit_lock, flags);
break;
case TO_INTERFACE_QUEUE:
ret = dev_queue_xmit(skb);
break;
default:
WARN_ON_ONCE(1);
}
}
return count;
}
static ssize_t nh_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct nh_private *p;
struct sk_buff *skb;
int ret;
unsigned long flags;
if (!count)
return count;
p = file->private_data;
if (!p->filter) {
return -EBADF;
}
wait_skb:
wait_event_interruptible(p->wq, !(skb_queue_empty(&p->skb_queue)));
if (signal_pending(current))
return -ERESTARTSYS;
spin_lock_irqsave(&nh_privs_lock, flags);
skb = skb_dequeue(&p->skb_queue);
spin_unlock_irqrestore(&nh_privs_lock, flags);
if (!skb)
goto wait_skb;
/* Save the dest mac now, it will be lost otherwise */
if (skb_dst(skb) && dst_get_neighbour(skb_dst(skb))) {
struct ethhdr *eth;
skb_push(skb, sizeof(struct ethhdr));
eth = (struct ethhdr *)skb->data;
skb_pull(skb, sizeof(struct ethhdr));
memcpy(eth->h_dest, dst_get_neighbour(skb_dst(skb))->ha, ETH_ALEN);
}
skb_push(skb, ETH_HLEN);
if (skb->len > count) {
kfree_skb(skb);
return -EINVAL;
}
ret = skb->len;
if (copy_to_user(buf, skb->data, skb->len)) {
printk("failed copy_to_user %d\n", skb->len);
kfree_skb(skb);
return -EFAULT;
}
kfree_skb(skb);
return ret;
}
static long nh_ioctl(struct file *file,
unsigned int req, unsigned long pointer)
{
struct nh_private *p;
struct nh_filter *filter;
struct nh_writer *writer;
int ret;
unsigned long flags;
p = file->private_data;
switch (req) {
case NH_SET_FILTER:
filter = kzalloc(sizeof(*filter), GFP_KERNEL);
if (!filter)
return -ENOMEM;
if (copy_from_user(filter, (void __user*)pointer, sizeof(*filter))) {
return -EFAULT;
}
p->filter = filter;
ret = setup_filter(p);
#if 0
printk("Got filter:\n\
u8 proto = %d\n\
u32 saddr = %ld\n\
u32 daddr = %ld\n\
u16 dport = %d\n\
u16 sport = %d\n\
char in_dev[255] = %s\n\
char out_dev[255] = %s\n\
int priority = %d\n\
int hooknum = %d\n\
int flags = %d\n", filter->proto, filter->saddr, filter->daddr, filter->dport, filter->sport,
filter->in_dev, filter->out_dev, filter->priority, filter->hooknum, filter->flags);
#endif
if (!ret) {
spin_lock_irqsave(&nh_privs_lock, flags);
list_add(&p->list, &nh_privs);
spin_unlock_irqrestore(&nh_privs_lock, flags);
} else {
kfree(p->filter);
}
return ret;
case NH_RM_FILTER:
if (p->filter) {
spin_lock_irqsave(&nh_privs_lock, flags);
list_del(&p->list);
spin_unlock_irqrestore(&nh_privs_lock, flags);
kfree(p->filter);
}
return 0;
case NH_SET_WRITE_MODE:
writer = kzalloc(sizeof(*writer), GFP_KERNEL);
if (!writer)
return -ENOMEM;
if (copy_from_user(writer, (void __user *)pointer, sizeof(*writer)))
return -EFAULT;
p->writer = writer;
p->writer->dest_dev = dev_get_by_name(NET_NAMESPACE writer->dest_dev_str);
return 0;
}
return -EINVAL;
}
static const struct file_operations net_hook_fops = {
.owner = THIS_MODULE,
.open = nh_open,
.release = nh_release,
.unlocked_ioctl = nh_ioctl,
.read = nh_read,
.write = nh_write,
};
static struct miscdevice net_hook_dev = {
NH_MINOR,
"net_hook",
&net_hook_fops
};
static int __init nh_init(void)
{
int ret;
ret = misc_register(&net_hook_dev);
if (ret)
printk(KERN_ERR "net_hook: can't misc_register on minor %d\n", NH_MINOR);
printk("hk: module loaded\n");
return ret;
}
module_init(nh_init);
static void __exit nh_exit(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(cb_in_use); i++) {
if (cb_in_use[i]) {
nf_unregister_hook(cb_in_use[i]);
kfree(cb_in_use[i]);
}
}
misc_deregister(&net_hook_dev);
printk("hk: module unloaded\n");
}
module_exit(nh_exit);