[ipt_ACCOUNT] / linux / net / ipv4 / netfilter / ipt_ACCOUNT.c

/*
 * This is a module which is used for counting packets.
 */
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/spinlock.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv4/ip_tables.h>

struct in_device;
#include <net/route.h>
#include <linux/netfilter_ipv4/ipt_ACCOUNT.h>

#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif

struct ipt_account_table *ipt_account_tables = NULL;
struct ipt_account_handle *ipt_account_handles = NULL;
void *ipt_account_tmpbuf = NULL;

// Spinlock used for manipulating the current accounting tables/data
static spinlock_t ipt_account_lock = SPIN_LOCK_UNLOCKED;
// Spinlock used for manipulating userspace handles/snapshot data
static spinlock_t ipt_account_userspace_lock = SPIN_LOCK_UNLOCKED;


/* Recursive free of all data structures */
void ipt_account_data_free(void *data, unsigned char depth)
{
    // Empty data set
    if (!data)
        return;
        
    // Free for 8 bit network
    if (depth == 0)
    {
        free_page((unsigned long)data);
        data = NULL;
        return;
    }
    
    // Free for 16 bit network
    if (depth == 1)
    {
        struct ipt_account_mask_16 *mask_16 = (struct ipt_account_mask_16 *)data;
        unsigned int b;
        for (b=0; b <= 255; b++)
        {
            if (mask_16->mask_24[b] != 0)
            {
                free_page((unsigned long)mask_16->mask_24[b]);
                mask_16->mask_24[b] = NULL;
            }
        }
        free_page((unsigned long)data);
        data = NULL;
        return;
    } 
   
    // Free for 24 bit network
    if (depth == 3)
    {
        unsigned int a, b;
        for (a=0; a <= 255; a++)
        {
            if (((struct ipt_account_mask_8 *)data)->mask_16[a])
            {
                struct ipt_account_mask_16 *mask_16 = (struct ipt_account_mask_16*)((struct ipt_account_mask_8 *)data)->mask_16[a];
                for (b=0; b <= 255; b++)
                {
                    if (mask_16->mask_24[b]) {
                        free_page((unsigned long)mask_16->mask_24[b]);
                        mask_16->mask_24[b] = NULL;
                    }
                }
                free_page((unsigned long)mask_16);
                mask_16 = NULL;
            }
        }
        free_page((unsigned long)data);
        data = NULL;
        return;
    }
    
    printk("ACCOUNT: ipt_account_data_free called with unknown depth: %d\n", depth);
    return;
}

/* Look for existing table / insert new one. Return internal ID or -1 on error */
int ipt_account_table_insert(char *name, unsigned int ip, unsigned int netmask)
{
    unsigned int i;

    DEBUGP("ACCOUNT: ipt_account_table_insert: %s, %u.%u.%u.%u/%u.%u.%u.%u\n", name, NIPQUAD(ip), NIPQUAD(netmask));

    // Look for existing table
    for (i = 0; i < ACCOUNT_MAX_TABLES; i++)
    {
        if (strncmp(ipt_account_tables[i].name, name, ACCOUNT_TABLE_NAME_LEN) == 0)
        {
            DEBUGP("ACCOUNT: Found existing slot: %d - %u.%u.%u.%u/%u.%u.%u.%u\n", i,
                   NIPQUAD(ipt_account_tables[i].ip), NIPQUAD(ipt_account_tables[i].netmask));
            
            if (ipt_account_tables[i].ip != ip || ipt_account_tables[i].netmask != netmask)
            {
                printk("ACCOUNT: Table %s found, but IP/netmask mismatch. IP/netmask found: %u.%u.%u.%u/%u.%u.%u.%u\n",
                        name, NIPQUAD(ipt_account_tables[i].ip), NIPQUAD(ipt_account_tables[i].netmask));
                return -1;
            }

            ipt_account_tables[i].refcount++;
            DEBUGP("ACCOUNT: Refcount: %d\n", ipt_account_tables[i].refcount);
            return i;
        }
    }

    // Insert new table
    for (i = 0; i < ACCOUNT_MAX_TABLES; i++)
    {
        // Found free slot
        if (ipt_account_tables[i].name[0] == 0)
        {
            DEBUGP("ACCOUNT: Found free slot: %d\n", i);
        
            strncpy (ipt_account_tables[i].name, name, ACCOUNT_TABLE_NAME_LEN-1);
            
            ipt_account_tables[i].ip = ip;
            ipt_account_tables[i].netmask = netmask;
            
            // Calculate netsize
            unsigned int j, calc_mask, netsize=0;
            calc_mask = htonl(netmask);
            for (j = 31; j > 0; j--)
            {
                if (calc_mask&(1<<j))
                    netsize++;
                else
                    break;
            }
            
            // Calculate depth from netsize
            if (netsize >= 24)
                ipt_account_tables[i].depth = 0;
            else if (netsize >= 16)
                ipt_account_tables[i].depth = 1;
            else if(netsize >= 8)
                ipt_account_tables[i].depth = 2;
            
            printk("ACCOUNT: calculated netsize: %u -> ipt_account_table depth %u\n", netsize, ipt_account_tables[i].depth);
                        
            ipt_account_tables[i].refcount++;
            if ((ipt_account_tables[i].data = (void *)get_zeroed_page(GFP_KERNEL)) == NULL)
            {
                printk("ACCOUNT: out of memory for data of table: %s\n", name);
                memset(&ipt_account_tables[i], 0, sizeof(struct ipt_account_table));
                return -1;
            }
            
            return i;
        }
    }
        
    // No free slot found
    printk("ACCOUNT: No free table slot found (max: %d). Please increase ACCOUNT_MAX_TABLES.\n", ACCOUNT_MAX_TABLES);
    return -1;
}

static int ipt_account_checkentry(const char *tablename,
    const struct ipt_entry *e,
    void *targinfo,
    unsigned int targinfosize,
    unsigned int hook_mask)
{
    struct ipt_account_info *info = targinfo;
    
    if (targinfosize != IPT_ALIGN(sizeof(struct ipt_account_info))) {
        DEBUGP("ACCOUNT: targinfosize %u != %u\n",
                targinfosize, IPT_ALIGN(sizeof(struct ipt_account_info)));
        return 0;
    }

    spin_lock_bh(&ipt_account_lock);
    int table_nr = ipt_account_table_insert(info->table_name, info->net_ip, info->net_mask);
    if (table_nr == -1)
    {
        printk("ACCOUNT: Table insert problem. Aborting\n");
        spin_unlock_bh(&ipt_account_lock);
        return 0;
    }
    // Table nr caching so we don't have to do an extra string compare for every packet
    info->table_nr = table_nr;
    
    spin_unlock_bh(&ipt_account_lock);

    return 1;
}

void ipt_account_deleteentry(void *targinfo, unsigned int targinfosize)
{
    unsigned int i;
    struct ipt_account_info *info = targinfo;
    
    if (targinfosize != IPT_ALIGN(sizeof(struct ipt_account_info))) {
        DEBUGP("ACCOUNT: targinfosize %u != %u\n",
                targinfosize, IPT_ALIGN(sizeof(struct ipt_account_info)));
    }

    spin_lock_bh(&ipt_account_lock);
    
    DEBUGP("ACCOUNT: ipt_account_deleteentry called for table: %s (#%d)\n", info->table_name, info->table_nr);
    
    info->table_nr = -1;    // Set back to original state
    
    // Look for table
    for (i = 0; i < ACCOUNT_MAX_TABLES; i++)
    {
        if (strncmp(ipt_account_tables[i].name, info->table_name, ACCOUNT_TABLE_NAME_LEN) == 0)
        {
            DEBUGP("ACCOUNT: Found table at slot: %d\n", i);
            
            ipt_account_tables[i].refcount--;
            DEBUGP("ACCOUNT: Refcount left: %d\n", ipt_account_tables[i].refcount);

            // Table not needed anymore?
            if (ipt_account_tables[i].refcount == 0)
            {
                DEBUGP("ACCOUNT: Destroying table at slot: %d\n", i);
                ipt_account_data_free(ipt_account_tables[i].data, ipt_account_tables[i].depth);
                memset(&ipt_account_tables[i], 0, sizeof(struct ipt_account_table));
            }
            
            spin_unlock_bh(&ipt_account_lock);
            return;
        }
    }

    // Table not found
    printk("ACCOUNT: Table %s not found for destroy\n", info->table_name);
    spin_unlock_bh(&ipt_account_lock);
}

void ipt_account_depth0_insert(struct ipt_account_mask_24 *mask_24, unsigned int net_ip, unsigned int netmask,
                               unsigned int src_ip, unsigned int dst_ip, unsigned int size, unsigned int *itemcount)
{
    unsigned char is_src = 0, is_dst = 0;
    
    DEBUGP("ACCOUNT: ipt_account_depth0_insert: %u.%u.%u.%u/%u.%u.%u.%u for net %u.%u.%u.%u/%u.%u.%u.%u, size: %u\n",
            NIPQUAD(src_ip), NIPQUAD(dst_ip), NIPQUAD(net_ip), NIPQUAD(netmask), size);
        
    // Check if src/dst is inside our network.
    // Special: net_ip = 0.0.0.0/0 gets stored as src in slot 0
    if (!netmask)
        src_ip = 0;
    if ((net_ip&netmask) == (src_ip&netmask))
        is_src = 1;
    if ((net_ip&netmask) == (dst_ip&netmask) && netmask)
        is_dst = 1;
    
    if (!is_src && !is_dst)
    {
        DEBUGP("ACCOUNT: Skipping packet %u.%u.%u.%u/%u.%u.%u.%u for net %u.%u.%u.%u/%u.%u.%u.%u\n",
                NIPQUAD(src_ip), NIPQUAD(dst_ip), NIPQUAD(net_ip), NIPQUAD(netmask));
        return;
    }
        
    // Check if this entry is new
    char is_src_new_ip = 0, is_dst_new_ip = 0;

    // Calculate array positions
    unsigned char src_slot = (unsigned char)((src_ip&0xFF000000) >> 24);
    unsigned char dst_slot = (unsigned char)((dst_ip&0xFF000000) >> 24);
    
    // Increase size counters
    if (is_src)
    {
        // Calculate network slot
        DEBUGP("ACCOUNT: Calculated SRC 8 bit network slot: %d\n", src_slot);
        if (!mask_24->ip[src_slot].src_packets && !mask_24->ip[src_slot].dst_packets)
            is_src_new_ip = 1;
        
        mask_24->ip[src_slot].src_packets++;
        mask_24->ip[src_slot].src_bytes+=size;
    }
    if (is_dst)
    {
        DEBUGP("ACCOUNT: Calculated DST 8 bit network slot: %d\n", dst_slot);
        if (!mask_24->ip[dst_slot].src_packets && !mask_24->ip[dst_slot].dst_packets)
            is_dst_new_ip = 1;
        
        mask_24->ip[dst_slot].dst_packets++;
        mask_24->ip[dst_slot].dst_bytes+=size;
    }
    
    // Increase itemcounter
    DEBUGP("ACCOUNT: Itemcounter before: %d\n", *itemcount);
    if (src_slot == dst_slot)
    {
        if (is_src_new_ip || is_dst_new_ip) {
            DEBUGP("ACCOUNT: src_slot == dst_slot: %d, %d\n", is_src_new_ip, is_dst_new_ip);
            (*itemcount)++;
        }
    } else {
        if (is_src_new_ip) {
            DEBUGP("ACCOUNT: New src_ip: %u.%u.%u.%u\n", NIPQUAD(src_ip));
            (*itemcount)++;
        }
        if (is_dst_new_ip) {
            DEBUGP("ACCOUNT: New dst_ip: %u.%u.%u.%u\n", NIPQUAD(dst_ip));
            (*itemcount)++;
        }
    }
    DEBUGP("ACCOUNT: Itemcounter after: %d\n", *itemcount);
}

void ipt_account_depth1_insert(struct ipt_account_mask_16 *mask_16, unsigned int net_ip, unsigned int netmask,
                               unsigned int src_ip, unsigned int dst_ip, unsigned int size, unsigned int *itemcount)
{
    // Do we need to process src IP?
    if ((net_ip&netmask) == (src_ip&netmask))
    {
        unsigned char slot = (unsigned char)((src_ip&0x00FF0000) >> 16);
        DEBUGP("ACCOUNT: Calculated SRC 16 bit network slot: %d\n", slot);
        
        // Do we need to create a new mask_24 bucket?
        if (!mask_16->mask_24[slot] && (mask_16->mask_24[slot] = (void *)get_zeroed_page(GFP_KERNEL)) == NULL)
        {
            printk("ACCOUNT: Can't process packet because out of memory!\n");
            return;
        }
        
        ipt_account_depth0_insert((struct ipt_account_mask_24 *)mask_16->mask_24[slot], net_ip, netmask,
                                    src_ip, 0, size, itemcount);
    }
    
    // Do we need to process dst IP?
    if ((net_ip&netmask) == (dst_ip&netmask))
    {
        unsigned char slot = (unsigned char)((dst_ip&0x00FF0000) >> 16);
        DEBUGP("ACCOUNT: Calculated DST 16 bit network slot: %d\n", slot);
        
        // Do we need to create a new mask_24 bucket?
        if (!mask_16->mask_24[slot] && (mask_16->mask_24[slot] = (void *)get_zeroed_page(GFP_KERNEL)) == NULL)
        {
            printk("ACCOUT: Can't process packet because out of memory!\n");
            return;
        }
        
        ipt_account_depth0_insert((struct ipt_account_mask_24 *)mask_16->mask_24[slot], net_ip, netmask,
                                    0, dst_ip, size, itemcount);
    }
}

void ipt_account_depth2_insert(struct ipt_account_mask_8 *mask_8, unsigned int net_ip, unsigned int netmask,
                               unsigned int src_ip, unsigned int dst_ip, unsigned int size, unsigned int *itemcount)
{
    // Do we need to process src IP?
    if ((net_ip&netmask) == (src_ip&netmask))
    {
        unsigned char slot = (unsigned char)((src_ip&0x0000FF00) >> 8);
        DEBUGP("ACCOUNT: Calculated SRC 24 bit network slot: %d\n", slot);
                
        // Do we need to create a new mask_24 bucket?
        if (!mask_8->mask_16[slot] && (mask_8->mask_16[slot] = (void *)get_zeroed_page(GFP_KERNEL)) == NULL)
        {
            printk("ACCOUNT: Can't process packet because out of memory!\n");
            return;
        }
        
        ipt_account_depth1_insert((struct ipt_account_mask_16 *)mask_8->mask_16[slot], net_ip, netmask,
                                    src_ip, 0, size, itemcount);
    }
    
    // Do we need to process dst IP?
    if ((net_ip&netmask) == (dst_ip&netmask))
    {
        unsigned char slot = (unsigned char)((dst_ip&0x0000FF00) >> 8);
        DEBUGP("ACCOUNT: Calculated DST 24 bit network slot: %d\n", slot);
        
        // Do we need to create a new mask_24 bucket?
        if (!mask_8->mask_16[slot] && (mask_8->mask_16[slot] = (void *)get_zeroed_page(GFP_KERNEL)) == NULL)
        {
            printk("ACCOUNT: Can't process packet because out of memory!\n");
            return;
        }
        
        ipt_account_depth1_insert((struct ipt_account_mask_16 *)mask_8->mask_16[slot], net_ip, netmask,
                                    0, dst_ip, size, itemcount);
    }
}

static unsigned int ipt_account_target(struct sk_buff **pskb,
    unsigned int hooknum,
    const struct net_device *in,
    const struct net_device *out,
    const void *targinfo,
    void *userinfo)
{
    const struct ipt_account_info *info = (const struct ipt_account_info *)targinfo;
    unsigned int src_ip = (*pskb)->nh.iph->saddr;
    unsigned int dst_ip = (*pskb)->nh.iph->daddr;
    unsigned int size = ntohs((*pskb)->nh.iph->tot_len);
    
    spin_lock_bh(&ipt_account_lock);
    
    if (ipt_account_tables[info->table_nr].name[0] == 0)
    {
        printk("ACCOUNT: ipt_account_target: Invalid table id %u. IPs %u.%u.%u.%u/%u.%u.%u.%u\n",
               info->table_nr, NIPQUAD(src_ip), NIPQUAD(dst_ip));
        spin_unlock_bh(&ipt_account_lock);
        return IPT_CONTINUE;
    }
    
    // 8 bit network or "any" network
    if (ipt_account_tables[info->table_nr].depth == 0)
    {
        // Count packet and check if the IP is new
        ipt_account_depth0_insert((struct ipt_account_mask_24 *)ipt_account_tables[info->table_nr].data,
                                  ipt_account_tables[info->table_nr].ip, ipt_account_tables[info->table_nr].netmask,
                                  src_ip, dst_ip, size, &ipt_account_tables[info->table_nr].itemcount);
        spin_unlock_bh(&ipt_account_lock);
        return IPT_CONTINUE;
    }    
    
    // 16 bit network
    if (ipt_account_tables[info->table_nr].depth == 1)
    {
        ipt_account_depth1_insert((struct ipt_account_mask_16 *)ipt_account_tables[info->table_nr].data,
                                  ipt_account_tables[info->table_nr].ip, ipt_account_tables[info->table_nr].netmask,
                                  src_ip, dst_ip, size, &ipt_account_tables[info->table_nr].itemcount);
        spin_unlock_bh(&ipt_account_lock);
        return IPT_CONTINUE;
    }
    
    // 24 bit network
    if (ipt_account_tables[info->table_nr].depth == 2)
    {
        ipt_account_depth2_insert((struct ipt_account_mask_8 *)ipt_account_tables[info->table_nr].data,
                                  ipt_account_tables[info->table_nr].ip, ipt_account_tables[info->table_nr].netmask,
                                  src_ip, dst_ip, size, &ipt_account_tables[info->table_nr].itemcount);
        spin_unlock_bh(&ipt_account_lock);
        return IPT_CONTINUE;
    }
    
    printk("ACCOUNT: ipt_account_target: Unable to process packet. Table id %u. IPs %u.%u.%u.%u/%u.%u.%u.%u\n",
            info->table_nr, NIPQUAD(src_ip), NIPQUAD(dst_ip));
    
    spin_unlock_bh(&ipt_account_lock);
    return IPT_CONTINUE;
}

/*
    Functions dealing with "handles":
    Handles are snapshots of a accounting state.
    
    read snapshots are only for debugging the code
    and are very expensive concerning speed/memory
    compared to read_and_flush.
    
    The functions aren't protected by spinlocks themselves
    as this is done in the ioctl part of the code.
*/

/*
    Find a free handle slot. Normally only one should be used,
    but there could be two or more applications accessing the data
    at the same time.
*/
int ipt_account_handle_find_slot(void)
{
    unsigned int i;
    // Insert new table
    for (i = 0; i < ACCOUNT_MAX_HANDLES; i++)
    {
        // Found free slot
        if (ipt_account_handles[i].data == NULL)
        {
            // Don't "mark" data as used as we are protected by a spinlock by the calling function.
            // handle_find_slot() is only a function to prevent code duplication.
            return i;
        }
    }
        
    // No free slot found
    printk("ACCOUNT: No free handle slot found (max: %u). Please increase ACCOUNT_MAX_HANDLES.\n", ACCOUNT_MAX_HANDLES);
    return -1;
}

int ipt_account_handle_free(unsigned int handle)
{
    if (handle >= ACCOUNT_MAX_HANDLES)
    {
        printk("ACCOUNT: Invalid handle for ipt_account_handle_free() specified: %u\n", handle);
        return -EINVAL;
    }
    
    ipt_account_data_free(ipt_account_handles[handle].data, ipt_account_handles[handle].depth);
    memset (&ipt_account_handles[handle], 0, sizeof (struct ipt_account_handle));
    return 0;
}

/* Prepare data for read without flush. Use only for debugging!
   Real applications should use read&flush as it's way more efficent */
int ipt_account_handle_prepare_read(char *tablename, unsigned int *count)
{
    int handle, i, table_nr=-1;
    
    for (i = 0; i < ACCOUNT_MAX_TABLES; i++)
        if (strncmp(ipt_account_tables[i].name, tablename, ACCOUNT_TABLE_NAME_LEN) == 0)
        {
            table_nr = i;
            break;
        }

    if (table_nr == -1)
    {
        printk("ACCOUNT: ipt_account_handle_prepare_read(): Table %s not found\n", tablename);
        return -1;
    }
            
    // Can't find a free handle slot?
    if ((handle = ipt_account_handle_find_slot()) == -1)
        return -1;
    
    // Fill up handle structure
    ipt_account_handles[handle].ip = ipt_account_tables[table_nr].ip;
    ipt_account_handles[handle].depth = ipt_account_tables[table_nr].depth;
    ipt_account_handles[handle].itemcount = ipt_account_tables[table_nr].itemcount;
    
    // allocate "root" table
    if ((ipt_account_handles[handle].data = (void*)get_zeroed_page(GFP_KERNEL)) == NULL)
    {
        printk("ACCOUNT: out of memory for root table in ipt_account_handle_prepare_read()\n");
        memset (&ipt_account_handles[handle], 0, sizeof(struct ipt_account_handle));
        return -1;        
    }
    
    // Recursive copy of complete data structure
    unsigned int depth = ipt_account_handles[handle].depth;
    if (depth == 0)
    {
        memcpy(ipt_account_handles[handle].data, ipt_account_tables[table_nr].data, sizeof(struct ipt_account_mask_24));
    } else if (depth == 1) {
        struct ipt_account_mask_16 *src_16 = (struct ipt_account_mask_16 *)ipt_account_tables[table_nr].data;
        struct ipt_account_mask_16 *network_16 = (struct ipt_account_mask_16 *)ipt_account_handles[handle].data;
        unsigned int b;
        
        for (b = 0; b <= 255; b++)
        {
            if (src_16->mask_24[b])
            {
                if ((network_16->mask_24[b] = (void*)get_zeroed_page(GFP_KERNEL)) == NULL)
                {
                    printk("ACCOUNT: out of memory during copy of 16 bit network in ipt_account_handle_prepare_read()\n");
                    ipt_account_data_free(ipt_account_handles[handle].data, depth);
                    memset (&ipt_account_handles[handle], 0, sizeof(struct ipt_account_handle));
                    return -1;                    
                }
                
                memcpy(network_16->mask_24[b], src_16->mask_24[b], sizeof(struct ipt_account_mask_24));
            }
        }
    } else if(depth == 2) {
        struct ipt_account_mask_8 *src_8 = (struct ipt_account_mask_8 *)ipt_account_tables[table_nr].data;
        struct ipt_account_mask_8 *network_8 = (struct ipt_account_mask_8 *)ipt_account_handles[handle].data;
        unsigned int a;
        
        for (a = 0; a <= 255; a++)
        {
            if (src_8->mask_16[a])
            {
                if ((network_8->mask_16[a] = (void*)get_zeroed_page(GFP_KERNEL)) == NULL)
                {
                    printk("ACCOUNT: out of memory during copy of 24 bit network in ipt_account_handle_prepare_read()\n");
                    ipt_account_data_free(ipt_account_handles[handle].data, depth);
                    memset (&ipt_account_handles[handle], 0, sizeof(struct ipt_account_handle));
                    return -1;                    
                }

                memcpy(network_8->mask_16[a], src_8->mask_16[a], sizeof(struct ipt_account_mask_16));
                    
                struct ipt_account_mask_16 *src_16 = src_8->mask_16[a];
                struct ipt_account_mask_16 *network_16 = network_8->mask_16[a];
                unsigned int b;
                
                for (b = 0; b <= 255; b++)
                {
                    if (src_16->mask_24[b])
                    {
                        if ((network_16->mask_24[b] = (void*)get_zeroed_page(GFP_KERNEL)) == NULL)
                        {
                            printk("ACCOUNT: out of memory during copy of 16 bit network in ipt_account_handle_prepare_read()\n");
                            ipt_account_data_free(ipt_account_handles[handle].data, depth);
                            memset (&ipt_account_handles[handle], 0, sizeof(struct ipt_account_handle));
                            return -1;                    
                        }
                        
                        memcpy(network_16->mask_24[b], src_16->mask_24[b], sizeof(struct ipt_account_mask_24));
                    }
                }
            }
        }
    }

    *count = ipt_account_tables[table_nr].itemcount;
    return handle;
}

/* Prepare data for read and flush it */
int ipt_account_handle_prepare_read_flush(char *tablename, unsigned int *count)
{
    int handle, i, table_nr=-1;
    
    for (i = 0; i < ACCOUNT_MAX_TABLES; i++)
        if (strncmp(ipt_account_tables[i].name, tablename, ACCOUNT_TABLE_NAME_LEN) == 0)
        {
            table_nr = i;
            break;
        }

    if (table_nr == -1)
    {
        printk("ACCOUNT: ipt_account_handle_prepare_read_flush(): Table %s not found\n", tablename);
        return -1;
    }
            
    // Can't find a free handle slot?
    if ((handle = ipt_account_handle_find_slot()) == -1)
        return -1;
    
    // Fill up handle structure
    ipt_account_handles[handle].ip = ipt_account_tables[table_nr].ip;
    ipt_account_handles[handle].depth = ipt_account_tables[table_nr].depth;
    ipt_account_handles[handle].itemcount = ipt_account_tables[table_nr].itemcount;
    ipt_account_handles[handle].data = ipt_account_tables[table_nr].data;
    *count = ipt_account_tables[table_nr].itemcount;

    // "Flush" table data
    ipt_account_tables[table_nr].data = (void*)get_zeroed_page(GFP_KERNEL);
    ipt_account_tables[table_nr].itemcount = 0;

    return handle;
}

/* Copy the actual that into a prepared buffer.
   We only copy entries != 0 to increase performance.
   The memory gets freed again in ipt_account_handle_free().
*/
int ipt_account_handle_get_data(unsigned int handle, void *buffer)
{
    struct ipt_account_handle_ip handle_ip;    
    unsigned int handle_ip_size = sizeof (struct ipt_account_handle_ip);
    unsigned int i, tmpbuf_pos=0;

    if (handle >= ACCOUNT_MAX_HANDLES)
    {
        printk("ACCOUNT: invalid handle for ipt_account_handle_get_data() specified: %u\n", handle);
        return -1;
    }
    
    if (ipt_account_handles[handle].data == NULL)
    {
        printk("ACCOUNT: handle %u is BROKEN: Contains no data\n", handle);
        return -1;
    }
    
    unsigned int net_ip = ipt_account_handles[handle].ip;
    unsigned int depth = ipt_account_handles[handle].depth;
    
    // 8 bit network
    if (depth == 0)
    {
        struct ipt_account_mask_24 *network = (struct ipt_account_mask_24*)ipt_account_handles[handle].data;
        for (i = 0; i <= 255; i++)
        {
            if (network->ip[i].src_packets || network->ip[i].dst_packets)
            {
                handle_ip.ip = net_ip | (i<<24);
                handle_ip.src_packets = network->ip[i].src_packets;
                handle_ip.src_bytes = network->ip[i].src_bytes;
                handle_ip.dst_packets = network->ip[i].dst_packets;
                handle_ip.dst_bytes = network->ip[i].dst_bytes;

                // Temporary buffer full? Flush to userspace
                if (tmpbuf_pos+handle_ip_size >= PAGE_SIZE)
                {
                    copy_to_user(buffer, ipt_account_tmpbuf, tmpbuf_pos);
                    tmpbuf_pos = 0;
                }
                memcpy(ipt_account_tmpbuf+tmpbuf_pos, &handle_ip, handle_ip_size);
                tmpbuf_pos += handle_ip_size;
            }
        }

        // Flush remaining data to userspace
        if (tmpbuf_pos)
            copy_to_user(buffer, ipt_account_tmpbuf, tmpbuf_pos);
        
        return 0;
    }
    
    // 16 bit network
    if (depth == 1)
    {
        struct ipt_account_mask_16 *network_16 = (struct ipt_account_mask_16*)ipt_account_handles[handle].data;
        unsigned int b;
        for (b = 0; b <= 255; b++)
        {
            if (network_16->mask_24[b])
            {
                struct ipt_account_mask_24 *network = (struct ipt_account_mask_24*)network_16->mask_24[b];
                for (i = 0; i <= 255; i++)
                {
                    if (network->ip[i].src_packets || network->ip[i].dst_packets)
                    {
                        handle_ip.ip = net_ip | (b << 16) | (i<<24);
                        handle_ip.src_packets = network->ip[i].src_packets;
                        handle_ip.src_bytes = network->ip[i].src_bytes;
                        handle_ip.dst_packets = network->ip[i].dst_packets;
                        handle_ip.dst_bytes = network->ip[i].dst_bytes;
        
                        // Temporary buffer full? Flush to userspace
                        if (tmpbuf_pos+handle_ip_size >= PAGE_SIZE)
                        {
                            copy_to_user(buffer, ipt_account_tmpbuf, tmpbuf_pos);
                            tmpbuf_pos = 0;
                        }
                        memcpy(ipt_account_tmpbuf+tmpbuf_pos, &handle_ip, handle_ip_size);
                        tmpbuf_pos += handle_ip_size;
                    }
                }
            }
        }
        
        // Flush remaining data to userspace
        if (tmpbuf_pos)
            copy_to_user(buffer, ipt_account_tmpbuf, tmpbuf_pos);
        
        return 0;
    }
    
    // 24 bit network
    if (depth == 2)
    {
        struct ipt_account_mask_8 *network_8 = (struct ipt_account_mask_8*)ipt_account_handles[handle].data;
        unsigned int a, b;
        for (a = 0; a <= 255; a++)
        {
            if (network_8->mask_16[a])
            {
                struct ipt_account_mask_16 *network_16 = (struct ipt_account_mask_16*)network_8->mask_16[a];
                for (b = 0; b <= 255; b++)
                {
                    if (network_16->mask_24[b])
                    {
                        struct ipt_account_mask_24 *network = (struct ipt_account_mask_24*)network_16->mask_24[b];
                        for (i = 0; i <= 255; i++)
                        {
                            if (network->ip[i].src_packets || network->ip[i].dst_packets)
                            {
                                handle_ip.ip = net_ip | (a << 8) | (b << 16) | (i<<24);
                                handle_ip.src_packets = network->ip[i].src_packets;
                                handle_ip.src_bytes = network->ip[i].src_bytes;
                                handle_ip.dst_packets = network->ip[i].dst_packets;
                                handle_ip.dst_bytes = network->ip[i].dst_bytes;
                
                                // Temporary buffer full? Flush to userspace
                                if (tmpbuf_pos+handle_ip_size >= PAGE_SIZE)
                                {
                                    copy_to_user(buffer, ipt_account_tmpbuf, tmpbuf_pos);
                                    tmpbuf_pos = 0;
                                }
                                memcpy(ipt_account_tmpbuf+tmpbuf_pos, &handle_ip, handle_ip_size);
                                tmpbuf_pos += handle_ip_size;
                            }
                        }
                    }
                }
            }
        }
        
        // Flush remaining data to userspace
        if (tmpbuf_pos)
            copy_to_user(buffer, ipt_account_tmpbuf, tmpbuf_pos);
        
        return 0;
    }
    
    return -1;
}

static int ipt_account_set_ctl(struct sock *sk, int cmd, void *user, unsigned int len)
{
    struct ipt_account_handle_sockopt handle;
    int ret = -EINVAL;

    if (!capable(CAP_NET_ADMIN))
            return -EPERM;
            
    switch (cmd)
    {
        case IPT_SO_SET_ACCOUNT_HANDLE_FREE:
            if (len != sizeof(struct ipt_account_handle_sockopt))
            {
                printk("ACCOUNT: ipt_account_set_ctl: wrong data size (%u != %u) for IPT_SO_SET_HANDLE_FREE\n", len, sizeof(struct ipt_account_handle_sockopt));
                break;
            }   
            
            if (copy_from_user (&handle, user, len))
            {
                printk("ACCOUNT: ipt_account_set_ctl: copy_from_user failed for IPT_SO_SET_HANDLE_FREE\n");
                break;
            }
            
            spin_lock_bh(&ipt_account_userspace_lock);
            ret = ipt_account_handle_free(handle.handle_nr);
            spin_unlock_bh(&ipt_account_userspace_lock);
            break;
        case IPT_SO_SET_ACCOUNT_HANDLE_FREE_ALL:
        {
            unsigned int i;
            spin_lock_bh(&ipt_account_userspace_lock);
            for (i = 0; i < ACCOUNT_MAX_HANDLES; i++)
                ipt_account_handle_free(i);
            spin_unlock_bh(&ipt_account_userspace_lock);
            ret = 0;
            break;
        }
        default:
            printk("ACCOUNT: ipt_account_set_ctl: unknown request %i\n", cmd);
    }

    return ret;
}

static int ipt_account_get_ctl(struct sock *sk, int cmd, void *user, int *len)
{
    struct ipt_account_handle_sockopt handle;
    int ret = -EINVAL;

    if (!capable(CAP_NET_ADMIN))
            return -EPERM;

    switch (cmd)
    {
        case IPT_SO_GET_ACCOUNT_PREPARE_READ_FLUSH:
        case IPT_SO_GET_ACCOUNT_PREPARE_READ:
            if (*len < sizeof(struct ipt_account_handle_sockopt))
            {
                printk("ACCOUNT: ipt_account_get_ctl: wrong data size (%u != %u) for IPT_SO_GET_ACCOUNT_PREPARE_READ/READ_FLUSH\n",
                       *len, sizeof(struct ipt_account_handle_sockopt));
                break;
            }   
            
            if (copy_from_user (&handle, user, sizeof(struct ipt_account_handle_sockopt)))
            {
                printk("ACCOUNT: ipt_account_get_ctl: copy_from_user failed for IPT_SO_GET_ACCOUNT_PREPARE_READ/READ_FLUSH\n");
                break;
            }
            
            spin_lock_bh(&ipt_account_lock);
            spin_lock_bh(&ipt_account_userspace_lock);
            if (cmd == IPT_SO_GET_ACCOUNT_PREPARE_READ_FLUSH)
                handle.handle_nr = ipt_account_handle_prepare_read_flush(handle.name, &handle.itemcount);
            else
                handle.handle_nr = ipt_account_handle_prepare_read(handle.name, &handle.itemcount);
            spin_unlock_bh(&ipt_account_userspace_lock);
            spin_unlock_bh(&ipt_account_lock);
                
            if (handle.handle_nr == -1)
            {
                printk("ACCOUNT: ipt_account_get_ctl: ipt_account_handle_prepare_read failed\n");
                break;
            }
            
            if (copy_to_user(user, &handle, sizeof(struct ipt_account_handle_sockopt)))
            {
                printk("ACCOUNT: ipt_account_set_ctl: copy_to_user failed for IPT_SO_GET_ACCOUNT_PREPARE_READ/READ_FLUSH\n");
                break;
            }
            ret = 0;
            break;
        case IPT_SO_GET_ACCOUNT_GET_DATA:
            if (*len < sizeof(struct ipt_account_handle_sockopt))
            {
                printk("ACCOUNT: ipt_account_get_ctl: wrong data size (%u != %u) for IPT_SO_GET_ACCOUNT_PREPARE_READ/READ_FLUSH\n",
                       *len, sizeof(struct ipt_account_handle_sockopt));
                break;
            }   
            
            if (copy_from_user (&handle, user, sizeof(struct ipt_account_handle_sockopt)))
            {
                printk("ACCOUNT: ipt_account_get_ctl: copy_from_user failed for IPT_SO_GET_ACCOUNT_PREPARE_READ/READ_FLUSH\n");
                break;
            }
            
            if (handle.handle_nr >= ACCOUNT_MAX_HANDLES)
            {
                printk("ACCOUNT: Invalid handle for IPT_SO_GET_ACCOUNT_GET_DATA: %u\n", handle.handle_nr);
                break;
            }
            
            if (*len < ipt_account_handles[handle.handle_nr].itemcount*sizeof(struct ipt_account_handle_ip))
            {
                printk("ACCOUNT: ipt_account_get_ctl: not enough space (%u < %u) to store data from IPT_SO_GET_ACCOUNT_GET_DATA\n",
                       *len, ipt_account_handles[handle.handle_nr].itemcount*sizeof(struct ipt_account_handle_ip));
                ret = -ENOMEM;
                break;
            }   
            
            spin_lock_bh(&ipt_account_userspace_lock);
            ret = ipt_account_handle_get_data(handle.handle_nr, user);
            spin_unlock_bh(&ipt_account_userspace_lock);
            if (ret)
            {
                printk("ACCOUNT: ipt_account_get_ctl: ipt_account_handle_get_data failed for handle %u\n", handle.handle_nr);
                break;
            }
            
            ret = 0;
            break;
        case IPT_SO_GET_ACCOUNT_GET_HANDLE_USAGE:
        {
            if (*len < sizeof(struct ipt_account_handle_sockopt))
            {
                printk("ACCOUNT: ipt_account_get_ctl: wrong data size (%u != %u) for IPT_SO_GET_ACCOUNT_GET_HANDLE_USAGE\n",
                       *len, sizeof(struct ipt_account_handle_sockopt));
                break;
            }   
            
            // Find out how many handles are in use
            unsigned int i;
            handle.itemcount = 0;
            spin_lock_bh(&ipt_account_userspace_lock);
            for (i = 0; i < ACCOUNT_MAX_HANDLES; i++)
                if (ipt_account_handles[i].data)
                    handle.itemcount++;
            spin_unlock_bh(&ipt_account_userspace_lock);
            
            if (copy_to_user(user, &handle, sizeof(struct ipt_account_handle_sockopt)))
            {
                printk("ACCOUNT: ipt_account_set_ctl: copy_to_user failed for IPT_SO_GET_ACCOUNT_GET_HANDLE_USAGE\n");
                break;
            }
            ret = 0;
            break;
        }
        case IPT_SO_GET_ACCOUNT_GET_TABLE_NAMES:
        {
            spin_lock_bh(&ipt_account_lock);
            
            // Determine size of table names
            unsigned int size = 0, i;
            for (i = 0; i < ACCOUNT_MAX_TABLES; i++)
            {
                if (ipt_account_tables[i].name[0] != 0)
                    size += strlen (ipt_account_tables[i].name) + 1;
            }
            size += 1;    // Terminating NULL character
            
            if (*len < size)
            {
                spin_unlock_bh(&ipt_account_lock);
                printk("ACCOUNT: ipt_account_get_ctl: not enough space (%u < %u) to store table names\n", *len, size);
                ret = -ENOMEM;
                break;
            }
            // Copy table names to userspace
            char *tnames = user;
            for (i = 0; i < ACCOUNT_MAX_TABLES; i++)
            {
                if (ipt_account_tables[i].name[0] != 0)
                {
                    int len = strlen (ipt_account_tables[i].name) + 1;
                    copy_to_user(tnames, ipt_account_tables[i].name, len);    // copy string + terminating zero
                    tnames += len;
                }
            }
            // Append terminating zero
            i = 0;
            copy_to_user(tnames, &i, 1);    
            spin_unlock_bh(&ipt_account_lock);
            ret = 0;
            break;
        }
        default:
            printk("ACCOUNT: ipt_account_get_ctl: unknown request %i\n", cmd);
    }

    return ret;
}

static struct ipt_target ipt_account_reg
= { { NULL, NULL }, "ACCOUNT", ipt_account_target, ipt_account_checkentry, ipt_account_deleteentry, 
    THIS_MODULE };

static struct nf_sockopt_ops ipt_account_sockopts
= { { NULL, NULL }, PF_INET, IPT_SO_SET_ACCOUNT_HANDLE_FREE, IPT_SO_SET_ACCOUNT_MAX+1, ipt_account_set_ctl,
    IPT_SO_GET_ACCOUNT_PREPARE_READ, IPT_SO_GET_ACCOUNT_MAX+1, ipt_account_get_ctl, 0, NULL  };
    
static int __init init(void)
{
    if (PAGE_SIZE < 4096)
    {
        printk("ACCOUNT: Sorry we need at least a PAGE_SIZE of 4096. Found: %lu\n", PAGE_SIZE);
        return -EINVAL;
    }

    if ((ipt_account_tables = kmalloc(ACCOUNT_MAX_TABLES*sizeof(struct ipt_account_table), GFP_KERNEL)) == NULL)
    {
        printk("ACCOUNT: Out of memory allocating account_tables structure");
        return -EINVAL;
    }
    memset(ipt_account_tables, 0, ACCOUNT_MAX_TABLES*sizeof(struct ipt_account_table));
                            
    if ((ipt_account_handles = kmalloc(ACCOUNT_MAX_HANDLES*sizeof(struct ipt_account_handle), GFP_KERNEL)) == NULL)
    {
        printk("ACCOUNT: Out of memory allocating account_handles structure");
        kfree (ipt_account_tables);
        ipt_account_tables = NULL;
        return -EINVAL;
    }
    memset(ipt_account_handles, 0, ACCOUNT_MAX_HANDLES*sizeof(struct ipt_account_handle));

    // Allocate one page as temporary storage
    if ((ipt_account_tmpbuf = (void*)__get_free_page(GFP_KERNEL)) == NULL)
    {
        printk("ACCOUNT: Out of memory for temporary buffer page\n");
        kfree(ipt_account_tables);
        kfree(ipt_account_handles);
        ipt_account_tables = NULL;
        ipt_account_handles = NULL;
        return -EINVAL;
    }
    
    /* Register setsockopt */
    if (nf_register_sockopt(&ipt_account_sockopts) < 0)
    {
        printk("ACCOUNT: Can't register sockopts. Aborting\n");
        
        kfree(ipt_account_tables);
        kfree(ipt_account_handles);
        free_page((unsigned long)ipt_account_tmpbuf);
        ipt_account_tables = NULL;
        ipt_account_handles = NULL;
        ipt_account_tmpbuf = NULL;
        
        return -EINVAL;
    }
    
    if (ipt_register_target(&ipt_account_reg))
            return -EINVAL;

    return 0;
}

static void __exit fini(void)
{
    ipt_unregister_target(&ipt_account_reg);

    nf_unregister_sockopt(&ipt_account_sockopts);
    
    kfree(ipt_account_tables);
    kfree(ipt_account_handles);
    free_page((unsigned long)ipt_account_tmpbuf);
    
    ipt_account_tables = NULL;
    ipt_account_handles = NULL;
    ipt_account_tmpbuf = NULL;
}

module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");