/* netfilter.c: look after the filters for various protocols.
 * Heavily influenced by the old firewall.c by David Bonn and Alan Cox.
 *
 * Thanks to Rob `CmdrTaco' Malda for not influencing this code in any
 * way.
 *
 * Rusty Russell (C)2000 -- This code is GPL.
 */
#include <linux/kernel.h>
#include <linux/netfilter.h>
#include <net/protocol.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/wait.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/if.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/proc_fs.h>
#include <linux/mutex.h>
#include <net/net_namespace.h>
#include <net/sock.h>

#include "nf_internals.h"

static DEFINE_MUTEX(afinfo_mutex);

struct nf_afinfo *nf_afinfo[NPROTO] __read_mostly;
EXPORT_SYMBOL(nf_afinfo);

int nf_register_afinfo(struct nf_afinfo *afinfo)
{
        int err;

        err = mutex_lock_interruptible(&afinfo_mutex);
        if (err < 0)
                return err;
        rcu_assign_pointer(nf_afinfo[afinfo->family], afinfo);
        mutex_unlock(&afinfo_mutex);
        return 0;
}
EXPORT_SYMBOL_GPL(nf_register_afinfo);

void nf_unregister_afinfo(struct nf_afinfo *afinfo)
{
        mutex_lock(&afinfo_mutex);
        rcu_assign_pointer(nf_afinfo[afinfo->family], NULL);
        mutex_unlock(&afinfo_mutex);
        synchronize_rcu();
}
EXPORT_SYMBOL_GPL(nf_unregister_afinfo);

/* In this code, we can be waiting indefinitely for userspace to
 * service a packet if a hook returns NF_QUEUE.  We could keep a count
 * of skbuffs queued for userspace, and not deregister a hook unless
 * this is zero, but that sucks.  Now, we simply check when the
 * packets come back: if the hook is gone, the packet is discarded. */
struct list_head nf_hooks[NPROTO][NF_MAX_HOOKS] __read_mostly;
EXPORT_SYMBOL(nf_hooks);
static DEFINE_MUTEX(nf_hook_mutex);

int nf_register_hook(struct nf_hook_ops *reg)
{
        struct list_head *i;
        int err;

        err = mutex_lock_interruptible(&nf_hook_mutex);
        if (err < 0)
                return err;
        list_for_each(i, &nf_hooks[reg->pf][reg->hooknum]) {
                if (reg->priority < ((struct nf_hook_ops *)i)->priority)
                        break;
        }
        list_add_rcu(&reg->list, i->prev);
        mutex_unlock(&nf_hook_mutex);
        return 0;
}
EXPORT_SYMBOL(nf_register_hook);

void nf_unregister_hook(struct nf_hook_ops *reg)
{
        mutex_lock(&nf_hook_mutex);
        list_del_rcu(&reg->list);
        mutex_unlock(&nf_hook_mutex);

        synchronize_net();
}
EXPORT_SYMBOL(nf_unregister_hook);

int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
{
        unsigned int i;
        int err = 0;

        for (i = 0; i < n; i++) {
                err = nf_register_hook(&reg[i]);
                if (err)
                        goto err;
        }
        return err;

err:
        if (i > 0)
                nf_unregister_hooks(reg, i);
        return err;
}
EXPORT_SYMBOL(nf_register_hooks);

void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
{
        unsigned int i;

        for (i = 0; i < n; i++)
                nf_unregister_hook(&reg[i]);
}
EXPORT_SYMBOL(nf_unregister_hooks);

unsigned int nf_iterate(struct list_head *head,
                        struct sk_buff *skb,
                        int hook,
                        const struct net_device *indev,
                        const struct net_device *outdev,
                        struct list_head **i,
                        int (*okfn)(struct sk_buff *),
                        int hook_thresh)
{
        unsigned int verdict;

        /*
         * The caller must not block between calls to this
         * function because of risk of continuing from deleted element.
         */
        list_for_each_continue_rcu(*i, head) {
                struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;

                if (hook_thresh > elem->priority)
                        continue;

                /* Optimization: we don't need to hold module
                   reference here, since function can't sleep. --RR */
                verdict = elem->hook(hook, skb, indev, outdev, okfn);
                if (verdict != NF_ACCEPT) {
#ifdef CONFIG_NETFILTER_DEBUG
                        if (unlikely((verdict & NF_VERDICT_MASK)
                                                        > NF_MAX_VERDICT)) {
                                NFDEBUG("Evil return from %p(%u).\n",
                                        elem->hook, hook);
                                continue;
                        }
#endif
                        if (verdict != NF_REPEAT)
                                return verdict;
                        *i = (*i)->prev;
                }
        }
        return NF_ACCEPT;
}


/* Returns 1 if okfn() needs to be executed by the caller,
 * -EPERM for NF_DROP, 0 otherwise. */
int nf_hook_slow(int pf, unsigned int hook, struct sk_buff *skb,
                 struct net_device *indev,
                 struct net_device *outdev,
                 int (*okfn)(struct sk_buff *),
                 int hook_thresh)
{
        struct list_head *elem;
        unsigned int verdict;
        int ret = 0;

        /* We may already have this, but read-locks nest anyway */
        rcu_read_lock();

        elem = &nf_hooks[pf][hook];
next_hook:
        verdict = nf_iterate(&nf_hooks[pf][hook], skb, hook, indev,
                             outdev, &elem, okfn, hook_thresh);
        if (verdict == NF_ACCEPT || verdict == NF_STOP) {
                ret = 1;
                goto unlock;
        } else if (verdict == NF_DROP) {
                kfree_skb(skb);
                ret = -EPERM;
        } else if ((verdict & NF_VERDICT_MASK)  == NF_QUEUE) {
                NFDEBUG("nf_hook: Verdict = QUEUE.\n");
                if (!nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
                              verdict >> NF_VERDICT_BITS))
                        goto next_hook;
        }
unlock:
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL(nf_hook_slow);


int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
{
        if (writable_len > skb->len)
                return 0;

        /* Not exclusive use of packet?  Must copy. */
        if (!skb_cloned(skb)) {
                if (writable_len <= skb_headlen(skb))
                        return 1;
        } else if (skb_clone_writable(skb, writable_len))
                return 1;

        if (writable_len <= skb_headlen(skb))
                writable_len = 0;
        else
                writable_len -= skb_headlen(skb);

        return !!__pskb_pull_tail(skb, writable_len);
}
EXPORT_SYMBOL(skb_make_writable);

void nf_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
                            __be32 from, __be32 to, int pseudohdr)
{
        __be32 diff[] = { ~from, to };
        if (skb->ip_summed != CHECKSUM_PARTIAL) {
                *sum = csum_fold(csum_partial(diff, sizeof(diff),
                                ~csum_unfold(*sum)));
                if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
                        skb->csum = ~csum_partial(diff, sizeof(diff),
                                                ~skb->csum);
        } else if (pseudohdr)
                *sum = ~csum_fold(csum_partial(diff, sizeof(diff),
                                csum_unfold(*sum)));
}
EXPORT_SYMBOL(nf_proto_csum_replace4);

#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
/* This does not belong here, but locally generated errors need it if connection
   tracking in use: without this, connection may not be in hash table, and hence
   manufactured ICMP or RST packets will not be associated with it. */
void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *);
EXPORT_SYMBOL(ip_ct_attach);

void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb)
{
        void (*attach)(struct sk_buff *, struct sk_buff *);

        if (skb->nfct) {
                rcu_read_lock();
                attach = rcu_dereference(ip_ct_attach);
                if (attach)
                        attach(new, skb);
                rcu_read_unlock();
        }
}
EXPORT_SYMBOL(nf_ct_attach);

void (*nf_ct_destroy