/*
 * Rusty Russell (C)2000 -- This code is GPL.
 * Patrick McHardy (c) 2006-2012
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <linux/seq_file.h>
#include <linux/rcupdate.h>
#include <net/protocol.h>
#include <net/netfilter/nf_queue.h>
#include <net/dst.h>

#include "nf_internals.h"

/*
 * Hook for nfnetlink_queue to register its queue handler.
 * We do this so that most of the NFQUEUE code can be modular.
 *
 * Once the queue is registered it must reinject all packets it
 * receives, no matter what.
 */
static const struct nf_queue_handler __rcu *queue_handler __read_mostly;

/* return EBUSY when somebody else is registered, return EEXIST if the
 * same handler is registered, return 0 in case of success. */
void nf_register_queue_handler(const struct nf_queue_handler *qh)
{
        /* should never happen, we only have one queueing backend in kernel */
        WARN_ON(rcu_access_pointer(queue_handler));
        rcu_assign_pointer(queue_handler, qh);
}
EXPORT_SYMBOL(nf_register_queue_handler);

/* The caller must flush their queue before this */
void nf_unregister_queue_handler(void)
{
        RCU_INIT_POINTER(queue_handler, NULL);
        synchronize_rcu();
}
EXPORT_SYMBOL(nf_unregister_queue_handler);

void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
{
        /* Release those devices we held, or Alexey will kill me. */
        if (entry->indev)
                dev_put(entry->indev);
        if (entry->outdev)
                dev_put(entry->outdev);
#ifdef CONFIG_BRIDGE_NETFILTER
        if (entry->skb->nf_bridge) {
                struct nf_bridge_info *nf_bridge = entry->skb->nf_bridge;

                if (nf_bridge->physindev)
                        dev_put(nf_bridge->physindev);
                if (nf_bridge->physoutdev)
                        dev_put(nf_bridge->physoutdev);
        }
#endif
        /* Drop reference to owner of hook which queued us. */
        module_put(entry->elem->owner);
}
EXPORT_SYMBOL_GPL(nf_queue_entry_release_refs);

/* Bump dev refs so they don't vanish while packet is out */
bool nf_queue_entry_get_refs(struct nf_queue_entry *entry)
{
        if (!try_module_get(entry->elem->owner))
                return false;

        if (entry->indev)
                dev_hold(entry->indev);
        if (entry->outdev)
                dev_hold(entry->outdev);
#ifdef CONFIG_BRIDGE_NETFILTER
        if (entry->skb->nf_bridge) {
                struct nf_bridge_info *nf_bridge = entry->skb->nf_bridge;
                struct net_device *physdev;

                physdev = nf_bridge->physindev;
                if (physdev)
                        dev_hold(physdev);
                physdev = nf_bridge->physoutdev;
                if (physdev)
                        dev_hold(physdev);
        }
#endif

        return true;
}
EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);

/*
 * Any packet that leaves via this function must come back
 * through nf_reinject().
 */
int nf_queue(struct sk_buff *skb,
                      struct nf_hook_ops *elem,
                      u_int8_t pf, unsigned int hook,
                      struct net_device *indev,
                      struct net_device *outdev,
                      int (*okfn)(struct sk_buff *),
                      unsigned int queuenum)
{
        int status = -ENOENT;
        struct nf_queue_entry *entry = NULL;
        const struct nf_afinfo *afinfo;
        const struct nf_queue_handler *qh;

        /* QUEUE == DROP if no one is waiting, to be safe. */
        rcu_read_lock();

        qh = rcu_dereference(queue_handler);
        if (!qh) {
                status = -ESRCH;
                goto err_unlock;
        }

        afinfo = nf_get_afinfo(pf);
        if (!afinfo)
                goto err_unlock;

        entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
        if (!entry) {
                status = -ENOMEM;
                goto err_unlock;
        }

        *entry = (struct nf_queue_entry) {
                .skb    = skb,
                .elem   = elem,
                .pf     = pf,
                .hook   = hook,
                .indev  = indev,
                .outdev = outdev,
                .okfn   = okfn,
                .size   = sizeof(*entry) + afinfo->route_key_size,
        };

        if (!nf_queue_entry_get_refs(entry)) {
                status = -ECANCELED;
                goto err_unlock;
        }
        skb_dst_force(skb);
        afinfo->saveroute(skb, entry);
        status = qh->outfn(entry, queuenum);

        rcu_read_unlock();

        if (status < 0) {
                nf_queue_entry_release_refs(entry);
                goto err;
        }

        return 0;

err_unlock:
        rcu_read_unlock();
err:
        kfree(entry);
        return status;
}

void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
{
        struct sk_buff *skb = entry->skb;
        struct nf_hook_ops *elem = entry->elem;
        const struct nf_afinfo *afinfo;
        int err;

        rcu_read_lock();

        nf_queue_entry_release_refs(entry);

        /* Continue traversal iff userspace said ok... */
        if (verdict == NF_REPEAT) {
                elem = list_entry(elem->list.prev, struct nf_hook_ops, list);
                verdict = NF_ACCEPT;
        }

        if (verdict == NF_ACCEPT) {
                afinfo = nf_get_afinfo(entry->pf);
                if (!afinfo || afinfo->reroute(skb, entry) < 0)
                        verdict = NF_DROP;
        }

        if (verdict == NF_ACCEPT) {
        next_hook:
                verdict = nf_iterate(&nf_hooks[entry->pf][entry->hook],
                                     skb, entry->hook,
                                     entry->indev, entry->outdev, &elem,
                                     entry->okfn, INT_MIN);
        }

        switch (verdict & NF_VERDICT_MASK) {
        case NF_ACCEPT:
        case NF_STOP:
                local_bh_disable();
                entry->okfn(skb);
                local_bh_enable();
                break;
        case NF_QUEUE:
                err = nf_queue(skb, elem, entry->pf, entry->hook,
                                entry->indev, entry->outdev, entry->okfn,
                                verdict >> NF_VERDICT_QBITS);
                if (err < 0) {
                        if (err == -ECANCELED)
                                goto next_hook;
                        if (err == -ESRCH &&
                           (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
                                goto next_hook;
                        kfree_skb(skb);
                }
                break;
        case NF_STOLEN:
                break;
        default:
                kfree_skb(skb);
        }
        rcu_read_unlock();
        kfree(entry);
}
EXPORT_SYMBOL(nf_reinject);