/*
 * 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/netfilter_bridge.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.
 */

/* 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(struct net *net, const struct nf_queue_handler *qh)
{
        /* should never happen, we only have one queueing backend in kernel */
        WARN_ON(rcu_access_pointer(net->nf.queue_handler));
        rcu_assign_pointer(net->nf.queue_handler, qh);
}
EXPORT_SYMBOL(nf_register_queue_handler);

/* The caller must flush their queue before this */
void nf_unregister_queue_handler(struct net *net)
{
        RCU_INIT_POINTER(net->nf.queue_handler, NULL);
}
EXPORT_SYMBOL(nf_unregister_queue_handler);

void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
{
        struct nf_hook_state *state = &entry->state;

        /* Release those devices we held, or Alexey will kill me. */
        if (state->in)
                dev_put(state->in);
        if (state->out)
                dev_put(state->out);
        if (state->sk)
                sock_put(state->sk);
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
        if (entry->skb->nf_bridge) {
                struct net_device *physdev;

                physdev = nf_bridge_get_physindev(entry->skb);
                if (physdev)
                        dev_put(physdev);
                physdev = nf_bridge_get_physoutdev(entry->skb);
                if (physdev)
                        dev_put(physdev);
        }
#endif
}
EXPORT_SYMBOL_GPL(nf_queue_entry_release_refs);

/* Bump dev refs so they don't vanish while packet is out */
void nf_queue_entry_get_refs(struct nf_queue_entry *entry)
{
        struct nf_hook_state *state = &entry->state;

        if (state->in)
                dev_hold(state->in);
        if (state->out)
                dev_hold(state->out);
        if (state->sk)
                sock_hold(state->sk);
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
        if (entry->skb->nf_bridge) {
                struct net_device *physdev;

                physdev = nf_bridge_get_physindev(entry->skb);
                if (physdev)
                        dev_hold(physdev);
                physdev = nf_bridge_get_physoutdev(entry->skb);
                if (physdev)
                        dev_hold(physdev);
        }
#endif
}
EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);

unsigned int nf_queue_nf_hook_drop(struct net *net)
{
        const struct nf_queue_handler *qh;
        unsigned int count = 0;

        rcu_read_lock();
        qh = rcu_dereference(net->nf.queue_handler);
        if (qh)
                count = qh->nf_hook_drop(net);
        rcu_read_unlock();

        return count;
}

static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
                      struct nf_hook_entry *hook_entry, unsigned int queuenum)
{
        int status = -ENOENT;
        struct nf_queue_entry *entry = NULL;
        const struct nf_afinfo *afinfo;
        const struct nf_queue_handler *qh;
        struct net *net = state->net;

        /* QUEUE == DROP if no one is waiting, to be safe. */
        qh = rcu_dereference(net->nf.queue_handler);
        if (!qh) {
                status = -ESRCH;
                goto err;
        }

        afinfo = nf_get_afinfo(state->pf);
        if (!afinfo)
                goto err;

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

        *entry = (struct nf_queue_entry) {
                .skb    = skb,
                .state  = *state,
                .hook   = hook_entry,
                .size   = sizeof(*entry) + afinfo->route_key_size,
        };

        nf_queue_entry_get_refs(entry);
        skb_dst_force(skb);
        afinfo->saveroute(skb, entry);
        status = qh->outfn(entry, queuenum);

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

        return 0;

err:
        kfree(entry);
        return status;
}

/* Packets leaving via this function must come back through nf_reinject(). */
int nf_queue(struct sk_buff *skb, struct nf_hook_state *state,
             struct nf_hook_entry **entryp, unsigned int verdict)
{
        struct nf_hook_entry *entry = *entryp;
        int ret;

        ret = __nf_queue(skb, state, entry, verdict >> NF_VERDICT_QBITS);
        if (ret < 0) {
                if (ret == -ESRCH &&
                    (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS)) {
                        *entryp = rcu_dereference(entry->next);
                        return 1;
                }
                kfree_skb(skb);
        }

        return 0;
}

static unsigned int nf_iterate(struct sk_buff *skb,
                               struct nf_hook_state *state,
                               struct nf_hook_entry **entryp)
{
        unsigned int verdict;

        do {
repeat:
                verdict = nf_hook_entry_hookfn((*entryp), skb, state);
                if (verdict != NF_ACCEPT) {
                        if (verdict != NF_REPEAT)
                                return verdict;
                        goto repeat;
                }
                *entryp = rcu_dereference((*entryp)->next);
        } while (*entryp);

        return NF_ACCEPT;
}

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

        nf_queue_entry_release_refs(entry);

        /* Continue traversal iff userspace said ok... */
        if (verdict == NF_REPEAT)
                verdict = nf_hook_entry_hookfn(hook_entry, skb, &entry->state);

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

        if (verdict == NF_ACCEPT) {
                hook_entry = rcu_dereference(hook_entry->next);
                if (hook_entry)
next_hook:
                        verdict = nf_iterate(skb, &entry->state, &hook_entry);
        }

        switch (verdict & NF_VERDICT_MASK) {
        case NF_ACCEPT:
        case NF_STOP:
okfn:
                local_bh_disable();
                entry->state.okfn(entry->state.net, entry->state.sk, skb);
                local_bh_enable();
                break;
        case NF_QUEUE:
                err = nf_queue(skb, &entry->state, &hook_entry, verdict);
                if (err == 1) {
                        if (hook_entry)
                                goto next_hook;
                        goto okfn;
                }
                break;
        case NF_STOLEN:
                break;
        default:
                kfree_skb(skb);
        }

        kfree(entry);
}
EXPORT_SYMBOL(nf_reinject);