#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/module.h>
#include <linux/if.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/rcupdate.h>
#include <net/net_namespace.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include "lkh_hook.h"


#define LKH_VERDICT_MASK 0x000000ff
#define LKH_VERDICT_QBITS 16

static inline int LKH_DROP_GETERR(int verdict)
{
    return -(verdict >> LKH_VERDICT_QBITS);
}

static inline int lkh_hook_entry_hookfn(const struct lkh_hook_entry *entry, struct sk_buff *skb, struct lkh_hook_state *state)
{
    return entry->hook(entry->priv, skb, state);
}

static inline void lkh_hook_state_init(struct lkh_hook_state *p,
                                      unsigned int hook,
                                      u_int8_t pf,
                                      struct net_device *indev,
                                      struct net_device *outdev,
                                      struct sock *sk,
                                      struct net *net)
{
    p->hook_stage = hook;
    p->pf = pf;
    p->in = indev;
    p->out = outdev;
    p->sk = sk;
    p->net = net;
}

int lkh_hook_slow(struct sk_buff *skb, struct lkh_hook_state *state,
		 const struct lkh_hook_entries *e, unsigned int s)
{
    unsigned int verdict;
    int ret;

    for (; s < e->num_hook_entries; s++) 
    {
        verdict = lkh_hook_entry_hookfn(&e->hooks[s], skb, state);

        switch (verdict & LKH_VERDICT_MASK) 
        {
            case LKH_ACCEPT:
                break;
            case LKH_DROP:
                kfree_skb(skb);
                ret = LKH_DROP_GETERR(verdict);
                if (ret == 0)
                {
                    ret = -EPERM;
                }
                return ret;
            default:
                return 0;
        }
    }

    return 1;
}

 /*********************************************************************************
* Description：  
*      转发流程调用钩子函数的处理报文的入口函数
* Input:  
*      pf - 优先级
*      hook_stage - 钩子函数调用阶段
*      sk - socket
*      skb - 报文描述符
*      indev - 入设备信息
*      outdev - 出设备信息
* Output: 
*       无
* Return: 
*       无
* Others: 
*      入口参数的定义和使用方法同netfilter一样
 **********************************************************************************/
int lkh_hook(u_int8_t pf, 
				 unsigned int hook_stage, 
				 struct net *net,
				 struct sock *sk, 
				 struct sk_buff *skb,
				 struct net_device *indev, 
				 struct net_device *outdev)
{
    struct lkh_hook_entries * hook_entrise;
    int ret = 1;
    bool find_flag = false;
    struct lkh_hook * hook_head;

    /* 查找对应网络空间的hook结构		  */
    list_for_each_entry(hook_head, &g_lkh_hook_handle.list, list) 
    {
        if (hook_head->net_ptr == net)
        { 
            find_flag = true;
            break;
        }
    }

    if (!find_flag)
    {
        return ret;
    }

    rcu_read_lock();

    switch (pf)
    {
        case LKH_PROTO_IPV4:
            hook_entrise = rcu_dereference(hook_head->hooks_ipv4[hook_stage]);
            break;
        case LKH_PROTO_IPV6:
            hook_entrise = rcu_dereference(hook_head->hooks_ipv6[hook_stage]);
            break;
        default:
            break;
    }

    if (hook_entrise != NULL) 
    {
        struct lkh_hook_state state;

        lkh_hook_state_init(&state, hook_stage, pf, indev, outdev, sk, net);

        ret = lkh_hook_slow(skb, &state, hook_entrise, 0);
    }

    rcu_read_unlock();

    return ret;
}

EXPORT_SYMBOL(lkh_hook);