打印netfilter hook点挂载函数信息

#include <linux/init.h>      /* __init and __exit macroses */
#include <linux/kernel.h>    /* KERN_INFO macros */
#include <linux/module.h>    /* required for all kernel modules */
#include <linux/moduleparam.h>    /* module_param() and MODULE_PARM_DESC() */
#include <linux/kallsyms.h>       /* sprint_symbol */
#include <linux/netfilter.h>   
#include <linux/netfilter_ipv4.h> /* NF_IP_PRI_FIRST */


MODULE_LICENSE("GPL");
MODULE_AUTHOR("yilipika");
MODULE_DESCRIPTION("List netfilter hooks");

/*
enum nf_inet_hooks {
    NF_INET_PRE_ROUTING,
     NF_INET_LOCAL_IN,
     NF_INET_FORWARD,
     NF_INET_LOCAL_OUT,
     NF_INET_POST_ROUTING,
     NF_INET_NUMHOOKS
};

enum {
     NFPROTO_UNSPEC =  0,
     NFPROTO_IPV4   =  2,
     NFPROTO_ARP    =  3,
     NFPROTO_BRIDGE =  7,
     NFPROTO_IPV6   = 10,
     NFPROTO_DECNET = 12,
     NFPROTO_NUMPROTO,
};
*/

char *hooks[] = {
    "NF_INET_PRE_ROUTING",
    "NF_INET_LOCAL_IN",
    "NF_INET_FORWARD",
    "NF_INET_LOCAL_OUT",
    "NF_INET_POST_ROUTING",
};

static unsigned int test_pre_routing(unsigned int hooknum,
                      struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    return NF_ACCEPT;
}

static unsigned int test_local_in(unsigned int hooknum,
                      struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    return NF_ACCEPT;
}

static unsigned int test_forward(unsigned int hooknum,
                      struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    return NF_ACCEPT;
}

static unsigned int test_local_out(unsigned int hooknum,
                      struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    return NF_ACCEPT;
}

static unsigned int test_post_routing(unsigned int hooknum,
                      struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    return NF_ACCEPT;
}

static struct nf_hook_ops nf_test_ops[] __read_mostly = {
    {
        .hook = test_pre_routing,
        .owner = THIS_MODULE,
        .pf = NFPROTO_IPV4,
        .hooknum = NF_INET_PRE_ROUTING,
        .priority = NF_IP_PRI_FIRST,
    },

    {
        .hook = test_local_in,
        .owner = THIS_MODULE,
        .pf = NFPROTO_IPV4,
        .hooknum = NF_INET_LOCAL_IN,
        .priority = NF_IP_PRI_FIRST,
    },

    {
        .hook = test_forward,
        .owner = THIS_MODULE,
        .pf = NFPROTO_IPV4,
        .hooknum = NF_INET_FORWARD,
        .priority = NF_IP_PRI_FIRST,
    },

    {
        .hook = test_local_out,
        .owner = THIS_MODULE,
        .pf = NFPROTO_IPV4,
        .hooknum = NF_INET_LOCAL_OUT,
        .priority = NF_IP_PRI_FIRST,
    },

    {
        .hook = test_post_routing,
        .owner = THIS_MODULE,
        .pf = NFPROTO_IPV4,
        .hooknum = NF_INET_POST_ROUTING,
        .priority = NF_IP_PRI_FIRST,
    },
};

static void list_netfilter_hooks(u8 nf_proto)
{
    int i;
    struct nf_hook_ops *elem;
    char hook_name[128];
    unsigned long addr;

    for (i = 0; i < NF_INET_NUMHOOKS; i++) {
        printk("\n>>>hook_num:%s<<<\n", hooks[i]);

        list_for_each_entry(elem, &nf_hooks[nf_proto][i], list) {
            memset(hook_name, 0, sizeof(hook_name));
            addr = (unsigned long)elem->hook;
            sprint_symbol(hook_name, addr);
            printk("%s\n", hook_name);
        }
        printk("\n\n");
    }
}


static int __init list_netfilter_hooks_init(void)
{
    printk("list_netfilter_hooks install\n");

    if (nf_register_hooks(nf_test_ops, ARRAY_SIZE(nf_test_ops)) < 0) {
        printk("nf_register_hooks failed\n");
    }   


    printk("NFPROTO_IPV4\n");
    list_netfilter_hooks(NFPROTO_IPV4);

    return 0;
}

static void __exit list_netfilter_hooks_exit(void)
{
    nf_unregister_hooks(nf_test_ops, ARRAY_SIZE(nf_test_ops));

    printk("list_netfilter_hooks uninstall\n");
}

module_init(list_netfilter_hooks_init);
module_exit(list_netfilter_hooks_exit);