c - 迁移到 4.1.23 的 Netfilter 内核模块 - 无法检索 ip header

Question

我们有一个来自 2.6 内核的 netfilter 内核模块，现在正在移植到 4.1.23。我的钩子(Hook)函数看起来坏了。我无法检索数据包 header 。

这是 2.6 内核的代码片段。这已经投入生产很长时间了。

    static unsigned int main_hook(unsigned int hooknum, struct sk_buff *skb, const struct net_device *in,const struct net_device *out, int (*okfn)(struct sk_buff*))
{
  //struct sk_buff *skb = (skb_p);
  struct iphdr *ih = (struct iphdr *)(skb->data);
  u32 saddr = ih->saddr;
  u32 daddr = ih->daddr;

在4.1.23查看netfilter.h并在网上搜索得到如下

static unsigned int main_hook(const struct nf_hook_ops *ops, struct sk_buff *skb, const struct nf_hook_state *state)
       {
          //struct sk_buff *skb = (skb_p);
          struct iphdr *ih = (struct iphdr *)(skb->data);
          u32 saddr = ih->saddr;
          u32 daddr = ih->daddr;

注册钩子(Hook)如下。

  netfilter_ops.hook              =       main_hook;
  netfilter_ops.pf                =       PF_INET;
  netfilter_ops.hooknum           =       NF_INET_FORWARD;
  netfilter_ops.priority          =       NF_IP_PRI_FIRST;
  netfilter_ops.owner             =       THIS_MODULE;
  nf_register_hook(&netfilter_ops);

我没有从 saddr 和 daddr 获取源 ip 和目标 ip。

删除所有内容并尝试跟随

static unsigned int main_hook(const struct nf_hook_ops *ops, struct sk_buff *skb, const struct nf_hook_state *state)
{
  struct iphdr *ip_header = (struct iphdr *) (skb->data);
  unsigned int src_ip = (unsigned int)ip_header->saddr;
  unsigned int dest_ip = (unsigned int)ip_header->daddr;
  printk("IP addres = %pI4  DEST = %pI4\n", &src_ip, &dest_ip);
  return NF_ACCEPT;

这是结果

[37501.345997] IP addres = 0.0.0.0  DEST = 0.0.0.0
[37506.337854] IP addres = 0.0.0.0  DEST = 0.0.0.0
[37511.345295] IP addres = 0.0.0.0  DEST = 0.0.0.0
[37516.337132] IP addres = 0.0.0.0  DEST = 0.0.0.0
[37521.344589] IP addres = 0.0.0.0  DEST = 0.0.0.0
[37526.336426] IP addres = 0.0.0.0  DEST = 0.0.0.0
[37531.343866] IP addres = 0.0.0.0  DEST = 0.0.0.0

也试过关注但是越来越垃圾

buff = (unsigned char *) skb->data;
for (i=0;i<60;i++) printk("%d.", buff[i]);
printk("\n");

我尝试使用函数获取数据(skb_network_header)，甚至尝试编写 hello world。 请帮忙。

Answer 1

尝试以这种方式提取:

struct iphdr *ip_hdr = (struct iphdr *)skb_network_header(skb);

并以这种方式访问​​:

printk("IP addres = %u  DEST = %u\n", ip_hdr->saddr, ip_hdr->daddr);