得到IP包的数据意义（简单实现例子）

 #include <stdio.h>
   #include <unistd.h>
   #include <linux/if_ether.h>
   #include <linux/ip.h>
   #include <linux/udp.h>
   #include <linux/types.h>

   void show_mac(const unsigned char *data);
   void show_ip(const unsigned char *data);
  void show_arp(const unsigned char *data);
  void show_udp(const unsigned char *data);
  void show_tcp(const unsigned char *data);
  void show_app(const unsigned char *data);

  int main()
  {
          unsigned char data[] = {
          0x00, 0x26, 0xc6, 0x41, 0x06, 0xb2, 0x00, 0x26,
          0xc6, 0x39, 0x8c, 0x36, 0x08, 0x00, 0x45, 0x00,
          0x00, 0x20, 0x00, 0x00, 0x40, 0x00, 0x40, 0x11,
          0x7a, 0x90, 0xc0, 0xa8, 0x1f, 0x72, 0xc0, 0xa8,
          0x1f, 0x7a, 0x94, 0x2b, 0x25, 0x37, 0x00, 0x0c,
          0xa0, 0x6d, 0x77, 0x61, 0x6e, 0x67
          };

          show_mac(data);

 }

  void show_mac(const unsigned char *data)
  {
          struct ethhdr *eth = (struct ethhdr *)data;
          printf("-------------物理层-------------\n");
          printf("目的MAC地址:  %02x:%02x:%02x:%02x:%02x:%02x\n",
                  eth->h_dest[], eth->h_dest[],
                  eth->h_dest[], eth->h_dest[],
                  eth->h_dest[], eth->h_dest[]
                  );
          printf("源端MAC地址:  %02x:%02x:%02x:%02x:%02x:%02x\n",
                  eth->h_source[], eth->h_source[],
                  eth->h_source[], eth->h_source[],
                  eth->h_source[], eth->h_source[]
                  );
          printf("使用的协议:   %04x\n\n", ntohs(eth->h_proto));
          if(ntohs(eth->h_proto) == 0x0800)
          show_ip(data);
          if(ntohs(eth->h_proto) == 0x0806)
          show_arp(data);
  }
  void show_ip(const unsigned char *data)
  {
          printf("-------------网络层-------------\n");

          struct iphdr *ip = (struct iphdr *)(data + sizeof(struct ethhdr));
          printf("版本号:       %d\n", ip->version);
          printf("IP首部长度:   %d\n", (ip->ihl)*);
          printf("服务类型:     %d\n", ip->tos);
          printf("总长度:       %d\n", ntohs(ip->tot_len));
          printf("标识:         %d\n", ip->id);
          printf("片偏移:       %d\n", ip->frag_off);
          printf("生存时间:     %d\n", ip->ttl);
          printf("上层使用协议: %d\n", ip->protocol);
          printf("首部检验和:   %d\n", ip->check);
          printf("源IP地址:     %s\n", inet_ntoa(ip->saddr));
          printf("目的IP地址:   %s\n\n", inet_ntoa(ip->daddr));
          if(ip->protocol == )
          show_tcp(data);
          if(ip->protocol == )
          show_udp(data);
  }
  void show_arp(const unsigned char *data)
  {

  }
  void show_udp(const unsigned char *data)
 {
          printf("-------------传输层-------------\n");
          struct udphdr *udp = (struct udphdr *)(data + sizeof(struct ethhdr)+ sizeof(struct iphdr));
          printf("源端口号:     %d\n", htons(udp->source));
          printf("目的端口号:   %d\n", htons(udp->dest));
          printf("UDP长度:      %d\n", htons(udp->len));
          printf("UDP检验和:    %x\n\n", htons(udp->check));
          show_app(data);
  }
  void show_tcp(const unsigned char *data)
  {

  }
  void show_app(const unsigned char *data)
  {
          printf("-------------应用层-------------\n");
          char *p = (char *)(data + sizeof(struct ethhdr)+ sizeof(struct iphdr)+sizeof(struct udphdr));
          printf("数据:%s\n\n", p);

  }