得到IP包的数据意义（简单实现例子）

1 #include <stdio.h>
  2 #include <unistd.h>
  3 #include <linux/if_ether.h>
  4 #include <linux/ip.h>
  5 #include <linux/udp.h>
  6 #include <linux/types.h>
  7 
  8 void show_mac(const unsigned char *data);
  9 void show_ip(const unsigned char *data);
 10 void show_arp(const unsigned char *data);
 11 void show_udp(const unsigned char *data);
 12 void show_tcp(const unsigned char *data);
 13 void show_app(const unsigned char *data);
 14 
 15 int main()
 16 {
 17         unsigned char data[1024] = {
 18         0x00, 0x26, 0xc6, 0x41, 0x06, 0xb2, 0x00, 0x26,
 19         0xc6, 0x39, 0x8c, 0x36, 0x08, 0x00, 0x45, 0x00,
 20         0x00, 0x20, 0x00, 0x00, 0x40, 0x00, 0x40, 0x11,
 21         0x7a, 0x90, 0xc0, 0xa8, 0x1f, 0x72, 0xc0, 0xa8,
 22         0x1f, 0x7a, 0x94, 0x2b, 0x25, 0x37, 0x00, 0x0c,
 23         0xa0, 0x6d, 0x77, 0x61, 0x6e, 0x67
 24         };
 25 
 26         show_mac(data);
 27 
28 }
 29 
 30 void show_mac(const unsigned char *data)
 31 {
 32         struct ethhdr *eth = (struct ethhdr *)data;
 33         printf("-------------物理层-------------
");
 34         printf("目的MAC地址:  %02x:%02x:%02x:%02x:%02x:%02x
",
 35                 eth->h_dest[0], eth->h_dest[1],
 36                 eth->h_dest[2], eth->h_dest[3],
 37                 eth->h_dest[4], eth->h_dest[5]
 38                 );
 39         printf("源端MAC地址:  %02x:%02x:%02x:%02x:%02x:%02x
",
 40                 eth->h_source[0], eth->h_source[1],
 41                 eth->h_source[2], eth->h_source[3],
 42                 eth->h_source[4], eth->h_source[5]
 43                 );
 44         printf("使用的协议:   %04x

", ntohs(eth->h_proto));
 45         if(ntohs(eth->h_proto) == 0x0800)
 46         show_ip(data);
 47         if(ntohs(eth->h_proto) == 0x0806)
 48         show_arp(data);
 49 }
 50 void show_ip(const unsigned char *data)
 51 {
 52         printf("-------------网络层-------------
");
53 
 54         struct iphdr *ip = (struct iphdr *)(data + sizeof(struct ethhdr));
 55         printf("版本号:       %d
", ip->version);
 56         printf("IP首部长度:   %d
", (ip->ihl)*4);
 57         printf("服务类型:     %d
", ip->tos);
 58         printf("总长度:       %d
", ntohs(ip->tot_len));
 59         printf("标识:         %d
", ip->id);
 60         printf("片偏移:       %d
", ip->frag_off);
 61         printf("生存时间:     %d
", ip->ttl);
 62         printf("上层使用协议: %d
", ip->protocol);
 63         printf("首部检验和:   %d
", ip->check);
 64         printf("源IP地址:     %s
", inet_ntoa(ip->saddr));
 65         printf("目的IP地址:   %s

", inet_ntoa(ip->daddr));
 66         if(ip->protocol == 6)
 67         show_tcp(data);
 68         if(ip->protocol == 17)
 69         show_udp(data);
 70 }
 71 void show_arp(const unsigned char *data)
 72 {
 73 
 74 }
 75 void show_udp(const unsigned char *data)
76 {
 77         printf("-------------传输层-------------
");
 78         struct udphdr *udp = (struct udphdr *)(data + sizeof(struct ethhdr)+ sizeof(struct iphdr));
 79         printf("源端口号:     %d
", htons(udp->source));
 80         printf("目的端口号:   %d
", htons(udp->dest));
 81         printf("UDP长度:      %d
", htons(udp->len));
 82         printf("UDP检验和:    %x

", htons(udp->check));
 83         show_app(data);
 84 }
 85 void show_tcp(const unsigned char *data)
 86 {
 87 
 88 }
 89 void show_app(const unsigned char *data)
 90 {
 91         printf("-------------应用层-------------
");
 92         char *p = (char *)(data + sizeof(struct ethhdr)+ sizeof(struct iphdr)+sizeof(struct udphdr));
 93         printf("数据:%s

", p);
 94 
 95 }