C++实现分析TCP、UDP、ICMP和IGMP协议

约定不等于承诺〃 2021-09-19 03:08 689阅读 0赞

**一 代码**

#include <sys/types.h>
    #include <sys/socket.h>
    #include <sys/ioctl.h>
    #include <net/if.h>
    #include <string.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <linux/if_packet.h>
    #include <netinet/if_ether.h>
    #include <netinet/in.h>
    #include <unistd.h> //for close
    
    
    typedef struct _iphdr //定义IP首部
    {
        unsigned char h_verlen; //4位首部长度+4位IP版本号
        unsigned char tos; //8位服务类型TOS
        unsigned short total_len; //16位总长度（字节）
        unsigned short ident; //16位标识
        unsigned short frag_and_flags; //3位标志位和13位片偏移
        unsigned char ttl; //8位生存时间 TTL
        unsigned char proto; //8位协议 (TCP, UDP 或其他)
        unsigned short checksum; //16位IP首部校验和
        unsigned int sourceIP; //32位源IP地址
        unsigned int destIP; //32位目的IP地址
    }IP_HEADER;
    
    typedef struct _udphdr //定义UDP首部
    {
        unsigned short uh_sport;    //16位源端口
        unsigned short uh_dport;    //16位目的端口
        unsigned int uh_len;//16位UDP包长度
        unsigned int uh_sum;//16位校验和
    }UDP_HEADER;
    
    typedef struct _tcphdr //定义TCP首部
    {
        unsigned short th_sport; //16位源端口
        unsigned short th_dport; //16位目的端口
        unsigned int th_seq; //32位序列号
        unsigned int th_ack; //32位确认号
        unsigned char th_lenres;//4位首部长度/6位保留字
        unsigned char th_flag; //6位标志位
        unsigned short th_win; //16位窗口大小
        unsigned short th_sum; //16位校验和
        unsigned short th_urp; //16位紧急数据偏移量
    }TCP_HEADER;
    
    typedef struct _icmphdr {  
        unsigned char  icmp_type;  
        unsigned char icmp_code; /* type sub code */  
        unsigned short icmp_cksum;  
        unsigned short icmp_id;  
        unsigned short icmp_seq;  
        /* This is not the std header, but we reserve space for time */  
        unsigned short icmp_timestamp;  
    }ICMP_HEADER;
    
    void analyseIP(IP_HEADER *ip);
    void analyseTCP(TCP_HEADER *tcp);
    void analyseUDP(UDP_HEADER *udp);
    void analyseICMP(ICMP_HEADER *icmp);
    
    
    int main(void)
    {
        int sockfd;
        IP_HEADER *ip;
        char buf[10240];
        ssize_t n;
        /* 如果使用SOCK_DGRAM，则捕获IP的数据报不需要以太网头 */
        if ((sockfd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) == -1)
        {    
            printf("socket error!\n");
            return 1;
        }
        while (1)
        {
            n = recv(sockfd, buf, sizeof(buf), 0);
            if (n == -1)
            {
                printf("recv error!\n");
                break;
            }
            else if (n == 0)
                continue;
            //接收数据不包括数据链路帧头，从IP首部开始接收
            ip = (IP_HEADER *)(buf);
            analyseIP(ip);      //分析IP数据报
            size_t iplen =  (ip->h_verlen & 0x0f) * 4;  //IP数据报长度
            
            if (ip->proto == IPPROTO_TCP)  //分析TCP数据报
            {
                TCP_HEADER *tcp = (TCP_HEADER *)(buf + iplen);
                analyseTCP(tcp);
            }
            else if (ip->proto == IPPROTO_UDP)   //分析UDP数据报
            {
                UDP_HEADER *udp = (UDP_HEADER *)(buf + iplen);
                analyseUDP(udp);
            }
            else if (ip->proto == IPPROTO_ICMP)        //分析ICMP数据报
            {
                ICMP_HEADER *icmp = (ICMP_HEADER *)(buf + iplen);
                analyseICMP(icmp);
            }
            else if (ip->proto == IPPROTO_IGMP)
            {
                printf("IGMP----\n");
            }
            else
            {
                printf("other protocol!\n");
            }        
            printf("\n\n");
        }
        close(sockfd);
        return 0;
    }
    
    void analyseIP(IP_HEADER *ip)        //分析出IP数据报的源IP和目的IP
    {
        unsigned char* p = (unsigned char*)&ip->sourceIP;
        printf("Source IP\t: %u.%u.%u.%u\n", p[0], p[1], p[2], p[3]);
        p = (unsigned char*)&ip->destIP;
        printf("Destination IP\t: %u.%u.%u.%u\n", p[0], p[1], p[2], p[3]);
    
    }
    
    void analyseTCP(TCP_HEADER *tcp)      //分析出TCP的源端口和目的端口
    {
        printf("TCP -----\n");
        printf("Source port: %u\n", ntohs(tcp->th_sport));
        printf("Dest port: %u\n", ntohs(tcp->th_dport));
    }
    
    void analyseUDP(UDP_HEADER *udp)        // 分析出UDP的源端口和目的端口
    {
        printf("UDP -----\n");
        printf("Source port: %u\n", ntohs(udp->uh_sport));
        printf("Dest port: %u\n", ntohs(udp->uh_dport));
    }
    
    void analyseICMP(ICMP_HEADER *icmp)          //分析出ICMP的类型和代码
    {
        printf("ICMP -----\n");
        printf("type: %u\n", icmp->icmp_type);
        printf("sub code: %u\n", icmp->icmp_code);
    }

**二 运行**

抓包结果如下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70]: /images/20210724/107dc7c0effb47db818ef40346c4d1d9.png