抓取TCP UDP ICMP

最新推荐文章于 2023-04-26 09:57:23 发布

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最新推荐文章于 2023-04-26 09:57:23 发布

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本文介绍了一个简单的网络数据包解析程序，该程序使用 C 语言实现，能够解析 IP、TCP、UDP 和 ICMP 数据包，并打印出关键信息，如源 IP、目的 IP、端口号等。

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#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#include <netinet/in.h>

typedef struct _iphdr  //定义ip首部
{
    unsigned char h_verlen; //4位首部长度甲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
    unsigned short ident; //16位标识
    unsigned short frag_and_flags;//3位标志位
    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; //16w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 _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 _udphdr      //定义UDP首部
{
    unsigned short uh_sprot;    //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 _icmphdr{
    unsigned char icmp_type;
    unsigned char icmp_code;
    unsigned short icmp_cksum;
    unsigned short icmp_id;
    unsigned short icmp_seq;
    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;
    if((sockfd=socket(PF_PACKET,SOCK_DGRAM,htons(ETH_P_IP)))<0){
        perror("socket");
        return 1;
    }
    while(1){
        n = recv(sockfd,buf,sizeof(buf),0);
        if(-1==n){
            printf("recv error\n");
            break;
        }else if(n==0)
            continue;
        ip = (IP_HEADER*)buf;
        //接收数据不包括数据链路帧头
        analyseIP(ip);
        size_t iplen = (ip->h_verlen&0x0f)*4;
        TCP_HEADER *tcp = (TCP_HEADER *)(buf+iplen);
        if(ip->proto==IPPROTO_TCP){
            TCP_HEADER *tcp = (TCP_HEADER*)(buf+iplen);
            analyseTCP(tcp);
        }else if(ip->proto ==IPPROTO_UDP){
            UDP_HEADER *udp = (UDP_HEADER*)(buf+iplen);
            analyseUDP(udp);
        }else if(ip->proto == IPPROTO_ICMP)
        {
            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");
        printf("\n\n");
    }
    close(sockfd);
    return 0;
}

void analyseIP(IP_HEADER *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)
{
    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)
{
    printf("UDP ------\n");
    printf("source port:%u\n",ntohs(udp->uh_sprot));
    printf("Dest port: %u\n", ntohs(udp->uh_dport));
}

void analyseICMP(ICMP_HEADER *icmp)
{
    printf("ICMP ------\n");
    printf("type: %u\n",icmp->icmp_type);
    printf("sub code: %u\n",icmp->icmp_code);
}