icmp协议分析C语言代码

以下是一个使用C语言实现的简单的ICMP协议分析代码，它可以发送和接收ICMP协议报文：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <errno.h>
#include <time.h>
#include <netinet/ip_icmp.h>

#define PACKET_SIZE 4096
#define MAX_WAIT_TIME 5
#define MAX_NO_PACKETS 3

char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];
int sockfd, datalen = 56;
int nsend = 0, nreceived = 0;
struct sockaddr_in dest_addr;
pid_t pid;

// 计算校验和
unsigned short cal_chksum(unsigned short *addr, int len) {
    int nleft = len;
    int sum = 0;
    unsigned short *w = addr;
    unsigned short answer = 0;

    while (nleft > 1) {
        sum += *w++;
        nleft -= 2;
    }

    if (nleft == 1) {
        *(unsigned char *)(&answer) = *(unsigned char *)w;
        sum += answer;
    }

    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    answer = ~sum;
    return answer;
}

// 发送ICMP报文
void send_packet() {
    memset(sendpacket, 0, sizeof(sendpacket));
    struct icmp *icmp_hdr = (struct icmp *)sendpacket;
    icmp_hdr->icmp_type = ICMP_ECHO;
    icmp_hdr->icmp_code = 0;
    icmp_hdr->icmp_cksum = 0;
    icmp_hdr->icmp_id = pid;
    icmp_hdr->icmp_seq = nsend++;
    memset(icmp_hdr->icmp_data, 0xa5, datalen);
    gettimeofday((struct timeval *)icmp_hdr->icmp_data, NULL);
    icmp_hdr->icmp_cksum = cal_chksum((unsigned short *)icmp_hdr, datalen + 8);
    sendto(sockfd, sendpacket, datalen + 8, 0, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
}

// 接收ICMP报文
void recv_packet() {
    int n;
    socklen_t fromlen;
    extern int errno;
    fromlen = sizeof(dest_addr);
    while (1) {
        if ((n = recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, (struct sockaddr *)&dest_addr, &fromlen)) < 0) {
            if (errno == EINTR) {
                continue;
            }
            perror("recvfrom error");
            return;
        }
        struct iphdr *ip_hdr = (struct iphdr *)recvpacket;
        int ip_hdr_len = ip_hdr->ihl << 2;
        struct icmp *icmp_hdr = (struct icmp *)(recvpacket + ip_hdr_len);
        int icmp_len = n - ip_hdr_len;
        if (icmp_hdr->icmp_type == ICMP_ECHOREPLY && icmp_hdr->icmp_id == pid) {
            struct timeval *tvsend = (struct timeval *)icmp_hdr->icmp_data;
            struct timeval tvrecv;
            gettimeofday(&tvrecv, NULL);
            double rtt = (tvrecv.tv_sec - tvsend->tv_sec) * 1000.0 + (tvrecv.tv_usec - tvsend->tv_usec) / 1000.0;
            printf("%d bytes from %s: icmp_seq=%u ttl=%d time=%.1f ms\n", icmp_len, inet_ntoa(dest_addr.sin_addr), icmp_hdr->icmp_seq, ip_hdr->ttl, rtt);
            nreceived++;
        }
    }
}

// 主函数
int main(int argc, char *argv[]) {
    struct hostent *host;
    struct protoent *protocol;
    unsigned long inaddr = 0l;
    int waittime = MAX_WAIT_TIME;
    int size = 50 * 1024;
    if (argc < 2) {
        printf("usage:%s hostname/IP address\n", argv[0]);
        exit(1);
    }
    if ((protocol = getprotobyname("icmp")) == NULL) {
        perror("getprotobyname");
        exit(1);
    }
    if ((sockfd = socket(AF_INET, SOCK_RAW, protocol->p_proto)) < 0) {
        perror("socket error");
        exit(1);
    }
    setuid(getuid());
    setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));
    bzero(&dest_addr, sizeof(dest_addr));
    dest_addr.sin_family = AF_INET;
    if (inaddr = inet_addr(argv[1]) == INADDR_NONE) {
        if ((host = gethostbyname(argv[1])) == NULL) {
            perror("gethostbyname error");
            exit(1);
        }
        memcpy((char *)&dest_addr.sin_addr, host->h_addr, host->h_length);
    } else {
        dest_addr.sin_addr.s_addr = inaddr;
    }
    pid = getpid();
    printf("PING %s(%s): %d bytes data in ICMP packets.\n", argv[1], inet_ntoa(dest_addr.sin_addr), datalen);
    while (nsend < MAX_NO_PACKETS) {
        send_packet();
        recv_packet();
        sleep(waittime);
    }
    printf("--- %s ping statistics ---\n", argv[1]);
    printf("%d packets transmitted, %d received, %%%d lost\n", nsend, nreceived, (nsend - nreceived) / nsend * 100);
    close(sockfd);
    return 0;
}