ping程序的设计与实现 linux

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/ip_icmp.h>
#include <arpa/inet.h>

#define BUF_SIZE 1024
#define PACKET_SIZE 64

unsigned short checksum(unsigned short *buf, int len) {
    unsigned long sum = 0;
    while (len > 1) {
        sum += *buf++;
        len -= 2;
    }
    if (len == 1) {
        sum += *(unsigned char *)buf;
    }
    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    return (unsigned short)(~sum);
}

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <IP address>\n", argv[0]);
        exit(1);
    }

    int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
    if (sockfd < 0) {
        perror("socket");
        exit(1);
    }

    struct sockaddr_in dest_addr;
    memset(&dest_addr, 0, sizeof(dest_addr));
    dest_addr.sin_family = AF_INET;
    inet_pton(AF_INET, argv[1], &dest_addr.sin_addr);

    char packet[PACKET_SIZE];
    memset(packet, 0, PACKET_SIZE);
    struct icmp *icmp_header = (struct icmp *)packet;
    icmp_header->icmp_type = ICMP_ECHO;
    icmp_header->icmp_code = 0;
    icmp_header->icmp_id = getpid();
    icmp_header->icmp_seq = 1;
    icmp_header->icmp_cksum = checksum((unsigned short *)icmp_header, PACKET_SIZE);

    struct timeval tv;
    gettimeofday(&tv, NULL);
    long send_time = tv.tv_sec * 1000 + tv.tv_usec / 1000;

    if (sendto(sockfd, packet, PACKET_SIZE, 0, (struct sockaddr *)&dest_addr, sizeof(dest_addr)) < 0) {
        perror("sendto");
        close(sockfd);
        exit(1);
    }

    char recv_packet[BUF_SIZE];
    struct sockaddr_in from_addr;
    socklen_t from_len = sizeof(from_addr);
    ssize_t recv_len = recvfrom(sockfd, recv_packet, BUF_SIZE, 0, (struct sockaddr *)&from_addr, &from_len);
    if (recv_len < 0) {
        perror("recvfrom");
        close(sockfd);
        exit(1);
    }

    gettimeofday(&tv, NULL);
    long recv_time = tv.tv_sec * 1000 + tv.tv_usec / 1000;
    long rtt = recv_time - send_time;

    printf("Received ping from %s: bytes=%d time=%ld ms\n", inet_ntoa(from_addr.sin_addr), recv_len, rtt);

    close(sockfd);
    return 0;
}