c实现ping域名

#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>
#include <errno.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 += *(unsigned short *)buf++;
        len -= 2;
    }
    if (len == 1) {
        sum += *(unsigned char *)buf;
    }
    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    return (unsigned short)(~sum);
}

int ping(const char *host) {
    int sockfd;
    struct sockaddr_in dest_addr;
    struct icmp icmp_header;
    char packet[PACKET_SIZE];
    char recv_packet[BUF_SIZE];
    struct timeval tv;
    fd_set readfds;
    int addr_len = sizeof(dest_addr);
    int packet_len = sizeof(struct icmp) + 1;

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

    memset(&dest_addr, 0, sizeof(dest_addr));
    dest_addr.sin_family = AF_INET;
    inet_pton(AF_INET, host, &dest_addr.sin_addr);

    memset(&icmp_header, 0, sizeof(icmp_header));
    icmp_header.icmp_type = ICMP_ECHO;
    icmp_header.icmp_code = 0;
    icmp_header.icmp_id = getpid();
    icmp_header.icmp_seq = 1;

    memset(packet, 0, PACKET_SIZE);
    memcpy(packet, &icmp_header, sizeof(icmp_header));
    icmp_header.icmp_cksum = checksum((unsigned short *)packet, packet_len);

    if (sendto(sockfd, packet, packet_len, 0, (struct sockaddr *)&dest_addr, addr_len) < 0) {
        perror("sendto");
        close(sockfd);
        return -1;
    }

    tv.tv_sec = 1;
    tv.tv_usec = 0;
    FD_ZERO(&readfds);
    FD_SET(sockfd, &readfds);

    if (select(sockfd + 1, &readfds, NULL, NULL, &tv) < 0) {
        perror("select");
        close(sockfd);
        return -1;
    } else if (FD_ISSET(sockfd, &readfds)) {
        if (recv(sockfd, recv_packet, BUF_SIZE, 0) < 0) {
            perror("recv");
            close(sockfd);
            return -1;
        }
        struct ip *ip_header = (struct ip *)recv_packet;
        struct icmp *recv_icmp_header = (struct icmp *)(recv_packet + (ip_header->ip_hl << 2));
        if (recv_icmp_header->icmp_type == ICMP_ECHOREPLY) {
            printf("Ping to %s successful, RTT: %ld ms\n", host, (recv_icmp_header->icmp_id - icmp_header.icmp_id) * 1000);
            close(sockfd);
            return 0;
        }
    }

    printf("Ping to %s failed\n", host);
    close(sockfd);
    return -1;
}

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