C语言实现ping的代码

以下是使用 C 语言实现的 ping 代码：

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

struct icmp_packet
{
    struct icmphdr header;
    char data[64];
};

void send_packet(int sockfd, struct sockaddr_in address, int seq_num)
{
    struct icmp_packet packet;
    packet.header.type = ICMP_ECHO;
    packet.header.code = 0;
    packet.header.un.echo.id = getpid();
    packet.header.un.echo.sequence = seq_num;
    memset(packet.data, 'A', 64);

    if (gettimeofday((struct timeval*) &packet.data, NULL) < 0)
    {
        perror("gettimeofday");
        exit(EXIT_FAILURE);
    }

    packet.header.checksum = 0;
    packet.header.checksum = htons(~(packet.header.checksum + sizeof(packet.header) + sizeof(packet.data)));

    if (sendto(sockfd, &packet, sizeof(packet), 0, (struct sockaddr*) &address, sizeof(address)) < 0)
    {
        perror("sendto");
        exit(EXIT_FAILURE);
    }
}

void receive_packet(int sockfd, int seq_num, struct sockaddr_in address, int timeout)
{
    fd_set descriptors;
    FD_ZERO(&descriptors);
    FD_SET(sockfd, &descriptors);

    struct timeval tv;
    tv.tv_sec = timeout;
    tv.tv_usec = 0;

    char buffer[4096];
    struct sockaddr_in sender_address;
    socklen_t sender_address_len = sizeof(sender_address);

    if (select(sockfd + 1, &descriptors, NULL, NULL, &tv) < 0)
    {
        perror("select");
        exit(EXIT_FAILURE);
    }

    if (FD_ISSET(sockfd, &descriptors))
    {
        if (recvfrom(sockfd, buffer, sizeof(buffer), 0, (struct sockaddr*) &sender_address, &sender_address_len) < 0)
        {
            perror("recvfrom");
            exit(EXIT_FAILURE);
        }

        struct icmphdr* header = (struct icmphdr*) buffer;

        if (header->type == ICMP_ECHOREPLY && header->un.echo.id == getpid() && header->un.echo.sequence == seq_num)
        {
            printf("%d bytes from %s: icmp_seq=%d ttl=%d\n", sizeof(buffer), inet_ntoa(sender_address.sin_addr), seq_num, header->ttl);
        }
        else
        {
            printf("Received invalid packet\n");
        }
    }
    else
    {
        printf("Request timed out\n");
    }
}

int main(int argc, char** argv)
{
    if (argc != 2)
    {
        printf("Usage: %s <host>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    char* host = argv[1];

    struct hostent* hostent = gethostbyname(host);
    if (!hostent)
    {
        perror("gethostbyname");
        exit(EXIT_FAILURE);
    }

    struct sockaddr_in address;
    address.sin_family = AF_INET;
    memcpy(&address.sin_addr, hostent->h_addr_list[0], hostent->h_length);

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

    int seq_num = 1;
    while (1)
    {
        send_packet(sockfd, address, seq_num);
        receive_packet(sockfd, seq_num, address, 1);
        seq_num++;
        sleep(1);
    }

    return 0;
}