Linux c原始套接字实现icmp

在Linux系统中，可以使用原始套接字实现ICMP协议的收发。以下是一个简单的示例代码：

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

#define PACKET_SIZE 4096
#define ICMP_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 ~sum;
}

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

    char buf[PACKET_SIZE];
    memset(buf, 0, sizeof(buf));

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

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

    struct icmp *icmp_packet = (struct icmp *)buf;
    icmp_packet->icmp_type = ICMP_ECHO;
    icmp_packet->icmp_code = 0;
    icmp_packet->icmp_id = getpid() & 0xffff;
    icmp_packet->icmp_seq = 0;
    memset(icmp_packet->icmp_data, 0, ICMP_PACKET_SIZE);
    icmp_packet->icmp_cksum = checksum((unsigned short *)icmp_packet, ICMP_PACKET_SIZE);

    int sent_bytes = sendto(sock, buf, sizeof(struct icmp), 0, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
    if (sent_bytes < 0) {
        perror("sendto");
        exit(1);
    }

    printf("Sent %d bytes to %s\n", sent_bytes, argv[1]);

    int recv_bytes = recv(sock, buf, PACKET_SIZE, 0);
    if (recv_bytes < 0) {
        perror("recv");
        exit(1);
    }

    struct iphdr *ip_packet = (struct iphdr *)buf;
    struct icmp *icmp_reply = (struct icmp *)(buf + (ip_packet->ihl << 2));
    printf("Received ICMP reply from %s\n", inet_ntoa(dest_addr.sin_addr));
    printf("ICMP type: %d, ICMP code: %d\n", icmp_reply->icmp_type, icmp_reply->icmp_code);

    close(sock);
    return 0;
}

该程序中，首先创建一个原始套接字，然后构造一个ICMP报文，发送到目标IP地址。接着等待接收ICMP回复报文，并解析其中的类型和代码。最后关闭套接字。需要注意的是，使用原始套接字需要root权限。