IP_HDRINCL socketopt

icmp_with_ip_hdrincl.c

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

#define SEND_BUF_LEN 64
#define RECV_BUF_LEN 128
#define SRC_IP "192.168.33.1"
#define DST_IP "192.168.33.10"

u_int16_t checksum(u_int16_t *data, int len);

int main(int argc, char *argv[]) {
    int s;
    char send_buf[SEND_BUF_LEN];
    struct sockaddr_in send_sa;
    int on = 1;
    struct ip *send_ip;
    struct icmp *send_icmp;

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

    if (setsockopt(s, IPPROTO_IP, IP_HDRINCL, &on, sizeof on) < 0) {
        perror("setsockopt(IP_HDRINCL)");
        exit(1);
    }

    // create icmp echo request
    memset(send_buf, 0, SEND_BUF_LEN);

    send_ip = (struct ip *) send_buf;
    send_ip->ip_v = IPVERSION;
    send_ip->ip_hl = sizeof (struct ip) >> 2;
    send_ip->ip_id = 0;
    send_ip->ip_len = htons(SEND_BUF_LEN);
    send_ip->ip_off = htons(0);
    send_ip->ip_ttl = 2;
    send_ip->ip_p = IPPROTO_ICMP;
    send_ip->ip_src.s_addr = inet_addr(SRC_IP);
    send_ip->ip_dst.s_addr = inet_addr(DST_IP);
    send_ip->ip_sum = 0;
    send_ip->ip_sum = checksum((u_int16_t *) send_ip, sizeof send_ip);

    send_icmp = (struct icmp *) (send_buf + (send_ip->ip_hl << 2));
    send_icmp->icmp_type = ICMP_ECHO;
    send_icmp->icmp_code = 0;
    send_icmp->icmp_cksum = 0;
    send_icmp->icmp_id = htons(1);
    send_icmp->icmp_seq = htons(1);
    send_icmp->icmp_cksum = checksum((u_int16_t *) send_icmp, SEND_BUF_LEN - sizeof send_ip);

    // set send_sa
    memset(&send_sa, 0, sizeof send_sa);
    send_sa.sin_family = AF_INET;
    send_sa.sin_addr.s_addr = inet_addr(DST_IP);

    if (sendto(s, send_buf, SEND_BUF_LEN, 0, (struct sockaddr *) &send_sa, sizeof send_sa) < 0) {
        perror("sendto");
        exit(1);
    }

    struct timeval tv;
    tv.tv_sec = 0;
    tv.tv_usec = 200 * 1000;

    char recv_buf[RECV_BUF_LEN];

    while (1) {
        fd_set readfd;
        struct ip *recv_ip;
        struct icmp *recv_icmp;
        int ihlen;

        FD_ZERO(&readfd);
        FD_SET(s, &readfd);

        if (select(s + 1, &readfd, NULL, NULL, &tv) <= 0) {
            break;
        }

        if (recvfrom(s, recv_buf, RECV_BUF_LEN, 0, NULL, NULL) < 0) {
            perror("recvfrom");
            exit(1);
        }

        recv_ip = (struct ip *) recv_buf;
        ihlen = recv_ip->ip_hl << 2;
        recv_icmp = (struct icmp *) (recv_buf + ihlen);

        if (recv_icmp->icmp_code == 0 && recv_icmp->icmp_type == ICMP_ECHOREPLY) {
            printf("echo reply from %s\n", inet_ntoa(recv_ip->ip_dst));
        } else {
            printf("unexpected reply from %s, icmp_code = %d, icmp_type = %d\n",
                    inet_ntoa(recv_ip->ip_dst), recv_icmp->icmp_code, recv_icmp->icmp_type);
        }
    }

    close(s);

    return 0;
}

u_int16_t checksum(u_int16_t *data, int len) {
    u_int32_t sum = 0;

    for (; len > 1; len -= 2) {
        sum += *data++;
        if (sum & 0x80000000) {
            sum = (sum & 0xffff) + (sum >> 16);
        }
    }

    if (len == 1) {
        u_int16_t i = 0;
        *((u_int8_t *) &i) = *((u_int8_t *) data);
        sum += i;
    }

    while (sum >> 16) {
        sum = (sum & 0xff) + (sum >> 16);
    }

    return ~sum;
}

icmp_without_ip_hdrincl.c

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

#define SEND_BUF_LEN 64
#define RECV_BUF_LEN 128
#define DST_IP "192.168.33.10"

u_int16_t checksum(u_int16_t *data, int len);

int main(int argc, char *argv[]) {
    int s;
    char send_buf[SEND_BUF_LEN];
    struct sockaddr_in send_sa;

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

    // create icmp echo request
    memset(send_buf, 0, SEND_BUF_LEN);
    ((struct icmp *) send_buf)->icmp_type = ICMP_ECHO;
    ((struct icmp *) send_buf)->icmp_code = 0;
    ((struct icmp *) send_buf)->icmp_cksum = 0;
    ((struct icmp *) send_buf)->icmp_id = htons(1);
    ((struct icmp *) send_buf)->icmp_seq = htons(1);
    ((struct icmp *) send_buf)->icmp_cksum = checksum((u_int16_t *) send_buf, SEND_BUF_LEN);

    // set send_sa
    memset(&send_sa, 0, sizeof send_sa);
    send_sa.sin_family = AF_INET;
    send_sa.sin_addr.s_addr = inet_addr(DST_IP);

    if (sendto(s, send_buf, SEND_BUF_LEN, 0, (struct sockaddr *) &send_sa, sizeof send_sa) < 0) {
        perror("sendto");
        exit(1);
    }

    struct timeval tv;
    tv.tv_sec = 0;
    tv.tv_usec = 200 * 1000;

    char recv_buf[RECV_BUF_LEN];

    while (1) {
        fd_set readfd;
        struct ip *ip;
        struct icmp *icmp;
        int ihlen;

        FD_ZERO(&readfd);
        FD_SET(s, &readfd);

        if (select(s + 1, &readfd, NULL, NULL, &tv) <= 0) {
            break;
        }

        if (recvfrom(s, recv_buf, RECV_BUF_LEN, 0, NULL, NULL) < 0) {
            perror("recvfrom");
            exit(1);
        }

        ip = (struct ip *) recv_buf;
        ihlen = ip->ip_hl << 2;
        icmp = (struct icmp *) (recv_buf + ihlen);

        if (icmp->icmp_code == 0 && icmp->icmp_type == ICMP_ECHOREPLY) {
            printf("echo reply from %s\n", inet_ntoa(ip->ip_dst));
        } else {
            printf("unexpected reply from %s, icmp_code = %d, icmp_type = %d\n",
                    inet_ntoa(ip->ip_dst), icmp->icmp_code, icmp->icmp_type);
        }
    }

    close(s);

    return 0;
}

u_int16_t checksum(u_int16_t *data, int len) {
    u_int32_t sum = 0;

    for (; len > 1; len -= 2) {
        sum += *data++;
        if (sum & 0x80000000) {
            sum = (sum & 0xffff) + (sum >> 16);
        }
    }

    if (len == 1) {
        u_int16_t i = 0;
        *((u_int8_t *) &i) = *((u_int8_t *) data);
        sum += i;
    }

    while (sum >> 16) {
        sum = (sum & 0xff) + (sum >> 16);
    }

    return ~sum;
}