pktgen

#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <errno.h>
#include <netinet/tcp.h>
#include <netinet/ip.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <signal.h>

extern char *optarg;

struct pseudo_header //needed for checksum calculation
{
    unsigned int saddr;
    unsigned int daddr;
    unsigned char placeholder;
    unsigned char protocol;
    unsigned short length;

    struct tcphdr tcp;
};

unsigned short csum(unsigned short *ptr, int n)
{
    long sum = 0;
    unsigned short oddbyte;
    unsigned short answer;

    while (n > 1)
    {
        sum += *ptr++;
        n -= 2;
    }

    if (n == 1)
    {
        oddbyte = 0;
        *((char *)&oddbyte) = *(char *)ptr;
        sum += oddbyte;
    }

    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    answer = ~sum;

    return answer;
}

unsigned long npackets = 0;
void timer_handler(int signum)
{
    printf("%d packets sent\n", npackets);
    exit(0);
}

void usage()
{
    printf("usage: yapktgen -s <source ip> -d <dest ip> -p <payload size> -d <duration in sec>\n");
    exit(1);
}

int main(int argc, char **argv)
{
    char datagram[65536], sip[16], dip[16];
    struct iphdr *iph = (struct iphdr *)datagram;
    struct tcphdr *tcph = (struct tcphdr *)(datagram + sizeof(struct ip));
    struct sockaddr_in sin;
    struct pseudo_header psh;
    int opt, sock, payload = 1024, duration = 10;
    struct itimerval timer;

    while ((opt = getopt(argc, argv, "s:d:p:t:")) != -1)
    {
        switch (opt)
        {
        case 's':
            strcpy(sip, optarg);
            break;
        case 'd':
            strcpy(dip, optarg);
            break;
        case 'p':
            payload = atoi(optarg);
            break;
        case 't':
            duration = atoi(optarg);
            break;
        default:
            fprintf(stderr, "Unknow option !");
            usage();
        }
    }

    if (sip == NULL || dip == NULL)
    {
        usage();
    }

    sock = socket(PF_INET, SOCK_RAW, IPPROTO_TCP);

    memset(datagram, 0, 65536);

    iph->ihl = 5;
    iph->version = 4;
    iph->tot_len = sizeof(struct ip) + sizeof(struct tcphdr) + payload;
    iph->id = htons(54321);
    iph->ttl = 255;
    iph->protocol = IPPROTO_TCP;
    iph->saddr = inet_addr(sip);
    iph->daddr = inet_addr(dip);
    iph->check = csum((unsigned short *)datagram, iph->tot_len >> 1);

    tcph->doff = 5;
    tcph->syn = 1;
    tcph->window = htons(5840);

    psh.saddr = iph->saddr;
    psh.daddr = iph->daddr;
    psh.placeholder = 0;
    psh.protocol = IPPROTO_TCP;
    psh.length = htons(20);

    memcpy(&psh.tcp, tcph, sizeof(struct tcphdr));

    int value = 1;
    if (setsockopt(sock, IPPROTO_IP, IP_HDRINCL, &value, sizeof(value)) < 0)
    {
        fprintf(stderr, "Error %s\n", strerror(errno));
        exit(1);
    }

    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = iph->daddr;

    /* Install timer_handler as the signal handler for SIGVTALRM. */
    if (signal(SIGALRM, timer_handler) == SIG_ERR)
    {
        fprintf(stderr, "Error %s\n", strerror(errno));
        exit(1);
    }
    
    timer.it_value.tv_sec = duration;
    timer.it_value.tv_usec = 0;
    timer.it_interval.tv_sec = 0;
    timer.it_interval.tv_usec = 0;

    printf("Start injection for :%d sec\n", duration);

    setitimer(ITIMER_REAL, &timer, NULL);

    unsigned long ports = 1;
    while (1)
    {
        int port1 = ports & 0xffff;
        int port2 = (ports >> 16) & 0xffff;

        tcph->source = htons(port1 > 0 ? port1 : 1);
        tcph->dest = htons(port2 > 0 ? port2 : 1);
        tcph->check = csum((unsigned short *)&psh, sizeof(struct pseudo_header));

        sin.sin_port = tcph->dest;

        if (sendto(sock, datagram, iph->tot_len, 0, (struct sockaddr *)&sin, sizeof(sin)) < 0)
        {
            fprintf(stderr, "Error %s\n", strerror(errno));
            exit(1);
        }
        npackets++;
        ports++;
    }

    return 0;
}

pktgen.bin