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#include "FiveLinux.ch"

function Main()

   MsgInfo( Ping( "192.168.0.22" ) )
   
return nil

#pragma BEGINDUMP   

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <string.h>
#include <unistd.h>

char dst_addr[20];
char src_addr[20];

static unsigned short in_cksum(unsigned short *, int);
static void parse_argvs(char**, char*, char* );
static void usage();
static char* getip();
static char* toip(char*);

HB_FUNC( PING )
{
   struct iphdr* ip;
   struct iphdr* ip_reply;
   struct icmphdr* icmp;
   struct sockaddr_in connection;
   char* packet;
   char* buffer;
   int sockfd;
   int optval;
   int addrlen;
   int siz;

   /*
   if (getuid() != 0)
   {
       fprintf(stderr, "%s: root privelidges needed\n", *(argv + 0));
       exit(EXIT_FAILURE);
   }
   */

   // parse_argvs(argv, dst_addr, src_addr);
   strncpy( dst_addr, toip( ( char * ) hb_parc( 1 ) ), 20 );
   strncpy( src_addr, toip( getip() ), 20 );
   // printf("Source address: %s\n", src_addr);
   // printf("Destination address: %s\n", dst_addr);

   /*
    * allocate all necessary memory
   */
   packet = malloc(sizeof(struct iphdr) + sizeof(struct icmphdr));
   buffer = malloc(sizeof(struct iphdr) + sizeof(struct icmphdr));
   /****************************************************************/

   ip = (struct iphdr*) packet;
   icmp = (struct icmphdr*) (packet + sizeof(struct iphdr));

   /*
    *  here the ip packet is set up
    */
   ip->ihl                     = 5;
   ip->version                 = 4;
   ip->tos                     = 0;
   ip->tot_len                 = sizeof(struct iphdr) + sizeof(struct icmphdr);
   ip->id                      = htons(0);
   ip->frag_off                = 0;
   ip->ttl                     = 64;
   ip->protocol                = IPPROTO_ICMP;
   ip->saddr                   = inet_addr(src_addr);
   ip->daddr                   = inet_addr(dst_addr);
   ip->check                   = in_cksum((unsigned short *)ip, sizeof(struct iphdr));

   if ((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) == -1)
   {
       hb_retl( FALSE );
       return;
       // perror("socket");
       // exit(EXIT_FAILURE);
   }

   /*
    *  IP_HDRINCL must be set on the socket so that
    *  the kernel does not attempt to automatically add
    *  a default ip header to the packet
    */

   setsockopt(sockfd, IPPROTO_IP, IP_HDRINCL, &optval, sizeof(int));

   /*
    *  here the icmp packet is created
    *  also the ip checksum is generated
    */
   icmp->type                  = ICMP_ECHO;
   icmp->code                  = 0;
   icmp->un.echo.id            = random();
   icmp->un.echo.sequence      = 0;
   icmp-> checksum             = in_cksum((unsigned short *)icmp, sizeof(struct icmphdr));


   connection.sin_family = AF_INET;
   connection.sin_addr.s_addr = inet_addr(dst_addr);

   /*
    *  now the packet is sent
    */

   sendto(sockfd, packet, ip->tot_len, 0, (struct sockaddr*)&connection, sizeof(struct sockaddr));
   // printf("Sent %d byte packet to %s\n", ip->tot_len, dst_addr);

   /*
    *  now we listen for responses
    */
   addrlen = sizeof(connection);
   if (( siz = recvfrom(sockfd, buffer, sizeof(struct iphdr) + sizeof(struct icmphdr), 0, (struct sockaddr *)&connection, &addrlen)) == -1)
   {
       hb_retl( FALSE );
       // perror("recv");
   }
   else
   {
       hb_retl( TRUE );
       // printf("Received %d byte reply from %s:\n", siz , dst_addr);
       // ip_reply = (struct iphdr*) buffer;
       // printf("ID: %d\n", ntohs(ip_reply->id));
       // printf("TTL: %d\n", ip_reply->ttl);
   }

   free(packet);
   free(buffer);
   close(sockfd);
   // return 0;
}

static void parse_argvs(char** argv, char* dst, char* src)
{
   int i;
   if(!(*(argv + 1)))
   {
       /* there are no options on the command line */
       usage();
       exit(EXIT_FAILURE);
   }
   if (*(argv + 1) && (!(*(argv + 2))))
   {
       /*
        *   only one argument provided
        *   assume it is the destination server
        *   source address is local host
        */
       strncpy(dst, *(argv + 1), 15);
       strncpy(src, getip(), 15);
       return;
   }
   else if ((*(argv + 1) && (*(argv + 2))))
   {
       /*
        *    both the destination and source address are defined
        *    for now only implemented is a source address and
        *    destination address
        */
       strncpy(dst, *(argv + 1), 15);
       i = 2;
       while(*(argv + i + 1))
       {
           if (strncmp(*(argv + i), "-s", 2) == 0)
           {
               strncpy(src, *(argv + i + 1), 15);
               break;
           }
           i++;
       }
   }

}

static void usage()
{
   fprintf(stderr, "\nUsage: pinger [destination] <-s [source]>\n");
   fprintf(stderr, "Destination must be provided\n");
   fprintf(stderr, "Source is optional\n\n");
}

static char* getip()
{
   char buffer[256];
   struct hostent* h;

   gethostname(buffer, 256);
   h = gethostbyname(buffer);

   return inet_ntoa(*(struct in_addr *)h->h_addr);

}

/*
 * return the ip address if host provided by DNS name
 */
static char* toip(char* address)
{
   struct hostent* h;
   h = gethostbyname(address);
   return inet_ntoa(*(struct in_addr *)h->h_addr);
}

/*
 * in_cksum --
 * Checksum routine for Internet Protocol
 * family headers (C Version)
 */
static unsigned short in_cksum(unsigned short *addr, int len)
{
   register int sum = 0;
   u_short answer = 0;
   register u_short *w = addr;
   register int nleft = len;
   /*
    * Our algorithm is simple, using a 32 bit accumulator (sum), we add
    * sequential 16 bit words to it, and at the end, fold back all the
    * carry bits from the top 16 bits into the lower 16 bits.
    */
   while (nleft > 1)
   {
         sum += *w++;
         nleft -= 2;
   }
   /* mop up an odd byte, if necessary */
   if (nleft == 1)
   {
         *(u_char *) (&answer) = *(u_char *) w;
         sum += answer;
   }
   /* add back carry outs from top 16 bits to low 16 bits */
   sum = (sum >> 16) + (sum & 0xffff);         /* add hi 16 to low 16 */
   sum += (sum >> 16);                         /* add carry */
   answer = ~sum;                              /* truncate to 16 bits */
   return (answer);
}

#pragma ENDDUMP