ping

isup.c

#define PING_TIMEOUT 2
struct in_addr ouraddr = { 0 };
unsigned long global_rtt = 0;

//nmap
/* A relatively fast (or at least short ;) ping function.  Doesn't require a 
   seperate checksum function */
int isup(struct in_addr target) {
  int res, retries = 3;
  struct sockaddr_in sock;
  /*type(8bit)=8, code(8)=0 (echo REQUEST), checksum(16)=34190, id(16)=31337 */
#ifdef __LITTLE_ENDIAN_BITFIELD
  unsigned char ping[64] = { 0x8, 0x0, 0x8e, 0x85, 0x69, 0x7A };
#else
  unsigned char ping[64] = { 0x8, 0x0, 0x85, 0x8e, 0x7A, 0x69 };
#endif
  int sd;
  struct timeval tv;
  struct timeval start, end;
 fd_set fd_read;
  struct {
    struct iphdr ip;
    unsigned char type;
    unsigned char code;
    unsigned short checksum;
    unsigned short identifier;
    char crap[16536];
  }  response;

sd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);

bzero((char *)&sock,sizeof(struct sockaddr_in));
sock.sin_family=AF_INET;
sock.sin_addr = target;

gettimeofday(&start, NULL);
while(--retries) {
  if ((res = sendto(sd,(char *) ping,64,0,(struct sockaddr *)&sock,
		    sizeof(struct sockaddr))) != 64) {
    printf("sendto in isup returned %d! skipping host.\n", res);
    return 0;
  }
  FD_ZERO(&fd_read);
  FD_SET(sd, &fd_read);
  tv.tv_sec = 0; 
  tv.tv_usec = 1e6 * (PING_TIMEOUT / 3.0);
  while(1) {
    if ((res = select(sd + 1, &fd_read, NULL, NULL, &tv)) != 1) 
	{
		printf("%d\n", res);
		  break;
	}
    else {
      read(sd,&response,sizeof(response));
		printf("Response %d %d %d %d", response.ip.saddr, response.type, response.code, response.identifier);

      if  (response.ip.saddr == target.s_addr &&  !response.type 
	   && !response.code   && response.identifier == 31337) {
	gettimeofday(&end, NULL);
	global_rtt = (end.tv_sec - start.tv_sec) * 1e6 + end.tv_usec - start.tv_usec;
	ouraddr.s_addr = response.ip.daddr;
	close(sd);
	return 1;       
      }
    }
  }
}
close(sd);
printf("UNREACHABLE. SOCKET CLOSED \n");
return 0;
}