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#define __FORCE_GLIBC
#include <features.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/param.h>
#include <netinet/in.h>
#include <netdb.h>
#include <fcntl.h>
#include <unistd.h>
#define HOSTID "/etc/hostid"
int sethostid(long int new_id)
{
int fd;
int ret;
if (geteuid() || getuid()) return __set_errno(EPERM);
if ((fd=__open(HOSTID,O_CREAT|O_WRONLY,0644))<0) return -1;
ret = __write(fd,(void *)&new_id,sizeof(new_id)) == sizeof(new_id)
? 0 : -1;
__close (fd);
return ret;
}
long int gethostid(void)
{
char host[MAXHOSTNAMELEN + 1];
int fd, id;
/* If hostid was already set the we can return that value.
* It is not an error if we cannot read this file. It is not even an
* error if we cannot read all the bytes, we just carry on trying...
*/
if ((fd=__open(HOSTID,O_RDONLY))>=0 && __read(fd,(void *)&id,sizeof(id)))
{
__close (fd);
return id;
}
if (fd >= 0) __close (fd);
/* Try some methods of returning a unique 32 bit id. Clearly IP
* numbers, if on the internet, will have a unique address. If they
* are not on the internet then we can return 0 which means they should
* really set this number via a sethostid() call. If their hostname
* returns the loopback number (i.e. if they have put their hostname
* in the /etc/hosts file with 127.0.0.1) then all such hosts will
* have a non-unique hostid, but it doesn't matter anyway and
* gethostid() will return a non zero number without the need for
* setting one anyway.
* Mitch
*/
if (gethostname(host,MAXHOSTNAMELEN)>=0 && *host) {
struct hostent *hp;
struct in_addr in;
if ((hp = gethostbyname(host)) == (struct hostent *)NULL)
/* This is not a error if we get here, as all it means is that
* this host is not on a network and/or they have not
* configured their network properly. So we return the unset
* hostid which should be 0, meaning that they should set it !!
*/
return 0;
else {
__memcpy((char *) &in, (char *) hp->h_addr, hp->h_length);
/* Just so it doesn't look exactly like the IP addr */
return(in.s_addr<<16|in.s_addr>>16);
}
}
else return 0;
}
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