Problem - Kevin Tafuro

if (errno != EINTR && errno != EAGAIN) return -1;
}
for (;;) {
he = gethostbyaddr((char *)&addr->sin_addr, sizeof(addr->sin_addr), AF_INET);
if (he) break;
if (h_errno = = HOST_NOT_FOUND) {
endhostent( );
return SPC_ERROR_NOREVERSE;
}
if (h_errno != TRY_AGAIN) {
endhostent( );
return -1;
}
}
hostname = strdup(he->h_name);
for (;;) {
if ((he = gethostbyname(hostname)) != 0) break;
if (h_errno = = HOST_NOT_FOUND) {
endhostent( );
free(hostname);
return SPC_ERROR_NOHOSTNAME;
}
if (h_errno != TRY_AGAIN) {
endhostent( );
free(hostname);
return -1;
}
}
/* Check all IP addresses returned for the hostname. If one matches, return
* 0 to indicate that the address is not likely being spoofed.
*/
for (i = 0; he->h_addr_list[i]; i++)
if (*(in_addr_t *)he->h_addr_list[i] = = addr->sin_addr.s_addr) {
*name = hostname;
endhostent( );
return 0;
}
/* No matches. Spoofing very likely */
free(hostname);
endhostent( );
return SPC_ERROR_BADHOSTNAME;
}
The next code listing contains several worker functions as well as the function spc_
host_init( ), which requires a single argument that is the name of a file from which
access restriction information is to be read. The access restriction information is read
from the file and stored in an in-memory list, which is then used by spc_host_check( )
(we’ll describe that function shortly).
Restricting Access Based on Hostname or IP Address | 381
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