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#include <alloca.h>
#include <sys/socket.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <resolv.h>
#include <arpa/nameser.h>
#include <stdlib.h>
#include <string.h>
/* This is dumb, but glibc doesn't like to do hostname lookups w/o libc.so */
union dns_response{
HEADER hdr;
u_char buf[PACKETSZ];
} ;
static int doQuery(char * query, int queryType,
char ** domainName, struct in_addr * ipNum) {
int len, ancount, type;
u_char * data, * end;
char name[MAXDNAME];
union dns_response response;
/* Give time to finish ethernet negotiation */
_res.retry = 3;
len = res_search(query, C_IN, queryType, (void *) &response,
sizeof(response));
if (len <= 0) return -1;
if (ntohs(response.hdr.rcode) != NOERROR) return -1;
ancount = ntohs(response.hdr.ancount);
if (ancount < 1) return -1;
data = response.buf + sizeof(HEADER);
end = response.buf + len;
/* skip the question */
data += dn_skipname(data, end) + QFIXEDSZ;
/* parse the answer(s) */
while (--ancount >= 0 && data < end) {
/* skip the domain name portion of the RR record */
data += dn_skipname(data, end);
/* get RR information */
GETSHORT(type, data);
data += INT16SZ; /* skipp class */
data += INT32SZ; /* skipp TTL */
GETSHORT(len, data);
if (type == T_PTR) {
/* we got a pointer */
len = dn_expand(response.buf, end, data, name, sizeof(name));
if (len <= 0) return -1;
if (queryType == T_PTR && domainName) {
/* we wanted a pointer */
*domainName = malloc(strlen(name) + 1);
strcpy(*domainName, name);
return 0;
}
} else if (type == T_A) {
/* we got an address */
if (queryType == T_A && ipNum) {
/* we wanted an address */
memcpy(ipNum, data, sizeof(*ipNum));
return 0;
}
}
/* move ahead to next RR */
data += len;
}
return -1;
}
char * mygethostbyaddr(char * ipnum) {
int rc;
char * result;
char * strbuf;
char * chptr;
char * splits[4];
int i;
_res.retry = 1;
strbuf = alloca(strlen(ipnum) + 1);
strcpy(strbuf, ipnum);
ipnum = alloca(strlen(strbuf) + 20);
for (i = 0; i < 4; i++) {
chptr = strbuf;
while (*chptr && *chptr != '.') chptr++;
*chptr = '\0';
if (chptr - strbuf > 3) return NULL;
splits[i] = strbuf;
strbuf = chptr + 1;
}
sprintf(ipnum, "%s.%s.%s.%s.in-addr.arpa", splits[3], splits[2],
splits[1], splits[0]);
rc = doQuery(ipnum, T_PTR, &result, NULL);
if (rc)
rc = doQuery(ipnum, T_PTR, &result, NULL);
if (rc)
return NULL;
else
return result;
}
int mygethostbyname(char * name, struct in_addr * addr) {
return doQuery(name, T_A, NULL, addr);
}
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