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#include <alloca.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <resolv.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <stdlib.h>
#include <string.h>
#include "dns.h"
/* This is dumb, but glibc doesn't like to do hostname lookups w/o libc.so */
/*
* IPv6 DNS extensions documented here:
* http://tools.ietf.org/html/rfc3596
*/
union dns_response{
HEADER hdr;
u_char buf[PACKETSZ];
};
static int doQuery(char * query, int queryType,
char ** domainName, void * ipNum, int family) {
int len, ancount, type;
u_char * data, * end;
char name[MAXDNAME];
union dns_response static_response, *response = &static_response;
size_t response_len = sizeof(static_response);
/* Give time to finish ethernet negotiation */
_res.retry = 3;
do {
len = res_search(query, C_IN, queryType, (void*)response, response_len);
if (len <= 0) return -1;
if (len < response_len) break;
if (response != &static_response) free(response);
if (len > 0x10000) return -1;
response_len = len + 1024;
response = malloc(response_len);
if (response == NULL) return -1;
} while (1);
if (len < sizeof(response->hdr)) {
if (response != &static_response) free(response);
return -1;
}
if (ntohs(response->hdr.rcode) != NOERROR) {
if (response != &static_response) free(response);
return -1;
}
ancount = ntohs(response->hdr.ancount);
if (ancount < 1) {
if (response != &static_response) free(response);
return -1;
}
data = response->buf + sizeof(HEADER);
end = response->buf + len;
/* skip the question */
len = dn_skipname(data, end);
if (len <= 0) {
if (response != &static_response) free(response);
return -1;
}
data += len + 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 */
if (data + 3 * INT16SZ + INT32SZ > end) {
if (response != &static_response) free(response);
return -1;
}
GETSHORT(type, data);
data += INT16SZ; /* skip class */
data += INT32SZ; /* skip 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) {
if (response != &static_response) free(response);
return -1;
}
if (queryType == T_PTR && domainName) {
/* we wanted a pointer */
*domainName = malloc(strlen(name) + 1);
strcpy(*domainName, name);
if (response != &static_response) free(response);
return 0;
}
} else if (type == T_A) {
/* we have an IPv4 address */
if (queryType == T_A && ipNum) {
memcpy(ipNum, data, sizeof(struct in_addr));
if (response != &static_response)
free(response);
return 0;
}
} else if (type == T_AAAA) {
/* we have an IPv6 address */
if (queryType == T_AAAA && ipNum) {
memcpy(ipNum, data, sizeof(struct in6_addr));
if (response != &static_response)
free(response);
return 0;
}
}
/* move ahead to next RR */
data += len;
}
if (response != &static_response) free(response);
return -1;
}
char * mygethostbyaddr(char * ipnum, int family) {
int i, j, ret;
char *buf = NULL;
char sbuf[5];
char *result = NULL;
char *octets[4];
char *octet = NULL;
char *parts[8];
char *partptr = NULL;
struct in6_addr addr6;
_res.retry = 1;
if (ipnum == NULL || (family != AF_INET && family != AF_INET6))
return NULL;
if (family == AF_INET) {
buf = strdup(ipnum);
octet = strtok(buf, ".");
i = 0;
while (octet != NULL) {
octets[i] = octet;
i++;
octet = strtok(NULL, ".");
}
if (i == 4) {
if (asprintf(&ipnum, "%s.%s.%s.%s.in-addr.arpa", octets[3],
octets[2], octets[1], octets[0]) == -1)
return NULL;
} else {
return NULL;
}
free(buf);
buf = NULL;
} else if (family == AF_INET6) {
if (!inet_pton(AF_INET6, ipnum, &addr6))
return NULL;
i = 7;
while (i >= 0) {
sprintf(sbuf, "%4x", ntohs(addr6.s6_addr16[i]));
sbuf[4] = '\0';
if ((parts[i] = malloc(8)) == NULL)
return NULL;
partptr = parts[i];
for (j = 3; j >= 0; j--) {
if (sbuf[j] == ' ')
*partptr = '0';
else
*partptr = sbuf[j];
partptr++;
if (j != 0) {
*partptr = '.';
partptr++;
}
}
i--;
}
if (asprintf(&ipnum, "%s.%s.%s.%s.%s.%s.%s.%s.ip6.arpa", parts[7],
parts[6], parts[5], parts[4], parts[3], parts[2],
parts[1], parts[0]) == -1)
return NULL;
for (j = 0; j < 8; j++) {
free(parts[j]);
parts[j] = NULL;
}
}
ret = doQuery(ipnum, T_PTR, &result, NULL, family);
if (ret)
ret = doQuery(ipnum, T_PTR, &result, NULL, family);
if (ret)
return NULL;
else
return result;
}
int mygethostbyname(char * name, void * addr, int family) {
int type;
if (family == AF_INET)
type = T_A;
else if (family == AF_INET6)
type = T_AAAA;
else
type = -1;
return doQuery(name, type, NULL, addr, family);
}
#if 0
int main(int argc, char **argv) {
struct in_addr addr;
struct in6_addr addr6;
char *ret = NULL;
/* IPv4 tests */
printf("hostname for %s is %s\n", "152.1.2.22",
mygethostbyaddr("152.1.2.22", AF_INET));
if (mygethostbyname("www.redhat.com", &addr, AF_INET) == 0) {
ret = malloc(48);
inet_ntop(AF_INET, &addr, ret, INET_ADDRSTRLEN);
printf("ip for www.redhat.com is %s\n", ret);
free(ret);
ret = NULL;
}
/* IPv6 tests */
printf("hostname for %s is %s\n", "fec0:acdc:1::1",
mygethostbyaddr("fec0:acdc:1::1", AF_INET6));
if (mygethostbyname("cutlet.ipv6.install.boston.redhat.com", &addr6, AF_INET6) == 0) {
ret = malloc(48);
inet_ntop(AF_INET6, &addr6, ret, INET6_ADDRSTRLEN);
printf("ip for cutlet.ipv6.install.boston.redhat.com is %s\n", ret);
free(ret);
ret = NULL;
}
return 0;
}
#endif
/* vim:set shiftwidth=4 softtabstop=4: */
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