int ares_parse_ptr_reply(const unsigned char *abuf, int alen, const void *addr,
int addrlen, int family, struct hostent **host)
{
unsigned int qdcount, ancount;
int status, i, rr_type, rr_class, rr_len;
long len;
const unsigned char *aptr;
char *ptrname, *hostname, *rr_name, *rr_data;
struct hostent *hostent;
int aliascnt = 0;
int alias_alloc = 8;
char ** aliases;
/* Set *host to NULL for all failure cases. */
*host = NULL;
/* Give up if abuf doesn't have room for a header. */
if (alen < HFIXEDSZ)
return ARES_EBADRESP;
/* Fetch the question and answer count from the header. */
qdcount = DNS_HEADER_QDCOUNT(abuf);
ancount = DNS_HEADER_ANCOUNT(abuf);
if (qdcount != 1)
return ARES_EBADRESP;
/* Expand the name from the question, and skip past the question. */
aptr = abuf + HFIXEDSZ;
status = ares__expand_name_for_response(aptr, abuf, alen, &ptrname, &len);
if (status != ARES_SUCCESS)
return status;
if (aptr + len + QFIXEDSZ > abuf + alen)
{
ares_free(ptrname);
return ARES_EBADRESP;
}
aptr += len + QFIXEDSZ;
/* Examine each answer resource record (RR) in turn. */
hostname = NULL;
aliases = ares_malloc(alias_alloc * sizeof(char *));
if (!aliases)
{
ares_free(ptrname);
return ARES_ENOMEM;
}
for (i = 0; i < (int)ancount; i++)
{
/* Decode the RR up to the data field. */
status = ares__expand_name_for_response(aptr, abuf, alen, &rr_name, &len);
if (status != ARES_SUCCESS)
break;
aptr += len;
if (aptr + RRFIXEDSZ > abuf + alen)
{
ares_free(rr_name);
status = ARES_EBADRESP;
break;
}
rr_type = DNS_RR_TYPE(aptr);
rr_class = DNS_RR_CLASS(aptr);
rr_len = DNS_RR_LEN(aptr);
aptr += RRFIXEDSZ;
if (aptr + rr_len > abuf + alen)
{
ares_free(rr_name);
status = ARES_EBADRESP;
break;
}
if (rr_class == C_IN && rr_type == T_PTR
&& strcasecmp(rr_name, ptrname) == 0)
{
/* Decode the RR data and set hostname to it. */
status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
&len);
if (status != ARES_SUCCESS)
{
ares_free(rr_name);
break;
}
if (hostname)
ares_free(hostname);
hostname = rr_data;
aliases[aliascnt] = ares_malloc((strlen(rr_data)+1) * sizeof(char));
if (!aliases[aliascnt])
{
ares_free(rr_name);
status = ARES_ENOMEM;
break;
}
strncpy(aliases[aliascnt], rr_data, strlen(rr_data)+1);
aliascnt++;
if (aliascnt >= alias_alloc) {
char **ptr;
alias_alloc *= 2;
ptr = ares_realloc(aliases, alias_alloc * sizeof(char *));
if(!ptr) {
ares_free(rr_name);
status = ARES_ENOMEM;
break;
}
aliases = ptr;
}
}
if (rr_class == C_IN && rr_type == T_CNAME)
{
/* Decode the RR data and replace ptrname with it. */
status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
&len);
if (status != ARES_SUCCESS)
{
ares_free(rr_name);
break;
}
ares_free(ptrname);
ptrname = rr_data;
}
ares_free(rr_name);
aptr += rr_len;
if (aptr > abuf + alen)
{ /* LCOV_EXCL_START: already checked above */
status = ARES_EBADRESP;
break;
} /* LCOV_EXCL_STOP */
}
if (status == ARES_SUCCESS && !hostname)
status = ARES_ENODATA;
if (status == ARES_SUCCESS)
{
/* We got our answer. Allocate memory to build the host entry. */
hostent = ares_malloc(sizeof(struct hostent));
if (hostent)
{
hostent->h_addr_list = ares_malloc(2 * sizeof(char *));
if (hostent->h_addr_list)
{
hostent->h_addr_list[0] = ares_malloc(addrlen);
if (hostent->h_addr_list[0])
{
hostent->h_aliases = ares_malloc((aliascnt+1) * sizeof (char *));
if (hostent->h_aliases)
{
/* Fill in the hostent and return successfully. */
hostent->h_name = hostname;
for (i=0 ; i<aliascnt ; i++)
hostent->h_aliases[i] = aliases[i];
hostent->h_aliases[aliascnt] = NULL;
hostent->h_addrtype = aresx_sitoss(family);
hostent->h_length = aresx_sitoss(addrlen);
memcpy(hostent->h_addr_list[0], addr, addrlen);
hostent->h_addr_list[1] = NULL;
*host = hostent;
ares_free(aliases);
ares_free(ptrname);
return ARES_SUCCESS;
}
ares_free(hostent->h_addr_list[0]);
}
ares_free(hostent->h_addr_list);
}
ares_free(hostent);
}
status = ARES_ENOMEM;
}
for (i=0 ; i<aliascnt ; i++)
if (aliases[i])
ares_free(aliases[i]);
ares_free(aliases);
if (hostname)
ares_free(hostname);
ares_free(ptrname);
return status;
}
/* Handle an answer from a server. */
static void process_answer(ares_channel channel, unsigned char *abuf,
int alen, int whichserver, int tcp,
struct timeval *now)
{
int tc, rcode, packetsz;
unsigned short id;
struct query *query;
struct list_node* list_head;
struct list_node* list_node;
/* If there's no room in the answer for a header, we can't do much
* with it. */
if (alen < HFIXEDSZ)
return;
/* Grab the query ID, truncate bit, and response code from the packet. */
id = DNS_HEADER_QID(abuf);
tc = DNS_HEADER_TC(abuf);
rcode = DNS_HEADER_RCODE(abuf);
/* Find the query corresponding to this packet. The queries are
* hashed/bucketed by query id, so this lookup should be quick. Note that
* both the query id and the questions must be the same; when the query id
* wraps around we can have multiple outstanding queries with the same query
* id, so we need to check both the id and question.
*/
query = NULL;
list_head = &(channel->queries_by_qid[id % ARES_QID_TABLE_SIZE]);
for (list_node = list_head->next; list_node != list_head;
list_node = list_node->next)
{
struct query *q = list_node->data;
if ((q->qid == id) && same_questions(q->qbuf, q->qlen, abuf, alen))
{
query = q;
break;
}
}
if (!query)
return;
packetsz = PACKETSZ;
/* If we use EDNS and server answers with one of these RCODES, the protocol
* extension is not understood by the responder. We must retry the query
* without EDNS enabled.
*/
if (channel->flags & ARES_FLAG_EDNS)
{
packetsz = channel->ednspsz;
if (rcode == NOTIMP || rcode == FORMERR || rcode == SERVFAIL)
{
int qlen = (query->tcplen - 2) - EDNSFIXEDSZ;
channel->flags ^= ARES_FLAG_EDNS;
query->tcplen -= EDNSFIXEDSZ;
query->qlen -= EDNSFIXEDSZ;
query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff);
query->tcpbuf[1] = (unsigned char)(qlen & 0xff);
DNS_HEADER_SET_ARCOUNT(query->tcpbuf + 2, 0);
query->tcpbuf = ares_realloc(query->tcpbuf, query->tcplen);
query->qbuf = query->tcpbuf + 2;
ares__send_query(channel, query, now);
return;
}
