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- /* $Id$ */
- /* Copyright 1998 by the Massachusetts Institute of Technology.
- *
- * Permission to use, copy, modify, and distribute this
- * software and its documentation for any purpose and without
- * fee is hereby granted, provided that the above copyright
- * notice appear in all copies and that both that copyright
- * notice and this permission notice appear in supporting
- * documentation, and that the name of M.I.T. not be used in
- * advertising or publicity pertaining to distribution of the
- * software without specific, written prior permission.
- * M.I.T. makes no representations about the suitability of
- * this software for any purpose. It is provided "as is"
- * without express or implied warranty.
- */
- #include "setup.h"
- #ifdef HAVE_SYS_SOCKET_H
- # include <sys/socket.h>
- #endif
- #ifdef HAVE_NETINET_IN_H
- # include <netinet/in.h>
- #endif
- #ifdef HAVE_NETDB_H
- # include <netdb.h>
- #endif
- #ifdef HAVE_ARPA_INET_H
- # include <arpa/inet.h>
- #endif
- #ifdef HAVE_ARPA_NAMESER_H
- # include <arpa/nameser.h>
- #else
- # include "nameser.h"
- #endif
- #ifdef HAVE_ARPA_NAMESER_COMPAT_H
- # include <arpa/nameser_compat.h>
- #endif
- #ifdef HAVE_STRINGS_H
- # include <strings.h>
- #endif
- #include <stdlib.h>
- #include <string.h>
- #ifdef HAVE_LIMITS_H
- # include <limits.h>
- #endif
- #include "ares.h"
- #include "ares_dns.h"
- #include "ares_private.h"
- int ares_parse_a_reply(const unsigned char *abuf, int alen,
- struct hostent **host,
- struct addrttl *addrttls, int *naddrttls)
- {
- unsigned int qdcount, ancount;
- int status, i, rr_type, rr_class, rr_len, rr_ttl, naddrs;
- int cname_ttl = INT_MAX; /* the TTL imposed by the CNAME chain */
- int naliases;
- long len;
- const unsigned char *aptr;
- char *hostname, *rr_name, *rr_data, **aliases;
- struct in_addr *addrs;
- struct hostent *hostent;
- const int max_addr_ttls = (addrttls && naddrttls) ? *naddrttls : 0;
- /* Set *host to NULL for all failure cases. */
- if (host)
- *host = NULL;
- /* Same with *naddrttls. */
- if (naddrttls)
- *naddrttls = 0;
- /* 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, &hostname, &len);
- if (status != ARES_SUCCESS)
- return status;
- if (aptr + len + QFIXEDSZ > abuf + alen)
- {
- free(hostname);
- return ARES_EBADRESP;
- }
- aptr += len + QFIXEDSZ;
- if (host)
- {
- /* Allocate addresses and aliases; ancount gives an upper bound for
- both. */
- addrs = malloc(ancount * sizeof(struct in_addr));
- if (!addrs)
- {
- free(hostname);
- return ARES_ENOMEM;
- }
- aliases = malloc((ancount + 1) * sizeof(char *));
- if (!aliases)
- {
- free(hostname);
- free(addrs);
- return ARES_ENOMEM;
- }
- }
- else
- {
- addrs = NULL;
- aliases = NULL;
- }
- naddrs = 0;
- naliases = 0;
- /* Examine each answer resource record (RR) in turn. */
- 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)
- {
- status = ARES_EBADRESP;
- break;
- }
- rr_type = DNS_RR_TYPE(aptr);
- rr_class = DNS_RR_CLASS(aptr);
- rr_len = DNS_RR_LEN(aptr);
- rr_ttl = DNS_RR_TTL(aptr);
- aptr += RRFIXEDSZ;
- if (rr_class == C_IN && rr_type == T_A
- && rr_len == sizeof(struct in_addr)
- && strcasecmp(rr_name, hostname) == 0)
- {
- if (addrs)
- {
- if (aptr + sizeof(struct in_addr) > abuf + alen)
- {
- status = ARES_EBADRESP;
- break;
- }
- memcpy(&addrs[naddrs], aptr, sizeof(struct in_addr));
- }
- if (naddrs < max_addr_ttls)
- {
- struct addrttl * const at = &addrttls[naddrs];
- if (aptr + sizeof(struct in_addr) > abuf + alen)
- {
- status = ARES_EBADRESP;
- break;
- }
- memcpy(&at->ipaddr, aptr, sizeof(struct in_addr));
- at->ttl = rr_ttl;
- }
- naddrs++;
- status = ARES_SUCCESS;
- }
- if (rr_class == C_IN && rr_type == T_CNAME)
- {
- /* Record the RR name as an alias. */
- if (aliases)
- aliases[naliases] = rr_name;
- else
- free(rr_name);
- naliases++;
- /* Decode the RR data and replace the hostname with it. */
- status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
- &len);
- if (status != ARES_SUCCESS)
- break;
- free(hostname);
- hostname = rr_data;
- /* Take the min of the TTLs we see in the CNAME chain. */
- if (cname_ttl > rr_ttl)
- cname_ttl = rr_ttl;
- }
- else
- free(rr_name);
- aptr += rr_len;
- if (aptr > abuf + alen)
- {
- status = ARES_EBADRESP;
- break;
- }
- }
- if (status == ARES_SUCCESS && naddrs == 0)
- status = ARES_ENODATA;
- if (status == ARES_SUCCESS)
- {
- /* We got our answer. */
- if (naddrttls)
- {
- const int n = naddrs < max_addr_ttls ? naddrs : max_addr_ttls;
- for (i = 0; i < n; i++)
- {
- /* Ensure that each A TTL is no larger than the CNAME TTL. */
- if (addrttls[i].ttl > cname_ttl)
- addrttls[i].ttl = cname_ttl;
- }
- *naddrttls = n;
- }
- if (aliases)
- aliases[naliases] = NULL;
- if (host)
- {
- /* Allocate memory to build the host entry. */
- hostent = malloc(sizeof(struct hostent));
- if (hostent)
- {
- hostent->h_addr_list = malloc((naddrs + 1) * sizeof(char *));
- if (hostent->h_addr_list)
- {
- /* Fill in the hostent and return successfully. */
- hostent->h_name = hostname;
- hostent->h_aliases = aliases;
- hostent->h_addrtype = AF_INET;
- hostent->h_length = sizeof(struct in_addr);
- for (i = 0; i < naddrs; i++)
- hostent->h_addr_list[i] = (char *) &addrs[i];
- hostent->h_addr_list[naddrs] = NULL;
- *host = hostent;
- return ARES_SUCCESS;
- }
- free(hostent);
- }
- status = ARES_ENOMEM;
- }
- }
- if (aliases)
- {
- for (i = 0; i < naliases; i++)
- free(aliases[i]);
- free(aliases);
- }
- free(addrs);
- free(hostname);
- return status;
- }
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