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authorAnas Nashif <anas.nashif@intel.com>2012-10-30 20:54:38 (GMT)
committerAnas Nashif <anas.nashif@intel.com>2012-10-30 20:54:38 (GMT)
commitb8e6c26b7b9608dffc84645f17fe4cf534af18dd (patch)
tree61d9fff2984aa043471a1c305cfc4c76d7a099fb /ares_parse_a_reply.c
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Imported Upstream version 1.7.5upstream/1.7.5
Diffstat (limited to 'ares_parse_a_reply.c')
-rw-r--r--ares_parse_a_reply.c263
1 files changed, 263 insertions, 0 deletions
diff --git a/ares_parse_a_reply.c b/ares_parse_a_reply.c
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+
+/* 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 "ares_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 ares_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)
+ {
+ 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);
+ 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)
+ {
+ free(rr_name);
+ status = ARES_EBADRESP;
+ break;
+ }
+ memcpy(&addrs[naddrs], aptr, sizeof(struct in_addr));
+ }
+ if (naddrs < max_addr_ttls)
+ {
+ struct ares_addrttl * const at = &addrttls[naddrs];
+ if (aptr + sizeof(struct in_addr) > abuf + alen)
+ {
+ free(rr_name);
+ 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 && naliases == 0)
+ /* the check for naliases to be zero is to make sure CNAME responses
+ don't get caught here */
+ 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;
+ if (!naddrs && addrs)
+ free(addrs);
+ *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;
+}