added ares_parse_mx_reply

2025-10-06 11:59:48 +00:00 · 2010-04-18 00:29:26 +02:00
parent f28874d323
commit 63918fca76
7 changed files with 286 additions and 0 deletions
--- a/ares_parse_mx_reply.c
+++ b/ares_parse_mx_reply.c
@ -0,0 +1,170 @@
+
+/* Copyright 1998 by the Massachusetts Institute of Technology.
+ * Copyright (C) 2010 Jeremy Lal <kapouer@melix.org>
+ *
+ * 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
+
+#include <stdlib.h>
+#include <string.h>
+#include "ares.h"
+#include "ares_dns.h"
+#include "ares_data.h"
+#include "ares_private.h"
+
+int
+ares_parse_mx_reply (const unsigned char *abuf, int alen,
+                      struct ares_mx_reply **mx_out)
+{
+  unsigned int qdcount, ancount, i;
+  const unsigned char *aptr, *vptr;
+  int status, rr_type, rr_class, rr_len;
+  long len;
+  char *hostname = NULL, *rr_name = NULL;
+  struct ares_mx_reply *mx_head = NULL;
+  struct ares_mx_reply *mx_last = NULL;
+  struct ares_mx_reply *mx_curr;
+
+  /* Set *mx_out to NULL for all failure cases. */
+  *mx_out = 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;
+  if (ancount == 0)
+    return ARES_ENODATA;
+
+  /* Expand the name from the question, and skip past the question. */
+  aptr = abuf + HFIXEDSZ;
+  status = ares_expand_name (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;
+
+  /* Examine each answer resource record (RR) in turn. */
+  for (i = 0; i < ancount; i++)
+    {
+      /* Decode the RR up to the data field. */
+      status = ares_expand_name (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);
+      aptr += RRFIXEDSZ;
+
+      /* Check if we are really looking at a MX record */
+      if (rr_class == C_IN && rr_type == T_MX)
+        {
+          /* parse the MX record itself */
+          if (rr_len < 2)
+            {
+              status = ARES_EBADRESP;
+              break;
+            }
+
+          /* Allocate storage for this MX answer appending it to the list */
+          mx_curr = ares_malloc_data(ARES_DATATYPE_MX_REPLY);
+          if (!mx_curr)
+            {
+              status = ARES_ENOMEM;
+              break;
+            }
+          if (mx_last)
+            {
+              mx_last->next = mx_curr;
+            }
+          else
+            {
+              mx_head = mx_curr;
+            }
+          mx_last = mx_curr;
+
+          vptr = aptr;
+          mx_curr->priority = ntohs (*((unsigned short *)vptr));
+          vptr += sizeof(unsigned short);
+
+          status = ares_expand_name (vptr, abuf, alen, &mx_curr->host, &len);
+          if (status != ARES_SUCCESS)
+            break;
+        }
+
+      /* Don't lose memory in the next iteration */
+      free (rr_name);
+      rr_name = NULL;
+
+      /* Move on to the next record */
+      aptr += rr_len;
+    }
+
+  if (hostname)
+    free (hostname);
+  if (rr_name)
+    free (rr_name);
+
+  /* clean up on error */
+  if (status != ARES_SUCCESS)
+    {
+      if (mx_head)
+        ares_free_data (mx_head);
+      return status;
+    }
+
+  /* everything looks fine, return the data */
+  *mx_out = mx_head;
+
+  return ARES_SUCCESS;
+}