- Jakub Hrozek added ares_parse_srv_reply() for SRV parsing

2009-09-04 21:56:14 +00:00
parent 223c0b980b
commit 2cf0f80e9f
6 changed files with 253 additions and 2 deletions
--- a/ares/ares_parse_srv_reply.c
+++ b/ares/ares_parse_srv_reply.c
@@ -0,0 +1,159 @@
+/* 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.
+ */
+
+/*
+ * ares_parse_srv_reply created by Jakub Hrozek <jhrozek@redhat.com>
+ *      on behalf of Red Hat - http://www.redhat.com
+ */
+
+#include "setup.h"
+
+#if defined(WIN32) && !defined(WATT32)
+#include "nameser.h"
+#else
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <arpa/nameser.h>
+#ifdef HAVE_ARPA_NAMESER_COMPAT_H
+#include <arpa/nameser_compat.h>
+#endif
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include "ares.h"
+#include "ares_dns.h"
+#include "ares_private.h"
+
+int
+ares_parse_srv_reply (const unsigned char *abuf, int alen,
+                      struct srv_reply **srv_out, int *nsrvreply)
+{
+  unsigned int qdcount, ancount;
+  const unsigned char *aptr;
+  int status, i, rr_type, rr_class, rr_len;
+  long len;
+  char *hostname = NULL, *rr_name = NULL;
+  struct srv_reply *srv = NULL;
+
+  /* Set *srv_out to NULL for all failure cases. */
+  if (srv_out)
+    *srv_out = NULL;
+  /* Same with *nsrvreply. */
+  if (nsrvreply)
+    *nsrvreply = 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;
+  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;
+
+  /* Allocate srv_reply array; ancount gives an upper bound */
+  srv = malloc ((ancount) * sizeof (struct srv_reply));
+  if (!srv)
+    {
+      free (hostname);
+      return ARES_ENOMEM;
+    }
+
+  /* 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 (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 SRV record */
+      if (rr_class == C_IN && rr_type == T_SRV)
+        {
+          /* parse the SRV record itself */
+          if (rr_len < 6)
+            {
+              status = ARES_EBADRESP;
+              break;
+            }
+
+          srv[i].priority = ntohs (*((uint16_t *)aptr));
+          aptr += sizeof(uint16_t);
+          srv[i].weight = ntohs (*((uint16_t *)aptr));
+          aptr += sizeof(uint16_t);
+          srv[i].port = ntohs (*((uint16_t *)aptr));
+          aptr += sizeof(uint16_t);
+
+          status = ares_expand_name (aptr, abuf, alen, &srv[i].host, &len);
+          if (status != ARES_SUCCESS)
+            break;
+
+          /* Move on to the next record */
+          aptr += len;
+
+          /* Don't lose memory in the next iteration */
+          free (rr_name);
+          rr_name = NULL;
+        }
+    }
+
+  /* clean up on error */
+  if (status != ARES_SUCCESS)
+    {
+      free (srv);
+      free (hostname);
+      free (rr_name);
+      return status;
+    }
+
+  /* everything looks fine, return the data */
+  *srv_out = srv;
+  *nsrvreply = ancount;
+
+  free (hostname);
+  free (rr_name);
+  return status;
+}