Jakub Hrozek added ares_parse_txt_reply() for TXT parsing

CHANGES

@@ -1,5 +1,8 @@
   Changelog for the c-ares project
 
+* October 29, 2009 (Daniel Stenberg)
+- Jakub Hrozek added ares_parse_txt_reply() for TXT parsing
+
 * October 23, 2009 (Yang Tse)
 - John Engelhart noticed an unreleased problem relative to a duplicate
   ARES_ECANCELLED error code value and missing error code description.

Makefile.inc

@@ -23,6 +23,8 @@ CSOURCES = ares__close_sockets.c	\
   ares_parse_ns_reply.c			\
   ares_parse_ptr_reply.c		\
   ares_parse_srv_reply.c		\
+  ares_parse_txt_reply.c		\
+  ares_free_txt_reply.c                 \
   ares_process.c			\
   ares_query.c				\
   ares_search.c				\

RELEASE-NOTES

@@ -1,4 +1,4 @@
-This is what's new and changed in the c-ares 1.6.1 release:
+This is what's new and changed in the c-ares 1.7.0 release:
 
 Changed:
 
@@ -11,6 +11,7 @@ Changed:
  o new --enable-curldebug configure option
  o ARES_ECANCELLED is now sent as reason for ares_cancel()
  o added ares_parse_srv_reply()
+ o added ares_parse_txt_reply()
 
 Fixed:
 

ares.h

@@ -436,6 +436,11 @@ struct ares_srv_reply {
   char *host;
 };
 
+struct ares_txt_reply {
+  unsigned int  length;
+  unsigned char *txt;
+};
+
 /*
 ** Parse the buffer, starting at *abuf and of length alen bytes, previously
 ** obtained from an ares_search call.  Put the results in *host, if nonnull.
@@ -472,6 +477,11 @@ CARES_EXTERN int ares_parse_srv_reply(const unsigned char* abuf,
                                       struct ares_srv_reply** srv_out,
                                       int *nsrvreply);
 
+CARES_EXTERN int ares_parse_txt_reply(const unsigned char* abuf,
+                                      int alen,
+                                      struct ares_txt_reply** txt_out,
+                                      int *nsrvreply);
+
 CARES_EXTERN void ares_free_string(void *str);
 
 CARES_EXTERN void ares_free_hostent(struct hostent *host);

ares_parse_txt_reply.3

@@ -0,0 +1,77 @@
+.\"
+.\" 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.
+.\"
+.TH ARES_PARSE_TXT_REPLY 3 "27 October 2009"
+.SH NAME
+ares_parse_txt_reply \- Parse a reply to a DNS query of type TXT into a
+struct ares_txt_reply
+.SH SYNOPSIS
+.nf
+.B #include <ares.h>
+.PP
+.B int ares_parse_txt_reply(const unsigned char* \fIabuf\fP, int \fIalen\fP,
+.B                         struct ares_txt_reply **\fItxt_out\fP, int *\fIntxtreply\fP);
+.fi
+.SH DESCRIPTION
+The
+.B ares_parse_txt_reply
+function parses the response to a query of type TXT into a
+.I struct ares_txt_reply 
+The parameters
+.I abuf
+and
+.I alen
+give the contents of the response.  The result is stored in allocated
+memory and a pointer to it stored into the variable pointed to by
+.IR txt_out .
+The number of responses is stored into the variable pointed to by
+.IR ntxtreply .
+It is the caller's responsibility to free the resulting
+.IR txt_out
+structure when it is no longer needed.
+.PP
+The structure 
+.I ares_txt_reply
+contains the following fields:
+.sp
+.in +4n
+.nf
+struct ares_txt_reply {
+  unsigned int  length;
+  unsigned char *txt;
+};
+.fi
+.in
+.PP
+.SH RETURN VALUES
+.B ares_parse_txt_reply
+can return any of the following values:
+.TP 15
+.B ARES_SUCCESS
+The response was successfully parsed.
+.TP 15
+.B ARES_EBADRESP
+The response was malformatted.
+.TP 15
+.B ARES_ENODATA
+The response did not contain an answer to the query.
+.TP 15
+.B ARES_ENOMEM
+Memory was exhausted.
+.SH SEE ALSO
+.BR ares_query (3)
+.SH AUTHOR
+Written by Jakub Hrozek <jhrozek@redhat.com>, on behalf of Red Hat, Inc http://www.redhat.com
+

ares_parse_txt_reply.c

@@ -0,0 +1,176 @@
+/* Copyright (C) 2009 Jakub Hrozek <jhrozek@redhat.com>
+*
+* 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"
+
+#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_txt_reply (const unsigned char *abuf, int alen,
+                      struct ares_txt_reply **txt_out, int *ntxtreply)
+{
+  unsigned char substr_len = 0;
+  unsigned char str_len = 0;
+  unsigned int qdcount, ancount;
+  const unsigned char *aptr;
+  const unsigned char *strptr;
+  int status, i, rr_type, rr_class, rr_len;
+  long len;
+  char *hostname = NULL, *rr_name = NULL;
+  struct ares_txt_reply *txt = NULL;
+
+  *txt_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;
+
+  /* Allocate ares_txt_reply array; ancount gives an upper bound */
+  txt = malloc ((ancount) * sizeof (struct ares_txt_reply));
+  if (!txt)
+    {
+      free (hostname);
+      return ARES_ENOMEM;
+    }
+  /* Zero out so we can safely free txt.txt even if NULL */
+  memset(txt, 0, ancount * sizeof (struct ares_txt_reply));
+
+  /* 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 TXT record */
+      if (rr_class == C_IN && rr_type == T_TXT)
+        {
+          /*
+           * There may be multiple substrings in a single TXT record. Each
+           * substring may be up to 255 characters in length, with a
+           * "length byte" indicating the size of the substring payload.
+           * RDATA contains both the length-bytes and payloads of all
+           * substrings contained therein.
+           */
+
+          /* Realloc would be expensive, compute the total length */
+          txt[i].length = 0;
+          strptr = aptr;
+          while (strptr < (aptr + rr_len))
+            {
+              memcpy ((void *) &substr_len, strptr, sizeof (unsigned char));
+              txt[i].length += substr_len;
+              strptr += substr_len + 1;
+            }
+
+          /* Including null byte */
+          txt[i].txt = malloc (sizeof (unsigned char) * (txt[i].length + 1));
+          if (txt[i].txt == NULL)
+            {
+              status = ARES_ENOMEM;
+              break;
+            }
+
+          /* Step through the list of substrings, concatenating them */
+          substr_len = 0;
+          str_len = 0;
+          strptr = aptr;
+          while (strptr < (aptr + rr_len))
+            {
+              memcpy ((void *) &substr_len, strptr, sizeof (unsigned char));
+              strptr++;
+              memcpy ((void *) txt[i].txt + str_len, strptr,
+                      sizeof (unsigned char) * substr_len);
+              str_len += substr_len;
+              strptr += substr_len;
+            }
+          /* Make sure we NULL-terminate */
+          txt[i].txt[txt[i].length] = '\0';
+
+          /* Move on to the next record */
+          aptr += rr_len;
+        }
+
+      /* Don't lose memory in the next iteration */
+      free (rr_name);
+      rr_name = NULL;
+    }
+
+  free (hostname);
+  free (rr_name);
+
+  /* clean up on error */
+  if (status != ARES_SUCCESS)
+    {
+      ares_free_txt_reply(txt, ancount);
+      return status;
+    }
+
+  /* everything looks fine, return the data */
+  *txt_out = txt;
+  *ntxtreply = ancount;
+  return 0;
+}