- Jakub Hrozek added ares_parse_srv_reply() for SRV parsing

ares/CHANGES

@@ -1,5 +1,8 @@
   Changelog for the c-ares project
 
+* 4 Sep 2009 (Daniel Stenberg)
+- Jakub Hrozek added ares_parse_srv_reply() for SRV parsing
+
 * 3 Aug 2009 (Daniel Stenberg)
 - Joshua Kwan fixed the init routine to fill in the defaults for stuff that
   fails to get inited by other means. This fixes a case of when the c-ares

ares/Makefile.inc

@@ -22,6 +22,7 @@ CSOURCES = ares__close_sockets.c	\
   ares_parse_aaaa_reply.c		\
   ares_parse_ns_reply.c			\
   ares_parse_ptr_reply.c		\
+  ares_parse_srv_reply.c		\
   ares_process.c			\
   ares_query.c				\
   ares_search.c				\

ares/RELEASE-NOTES

@@ -10,6 +10,7 @@ Changed:
  o new ares_library_init() and ares_library_cleanup() functions
  o new --enable-curldebug configure option
  o ARES_ECANCELLED is now sent as reason for ares_cancel()
+ o added ares_parse_srv_reply()
 
 Fixed:
 
@@ -22,6 +23,6 @@ Fixed:
 Thanks go to these friendly people for their efforts and contributions:
 
  Phil Blundell, Japheth Cleaver, Yang Tse, Gregor Jasny, Joshua Kwan,
- Timo Teras
+ Timo Teras, Jakub Hrozek
 
 Have fun!

ares/ares.h

@@ -1,6 +1,6 @@
 /* $Id$ */
 
-/* Copyright 1998 by the Massachusetts Institute of Technology.
+/* Copyright 1998, 2009 by the Massachusetts Institute of Technology.
  * Copyright (C) 2007-2009 by Daniel Stenberg
  *
  * Permission to use, copy, modify, and distribute this
@@ -322,6 +322,13 @@ struct addr6ttl {
   int             ttl;
 };
 
+struct srv_reply {
+  u_int16_t weight;
+  u_int16_t priority;
+  u_int16_t port;
+  char *host;
+};
+
 /*
 ** 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.
@@ -339,6 +346,8 @@ int ares_parse_ptr_reply(const unsigned char *abuf, int alen, const void *addr,
                          int addrlen, int family, struct hostent **host);
 int ares_parse_ns_reply(const unsigned char *abuf, int alen,
                         struct hostent **host);
+int ares_parse_srv_reply(const unsigned char* abuf, int alen,
+                         struct srv_reply** srv_out, int *nsrvreply);
 void ares_free_string(void *str);
 void ares_free_hostent(struct hostent *host);
 const char *ares_strerror(int code);

ares/ares_parse_srv_reply.3

@@ -0,0 +1,78 @@
+.\"
+.\" 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_SRV_REPLY 3 "4 August 2009"
+.SH NAME
+ares_parse_srv_reply \- Parse a reply to a DNS query of type SRV into a
+struct srv_reply
+.SH SYNOPSIS
+.nf
+.B #include <ares.h>
+.PP
+.B int ares_parse_srv_reply(const unsigned char* \fIabuf\fP, int \fIalen\fP,
+.B                          struct srv_reply** \fIsrv_out\fP, int *\fInsrvreply\fP);
+.fi
+.SH DESCRIPTION
+The
+.B ares_parse_srv_reply
+function parses the response to a query of type SRV into a
+.I struct srv_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 srv_out .
+The number of responses is stored into the variable pointed to by
+.IR nsrvreply .
+It is the caller's responsibility to free the resulting
+.IR srv_out
+structure when it is no longer needed.
+.PP
+The structure 
+.I srv_reply
+contains the following fields:
+.sp
+.in +4n
+.nf
+struct srv_reply {
+    u_int16_t weight;
+    u_int16_t priority;
+    u_int16_t port;
+    char *host;
+};
+.fi
+.in
+.PP
+.SH RETURN VALUES
+.B ares_parse_srv_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/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;
+}