Added new feature (rfc2671)

Makefile.inc

@@ -20,6 +20,7 @@ CSOURCES = ares__close_sockets.c	\
   ares_library_init.c			\
   ares_llist.c				\
   ares_mkquery.c			\
+  ares_create_query.c			\
   ares_nowarn.c				\
   ares_options.c			\
   ares_parse_a_reply.c			\
@@ -92,6 +93,7 @@ MANPAGES = ares_cancel.3		\
   ares_library_cleanup.3		\
   ares_library_init.3			\
   ares_mkquery.3			\
+  ares_create_query.3			\
   ares_parse_a_reply.3			\
   ares_parse_aaaa_reply.3		\
   ares_parse_mx_reply.3			\
@@ -133,6 +135,7 @@ HTMLPAGES = ares_cancel.html		\
   ares_library_cleanup.html		\
   ares_library_init.html		\
   ares_mkquery.html			\
+  ares_create_query.html			\
   ares_parse_a_reply.html		\
   ares_parse_aaaa_reply.html		\
   ares_parse_mx_reply.html		\
@@ -173,6 +176,7 @@ PDFPAGES = ares_cancel.pdf		\
   ares_library_cleanup.pdf		\
   ares_library_init.pdf			\
   ares_mkquery.pdf			\
+  ares_create_query.pdf			\
   ares_parse_a_reply.pdf		\
   ares_parse_aaaa_reply.pdf		\
   ares_parse_mx_reply.pdf		\

ares.h

@@ -143,6 +143,7 @@ extern "C" {
 #define ARES_FLAG_NOSEARCH      (1 << 5)
 #define ARES_FLAG_NOALIASES     (1 << 6)
 #define ARES_FLAG_NOCHECKRESP   (1 << 7)
+#define ARES_FLAG_EDNS          (1 << 8)
 
 /* Option mask values */
 #define ARES_OPT_FLAGS          (1 << 0)
@@ -160,6 +161,7 @@ extern "C" {
 #define ARES_OPT_SOCK_RCVBUF    (1 << 12)
 #define ARES_OPT_TIMEOUTMS      (1 << 13)
 #define ARES_OPT_ROTATE         (1 << 14)
+#define ARES_OPT_EDNSPSZ        (1 << 15)
 
 /* Nameinfo flag values */
 #define ARES_NI_NOFQDN                  (1 << 0)
@@ -265,6 +267,7 @@ struct ares_options {
   void *sock_state_cb_data;
   struct apattern *sortlist;
   int nsort;
+  int ednspsz;
 };
 
 struct hostent;
@@ -403,6 +406,15 @@ CARES_EXTERN void ares_process_fd(ares_channel channel,
                                   ares_socket_t read_fd,
                                   ares_socket_t write_fd);
 
+CARES_EXTERN int ares_create_query(const char *name,
+                                   int dnsclass,
+                                   int type,
+                                   unsigned short id,
+                                   int rd,
+                                   unsigned char **buf,
+                                   int *buflen,
+                                   int max_udp_size);
+
 CARES_EXTERN int ares_mkquery(const char *name,
                               int dnsclass,
                               int type,

ares_create_query.3

@@ -0,0 +1,79 @@
+.\"
+.\" Copyright 1998, 2000 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_CREATE_QUERY 3 "20 Nov 2009"
+.SH NAME
+ares_create_query \- Compose a single-question DNS query buffer
+.SH SYNOPSIS
+.nf
+.B #include <ares.h>
+.PP
+.B int ares_create_query(const char *\fIname\fP, int \fIdnsclass\fP,\
+                         int \fItype\fP,
+.B		                   unsigned short \fIid\fP, int \fIrd\fP,\
+                         unsigned char **\fIbuf\fP,
+.B		                   int *\fIbuflen\fP, int \fImax_udp_size\fP)
+.fi
+.SH DESCRIPTION
+The
+.B ares_create_query
+function composes a DNS query with a single question.
+The parameter
+.I name
+gives the query name as a NUL-terminated C string of period-separated
+labels optionally ending with a period; periods and backslashes within
+a label must be escaped with a backlash.  The parameters
+.I dnsclass
+and
+.I type
+give the class and type of the query using the values defined in
+.BR <arpa/nameser.h> .
+The parameter
+.I id
+gives a 16-bit identifier for the query.  The parameter
+.I rd
+should be nonzero if recursion is desired, zero if not.  The query
+will be placed in an allocated buffer, a pointer to which will be
+stored in the variable pointed to by
+.IR buf ,
+and the length of which will be stored in the variable pointed to by
+.IR buflen .
+It is the caller's responsibility to free this buffer using
+\fIares_free_string(3)\fP when it is no longer needed.
+The parameter
+.I max_udp_size
+should be nonzero to activate EDNS. Usage of \fIares_create_query(3)\fP\ with
+.I max_udp_size
+set to zero is equivalent to \fIares_mkquery(3)\fP.
+.SH RETURN VALUES
+.B ares_create_query
+can return any of the following values:
+.TP 15
+.B ARES_SUCCESS
+Construction of the DNS query succeeded.
+.TP 15
+.B ARES_EBADNAME
+The query name
+.I name
+could not be encoded as a domain name, either because it contained a
+zero-length label or because it contained a label of more than 63
+characters.
+.TP 15
+.B ARES_ENOMEM
+Memory was exhausted.
+.SH SEE ALSO
+.BR ares_expand_name (3),
+.BR ares_free_string (3)
+.SH AUTHOR

ares_create_query.c

@@ -0,0 +1,209 @@
+
+/* 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_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_private.h"
+
+/* Header format, from RFC 1035:
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                      ID                       |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    QDCOUNT                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    ANCOUNT                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    NSCOUNT                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    ARCOUNT                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ * AA, TC, RA, and RCODE are only set in responses.  Brief description
+ * of the remaining fields:
+ *      ID      Identifier to match responses with queries
+ *      QR      Query (0) or response (1)
+ *      Opcode  For our purposes, always QUERY
+ *      RD      Recursion desired
+ *      Z       Reserved (zero)
+ *      QDCOUNT Number of queries
+ *      ANCOUNT Number of answers
+ *      NSCOUNT Number of name server records
+ *      ARCOUNT Number of additional records
+ *
+ * Question format, from RFC 1035:
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                                               |
+ *  /                     QNAME                     /
+ *  /                                               /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                     QTYPE                     |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                     QCLASS                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ * The query name is encoded as a series of labels, each represented
+ * as a one-byte length (maximum 63) followed by the text of the
+ * label.  The list is terminated by a label of length zero (which can
+ * be thought of as the root domain).
+ */
+
+int ares_create_query(const char *name, int dnsclass, int type,
+                      unsigned short id, int rd, unsigned char **buf,
+                      int *buflen, int max_udp_size)
+{
+  int len;
+  unsigned char *q;
+  const char *p;
+
+  /* Set our results early, in case we bail out early with an error. */
+  *buflen = 0;
+  *buf = NULL;
+
+  /* Compute the length of the encoded name so we can check buflen.
+   * Start counting at 1 for the zero-length label at the end. */
+  len = 1;
+  for (p = name; *p; p++)
+    {
+      if (*p == '\\' && *(p + 1) != 0)
+        p++;
+      len++;
+    }
+  /* If there are n periods in the name, there are n + 1 labels, and
+   * thus n + 1 length fields, unless the name is empty or ends with a
+   * period.  So add 1 unless name is empty or ends with a period.
+   */
+  if (*name && *(p - 1) != '.')
+    len++;
+
+  /* Immediately reject names that are longer than the maximum of 255
+   * bytes that's specified in RFC 1035 ("To simplify implementations,
+   * the total length of a domain name (i.e., label octets and label
+   * length octets) is restricted to 255 octets or less."). We aren't
+   * doing this just to be a stickler about RFCs. For names that are
+   * too long, 'dnscache' closes its TCP connection to us immediately
+   * (when using TCP) and ignores the request when using UDP, and
+   * BIND's named returns ServFail (TCP or UDP). Sending a request
+   * that we know will cause 'dnscache' to close the TCP connection is
+   * painful, since that makes any other outstanding requests on that
+   * connection fail. And sending a UDP request that we know
+   * 'dnscache' will ignore is bad because resources will be tied up
+   * until we time-out the request.
+   */
+  if (len > MAXCDNAME)
+    return ARES_EBADNAME;
+
+  *buflen = len + HFIXEDSZ + QFIXEDSZ + (max_udp_size ? EDNSFIXEDSZ : 0);
+  *buf = malloc(*buflen);
+  if (!*buf)
+      return ARES_ENOMEM;
+
+  /* Set up the header. */
+  q = *buf;
+  memset(q, 0, HFIXEDSZ);
+  DNS_HEADER_SET_QID(q, id);
+  DNS_HEADER_SET_OPCODE(q, QUERY);
+  if (rd) {
+    DNS_HEADER_SET_RD(q, 1);
+  }
+  else {
+    DNS_HEADER_SET_RD(q, 0);
+  }
+  DNS_HEADER_SET_QDCOUNT(q, 1);
+
+  if (max_udp_size) {
+      DNS_HEADER_SET_ARCOUNT(q, 1);
+  }
+
+  /* A name of "." is a screw case for the loop below, so adjust it. */
+  if (strcmp(name, ".") == 0)
+    name++;
+
+  /* Start writing out the name after the header. */
+  q += HFIXEDSZ;
+  while (*name)
+    {
+      if (*name == '.')
+        return ARES_EBADNAME;
+
+      /* Count the number of bytes in this label. */
+      len = 0;
+      for (p = name; *p && *p != '.'; p++)
+        {
+          if (*p == '\\' && *(p + 1) != 0)
+            p++;
+          len++;
+        }
+      if (len > MAXLABEL)
+        return ARES_EBADNAME;
+
+      /* Encode the length and copy the data. */
+      *q++ = (unsigned char)len;
+      for (p = name; *p && *p != '.'; p++)
+        {
+          if (*p == '\\' && *(p + 1) != 0)
+            p++;
+          *q++ = *p;
+        }
+
+      /* Go to the next label and repeat, unless we hit the end. */
+      if (!*p)
+        break;
+      name = p + 1;
+    }
+
+  /* Add the zero-length label at the end. */
+  *q++ = 0;
+
+  /* Finish off the question with the type and class. */
+  DNS_QUESTION_SET_TYPE(q, type);
+  DNS_QUESTION_SET_CLASS(q, dnsclass);
+
+  if (max_udp_size)
+  {
+      q += QFIXEDSZ;
+      memset(q, 0, EDNSFIXEDSZ);
+      q++;
+      DNS_RR_SET_TYPE(q, ns_t_opt);
+      DNS_RR_SET_CLASS(q, max_udp_size);
+  }
+
+  return ARES_SUCCESS;
+}

ares_dns.h

@@ -95,9 +95,9 @@
 #define DNS_RR_LEN(r)                   DNS__16BIT((r) + 8)
 
 /* Macros for constructing the fixed part of a DNS resource record */
-#define DNS_RR_SET_TYPE(r)              DNS__SET16BIT(r, v)
-#define DNS_RR_SET_CLASS(r)             DNS__SET16BIT((r) + 2, v)
-#define DNS_RR_SET_TTL(r)               DNS__SET32BIT((r) + 4, v)
-#define DNS_RR_SET_LEN(r)               DNS__SET16BIT((r) + 8, v)
+#define DNS_RR_SET_TYPE(r, v)           DNS__SET16BIT(r, v)
+#define DNS_RR_SET_CLASS(r, v)          DNS__SET16BIT((r) + 2, v)
+#define DNS_RR_SET_TTL(r, v)            DNS__SET32BIT((r) + 4, v)
+#define DNS_RR_SET_LEN(r, v)            DNS__SET16BIT((r) + 8, v)
 
 #endif /* HEADER_CARES_DNS_H */