--- /dev/null
+
+/* 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_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 "ares.h"
+#include "ares_dns.h"
+#include "ares_private.h"
+
+#ifndef T_OPT
+# define T_OPT 41 /* EDNS0 option (meta-RR) */
+#endif
+
+/* 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 **bufp,
+ int *buflenp, int max_udp_size)
+{
+ size_t len;
+ unsigned char *q;
+ const char *p;
+ size_t buflen;
+ unsigned char *buf;
+
+ /* Per RFC 7686, reject queries for ".onion" domain names with NXDOMAIN. */
+ if (ares__is_onion_domain(name))
+ return ARES_ENOTFOUND;
+
+ /* Set our results early, in case we bail out early with an error. */
+ *buflenp = 0;
+ *bufp = NULL;
+
+ /* Allocate a memory area for the maximum size this packet might need. +2
+ * is for the length byte and zero termination if no dots or ecscaping is
+ * used.
+ */
+ len = strlen(name) + 2 + HFIXEDSZ + QFIXEDSZ +
+ (max_udp_size ? EDNSFIXEDSZ : 0);
+ buf = ares_malloc(len);
+ 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 == '.') {
+ ares_free (buf);
+ 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) {
+ ares_free (buf);
+ 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);
+
+ q += QFIXEDSZ;
+ if (max_udp_size)
+ {
+ memset(q, 0, EDNSFIXEDSZ);
+ q++;
+ DNS_RR_SET_TYPE(q, T_OPT);
+ DNS_RR_SET_CLASS(q, max_udp_size);
+ q += (EDNSFIXEDSZ-1);
+ }
+ buflen = (q - buf);
+
+ /* 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."). */
+ if (buflen > (size_t)(MAXCDNAME + HFIXEDSZ + QFIXEDSZ +
+ (max_udp_size ? EDNSFIXEDSZ : 0))) {
+ ares_free (buf);
+ return ARES_EBADNAME;
+ }
+
+ /* we know this fits in an int at this point */
+ *buflenp = (int) buflen;
+ *bufp = buf;
+
+ return ARES_SUCCESS;
+}
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