src/tscore/ink_res_mkquery.cc - trafficserver - Git at Google

 /*
  * Copyright (c) 1985, 1993
  *    The Regents of the University of California.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */

 /*
  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
  * copyright notice and this permission notice appear in all copies, and that
  * the name of Digital Equipment Corporation not be used in advertising or
  * publicity pertaining to distribution of the document or software without
  * specific, written prior permission.
  *
  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  * SOFTWARE.
  */

 /*
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
  * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
  * copyright notice and this permission notice appear in all copies.
  *
  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */

 #include "tscore/ink_config.h"
 #include "tscore/ink_defs.h"

 #include <sys/types.h>
 #include <sys/param.h>
 #include <netinet/in.h>
 #include <arpa/nameser.h>
 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
 #include <arpa/nameser_compat.h>
 #endif
 #include <netdb.h>
 #include <resolv.h>
 #include <cstdio>
 #include <cstring>

 #include "tscore/ink_error.h"
 #include "tscore/ink_resolver.h"

 #define SPRINTF(x) (sprintf x)

 /*%
  * Form all types of queries.
  * Returns the size of the result or -1.
  */
 int
 ink_res_mkquery(ink_res_state statp, int op,               /*!< opcode of query  */
                 const char *dname,                         /*!< domain name  */
                 int _class, int type,                      /*!< _class and type of query  */
                 const u_char *data,                        /*!< resource record data  */
                 int datalen,                               /*!< length of data  */
                 const u_char * /* newrr_in  ATS_UNUSED */, /*!< new rr for modify or append  */
                 u_char *buf,                               /*!< buffer to put query  */
                 int buflen)                                /*!< size of buffer  */
 {
   HEADER *hp;
   u_char *cp, *ep;
   int n;
   u_char *dnptrs[20], **dpp, **lastdnptr;

   /*
    * Initialize header fields.
    */
   if ((buf == nullptr) || (buflen < HFIXEDSZ)) {
     return (-1);
   }
   memset(buf, 0, HFIXEDSZ);
   hp         = reinterpret_cast<HEADER *>(buf);
   hp->id     = htons(++statp->id);
   hp->opcode = op;
   hp->rd     = (statp->options & INK_RES_RECURSE) != 0U;
   hp->rcode  = NOERROR;
   cp         = buf + HFIXEDSZ;
   ep         = buf + buflen;
   dpp        = dnptrs;
   *dpp++     = buf;
   *dpp++     = nullptr;
   lastdnptr  = dnptrs + sizeof dnptrs / sizeof dnptrs[0];
   /*
    * perform opcode specific processing
    */
   switch (op) {
   case QUERY: /*FALLTHROUGH*/
   case NS_NOTIFY_OP:
     if (ep - cp < QFIXEDSZ) {
       return (-1);
     }
     if ((n = dn_comp(dname, cp, ep - cp - QFIXEDSZ, dnptrs, lastdnptr)) < 0) {
       return (-1);
     }
     cp += n;
     NS_PUT16(type, cp);
     NS_PUT16(_class, cp);
     hp->qdcount = htons(1);
     if (op == QUERY || data == nullptr) {
       break;
     }
     /*
      * Make an additional record for completion domain.
      */
     if ((ep - cp) < RRFIXEDSZ) {
       return (-1);
     }
     n = dn_comp(reinterpret_cast<const char *>(data), cp, ep - cp - RRFIXEDSZ, dnptrs, lastdnptr);
     if (n < 0) {
       return (-1);
     }
     cp += n;
     NS_PUT16(T_NULL, cp);
     NS_PUT16(_class, cp);
     NS_PUT32(0, cp);
     NS_PUT16(0, cp);
     hp->arcount = htons(1);
     break;

   case IQUERY:
     /*
      * Initialize answer section
      */
     if (ep - cp < 1 + RRFIXEDSZ + datalen) {
       return (-1);
     }
     *cp++ = '\0'; /*%< no domain name */
     NS_PUT16(type, cp);
     NS_PUT16(_class, cp);
     NS_PUT32(0, cp);
     NS_PUT16(datalen, cp);
     if (datalen) {
       memcpy(cp, data, datalen);
       cp += datalen;
     }
     hp->ancount = htons(1);
     break;

   default:
     return (-1);
   }
   return (cp - buf);
 }

 /* Public. */

 /*%
  *	Thinking in noninternationalized USASCII (per the DNS spec),
  *	is this character visible and not a space when printed ?
  *
  * return:
  *\li	boolean.
  */
 static int
 printable(int ch)
 {
   return (ch > 0x20 && ch < 0x7f);
 }

 static const char digits[] = "0123456789";

 static int
 labellen(const u_char *lp)
 {
   int bitlen;
   u_char l = *lp;

   if ((l & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
     /* should be avoided by the caller */
     return (-1);
   }

   if ((l & NS_CMPRSFLGS) == INK_NS_TYPE_ELT) {
     if (l == INK_DNS_LABELTYPE_BITSTRING) {
       if ((bitlen = *(lp + 1)) == 0) {
         bitlen = 256;
       }
       return ((bitlen + 7) / 8 + 1);
     }
     return (-1); /*%< unknown ELT */
   }
   return (l);
 }

 static int
 decode_bitstring(const unsigned char **cpp, char *dn, const char *eom)
 {
   const unsigned char *cp = *cpp;
   char *beg               = dn, tc;
   int b, blen, plen, i;

   if ((blen = (*cp & 0xff)) == 0) {
     blen = 256;
   }
   plen = (blen + 3) / 4;
   plen += sizeof("\\[x/]") + (blen > 99 ? 3 : (blen > 9) ? 2 : 1);
   if (dn + plen >= eom) {
     return (-1);
   }

   cp++;
   i = SPRINTF((dn, "\\[x"));
   if (i < 0) {
     return (-1);
   }
   dn += i;
   for (b = blen; b > 7; b -= 8, cp++) {
     i = SPRINTF((dn, "%02x", *cp & 0xff));
     if (i < 0) {
       return (-1);
     }
     dn += i;
   }
   if (b > 4) {
     tc = *cp++;
     i  = SPRINTF((dn, "%02x", tc & (0xff << (8 - b))));
     if (i < 0) {
       return (-1);
     }
     dn += i;
   } else if (b > 0) {
     tc = *cp++;
     i  = SPRINTF((dn, "%1x", ((tc >> 4) & 0x0f) & (0x0f << (4 - b))));
     if (i < 0) {
       return (-1);
     }
     dn += i;
   }
   i = SPRINTF((dn, "/%d]", blen));
   if (i < 0) {
     return (-1);
   }
   dn += i;

   *cpp = cp;
   return (dn - beg);
 }

 /*%
  *	Thinking in noninternationalized USASCII (per the DNS spec),
  *	is this character special ("in need of quoting") ?
  *
  * return:
  *\li	boolean.
  */
 static int
 special(int ch)
 {
   switch (ch) {
   case 0x22: /*%< '"' */
   case 0x2E: /*%< '.' */
   case 0x3B: /*%< ';' */
   case 0x5C: /*%< '\\' */
   case 0x28: /*%< '(' */
   case 0x29: /*%< ')' */
   /* Special modifiers in zone files. */
   case 0x40: /*%< '@' */
   case 0x24: /*%< '$' */
     return (1);
   default:
     return (0);
   }
 }

 /*%
  *	Convert an encoded domain name to printable ascii as per RFC1035.

  * return:
  *\li	Number of bytes written to buffer, or -1 (with errno set)
  *
  * notes:
  *\li	The root is returned as "."
  *\li	All other domains are returned in non absolute form
  */
 int
 ink_ns_name_ntop(const u_char *src, char *dst, size_t dstsiz)
 {
   const u_char *cp;
   char *dn, *eom;
   u_char c;
   unsigned n;
   int l;

   cp  = src;
   dn  = dst;
   eom = dst + dstsiz;

   while ((n = *cp++) != 0) {
     if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
       /* Some kind of compression pointer. */
       errno = EMSGSIZE;
       return (-1);
     }
     if (dn != dst) {
       if (dn >= eom) {
         errno = EMSGSIZE;
         return (-1);
       }
       *dn++ = '.';
     }
     if ((l = labellen(cp - 1)) < 0) {
       errno = EMSGSIZE; /*%< XXX */
       return (-1);
     }
     if (dn + l >= eom) {
       errno = EMSGSIZE;
       return (-1);
     }
     if ((n & NS_CMPRSFLGS) == INK_NS_TYPE_ELT) {
       int m;

       if (n != INK_DNS_LABELTYPE_BITSTRING) {
         /* XXX: labellen should reject this case */
         errno = EINVAL;
         return (-1);
       }
       if ((m = decode_bitstring(&cp, dn, eom)) < 0) {
         errno = EMSGSIZE;
         return (-1);
       }
       dn += m;
       continue;
     }
     for ((void)nullptr; l > 0; l--) {
       c = *cp++;
       if (special(c)) {
         if (dn + 1 >= eom) {
           errno = EMSGSIZE;
           return (-1);
         }
         *dn++ = '\\';
         *dn++ = static_cast<char>(c);
       } else if (!printable(c)) {
         if (dn + 3 >= eom) {
           errno = EMSGSIZE;
           return (-1);
         }
         *dn++ = '\\';
         *dn++ = digits[c / 100];
         *dn++ = digits[(c % 100) / 10];
         *dn++ = digits[c % 10];
       } else {
         if (dn >= eom) {
           errno = EMSGSIZE;
           return (-1);
         }
         *dn++ = static_cast<char>(c);
       }
     }
   }
   if (dn == dst) {
     if (dn >= eom) {
       errno = EMSGSIZE;
       return (-1);
     }
     *dn++ = '.';
   }
   if (dn >= eom) {
     errno = EMSGSIZE;
     return (-1);
   }
   *dn++ = '\0';
   return (dn - dst);
 }

 /*%
  *	Convert an encoded domain name to printable ascii as per RFC1035.

  * return:
  *\li	Number of bytes written to buffer, or -1 (with errno set)
  *
  * notes:
  *\li	The root is returned as "."
  *\li	All other domains are returned in non absolute form
  */
 #if defined(linux)
 int
 ns_name_ntop(const u_char *src, char *dst, size_t dstsiz) __THROW
 #else
 int
 ns_name_ntop(const u_char *src, char *dst, size_t dstsiz)
 #endif
 {
   const u_char *cp;
   char *dn, *eom;
   u_char c;
   unsigned n;
   int l;

   cp  = src;
   dn  = dst;
   eom = dst + dstsiz;

   while ((n = *cp++) != 0) {
     if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
       /* Some kind of compression pointer. */
       errno = EMSGSIZE;
       return (-1);
     }
     if (dn != dst) {
       if (dn >= eom) {
         errno = EMSGSIZE;
         return (-1);
       }
       *dn++ = '.';
     }
     if ((l = labellen(cp - 1)) < 0) {
       errno = EMSGSIZE; /*%< XXX */
       return (-1);
     }
     if (dn + l >= eom) {
       errno = EMSGSIZE;
       return (-1);
     }
     if ((n & NS_CMPRSFLGS) == INK_NS_TYPE_ELT) {
       int m;

       if (n != INK_DNS_LABELTYPE_BITSTRING) {
         /* XXX: labellen should reject this case */
         errno = EINVAL;
         return (-1);
       }
       if ((m = decode_bitstring(&cp, dn, eom)) < 0) {
         errno = EMSGSIZE;
         return (-1);
       }
       dn += m;
       continue;
     }
     for ((void)nullptr; l > 0; l--) {
       c = *cp++;
       if (special(c)) {
         if (dn + 1 >= eom) {
           errno = EMSGSIZE;
           return (-1);
         }
         *dn++ = '\\';
         *dn++ = static_cast<char>(c);
       } else if (!printable(c)) {
         if (dn + 3 >= eom) {
           errno = EMSGSIZE;
           return (-1);
         }
         *dn++ = '\\';
         *dn++ = digits[c / 100];
         *dn++ = digits[(c % 100) / 10];
         *dn++ = digits[c % 10];
       } else {
         if (dn >= eom) {
           errno = EMSGSIZE;
           return (-1);
         }
         *dn++ = static_cast<char>(c);
       }
     }
   }
   if (dn == dst) {
     if (dn >= eom) {
       errno = EMSGSIZE;
       return (-1);
     }
     *dn++ = '.';
   }
   if (dn >= eom) {
     errno = EMSGSIZE;
     return (-1);
   }
   *dn++ = '\0';
   return (dn - dst);
 }

 HostResStyle
 ats_host_res_from(int family, HostResPreferenceOrder const &order)
 {
   bool v4 = false, v6 = false;
   HostResPreference client = AF_INET6 == family ? HOST_RES_PREFER_IPV6 : HOST_RES_PREFER_IPV4;

   for (auto p : order) {
     if (HOST_RES_PREFER_CLIENT == p) {
       p = client; // CLIENT -> actual value
     }
     if (HOST_RES_PREFER_IPV4 == p) {
       if (v6) {
         return HOST_RES_IPV6;
       } else {
         v4 = true;
       }
     } else if (HOST_RES_PREFER_IPV6 == p) {
       if (v4) {
         return HOST_RES_IPV4;
       } else {
         v6 = true;
       }
     } else {
       break;
     }
   }
   if (v4) {
     return HOST_RES_IPV4_ONLY;
   } else if (v6) {
     return HOST_RES_IPV6_ONLY;
   }
   return HOST_RES_NONE;
 }

 void
 ats_force_order_by_family(sockaddr const *addr, HostResPreferenceOrder order)
 {
   HostResPreferenceOrder::size_type pos{0};
   if (ats_is_ip6(addr)) {
     order[pos++] = HOST_RES_PREFER_IPV6;
   } else if (ats_is_ip4(addr)) {
     order[pos++] = HOST_RES_PREFER_IPV4;
   }
   for (; pos < order.size(); pos++) {
     order[pos] = HOST_RES_PREFER_NONE;
   }
 }
	/*
	* Copyright (c) 1985, 1993
	* The Regents of the University of California. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. Neither the name of the University nor the names of its contributors
	* may be used to endorse or promote products derived from this software
	* without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*/

	/*
	* Portions Copyright (c) 1993 by Digital Equipment Corporation.
	*
	* Permission to use, copy, modify, and distribute this software for any
	* purpose with or without fee is hereby granted, provided that the above
	* copyright notice and this permission notice appear in all copies, and that
	* the name of Digital Equipment Corporation not be used in advertising or
	* publicity pertaining to distribution of the document or software without
	* specific, written prior permission.
	*
	* THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
	* WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
	* CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
	* DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
	* PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
	* ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
	* SOFTWARE.
	*/

	/*
	* Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
	* Portions Copyright (c) 1996-1999 by Internet Software Consortium.
	*
	* Permission to use, copy, modify, and distribute this software for any
	* purpose with or without fee is hereby granted, provided that the above
	* copyright notice and this permission notice appear in all copies.
	*
	* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
	* OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	*/

	#include "tscore/ink_config.h"
	#include "tscore/ink_defs.h"

	#include <sys/types.h>
	#include <sys/param.h>
	#include <netinet/in.h>
	#include <arpa/nameser.h>
	#ifdef HAVE_ARPA_NAMESER_COMPAT_H
	#include <arpa/nameser_compat.h>
	#endif
	#include <netdb.h>
	#include <resolv.h>
	#include <cstdio>
	#include <cstring>

	#include "tscore/ink_error.h"
	#include "tscore/ink_resolver.h"

	#define SPRINTF(x) (sprintf x)

	/*%
	* Form all types of queries.
	* Returns the size of the result or -1.
	*/
	int
	ink_res_mkquery(ink_res_state statp, int op, /!< opcode of query /
	const char dname, /!< domain name */
	int _class, int type, /!< _class and type of query /
	const u_char data, /!< resource record data */
	int datalen, /!< length of data /
	const u_char * /* newrr_in ATS_UNUSED /, /!< new rr for modify or append */
	u_char buf, /!< buffer to put query */
	int buflen) /!< size of buffer /
	{
	HEADER *hp;
	u_char cp, ep;
	int n;
	u_char dnptrs[20], dpp, *lastdnptr;

	/*
	* Initialize header fields.
	*/
	if ((buf == nullptr) \|\| (buflen < HFIXEDSZ)) {
	return (-1);
	}
	memset(buf, 0, HFIXEDSZ);
	hp = reinterpret_cast<HEADER *>(buf);
	hp->id = htons(++statp->id);
	hp->opcode = op;
	hp->rd = (statp->options & INK_RES_RECURSE) != 0U;
	hp->rcode = NOERROR;
	cp = buf + HFIXEDSZ;
	ep = buf + buflen;
	dpp = dnptrs;
	*dpp++ = buf;
	*dpp++ = nullptr;
	lastdnptr = dnptrs + sizeof dnptrs / sizeof dnptrs[0];
	/*
	* perform opcode specific processing
	*/
	switch (op) {
	case QUERY: /FALLTHROUGH/
	case NS_NOTIFY_OP:
	if (ep - cp < QFIXEDSZ) {
	return (-1);
	}
	if ((n = dn_comp(dname, cp, ep - cp - QFIXEDSZ, dnptrs, lastdnptr)) < 0) {
	return (-1);
	}
	cp += n;
	NS_PUT16(type, cp);
	NS_PUT16(_class, cp);
	hp->qdcount = htons(1);
	if (op == QUERY \|\| data == nullptr) {
	break;
	}
	/*
	* Make an additional record for completion domain.
	*/
	if ((ep - cp) < RRFIXEDSZ) {
	return (-1);
	}
	n = dn_comp(reinterpret_cast<const char *>(data), cp, ep - cp - RRFIXEDSZ, dnptrs, lastdnptr);
	if (n < 0) {
	return (-1);
	}
	cp += n;
	NS_PUT16(T_NULL, cp);
	NS_PUT16(_class, cp);
	NS_PUT32(0, cp);
	NS_PUT16(0, cp);
	hp->arcount = htons(1);
	break;

	case IQUERY:
	/*
	* Initialize answer section
	*/
	if (ep - cp < 1 + RRFIXEDSZ + datalen) {
	return (-1);
	}
	cp++ = '\0'; /%< no domain name */
	NS_PUT16(type, cp);
	NS_PUT16(_class, cp);
	NS_PUT32(0, cp);
	NS_PUT16(datalen, cp);
	if (datalen) {
	memcpy(cp, data, datalen);
	cp += datalen;
	}
	hp->ancount = htons(1);
	break;

	default:
	return (-1);
	}
	return (cp - buf);
	}

	/* Public. */

	/*%
	* Thinking in noninternationalized USASCII (per the DNS spec),
	* is this character visible and not a space when printed ?
	*
	* return:
	*\li boolean.
	*/
	static int
	printable(int ch)
	{
	return (ch > 0x20 && ch < 0x7f);
	}

	static const char digits[] = "0123456789";

	static int
	labellen(const u_char *lp)
	{
	int bitlen;
	u_char l = *lp;

	if ((l & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
	/* should be avoided by the caller */
	return (-1);
	}

	if ((l & NS_CMPRSFLGS) == INK_NS_TYPE_ELT) {
	if (l == INK_DNS_LABELTYPE_BITSTRING) {
	if ((bitlen = *(lp + 1)) == 0) {
	bitlen = 256;
	}
	return ((bitlen + 7) / 8 + 1);
	}
	return (-1); /%< unknown ELT /
	}
	return (l);
	}

	static int
	decode_bitstring(const unsigned char *cpp, char dn, const char *eom)
	{
	const unsigned char cp = cpp;
	char *beg = dn, tc;
	int b, blen, plen, i;

	if ((blen = (*cp & 0xff)) == 0) {
	blen = 256;
	}
	plen = (blen + 3) / 4;
	plen += sizeof("\\[x/]") + (blen > 99 ? 3 : (blen > 9) ? 2 : 1);
	if (dn + plen >= eom) {
	return (-1);
	}

	cp++;
	i = SPRINTF((dn, "\\[x"));
	if (i < 0) {
	return (-1);
	}
	dn += i;
	for (b = blen; b > 7; b -= 8, cp++) {
	i = SPRINTF((dn, "%02x", *cp & 0xff));
	if (i < 0) {
	return (-1);
	}
	dn += i;
	}
	if (b > 4) {
	tc = *cp++;
	i = SPRINTF((dn, "%02x", tc & (0xff << (8 - b))));
	if (i < 0) {
	return (-1);
	}
	dn += i;
	} else if (b > 0) {
	tc = *cp++;
	i = SPRINTF((dn, "%1x", ((tc >> 4) & 0x0f) & (0x0f << (4 - b))));
	if (i < 0) {
	return (-1);
	}
	dn += i;
	}
	i = SPRINTF((dn, "/%d]", blen));
	if (i < 0) {
	return (-1);
	}
	dn += i;

	*cpp = cp;
	return (dn - beg);
	}

	/*%
	* Thinking in noninternationalized USASCII (per the DNS spec),
	* is this character special ("in need of quoting") ?
	*
	* return:
	*\li boolean.
	*/
	static int
	special(int ch)
	{
	switch (ch) {
	case 0x22: /%< '"' /
	case 0x2E: /%< '.' /
	case 0x3B: /%< ';' /
	case 0x5C: /%< '\\' /
	case 0x28: /%< '(' /
	case 0x29: /%< ')' /
	/* Special modifiers in zone files. */
	case 0x40: /%< '@' /
	case 0x24: /%< '$' /
	return (1);
	default:
	return (0);
	}
	}

	/*%
	* Convert an encoded domain name to printable ascii as per RFC1035.

	* return:
	*\li Number of bytes written to buffer, or -1 (with errno set)
	*
	* notes:
	*\li The root is returned as "."
	*\li All other domains are returned in non absolute form
	*/
	int
	ink_ns_name_ntop(const u_char src, char dst, size_t dstsiz)
	{
	const u_char *cp;
	char dn, eom;
	u_char c;
	unsigned n;
	int l;

	cp = src;
	dn = dst;
	eom = dst + dstsiz;

	while ((n = *cp++) != 0) {
	if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
	/* Some kind of compression pointer. */
	errno = EMSGSIZE;
	return (-1);
	}
	if (dn != dst) {
	if (dn >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '.';
	}
	if ((l = labellen(cp - 1)) < 0) {
	errno = EMSGSIZE; /%< XXX /
	return (-1);
	}
	if (dn + l >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	if ((n & NS_CMPRSFLGS) == INK_NS_TYPE_ELT) {
	int m;

	if (n != INK_DNS_LABELTYPE_BITSTRING) {
	/* XXX: labellen should reject this case */
	errno = EINVAL;
	return (-1);
	}
	if ((m = decode_bitstring(&cp, dn, eom)) < 0) {
	errno = EMSGSIZE;
	return (-1);
	}
	dn += m;
	continue;
	}
	for ((void)nullptr; l > 0; l--) {
	c = *cp++;
	if (special(c)) {
	if (dn + 1 >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '\\';
	*dn++ = static_cast<char>(c);
	} else if (!printable(c)) {
	if (dn + 3 >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '\\';
	*dn++ = digits[c / 100];
	*dn++ = digits[(c % 100) / 10];
	*dn++ = digits[c % 10];
	} else {
	if (dn >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = static_cast<char>(c);
	}
	}
	}
	if (dn == dst) {
	if (dn >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '.';
	}
	if (dn >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '\0';
	return (dn - dst);
	}

	/*%
	* Convert an encoded domain name to printable ascii as per RFC1035.

	* return:
	*\li Number of bytes written to buffer, or -1 (with errno set)
	*
	* notes:
	*\li The root is returned as "."
	*\li All other domains are returned in non absolute form
	*/
	#if defined(linux)
	int
	ns_name_ntop(const u_char src, char dst, size_t dstsiz) __THROW
	#else
	int
	ns_name_ntop(const u_char src, char dst, size_t dstsiz)
	#endif
	{
	const u_char *cp;
	char dn, eom;
	u_char c;
	unsigned n;
	int l;

	cp = src;
	dn = dst;
	eom = dst + dstsiz;

	while ((n = *cp++) != 0) {
	if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
	/* Some kind of compression pointer. */
	errno = EMSGSIZE;
	return (-1);
	}
	if (dn != dst) {
	if (dn >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '.';
	}
	if ((l = labellen(cp - 1)) < 0) {
	errno = EMSGSIZE; /%< XXX /
	return (-1);
	}
	if (dn + l >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	if ((n & NS_CMPRSFLGS) == INK_NS_TYPE_ELT) {
	int m;

	if (n != INK_DNS_LABELTYPE_BITSTRING) {
	/* XXX: labellen should reject this case */
	errno = EINVAL;
	return (-1);
	}
	if ((m = decode_bitstring(&cp, dn, eom)) < 0) {
	errno = EMSGSIZE;
	return (-1);
	}
	dn += m;
	continue;
	}
	for ((void)nullptr; l > 0; l--) {
	c = *cp++;
	if (special(c)) {
	if (dn + 1 >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '\\';
	*dn++ = static_cast<char>(c);
	} else if (!printable(c)) {
	if (dn + 3 >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '\\';
	*dn++ = digits[c / 100];
	*dn++ = digits[(c % 100) / 10];
	*dn++ = digits[c % 10];
	} else {
	if (dn >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = static_cast<char>(c);
	}
	}
	}
	if (dn == dst) {
	if (dn >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '.';
	}
	if (dn >= eom) {
	errno = EMSGSIZE;
	return (-1);
	}
	*dn++ = '\0';
	return (dn - dst);
	}

	HostResStyle
	ats_host_res_from(int family, HostResPreferenceOrder const &order)
	{
	bool v4 = false, v6 = false;
	HostResPreference client = AF_INET6 == family ? HOST_RES_PREFER_IPV6 : HOST_RES_PREFER_IPV4;

	for (auto p : order) {
	if (HOST_RES_PREFER_CLIENT == p) {
	p = client; // CLIENT -> actual value
	}
	if (HOST_RES_PREFER_IPV4 == p) {
	if (v6) {
	return HOST_RES_IPV6;
	} else {
	v4 = true;
	}
	} else if (HOST_RES_PREFER_IPV6 == p) {
	if (v4) {
	return HOST_RES_IPV4;
	} else {
	v6 = true;
	}
	} else {
	break;
	}
	}
	if (v4) {
	return HOST_RES_IPV4_ONLY;
	} else if (v6) {
	return HOST_RES_IPV6_ONLY;
	}
	return HOST_RES_NONE;
	}

	void
	ats_force_order_by_family(sockaddr const *addr, HostResPreferenceOrder order)
	{
	HostResPreferenceOrder::size_type pos{0};
	if (ats_is_ip6(addr)) {
	order[pos++] = HOST_RES_PREFER_IPV6;
	} else if (ats_is_ip4(addr)) {
	order[pos++] = HOST_RES_PREFER_IPV4;
	}
	for (; pos < order.size(); pos++) {
	order[pos] = HOST_RES_PREFER_NONE;
	}
	}