text: /*
   * Copyright (C) 2009, 2012-2014  Internet Systems Consortium, Inc. ("ISC")
   *
   * Permission to use, copy, modify, and/or 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.
   */
  
  /* $Id: getaddrinfo.c,v 1.3 2009/09/02 23:48:02 tbox Exp $ */
  
  /*! \file */
  
  /**
   *    getaddrinfo() is used to get a list of IP addresses and port
   *    numbers for host hostname and service servname as defined in RFC3493.
   *    hostname and servname are pointers to null-terminated strings
   *    or NULL. hostname is either a host name or a numeric host address
   *    string: a dotted decimal IPv4 address or an IPv6 address. servname is
   *    either a decimal port number or a service name as listed in
   *    /etc/services.
   *
   *    If the operating system does not provide a struct addrinfo, the
   *    following structure is used:
   *
   * \code
   * struct  addrinfo {
   *         int             ai_flags;       // AI_PASSIVE, AI_CANONNAME
   *         int             ai_family;      // PF_xxx
   *         int             ai_socktype;    // SOCK_xxx
   *         int             ai_protocol;    // 0 or IPPROTO_xxx for IPv4 and IPv6
   *         size_t          ai_addrlen;     // length of ai_addr
   *         char            *ai_canonname;  // canonical name for hostname
   *         struct sockaddr *ai_addr;       // binary address
   *         struct addrinfo *ai_next;       // next structure in linked list
   * };
   * \endcode
   *
   *
   *    hints is an optional pointer to a struct addrinfo. This structure can
   *    be used to provide hints concerning the type of socket that the caller
   *    supports or wishes to use. The caller can supply the following
   *    structure elements in *hints:
   *
   * <ul>
   *    <li>ai_family:
   *           The protocol family that should be used. When ai_family is set
   *           to PF_UNSPEC, it means the caller will accept any protocol
   *           family supported by the operating system.</li>
   *
   *    <li>ai_socktype:
   *           denotes the type of socket -- SOCK_STREAM, SOCK_DGRAM or
   *           SOCK_RAW -- that is wanted. When ai_socktype is zero the caller
   *           will accept any socket type.</li>
   *
   *    <li>ai_protocol:
   *           indicates which transport protocol is wanted: IPPROTO_UDP or
   *           IPPROTO_TCP. If ai_protocol is zero the caller will accept any
   *           protocol.</li>
   *
   *    <li>ai_flags:
   *           Flag bits. If the AI_CANONNAME bit is set, a successful call to
   *           getaddrinfo() will return a null-terminated string
   *           containing the canonical name of the specified hostname in
   *           ai_canonname of the first addrinfo structure returned. Setting
   *           the AI_PASSIVE bit indicates that the returned socket address
   *           structure is intended for used in a call to bind(2). In this
   *           case, if the hostname argument is a NULL pointer, then the IP
   *           address portion of the socket address structure will be set to
   *           INADDR_ANY for an IPv4 address or IN6ADDR_ANY_INIT for an IPv6
   *           address.<br /><br />
   *
   *           When ai_flags does not set the AI_PASSIVE bit, the returned
   *           socket address structure will be ready for use in a call to
   *           connect(2) for a connection-oriented protocol or connect(2),
   *           sendto(2), or sendmsg(2) if a connectionless protocol was
   *           chosen. The IP address portion of the socket address structure
   *           will be set to the loopback address if hostname is a NULL
   *           pointer and AI_PASSIVE is not set in ai_flags.<br /><br />
   *
   *           If ai_flags is set to AI_NUMERICHOST it indicates that hostname
   *           should be treated as a numeric string defining an IPv4 or IPv6
   *           address and no name resolution should be attempted.
   * </li></ul>
   *
   *    All other elements of the struct addrinfo passed via hints must be
   *    zero.
   *
   *    A hints of NULL is treated as if the caller provided a struct addrinfo
   *    initialized to zero with ai_familyset to PF_UNSPEC.
   *
   *    After a successful call to getaddrinfo(), *res is a pointer to a
   *    linked list of one or more addrinfo structures. Each struct addrinfo
   *    in this list cn be processed by following the ai_next pointer, until a
   *    NULL pointer is encountered. The three members ai_family, ai_socktype,
   *    and ai_protocol in each returned addrinfo structure contain the
   *    corresponding arguments for a call to socket(2). For each addrinfo
   *    structure in the list, the ai_addr member points to a filled-in socket
   *    address structure of length ai_addrlen.
   *
   *    All of the information returned by getaddrinfo() is dynamically
   *    allocated: the addrinfo structures, and the socket address structures
   *    and canonical host name strings pointed to by the addrinfostructures.
   *    Memory allocated for the dynamically allocated structures created by a
   *    successful call to getaddrinfo() is released by freeaddrinfo().
   *    ai is a pointer to a struct addrinfo created by a call to getaddrinfo().
   *
   * \section irsreturn RETURN VALUES
   *
   *    getaddrinfo() returns zero on success or one of the error codes
   *    listed in gai_strerror() if an error occurs. If both hostname and
   *    servname are NULL getaddrinfo() returns #EAI_NONAME.
   *
   * \section irssee SEE ALSO
   *
   *    getaddrinfo(), freeaddrinfo(),
   *    gai_strerror(), RFC3493, getservbyname(3), connect(2),
   *    sendto(2), sendmsg(2), socket(2).
   */
  
  #include <config.h>
  
  #include <stdlib.h>
  #include <string.h>
  #include <errno.h>
  
  #include <isc/app.h>
  #include <isc/buffer.h>
  #include <isc/lib.h>
  #include <isc/mem.h>
  #include <isc/sockaddr.h>
  #include <isc/string.h>
  #include <isc/util.h>
  
  #include <dns/client.h>
  #include <dns/fixedname.h>
  #include <dns/name.h>
  #include <dns/rdata.h>
  #include <dns/rdataset.h>
  #include <dns/rdatastruct.h>
  #include <dns/rdatatype.h>
  #include <dns/result.h>
  
  #include <irs/context.h>
  #include <irs/netdb.h>
  #include <irs/resconf.h>
  
  #define SA(addr)	((struct sockaddr *)(addr))
  #define SIN(addr)	((struct sockaddr_in *)(addr))
  #define SIN6(addr)	((struct sockaddr_in6 *)(addr))
  #define SLOCAL(addr)	((struct sockaddr_un *)(addr))
  
  /*! \struct addrinfo
   */
  static struct addrinfo
  	*ai_concat(struct addrinfo *ai1, struct addrinfo *ai2),
  	*ai_reverse(struct addrinfo *oai),
  	*ai_clone(struct addrinfo *oai, int family),
  	*ai_alloc(int family, int addrlen);
  #ifdef AF_LOCAL
  static int get_local(const char *name, int socktype, struct addrinfo **res);
  #endif
  
  static int
  resolve_name(int family, const char *hostname, int flags,
  	     struct addrinfo **aip, int socktype, int port);
  
  static int add_ipv4(const char *hostname, int flags, struct addrinfo **aip,
  		    int socktype, int port);
  static int add_ipv6(const char *hostname, int flags, struct addrinfo **aip,
  		    int socktype, int port);
  static void set_order(int, int (**)(const char *, int, struct addrinfo **,
  				    int, int));
  static void _freeaddrinfo(struct addrinfo *ai);
  
  #define FOUND_IPV4	0x1
  #define FOUND_IPV6	0x2
  #define FOUND_MAX	2
  
  #define ISC_AI_MASK (AI_PASSIVE|AI_CANONNAME|AI_NUMERICHOST)
  /*%
   * Get a list of IP addresses and port numbers for host hostname and
   * service servname.
   */
  int
  getaddrinfo(const char *hostname, const char *servname,
  	    const struct addrinfo *hints, struct addrinfo **res)
  {
  	struct servent *sp;
  	const char *proto;
  	int family, socktype, flags, protocol;
  	struct addrinfo *ai, *ai_list;
  	int err = 0;
  	int port, i;
  	int (*net_order[FOUND_MAX+1])(const char *, int, struct addrinfo **,
  				      int, int);
  
  	if (hostname == NULL && servname == NULL)
  		return (EAI_NONAME);
  
  	proto = NULL;
  	if (hints != NULL) {
  		if ((hints->ai_flags & ~(ISC_AI_MASK)) != 0)
  			return (EAI_BADFLAGS);
  		if (hints->ai_addrlen || hints->ai_canonname ||
  		    hints->ai_addr || hints->ai_next) {
  			errno = EINVAL;
  			return (EAI_SYSTEM);
  		}
  		family = hints->ai_family;
  		socktype = hints->ai_socktype;
  		protocol = hints->ai_protocol;
  		flags = hints->ai_flags;
  		switch (family) {
  		case AF_UNSPEC:
  			switch (hints->ai_socktype) {
  			case SOCK_STREAM:
  				proto = "tcp";
  				break;
  			case SOCK_DGRAM:
  				proto = "udp";
  				break;
  			}
  			break;
  		case AF_INET:
  		case AF_INET6:
  			switch (hints->ai_socktype) {
  			case 0:
  				break;
  			case SOCK_STREAM:
  				proto = "tcp";
  				break;
  			case SOCK_DGRAM:
  				proto = "udp";
  				break;
  			case SOCK_RAW:
  				break;
  			default:
  				return (EAI_SOCKTYPE);
  			}
  			break;
  #ifdef	AF_LOCAL
  		case AF_LOCAL:
  			switch (hints->ai_socktype) {
  			case 0:
  				break;
  			case SOCK_STREAM:
  				break;
  			case SOCK_DGRAM:
  				break;
  			default:
  				return (EAI_SOCKTYPE);
  			}
  			break;
  #endif
  		default:
  			return (EAI_FAMILY);
  		}
  	} else {
  		protocol = 0;
  		family = 0;
  		socktype = 0;
  		flags = 0;
  	}
  
  #ifdef	AF_LOCAL
  	/*!
  	 * First, deal with AF_LOCAL.  If the family was not set,
  	 * then assume AF_LOCAL if the first character of the
  	 * hostname/servname is '/'.
  	 */
  
  	if (hostname != NULL &&
  	    (family == AF_LOCAL || (family == 0 && *hostname == '/')))
  		return (get_local(hostname, socktype, res));
  
  	if (servname != NULL &&
  	    (family == AF_LOCAL || (family == 0 && *servname == '/')))
  		return (get_local(servname, socktype, res));
  #endif
  
  	/*
  	 * Ok, only AF_INET and AF_INET6 left.
  	 */
  	ai_list = NULL;
  
  	/*
  	 * First, look up the service name (port) if it was
  	 * requested.  If the socket type wasn't specified, then
  	 * try and figure it out.
  	 */
  	if (servname != NULL) {
  		char *e;
  
  		port = strtol(servname, &e, 10);
  		if (*e == '\0') {
  			if (socktype == 0)
  				return (EAI_SOCKTYPE);
  			if (port < 0 || port > 65535)
  				return (EAI_SERVICE);
  			port = htons((unsigned short) port);
  		} else {
  			sp = getservbyname(servname, proto);
  			if (sp == NULL)
  				return (EAI_SERVICE);
  			port = sp->s_port;
  			if (socktype == 0) {
  				if (strcmp(sp->s_proto, "tcp") == 0)
  					socktype = SOCK_STREAM;
  				else if (strcmp(sp->s_proto, "udp") == 0)
  					socktype = SOCK_DGRAM;
  			}
  		}
  	} else
  		port = 0;
  
  	/*
  	 * Next, deal with just a service name, and no hostname.
  	 * (we verified that one of them was non-null up above).
  	 */
  	if (hostname == NULL && (flags & AI_PASSIVE) != 0) {
  		if (family == AF_INET || family == 0) {
  			ai = ai_alloc(AF_INET, sizeof(struct sockaddr_in));
  			if (ai == NULL)
  				return (EAI_MEMORY);
  			ai->ai_socktype = socktype;
  			ai->ai_protocol = protocol;
  			SIN(ai->ai_addr)->sin_port = port;
  			ai->ai_next = ai_list;
  			ai_list = ai;
  		}
  
  		if (family == AF_INET6 || family == 0) {
  			ai = ai_alloc(AF_INET6, sizeof(struct sockaddr_in6));
  			if (ai == NULL) {
  				_freeaddrinfo(ai_list);
  				return (EAI_MEMORY);
  			}
  			ai->ai_socktype = socktype;
  			ai->ai_protocol = protocol;
  			SIN6(ai->ai_addr)->sin6_port = port;
  			ai->ai_next = ai_list;
  			ai_list = ai;
  		}
  
  		*res = ai_list;
  		return (0);
  	}
  
  	/*
  	 * If the family isn't specified or AI_NUMERICHOST specified, check
  	 * first to see if it is a numeric address.
  	 * Though the gethostbyname2() routine will recognize numeric addresses,
  	 * it will only recognize the format that it is being called for.  Thus,
  	 * a numeric AF_INET address will be treated by the AF_INET6 call as
  	 * a domain name, and vice versa.  Checking for both numerics here
  	 * avoids that.
  	 */
  	if (hostname != NULL &&
  	    (family == 0 || (flags & AI_NUMERICHOST) != 0)) {
  		char abuf[sizeof(struct in6_addr)];
  		char nbuf[NI_MAXHOST];
  		int addrsize, addroff;
  #ifdef IRS_HAVE_SIN6_SCOPE_ID
  		char *p, *ep;
  		char ntmp[NI_MAXHOST];
  		isc_uint32_t scopeid;
  #endif
  
  #ifdef IRS_HAVE_SIN6_SCOPE_ID
  		/*
  		 * Scope identifier portion.
  		 */
  		ntmp[0] = '\0';
  		if (strchr(hostname, '%') != NULL) {
  			strncpy(ntmp, hostname, sizeof(ntmp) - 1);
  			ntmp[sizeof(ntmp) - 1] = '\0';
  			p = strchr(ntmp, '%');
  			ep = NULL;
  
  			/*
  			 * Vendors may want to support non-numeric
  			 * scopeid around here.
  			 */
  
  			if (p != NULL)
  				scopeid = (isc_uint32_t)strtoul(p + 1,
  								&ep, 10);
  			if (p != NULL && ep != NULL && ep[0] == '\0')
  				*p = '\0';
  			else {
  				ntmp[0] = '\0';
  				scopeid = 0;
  			}
  		} else
  			scopeid = 0;
  #endif
  
  		if (inet_pton(AF_INET, hostname, (struct in_addr *)abuf)
  		    == 1) {
  			if (family == AF_INET6) {
  				/*
  				 * Convert to a V4 mapped address.
  				 */
  				struct in6_addr *a6 = (struct in6_addr *)abuf;
  				memmove(&a6->s6_addr[12], &a6->s6_addr[0], 4);
  				memset(&a6->s6_addr[10], 0xff, 2);
  				memset(&a6->s6_addr[0], 0, 10);
  				goto inet6_addr;
  			}
  			addrsize = sizeof(struct in_addr);
  			addroff = (char *)(&SIN(0)->sin_addr) - (char *)0;
  			family = AF_INET;
  			goto common;
  #ifdef IRS_HAVE_SIN6_SCOPE_ID
  		} else if (ntmp[0] != '\0' &&
  			   inet_pton(AF_INET6, ntmp, abuf) == 1) {
  			if (family && family != AF_INET6)
  				return (EAI_NONAME);
  			addrsize = sizeof(struct in6_addr);
  			addroff = (char *)(&SIN6(0)->sin6_addr) - (char *)0;
  			family = AF_INET6;
  			goto common;
  #endif
  		} else if (inet_pton(AF_INET6, hostname, abuf) == 1) {
  			if (family != 0 && family != AF_INET6)
  				return (EAI_NONAME);
  		inet6_addr:
  			addrsize = sizeof(struct in6_addr);
  			addroff = (char *)(&SIN6(0)->sin6_addr) - (char *)0;
  			family = AF_INET6;
  
  		common:
  			ai = ai_alloc(family,
  				      ((family == AF_INET6) ?
  				       sizeof(struct sockaddr_in6) :
  				       sizeof(struct sockaddr_in)));
  			if (ai == NULL)
  				return (EAI_MEMORY);
  			ai_list = ai;
  			ai->ai_socktype = socktype;
  			SIN(ai->ai_addr)->sin_port = port;
  			memmove((char *)ai->ai_addr + addroff, abuf, addrsize);
  			if ((flags & AI_CANONNAME) != 0) {
  #ifdef IRS_HAVE_SIN6_SCOPE_ID
  				if (ai->ai_family == AF_INET6)
  					SIN6(ai->ai_addr)->sin6_scope_id =
  						scopeid;
  #endif
  				if (getnameinfo(ai->ai_addr,
  						(socklen_t)ai->ai_addrlen,
  						nbuf, sizeof(nbuf), NULL, 0,
  						NI_NUMERICHOST) == 0) {
  					ai->ai_canonname = strdup(nbuf);
  					if (ai->ai_canonname == NULL) {
  						_freeaddrinfo(ai);
  						return (EAI_MEMORY);
  					}
  				} else {
  					/* XXX raise error? */
  					ai->ai_canonname = NULL;
  				}
  			}
  			goto done;
  		} else if ((flags & AI_NUMERICHOST) != 0) {
  			return (EAI_NONAME);
  		}
  	}
  
  	if (hostname == NULL && (flags & AI_PASSIVE) == 0) {
  		set_order(family, net_order);
  		for (i = 0; i < FOUND_MAX; i++) {
  			if (net_order[i] == NULL)
  				break;
  			err = (net_order[i])(hostname, flags, &ai_list,
  					     socktype, port);
  			if (err != 0) {
  				if (ai_list != NULL) {
  					_freeaddrinfo(ai_list);
  					ai_list = NULL;
  				}
  				break;
  			}
  		}
  	} else
  		err = resolve_name(family, hostname, flags, &ai_list,
  				   socktype, port);
  
  	if (ai_list == NULL) {
  		if (err == 0)
  			err = EAI_NONAME;
  		return (err);
  	}
  
  done:
  	ai_list = ai_reverse(ai_list);
  
  	*res = ai_list;
  	return (0);
  }
  
  typedef struct gai_restrans {
  	dns_clientrestrans_t	*xid;
  	isc_boolean_t		is_inprogress;
  	int			error;
  	struct addrinfo		ai_sentinel;
  	struct gai_resstate	*resstate;
  } gai_restrans_t;
  
  typedef struct gai_resstate {
  	isc_mem_t			*mctx;
  	struct gai_statehead		*head;
  	dns_fixedname_t			fixedname;
  	dns_name_t			*qname;
  	gai_restrans_t			*trans4;
  	gai_restrans_t			*trans6;
  	ISC_LINK(struct gai_resstate)	link;
  } gai_resstate_t;
  
  typedef struct gai_statehead {
  	int				ai_family;
  	int				ai_flags;
  	int				ai_socktype;
  	int				ai_port;
  	isc_appctx_t			*actx;
  	dns_client_t			*dnsclient;
  	ISC_LIST(struct gai_resstate)	resstates;
  	unsigned int			activestates;
  } gai_statehead_t;
  
  static isc_result_t
  make_resstate(isc_mem_t *mctx, gai_statehead_t *head, const char *hostname,
  	      const char *domain, gai_resstate_t **statep)
  {
  	isc_result_t result;
  	gai_resstate_t *state;
  	dns_fixedname_t fixeddomain;
  	dns_name_t *qdomain;
  	unsigned int namelen;
  	isc_buffer_t b;
  	isc_boolean_t need_v4 = ISC_FALSE;
  	isc_boolean_t need_v6 = ISC_FALSE;
  
  	state = isc_mem_get(mctx, sizeof(*state));
  	if (state == NULL)
  		return (ISC_R_NOMEMORY);
  
  	/* Construct base domain name */
  	namelen = strlen(domain);
  	isc_buffer_constinit(&b, domain, namelen);
  	isc_buffer_add(&b, namelen);
  	dns_fixedname_init(&fixeddomain);
  	qdomain = dns_fixedname_name(&fixeddomain);
  	result = dns_name_fromtext(qdomain, &b, dns_rootname, 0, NULL);
  	if (result != ISC_R_SUCCESS) {
  		isc_mem_put(mctx, state, sizeof(*state));
  		return (result);
  	}
  
  	/* Construct query name */
  	namelen = strlen(hostname);
  	isc_buffer_constinit(&b, hostname, namelen);
  	isc_buffer_add(&b, namelen);
  	dns_fixedname_init(&state->fixedname);
  	state->qname = dns_fixedname_name(&state->fixedname);
  	result = dns_name_fromtext(state->qname, &b, qdomain, 0, NULL);
  	if (result != ISC_R_SUCCESS) {
  		isc_mem_put(mctx, state, sizeof(*state));
  		return (result);
  	}
  
  	if (head->ai_family == AF_UNSPEC || head->ai_family == AF_INET)
  		need_v4 = ISC_TRUE;
  	if (head->ai_family == AF_UNSPEC || head->ai_family == AF_INET6)
  		need_v6 = ISC_TRUE;
  
  	state->trans6 = NULL;
  	state->trans4 = NULL;
  	if (need_v4) {
  		state->trans4 = isc_mem_get(mctx, sizeof(gai_restrans_t));
  		if (state->trans4 == NULL) {
  			isc_mem_put(mctx, state, sizeof(*state));
  			return (ISC_R_NOMEMORY);
  		}
  		state->trans4->error = 0;
  		state->trans4->xid = NULL;
  		state->trans4->resstate = state;
  		state->trans4->is_inprogress = ISC_TRUE;
  		state->trans4->ai_sentinel.ai_next = NULL;
  	}
  	if (need_v6) {
  		state->trans6 = isc_mem_get(mctx, sizeof(gai_restrans_t));
  		if (state->trans6 == NULL) {
  			if (state->trans4 != NULL)
  				isc_mem_put(mctx, state->trans4,
  					    sizeof(*state->trans4));
  			isc_mem_put(mctx, state, sizeof(*state));
  			return (ISC_R_NOMEMORY);
  		}
  		state->trans6->error = 0;
  		state->trans6->xid = NULL;
  		state->trans6->resstate = state;
  		state->trans6->is_inprogress = ISC_TRUE;
  		state->trans6->ai_sentinel.ai_next = NULL;
  	}
  
  	state->mctx = mctx;
  	state->head = head;
  	ISC_LINK_INIT(state, link);
  
  	*statep = state;
  
  	return (ISC_R_SUCCESS);
  }
  
  static isc_result_t
  make_resstates(isc_mem_t *mctx, const char *hostname, gai_statehead_t *head,
  	       irs_resconf_t *resconf)
  {
  	isc_result_t result;
  	irs_resconf_searchlist_t *searchlist;
  	irs_resconf_search_t *searchent;
  	gai_resstate_t *resstate, *resstate0;
  
  	resstate0 = NULL;
  	result = make_resstate(mctx, head, hostname, ".", &resstate0);
  	if (result != ISC_R_SUCCESS)
  		return (result);
  
  	searchlist = irs_resconf_getsearchlist(resconf);
  	for (searchent = ISC_LIST_HEAD(*searchlist); searchent != NULL;
  	     searchent = ISC_LIST_NEXT(searchent, link)) {
  		resstate = NULL;
  		result = make_resstate(mctx, head, hostname,
  				       (const char *)searchent->domain,
  				       &resstate);
  		if (result != ISC_R_SUCCESS)
  			break;
  
  		ISC_LIST_APPEND(head->resstates, resstate, link);
  		head->activestates++;
  	}
  
  	/*
  	 * Insert the original hostname either at the head or the tail of the
  	 * state list, depending on the number of labels contained in the
  	 * original name and the 'ndots' configuration parameter.
  	 */
  	if (dns_name_countlabels(resstate0->qname) >
  	    irs_resconf_getndots(resconf) + 1) {
  		ISC_LIST_PREPEND(head->resstates, resstate0, link);
  	} else
  		ISC_LIST_APPEND(head->resstates, resstate0, link);
  	head->activestates++;
  
  	if (result != ISC_R_SUCCESS) {
  		while ((resstate = ISC_LIST_HEAD(head->resstates)) != NULL) {
  			ISC_LIST_UNLINK(head->resstates, resstate, link);
  			if (resstate->trans4 != NULL) {
  				isc_mem_put(mctx, resstate->trans4,
  					    sizeof(*resstate->trans4));
  			}
  			if (resstate->trans6 != NULL) {
  				isc_mem_put(mctx, resstate->trans6,
  					    sizeof(*resstate->trans6));
  			}
  
  			isc_mem_put(mctx, resstate, sizeof(*resstate));
  		}
  	}
  
  	return (result);
  }
  
  static void
  process_answer(isc_task_t *task, isc_event_t *event) {
  	int error = 0, family;
  	gai_restrans_t *trans = event->ev_arg;
  	gai_resstate_t *resstate;
  	dns_clientresevent_t *rev = (dns_clientresevent_t *)event;
  	dns_rdatatype_t qtype;
  	dns_name_t *name;
  
  	REQUIRE(trans != NULL);
  	resstate = trans->resstate;
  	REQUIRE(resstate != NULL);
  	REQUIRE(task != NULL);
  
  	if (trans == resstate->trans4) {
  		family = AF_INET;
  		qtype = dns_rdatatype_a;
  	} else {
  		INSIST(trans == resstate->trans6);
  		family = AF_INET6;
  		qtype = dns_rdatatype_aaaa;
  	}
  
  	INSIST(trans->is_inprogress);
  	trans->is_inprogress = ISC_FALSE;
  
  	switch (rev->result) {
  	case ISC_R_SUCCESS:
  	case DNS_R_NCACHENXDOMAIN: /* treat this as a fatal error? */
  	case DNS_R_NCACHENXRRSET:
  		break;
  	default:
  		switch (rev->vresult) {
  		case DNS_R_SIGINVALID:
  		case DNS_R_SIGEXPIRED:
  		case DNS_R_SIGFUTURE:
  		case DNS_R_KEYUNAUTHORIZED:
  		case DNS_R_MUSTBESECURE:
  		case DNS_R_COVERINGNSEC:
  		case DNS_R_NOTAUTHORITATIVE:
  		case DNS_R_NOVALIDKEY:
  		case DNS_R_NOVALIDDS:
  		case DNS_R_NOVALIDSIG:
  			error = EAI_INSECUREDATA;
  			break;
  		default:
  			error = EAI_FAIL;
  		}
  		goto done;
  	}
  
  	/* Parse the response and construct the addrinfo chain */
  	for (name = ISC_LIST_HEAD(rev->answerlist); name != NULL;
  	     name = ISC_LIST_NEXT(name, link)) {
  		isc_result_t result;
  		dns_rdataset_t *rdataset;
  		isc_buffer_t b;
  		isc_region_t r;
  		char t[1024];
  
  		for (rdataset = ISC_LIST_HEAD(name->list);
  		     rdataset != NULL;
  		     rdataset = ISC_LIST_NEXT(rdataset, link)) {
  			if (!dns_rdataset_isassociated(rdataset))
  				continue;
  			if (rdataset->type != qtype)
  				continue;
  
  			if ((resstate->head->ai_flags & AI_CANONNAME) != 0) {
  				isc_buffer_init(&b, t, sizeof(t));
  				result = dns_name_totext(name, ISC_TRUE, &b);
  				if (result != ISC_R_SUCCESS) {
  					error = EAI_FAIL;
  					goto done;
  				}
  				isc_buffer_putuint8(&b, '\0');
  				isc_buffer_usedregion(&b, &r);
  			}
  
  			for (result = dns_rdataset_first(rdataset);
  			     result == ISC_R_SUCCESS;
  			     result = dns_rdataset_next(rdataset)) {
  				struct addrinfo *ai;
  				dns_rdata_t rdata;
  				dns_rdata_in_a_t rdata_a;
  				dns_rdata_in_aaaa_t rdata_aaaa;
  
  				ai = ai_alloc(family,
  					      ((family == AF_INET6) ?
  					       sizeof(struct sockaddr_in6) :
  					       sizeof(struct sockaddr_in)));
  				if (ai == NULL) {
  					error = EAI_MEMORY;
  					goto done;
  				}
  				ai->ai_socktype = resstate->head->ai_socktype;
  				ai->ai_next = trans->ai_sentinel.ai_next;
  				trans->ai_sentinel.ai_next = ai;
  
  				/*
  				 * Set AF-specific parameters
  				 * (IPv4/v6 address/port)
  				 */
  				dns_rdata_init(&rdata);
  				switch (family) {
  				case AF_INET:
  					dns_rdataset_current(rdataset, &rdata);
  					result = dns_rdata_tostruct(&rdata, &rdata_a,
  								    NULL);
  					RUNTIME_CHECK(result == ISC_R_SUCCESS);
  					SIN(ai->ai_addr)->sin_port =
  						resstate->head->ai_port;
  					memmove(&SIN(ai->ai_addr)->sin_addr,
  						&rdata_a.in_addr, 4);
  					dns_rdata_freestruct(&rdata_a);
  					break;
  				case AF_INET6:
  					dns_rdataset_current(rdataset, &rdata);
  					result = dns_rdata_tostruct(&rdata, &rdata_aaaa,
  								    NULL);
  					RUNTIME_CHECK(result == ISC_R_SUCCESS);
  					SIN6(ai->ai_addr)->sin6_port =
  						resstate->head->ai_port;
  					memmove(&SIN6(ai->ai_addr)->sin6_addr,
  						&rdata_aaaa.in6_addr, 16);
  					dns_rdata_freestruct(&rdata_aaaa);
  					break;
  				}
  
  				if ((resstate->head->ai_flags & AI_CANONNAME)
  				    != 0) {
  					ai->ai_canonname =
  						strdup((const char *)r.base);
  					if (ai->ai_canonname == NULL) {
  						error = EAI_MEMORY;
  						goto done;
  					}
  				}
  			}
  		}
  	}
  
   done:
  	dns_client_freeresanswer(resstate->head->dnsclient, &rev->answerlist);
  	dns_client_destroyrestrans(&trans->xid);
  
  	isc_event_free(&event);
  
  	/* Make sure that error == 0 iff we have a non-empty list */
  	if (error == 0) {
  		if (trans->ai_sentinel.ai_next == NULL)
  			error = EAI_NONAME;
  	} else {
  		if (trans->ai_sentinel.ai_next != NULL) {
  			_freeaddrinfo(trans->ai_sentinel.ai_next);
  			trans->ai_sentinel.ai_next = NULL;
  		}
  	}
  	trans->error = error;
  
  	/* Check whether we are done */
  	if ((resstate->trans4 == NULL || !resstate->trans4->is_inprogress) &&
  	    (resstate->trans6 == NULL || !resstate->trans6->is_inprogress)) {
  		/*
  		 * We're done for this state.  If there is no other outstanding
  		 * state, we can exit.
  		 */
  		resstate->head->activestates--;
  		if (resstate->head->activestates == 0) {
  			isc_app_ctxsuspend(resstate->head->actx);
  			return;
  		}
  
  		/*
  		 * There are outstanding states, but if we are at the head
  		 * of the state list (i.e., at the highest search priority)
  		 * and have any answer, we can stop now by canceling the
  		 * others.
  		 */
  		if (resstate == ISC_LIST_HEAD(resstate->head->resstates)) {
  			if ((resstate->trans4 != NULL &&
  			     resstate->trans4->ai_sentinel.ai_next != NULL) ||
  			    (resstate->trans6 != NULL &&
  			     resstate->trans6->ai_sentinel.ai_next != NULL)) {
  				gai_resstate_t *rest;
  
  				for (rest = ISC_LIST_NEXT(resstate, link);
  				     rest != NULL;
  				     rest = ISC_LIST_NEXT(rest, link)) {
  					if (rest->trans4 != NULL &&
  					    rest->trans4->xid != NULL)
  						dns_client_cancelresolve(
  							rest->trans4->xid);
  					if (rest->trans6 != NULL &&
  					    rest->trans6->xid != NULL)
  						dns_client_cancelresolve(
  							rest->trans6->xid);
  				}
  			} else {
  				/*
  				 * This search fails, so we move to the tail
  				 * of the list so that the next entry will
  				 * have the highest priority.
  				 */
  				ISC_LIST_UNLINK(resstate->head->resstates,
  						resstate, link);
  				ISC_LIST_APPEND(resstate->head->resstates,
  						resstate, link);
  			}
  		}
  	}
  }
  
  static int
  resolve_name(int family, const char *hostname, int flags,
  	     struct addrinfo **aip, int socktype, int port)
  {
  	isc_result_t result;
  	irs_context_t *irsctx;
  	irs_resconf_t *conf;
  	isc_mem_t *mctx;
  	isc_appctx_t *actx;
  	isc_task_t *task;
  	int terror = 0;
  	int error = 0;
  	dns_client_t *client;
  	gai_resstate_t *resstate;
  	gai_statehead_t head;
  	isc_boolean_t all_fail = ISC_TRUE;
  
  	/* get IRS context and the associated parameters */
  	irsctx = NULL;
  	result = irs_context_get(&irsctx);
  	if (result != ISC_R_SUCCESS)
  		return (EAI_FAIL);
  	actx = irs_context_getappctx(irsctx);
  
  	mctx = irs_context_getmctx(irsctx);
  	task = irs_context_gettask(irsctx);
  	conf = irs_context_getresconf(irsctx);
  	client = irs_context_getdnsclient(irsctx);
  
  	/* construct resolution states */
  	head.activestates = 0;
  	head.ai_family = family;
  	head.ai_socktype = socktype;
  	head.ai_flags = flags;
  	head.ai_port = port;
  	head.actx = actx;
  	head.dnsclient = client;
  	ISC_LIST_INIT(head.resstates);
  	result = make_resstates(mctx, hostname, &head, conf);
  	if (result != ISC_R_SUCCESS)
  		return (EAI_FAIL);
  
  	for (resstate = ISC_LIST_HEAD(head.resstates);
  	     resstate != NULL; resstate = ISC_LIST_NEXT(resstate, link)) {
  		if (resstate->trans4 != NULL) {
  			result = dns_client_startresolve(client,
  							 resstate->qname,
  							 dns_rdataclass_in,
  							 dns_rdatatype_a,
  							 0, task,
  							 process_answer,
  							 resstate->trans4,
  							 &resstate->trans4->xid);
  			if (result == ISC_R_SUCCESS) {
  				resstate->trans4->is_inprogress = ISC_TRUE;
  				all_fail = ISC_FALSE;
  			} else
  				resstate->trans4->is_inprogress = ISC_FALSE;
  		}
  		if (resstate->trans6 != NULL) {
  			result = dns_client_startresolve(client,
  							 resstate->qname,
  							 dns_rdataclass_in,
  							 dns_rdatatype_aaaa,
  							 0, task,
  							 process_answer,
  							 resstate->trans6,
  							 &resstate->trans6->xid);
  			if (result == ISC_R_SUCCESS) {
  				resstate->trans6->is_inprogress = ISC_TRUE;
  				all_fail = ISC_FALSE;
  			} else
  				resstate->trans6->is_inprogress= ISC_FALSE;
  		}
  	}
  	if (!all_fail) {
  		/* Start all the events */
  		isc_app_ctxrun(actx);
  	} else
  		error = EAI_FAIL;
  
  	/* Cleanup */
  	while ((resstate = ISC_LIST_HEAD(head.resstates)) != NULL) {
  		int terror4 = 0, terror6 = 0;
  
  		ISC_LIST_UNLINK(head.resstates, resstate, link);
  
  		if (*aip == NULL) {
  			struct addrinfo *sentinel4 = NULL;
  			struct addrinfo *sentinel6 = NULL;
  
  			if (resstate->trans4 != NULL) {
  				sentinel4 =
  					resstate->trans4->ai_sentinel.ai_next;
  				resstate->trans4->ai_sentinel.ai_next = NULL;
  			}
  			if (resstate->trans6 != NULL) {
  				sentinel6 =
  					resstate->trans6->ai_sentinel.ai_next;
  				resstate->trans6->ai_sentinel.ai_next = NULL;
  			}
  			*aip = ai_concat(sentinel4, sentinel6);
  		}
  
  		if (resstate->trans4 != NULL) {
  			INSIST(resstate->trans4->xid == NULL);
  			terror4 = resstate->trans4->error;
  			isc_mem_put(mctx, resstate->trans4,
  				    sizeof(*resstate->trans4));
  		}
  		if (resstate->trans6 != NULL) {
  			INSIST(resstate->trans6->xid == NULL);
  			terror6 = resstate->trans6->error;
  			isc_mem_put(mctx, resstate->trans6,
  				    sizeof(*resstate->trans6));
  		}
  
  		/*
  		 * If the entire lookup fails, we need to choose an appropriate
  		 * error code from individual codes.  We'll try to provide as
  		 * specific a code as possible.  In general, we are going to
  		 * find an error code other than EAI_NONAME (which is too
  		 * generic and may actually not be problematic in some cases).
  		 * EAI_NONAME will be set below if no better code is found.
  		 */
  		if (terror == 0 || terror == EAI_NONAME) {
  			if (terror4 != 0 && terror4 != EAI_NONAME)
  				terror = terror4;
  			else if (terror6 != 0 && terror6 != EAI_NONAME)
  				terror = terror6;
  		}
  
  		isc_mem_put(mctx, resstate, sizeof(*resstate));
  	}
  
  	if (*aip == NULL) {
  		error = terror;
  		if (error == 0)
  			error = EAI_NONAME;
  	}
  
  #if 1	/*  XXX: enabled for finding leaks.  should be cleaned up later. */
  	isc_app_ctxfinish(actx);
  	irs_context_destroy(&irsctx);
  #endif
  
  	return (error);
  }
  
  static char *
  irs_strsep(char **stringp, const char *delim) {
  	char *string = *stringp;
  	char *s;
  	const char *d;
  	char sc, dc;
  
  	if (string == NULL)
  		return (NULL);
  
  	for (s = string; *s != '\0'; s++) {
  		sc = *s;
  		for (d = delim; (dc = *d) != '\0'; d++)
  			if (sc == dc) {
  				*s++ = '\0';
  				*stringp = s;
  				return (string);
  			}
  	}
  	*stringp = NULL;
  	return (string);
  }
  
  static void
  set_order(int family, int (**net_order)(const char *, int, struct addrinfo **,
  					int, int))
  {
  	char *order, *tok;
  	int found;
  
  	if (family) {
  		switch (family) {
  		case AF_INET:
  			*net_order++ = add_ipv4;
  			break;
  		case AF_INET6:
  			*net_order++ = add_ipv6;
  			break;
  		}
  	} else {
  		order = getenv("NET_ORDER");
  		found = 0;
  		while (order != NULL) {
  			/*
  			 * We ignore any unknown names.
  			 */
  			tok = irs_strsep(&order, ":");
  			if (strcasecmp(tok, "inet6") == 0) {
  				if ((found & FOUND_IPV6) == 0)
  					*net_order++ = add_ipv6;
  				found |= FOUND_IPV6;
  			} else if (strcasecmp(tok, "inet") == 0 ||
  			    strcasecmp(tok, "inet4") == 0) {
  				if ((found & FOUND_IPV4) == 0)
  					*net_order++ = add_ipv4;
  				found |= FOUND_IPV4;
  			}
  		}
  
  		/*
  		 * Add in anything that we didn't find.
  		 */
  		if ((found & FOUND_IPV4) == 0)
  			*net_order++ = add_ipv4;
  		if ((found & FOUND_IPV6) == 0)
  			*net_order++ = add_ipv6;
  	}
  	*net_order = NULL;
  	return;
  }
  
  static char v4_loop[4] = { 127, 0, 0, 1 };
  
  static int
  add_ipv4(const char *hostname, int flags, struct addrinfo **aip,
  	 int socktype, int port)
  {
  	struct addrinfo *ai;
  
  	UNUSED(hostname);
  	UNUSED(flags);
  
  	ai = ai_clone(*aip, AF_INET); /* don't use ai_clone() */
  	if (ai == NULL) {
  		_freeaddrinfo(*aip);
  		return (EAI_MEMORY);
  	}
  
  	*aip = ai;
  	ai->ai_socktype = socktype;
  	SIN(ai->ai_addr)->sin_port = port;
  	memmove(&SIN(ai->ai_addr)->sin_addr, v4_loop, 4);
  
  	return (0);
  }
  
  static char v6_loop[16] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 };
  
  static int
  add_ipv6(const char *hostname, int flags, struct addrinfo **aip,
  	 int socktype, int port)
  {
  	struct addrinfo *ai;
  
  	UNUSED(hostname);
  	UNUSED(flags);
  
  	ai = ai_clone(*aip, AF_INET6); /* don't use ai_clone() */
  	if (ai == NULL)
  		return (EAI_MEMORY);
  
  	*aip = ai;
  	ai->ai_socktype = socktype;
  	SIN6(ai->ai_addr)->sin6_port = port;
  	memmove(&SIN6(ai->ai_addr)->sin6_addr, v6_loop, 16);
  
  	return (0);
  }
  
  /*% Free address info. */
  void
  freeaddrinfo(struct addrinfo *ai) {
  	_freeaddrinfo(ai);
  }
  
  static void
  _freeaddrinfo(struct addrinfo *ai) {
  	struct addrinfo *ai_next;
  
  	while (ai != NULL) {
  		ai_next = ai->ai_next;
  		if (ai->ai_addr != NULL)
  			free(ai->ai_addr);
  		if (ai->ai_canonname)
  			free(ai->ai_canonname);
  		free(ai);
  		ai = ai_next;
  	}
  }
  
  #ifdef AF_LOCAL
  static int
  get_local(const char *name, int socktype, struct addrinfo **res) {
  	struct addrinfo *ai;
  	struct sockaddr_un *slocal;
  
  	if (socktype == 0)
  		return (EAI_SOCKTYPE);
  
  	ai = ai_alloc(AF_LOCAL, sizeof(*slocal));
  	if (ai == NULL)
  		return (EAI_MEMORY);
  
  	slocal = SLOCAL(ai->ai_addr);
  	strlcpy(slocal->sun_path, name, sizeof(slocal->sun_path));
  
  	ai->ai_socktype = socktype;
  	/*
  	 * ai->ai_flags, ai->ai_protocol, ai->ai_canonname,
  	 * and ai->ai_next were initialized to zero.
  	 */
  
  	*res = ai;
  	return (0);
  }
  #endif
  
  /*!
   * Allocate an addrinfo structure, and a sockaddr structure
   * of the specificed length.  We initialize:
   *	ai_addrlen
   *	ai_family
   *	ai_addr
   *	ai_addr->sa_family
   *	ai_addr->sa_len	(IRS_PLATFORM_HAVESALEN)
   * and everything else is initialized to zero.
   */
  static struct addrinfo *
  ai_alloc(int family, int addrlen) {
  	struct addrinfo *ai;
  
  	ai = (struct addrinfo *)calloc(1, sizeof(*ai));
  	if (ai == NULL)
  		return (NULL);
  
  	ai->ai_addr = SA(calloc(1, addrlen));
  	if (ai->ai_addr == NULL) {
  		free(ai);
  		return (NULL);
  	}
  	ai->ai_addrlen = addrlen;
  	ai->ai_family = family;
  	ai->ai_addr->sa_family = family;
  #ifdef IRS_PLATFORM_HAVESALEN
  	ai->ai_addr->sa_len = addrlen;
  #endif
  	return (ai);
  }
  
  static struct addrinfo *
  ai_clone(struct addrinfo *oai, int family) {
  	struct addrinfo *ai;
  
  	ai = ai_alloc(family, ((family == AF_INET6) ?
  	    sizeof(struct sockaddr_in6) : sizeof(struct sockaddr_in)));
  
  	if (ai == NULL) {
  		if (oai != NULL)
  			freeaddrinfo(oai);
  		return (NULL);
  	}
  	if (oai == NULL)
  		return (ai);
  
  	ai->ai_flags = oai->ai_flags;
  	ai->ai_socktype = oai->ai_socktype;
  	ai->ai_protocol = oai->ai_protocol;
  	ai->ai_canonname = NULL;
  	ai->ai_next = oai;
  	return (ai);
  }
  
  static struct addrinfo *
  ai_reverse(struct addrinfo *oai) {
  	struct addrinfo *nai, *tai;
  
  	nai = NULL;
  
  	while (oai != NULL) {
  		/*
  		 * Grab one off the old list.
  		 */
  		tai = oai;
  		oai = oai->ai_next;
  		/*
  		 * Put it on the front of the new list.
  		 */
  		tai->ai_next = nai;
  		nai = tai;
  	}
  	return (nai);
  }
  
  
  static struct addrinfo *
  ai_concat(struct addrinfo *ai1, struct addrinfo *ai2) {
  	struct addrinfo *ai_tmp;
  
  	if (ai1 == NULL)
  		return (ai2);
  	else if (ai2 == NULL)
  		return (ai1);
  
  	for (ai_tmp = ai1; ai_tmp != NULL && ai_tmp->ai_next != NULL;
  	     ai_tmp = ai_tmp->ai_next)
  		;
  
  	ai_tmp->ai_next = ai2;
  
  	return (ai1);
  }
  