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RESOLVER(3)	       FreeBSD Library Functions Manual		   RESOLVER(3)

     res_ninit,	res_ourserver_p, fp_resstat, res_hostalias, res_pquery,
     res_nquery, res_nsearch, res_nquerydomain,	res_nmkquery, res_nsend,
     res_nupdate, res_nmkupdate, res_nclose, res_nsendsigned, res_findzonecut,
     res_getservers, res_setservers, res_ndestroy, dn_comp, dn_expand,
     hstrerror,	res_init, res_isourserver, fp_nquery, p_query, hostalias,
     res_query,	res_search, res_querydomain, res_mkquery, res_send,
     res_update, res_close, herror -- resolver routines

     #include <sys/types.h>
     #include <netinet/in.h>
     #include <arpa/nameser.h>
     #include <resolv.h>
     #include <res_update.h>

     typedef struct __res_state	*res_state;

     res_ninit(res_state statp);

     res_ourserver_p(const res_state statp, const struct sockaddr_in *addr);

     fp_resstat(const res_state	statp, FILE *fp);

     const char	*
     res_hostalias(const res_state statp, const	char *name, char *buf,
	 size_t	buflen);

     res_pquery(const res_state	statp, const u_char *msg, int msglen,
	 FILE *fp);

     res_nquery(res_state statp, const char *dname, int	class, int type,
	 u_char	*answer, int anslen);

     res_nsearch(res_state statp, const	char *dname, int class,	int type,
	 u_char	* answer, int anslen);

     res_nquerydomain(res_state	statp, const char *name, const char *domain,
	 int class, int	type, u_char *answer, int anslen);

     res_nmkquery(res_state statp, int op, const char *dname, int class,
	 int type, const u_char	*data, int datalen, const u_char *newrr,
	 u_char	*buf, int buflen);

     res_nsend(res_state statp,	const u_char *msg, int msglen, u_char *answer,
	 int anslen);

     res_nupdate(res_state statp, ns_updrec *rrecp_in);

     res_nmkupdate(res_state statp, ns_updrec *rrecp_in, u_char	*buf,
	 int buflen);

     res_nclose(res_state statp);

     res_nsendsigned(res_state statp, const u_char *msg, int msglen,
	 ns_tsig_key *key, u_char *answer, int anslen);

     res_findzonecut(res_state statp, const char *dname, ns_class class,
	 int options, char *zname, size_t zsize, struct	in_addr	*addrs,
	 int naddrs);

     res_getservers(res_state statp, union res_sockaddr_union *set, int	cnt);

     res_setservers(res_state statp, const union res_sockaddr_union *set,
	 int cnt);

     res_ndestroy(res_state statp);

     dn_comp(const char	*exp_dn, u_char	*comp_dn, int length, u_char **dnptrs,
	 u_char	**lastdnptr);

     dn_expand(const u_char *msg, const	u_char *eomorig,
	 const u_char *comp_dn,	char *exp_dn, int length);

     const char	*
     hstrerror(int err);

     #include <sys/types.h>
     #include <netinet/in.h>
     #include <arpa/nameser.h>
     #include <resolv.h>
     #include <res_update.h>


     res_isourserver(const struct sockaddr_in *addr);

     fp_nquery(const u_char *msg, int msglen, FILE *fp);

     p_query(const u_char *msg,	FILE *fp);

     const char	*
     hostalias(const char *name);

     res_query(const char *dname, int class, int type, u_char *answer,
	 int anslen);

     res_search(const char *dname, int class, int type,	u_char *answer,
	 int anslen);

     res_querydomain(const char	*name, const char *domain, int class,
	 int type, u_char *answer, int anslen);

     res_mkquery(int op, const char *dname, int	class, int type,
	 const char *data, int datalen,	struct rrec *newrr, u_char *buf,
	 int buflen);

     res_send(const u_char *msg, int msglen, u_char *answer, int anslen);

     res_update(ns_updrec *rrecp_in);


     herror(const char *s);

     These routines are	used for making, sending and interpreting query	and
     reply messages with Internet domain name servers.

     State information is kept in statp	and is used to control the behavior of
     these functions.  statp should be set to all zeros	prior to the first
     call to any of these functions.

     The functions res_init(), res_isourserver(), fp_nquery(), p_query(),
     hostalias(), res_query(), res_search(), res_querydomain(),	res_mkquery(),
     res_send(), res_update(), res_close() and herror()	are deprecated and are
     supplied for compatability	with old source	code.  They use	global config-
     uration and state information that	is kept	in the structure _res rather
     than that referenced through statp.

     Most of the values	in statp and _res are initialized on the first call to
     res_ninit() / res_init() to reasonable defaults and can be	ignored.  Op-
     tions stored in statp-_options / _res.options are defined in resolv.h and
     are as follows.  Options are stored as a simple bit mask containing the
     bitwise "OR" of the options enabled.

	      True if the initial name server address and default domain name
	      are initialized (i.e., res_ninit() / res_init() has been

	      Print debugging messages.

	      Accept authoritative answers only.  Should continue until	it
	      finds an authoritative answer or finds an	error.	Currently this
	      is not implemented.

	      Use TCP connections for queries instead of UDP datagrams.

	      Used with	RES_USEVC to keep the TCP connection open between
	      queries.	This is	useful only in programs	that regularly do many
	      queries.	UDP should be the normal mode used.

	      Ignore truncation	errors,	i.e., don't retry with TCP.

	      Set the recursion-desired	bit in queries.	 This is the default.
	      (res_nsend() / res_send()	does not do iterative queries and ex-
	      pects the	name server to handle recursion.)

	      If set, res_nsearch() / res_search() will	append the default do-
	      main name	to single-component names (those that do not contain a
	      dot).  This option is enabled by default.

	      If this option is	set, res_nsearch() / res_search() will search
	      for host names in	the current domain and in parent domains; see
	      hostname(7).  This is used by the	standard host lookup routine
	      gethostbyname(3).	 This option is	enabled	by default.

	      This option turns	off the	user level aliasing feature controlled
	      by the HOSTALIASES environment variable.	Network	daemons	should
	      set this option.

	      This option causes gethostbyname(3) to look for AAAA records be-
	      fore looking for A records if none are found.

	      This options causes the res_nsend() / res_send() to rotate the
	      list of nameservers in statp-_nsaddr_list	/ _res.nsaddr_list.

	      This option causes res_nsendsigned() to leave the	message	un-
	      changed after TSIG verification; otherwise the TSIG record would
	      be removed and the header	updated.

	      This option causes res_nsearch() to not attempt to resolve a un-
	      qualified	name as	if it were a top level domain (TLD).  This op-
	      tion can cause problems if the site has "localhost" as a TLD
	      rather than having localhost on one or more elements of the
	      search list.  This option	has no effect if neither RES_DEFNAMES
	      or RES_DNSRCH is set.

     The res_ninit() / res_init() routine reads	the configuration file (if
     any; see resolver(5)) to get the default domain name, search list and the
     Internet address of the local name	server(s).  If no server is config-
     ured, the host running the	resolver is tried.  The	current	domain name is
     defined by	the hostname if	not specified in the configuration file; it
     can be overridden by the environment variable LOCALDOMAIN.	 This environ-
     ment variable may contain several blank-separated tokens if you wish to
     override the "search list"	on a per-process basis.	 This is similar to
     the search	command	in the configuration file.  Another environment	vari-
     able ("RES_OPTIONS") can be set to	override certain internal resolver op-
     tions which are otherwise set by changing fields in the statp / _res
     structure or are inherited	from the configuration file's options command.
     The syntax	of the "RES_OPTIONS" environment variable is explained in
     resolver(5).  Initialization normally occurs on the first call to one of
     the other resolver	routines.

     The memory	referred to by statp must be set to all	zeros prior to the
     first call	to res_ninit().	 res_ndestroy()	should be call to free memory
     allocated by res_ninit() after last use.

     The res_nquery() /	res_query() functions provides interfaces to the
     server query mechanism.  They constructs a	query, sends it	to the local
     server, awaits a response,	and makes preliminary checks on	the reply.
     The query requests	information of the specified type and class for	the
     specified fully-qualified domain name dname.  The reply message is	left
     in	the answer buffer with length anslen supplied by the caller.
     res_nquery() / res_query()	return -1 on error or the length of the	an-

     The res_nsearch() / res_search() routines make a query and	awaits a re-
     sponse like res_nquery() /	res_query(), but in addition, it implements
     the default and search rules controlled by	the RES_DEFNAMES and
     RES_DNSRCH	options.  It returns the length	of the first successful	reply
     which is stored in	answer or -1 on	error.

     The remaining routines are	lower-level routines used by res_nquery() /
     res_query().  The res_nmkquery() /	res_mkquery() functions	constructs a
     standard query message and	places it in buf.  It returns the size of the
     query, or -1 if the query is larger than buflen.  The query type op is
     usually QUERY, but	can be any of the query	types defined in
     _arpa/nameser.h_.	The domain name	for the	query is given by dname.
     Newrr is currently	unused but is intended for making update messages.

     The res_nsend() / res_send() / res_nsendsigned() routines sends a pre-
     formatted query and returns an answer.  It	will call res_ninit() /
     res_init()	if RES_INIT is not set,	send the query to the local name
     server, and handle	timeouts and retries.  Additionally, res_nsendsigned()
     will use TSIG signatures to add authentication to the query and verify
     the response.  In this case, only one nameserver will be contacted.  The
     length of the reply message is returned, or -1 if there were errors.

     res_nquery() / res_query(), res_nsearch() / res_search() and res_nsend()
     / res_send() return a length that may be bigger than anslen.  In that
     case the query should be retried with a bigger buffer.  NOTE the answer
     to	the second query may be	larger still so	supplying a buffer that	bigger
     that the answer returned by the previous query is recommended.

     answer MUST be big	enough to receive a maximum UDP	response from the
     server or parts of	the answer will	be silently discarded.	The default
     maximum UDP response size is 512 bytes.

     The function res_ourserver_p() returns true when inp is one of the
     servers in	statp-_nsaddr_list / _res.nsaddr_list.

     The functions fp_nquery() / p_query() print out the query and any answer
     in	msg on fp.  p_query() is equivalent to fp_nquery() with	msglen set to

     The function fp_resstat() prints out the active flag bits in
     statp-_options preceeded by the text ";; res options:" on file.

     The functions res_hostalias() / hostalias() lookup	up name	in the file
     referred to by the	HOSTALIASES files return a fully qualified hostname if
     found or NULL if not found	or an error occurred.  res_hostalias() uses
     buf to store the result in, hostalias() uses a static buffer.

     The functions res_getservers() and	res_setservers() are used to get and
     set the list of server to be queried.

     The functions res_nupdate() / res_update()	take a list of ns_updrec
     rrecp_in.	Identifies the containing zone for each	record and groups the
     records according to containing zone maintaining in zone order then sends
     and update	request	to the servers for these zones.	 The number of zones
     updated is	returned or -1 on error.  Note that res_nupdate() will perform
     TSIG authenticated	dynamic	update operations if the key is	not NULL.

     The function res_findzonecut() discovers the closest enclosing zone cut
     for a specified domain name, and finds the	IP addresses of	the zone's
     master servers.

     The functions res_nmkupdate() / res_mkupdate() take a linked list of
     ns_updrec rrecp_in	and construct a	UPDATE message in buf.
     res_nmkupdate() / res_mkupdate() return the length	of the constructed
     message on	no error or one	of the following error values.

     -1	An error occurred parsing rrecp_in.

     -2	The buffer buf was too small.

     -3	The first record was not a zone	section	or there was a section order
     problem.  The section order is S_ZONE, S_PREREQ and S_UPDATE.

     -4	A number overflow occurred.

     -5	Unknown	operation or no	records.

     The functions res_nclose()	/ res_close() close any	open files referenced
     through statp / _res.

     The function res_ndestroy() calls res_nclose() then frees any memory al-
     located by	res_ninit().

     The dn_comp() function compresses the domain name exp_dn and stores it in
     comp_dn.  The size	of the compressed name is returned or -1 if there were
     errors.  The size of the array pointed to by comp_dn is given by length.
     The compression uses an array of pointers dnptrs to previously-compressed
     names in the current message.  The	first pointer points to	to the begin-
     ning of the message and the list ends with	NULL.  The limit to the	array
     is	specified by lastdnptr.	 A side	effect of dn_comp() is to update the
     list of pointers for labels inserted into the message as the name is com-
     pressed.  If dnptr	is NULL, names are not compressed.  If lastdnptr is
     NULL, the list of labels is not updated.

     The dn_expand() entry expands the compressed domain name comp_dn to a
     full domain name.	The compressed name is contained in a query or reply
     message; msg is a pointer to the beginning	of the message.	 eomorig is a
     pointer to	the first location after the message.  The uncompressed	name
     is	placed in the buffer indicated by exp_dn which is of size length.  The
     size of compressed	name is	returned or -1 if there	was an error.

     The variables statp-_res_h_errno /	_res.res_h_errno and external variable
     h_errno is	set whenever an	error occurs during resolver operation.	 The
     following definitions are given in	_netdb.h_:

     #define NETDB_INTERNAL -1	/* see errno */
     #define NETDB_SUCCESS  0	/* no problem */
     #define HOST_NOT_FOUND 1	/* Authoritative Answer	Host not found */
     #define TRY_AGAIN	    2	/* Non-Authoritative not found,	or SERVFAIL */
     #define NO_RECOVERY    3	/* Non-Recoverable: FORMERR, REFUSED, NOTIMP */
     #define NO_DATA	    4	/* Valid name, no data for requested type */

     The herror() function writes a message to the diagnostic output consist-
     ing of the	string parameter s, the	constant string	": ", and a message
     corresponding to the value	of h_errno.

     The hstrerror() function returns a	string which is	the message text cor-
     responding	to the value of	the err	parameter.

     /etc/resolv.conf	   See resolver(5).

     gethostbyname(3), hostname(7), resolver(5); RFC1032, RFC1033, RFC1034,
     RFC1035, RFC974; SMM:11, "Name Server Operations Guide for	BIND"

4th Berkeley Distribution	 July 4, 2000	     4th Berkeley Distribution


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