235 lines
6.8 KiB
Plaintext
235 lines
6.8 KiB
Plaintext
.\" Copyright (c) 1985 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms are permitted
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.\" provided that the above copyright notice and this paragraph are
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.\" duplicated in all such forms and that any documentation,
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.\" advertising materials, and other materials related to such
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.\" distribution and use acknowledge that the software was developed
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.\" by the University of California, Berkeley. The name of the
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.\" University may not be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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.\"
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.\" @(#)resolver.3 6.3 (Berkeley) 12/14/89
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.\"
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.TH res_query 3N
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.SH NAME
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res_query, res_search, res_mkquery, res_send, res_init, dn_comp, dn_expand \- resolver routines
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.SH SYNOPSIS
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.nf
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\f3#include <sys/types.h>\f1
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\f3#include <netinet/in.h>\f1
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\f3#include <arpa/nameser.h>\f1
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\f3#include <resolv.h>\f1
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.sp .8v
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\f3int res_query (const char *dname, int class, int type,\f1
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\f3 u_char *answer, int anslen);\f1
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.sp .8v
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\f3int res_search (const char *dname, int class, int type,\f1
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\f3 u_char *answer, int anslen);\f1
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.sp .8v
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\f3int res_mkquery (int op, const char *dname, int class, int type,\f1
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\f3 const char *data, int datalen, const char *newrr,\f1
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\f3 char *buf, int buflen);\f1
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.sp .8v
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\f3int res_send (const char *msg, int msglen, char *answer, int anslen);\f1
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.sp .8v
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\f3int res_init (void);\f1
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.sp .8v
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\f3int dn_comp (const u_char *exp_dn, u_char *comp_dn, int length,\f1
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\f3 u_char **dnptrs, u_char **lastdnptr);\f1
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.sp .8v
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\f3int dn_expand (const u_char *msg, const u_char *eomorig,\f1
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\f3 const u_char *comp_dn, char *exp_dn, int length);\f1
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.fi
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.SH DESCRIPTION
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These routines are used for making, sending, and interpreting
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query and reply messages with Internet domain name servers.
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.PP
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Global configuration and state information that is used by the
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resolver routines is kept in the structure
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.IR _res .
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Most of the values have reasonable defaults and can be ignored.
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Options
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stored in
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.I _res.options
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are defined in
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.I resolv.h
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and are as follows.
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Options are stored as a simple bit mask containing the bitwise ``or''
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of the options enabled.
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.IP RES_INIT 15
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True if the initial name server address and default domain name are
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initialized
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.RI ( res_init
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has been called).
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.IP RES_DEBUG
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Print debugging messages.
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.IP RES_AAONLY
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Accept authoritative answers only.
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With this option,
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.I res_send
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should continue until it finds an authoritative answer or finds an error.
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Currently this is not implemented.
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.IP RES_USEVC
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Use TCP connections for queries instead of UDP datagrams.
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.IP RES_STAYOPEN
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Used with RES_USEVC to keep the TCP connection open between
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queries.
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This is useful only in programs that regularly do many queries.
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UDP should be the normal mode used.
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.IP RES_IGNTC
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Unused currently (ignore truncation errors; don't retry with TCP).
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.IP RES_RECURSE
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Set the recursion-desired bit in queries.
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This is the default.
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.RI ( res_send
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does not do iterative queries and expects the name server
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to handle recursion.)
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.IP RES_DEFNAMES
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If set,
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.I res_search
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appends the default domain name to single-component names
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(those that do not contain a dot).
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This option is enabled by default.
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.IP RES_DNSRCH
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If this option is set,
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.I res_search
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searches for hostnames in the current domain and in parent domains; see
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.IR hostname (5).
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This is used by the standard host lookup routine
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.IR gethostbyname (3N).
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This option is enabled by default.
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.PP
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The
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.I res_init
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routine
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reads the configuration file (if any; see
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.IR resolver (4))
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to get the default domain name,
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search list and
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the Internet address of the local name server(s).
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If no server is configured, the host running
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the resolver is tried.
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The current domain name is defined by the hostname
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if not specified in the configuration file;
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it can be overridden by the environment variable LOCALDOMAIN.
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Initialization normally occurs on the first call
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to one of the following routines.
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.PP
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The
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.I res_query
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function provides an interface to the server query mechanism.
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It constructs a query, sends it to the local server,
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awaits a response, and makes preliminary checks on the reply.
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The query requests information of the specified
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.I type
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and
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.I class
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for the specified fully-qualified domain name
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.IR dname .
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The reply message is left in the
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.I answer
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buffer with length
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.I anslen
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supplied by the caller.
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.PP
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The
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.I res_search
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routine makes a query and awaits a response like
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.IR res_query ,
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but in addition, it implements the default and search rules
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controlled by the RES_DEFNAMES and RES_DNSRCH options.
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It returns the first successful reply.
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.PP
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The remaining routines are lower-level routines used by
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.IR res_query .
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The
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.I res_mkquery
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function
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constructs a standard query message and places it in
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.IR buf .
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It returns the size of the query, or \-1 if the query is
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larger than
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.IR buflen .
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The query type
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.I op
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is usually QUERY, but can be any of the query types defined in
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.IR <arpa/nameser.h> .
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The domain name for the query is given by
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.IR dname .
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.I newrr
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is currently unused but is intended for making update messages.
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.PP
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The
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.I res_send
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routine
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sends a preformatted query and returns an answer.
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It calls
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.I res_init
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if RES_INIT is not set, sends the query to the local name server, and
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handles timeouts and retries.
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The length of the reply message is returned, or
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\-1 if there were errors.
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.PP
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The
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.I dn_comp
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function
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compresses the domain name
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.I exp_dn
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and stores it in
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.IR comp_dn .
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The size of the compressed name is returned or \-1 if there were errors.
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The size of the array pointed to by
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.I comp_dn
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is given by
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.IR length .
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The compression uses
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an array of pointers
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.I dnptrs
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to previously-compressed names in the current message.
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The first pointer points to
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the beginning of the message and the list ends with NULL.
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The limit to the array is specified by
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.IR lastdnptr .
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A side effect of
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.I dn_comp
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is to update the list of pointers for
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labels inserted into the message
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as the name is compressed.
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If
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.I dnptr
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is NULL, names are not compressed.
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If
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.I lastdnptr
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is NULL, the list of labels is not updated.
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.PP
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The
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.I dn_expand
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entry
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expands the compressed domain name
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.I comp_dn
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to a full domain name
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The compressed name is contained in a query or reply message;
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.I msg
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is a pointer to the beginning of the message.
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The uncompressed name is placed in the buffer indicated by
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.IR exp_dn ,
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which is of size
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.IR length .
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The size of compressed name is returned or \-1 if there was an error.
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.SH FILES
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/etc/resolv.conf see resolver(4)
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.SH "SEE ALSO"
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named(1M),
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gethostbyname(3N),
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resolver(4),
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hostname(5).
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.PP
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RFC1032, RFC1033, RFC1034, RFC1035, RFC974
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.PP
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\f2IRIX Admin: Networking and Mail\f1
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