contrib/bind-9.2.4rc7/lib/lwres/man/lwres_resutil.3

   1 .\" Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
   2 .\" Copyright (C) 2000, 2001  Internet Software Consortium.
   3 .\"
   4 .\" Permission to use, copy, modify, and distribute this software for any
   5 .\" purpose with or without fee is hereby granted, provided that the above
   6 .\" copyright notice and this permission notice appear in all copies.
   7 .\"
   8 .\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
   9 .\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  10 .\" AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
  11 .\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
  12 .\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
  13 .\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  14 .\" PERFORMANCE OF THIS SOFTWARE.
  15 .\"
  16 .\" $Id: lwres_resutil.3,v 1.14.2.2 2004/03/15 04:45:05 marka Exp $
  17 .\"
  18 .TH "LWRES_RESUTIL" "3" "Jun 30, 2000" "BIND9" ""
  19 .SH NAME
  20 lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr \- lightweight resolver utility functions
  21 .SH SYNOPSIS
  22 \fB#include <lwres/lwres.h>
  23 .sp
  24 .na
  25 lwres_result_t
  26 lwres_string_parse(lwres_buffer_t *b, char **c, lwres_uint16_t *len);
  27 .ad
  28 .sp
  29 .na
  30 lwres_result_t
  31 lwres_addr_parse(lwres_buffer_t *b, lwres_addr_t *addr);
  32 .ad
  33 .sp
  34 .na
  35 lwres_result_t
  36 lwres_getaddrsbyname(lwres_context_t *ctx, const char *name, lwres_uint32_t addrtypes, lwres_gabnresponse_t **structp);
  37 .ad
  38 .sp
  39 .na
  40 lwres_result_t
  41 lwres_getnamebyaddr(lwres_context_t *ctx, lwres_uint32_t addrtype, lwres_uint16_t addrlen, const unsigned char *addr, lwres_gnbaresponse_t **structp);
  42 .ad
  43 \fR
  44 .SH "DESCRIPTION"
  45 .PP
  46 \fBlwres_string_parse()\fR retrieves a DNS-encoded
  47 string starting the current pointer of lightweight resolver buffer
  48 \fIb\fR: i.e. b->current.
  49 When the function returns, the address of the first byte of the
  50 encoded string is returned via \fI*c\fR and the
  51 length of that string is given by \fI*len\fR. The
  52 buffer's current pointer is advanced to point at the character
  53 following the string length, the encoded string, and the trailing
  54 \fBNULL\fR character.
  55 .PP
  56 \fBlwres_addr_parse()\fR extracts an address from the
  57 buffer \fIb\fR. The buffer's current pointer
  58 b->current is presumed to point at an encoded
  59 address: the address preceded by a 32-bit protocol family identifier
  60 and a 16-bit length field. The encoded address is copied to
  61 addr->address and
  62 addr->length indicates the size in bytes of
  63 the address that was copied. b->current is
  64 advanced to point at the next byte of available data in the buffer
  65 following the encoded address.
  66 .PP
  67 \fBlwres_getaddrsbyname()\fR
  68 and
  69 \fBlwres_getnamebyaddr()\fR
  70 use the
  71 \fBlwres_gnbaresponse_t\fR
  72 structure defined below:
  73 .sp
  74 .nf
  75 typedef struct {
  76         lwres_uint32_t          flags;
  77         lwres_uint16_t          naliases;
  78         lwres_uint16_t          naddrs;
  79         char                   *realname;
  80         char                  **aliases;
  81         lwres_uint16_t          realnamelen;
  82         lwres_uint16_t         *aliaslen;
  83         lwres_addrlist_t        addrs;
  84         void                   *base;
  85         size_t                  baselen;
  86 } lwres_gabnresponse_t;
  87 .sp
  88 .fi
  89 The contents of this structure are not manipulated directly but
  90 they are controlled through the
  91 \fBlwres_gabn\fR(3)
  92 functions.
  93 .PP
  94 The lightweight resolver uses
  95 \fBlwres_getaddrsbyname()\fR to perform foward lookups.
  96 Hostname \fIname\fR is looked up using the resolver
  97 context \fIctx\fR for memory allocation.
  98 \fIaddrtypes\fR is a bitmask indicating which type of
  99 addresses are to be looked up. Current values for this bitmask are
 100 \fBLWRES_ADDRTYPE_V4\fR for IPv4 addresses and
 101 \fBLWRES_ADDRTYPE_V6\fR for IPv6 addresses. Results of the
 102 lookup are returned in \fI*structp\fR.
 103 .PP
 104 \fBlwres_getnamebyaddr()\fR performs reverse lookups.
 105 Resolver context \fIctx\fR is used for memory
 106 allocation. The address type is indicated by
 107 \fIaddrtype\fR: \fBLWRES_ADDRTYPE_V4\fR or
 108 \fBLWRES_ADDRTYPE_V6\fR. The address to be looked up is given
 109 by \fIaddr\fR and its length is
 110 \fIaddrlen\fR bytes. The result of the function call
 111 is made available through \fI*structp\fR.
 112 .SH "RETURN VALUES"
 113 .PP
 114 Successful calls to
 115 \fBlwres_string_parse()\fR
 116 and
 117 \fBlwres_addr_parse()\fR
 118 return
 119 LWRES_R_SUCCESS.
 120 Both functions return
 121 LWRES_R_FAILURE
 122 if the buffer is corrupt or
 123 LWRES_R_UNEXPECTEDEND
 124 if the buffer has less space than expected for the components of the
 125 encoded string or address.
 126 .PP
 127 \fBlwres_getaddrsbyname()\fR
 128 returns
 129 LWRES_R_SUCCESS
 130 on success and it returns
 131 LWRES_R_NOTFOUND
 132 if the hostname
 133 \fIname\fR
 134 could not be found.
 135 .PP
 136 LWRES_R_SUCCESS
 137 is returned by a successful call to
 138 \fBlwres_getnamebyaddr()\fR.
 139 .PP
 140 Both
 141 \fBlwres_getaddrsbyname()\fR
 142 and
 143 \fBlwres_getnamebyaddr()\fR
 144 return
 145 LWRES_R_NOMEMORY
 146 when memory allocation requests fail and
 147 LWRES_R_UNEXPECTEDEND
 148 if the buffers used for sending queries and receiving replies are too
 149 small.
 150 .SH "SEE ALSO"
 151 .PP
 152 \fBlwres_buffer\fR(3),
 153 \fBlwres_gabn\fR(3).