lib/liblwres/man/lwres_resutil.3

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  17 .TH "LWRES_RESUTIL" "3" "Jun 30, 2000" "BIND9" ""
  18 .SH NAME
  19 lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr \- lightweight resolver utility functions
  20 .SH SYNOPSIS
  21 \fB#include <lwres/lwres.h>
  22 .sp
  23 .na
  24 lwres_result_t
  25 lwres_string_parse(lwres_buffer_t *b, char **c, lwres_uint16_t *len);
  26 .ad
  27 .sp
  28 .na
  29 lwres_result_t
  30 lwres_addr_parse(lwres_buffer_t *b, lwres_addr_t *addr);
  31 .ad
  32 .sp
  33 .na
  34 lwres_result_t
  35 lwres_getaddrsbyname(lwres_context_t *ctx, const char *name, lwres_uint32_t addrtypes, lwres_gabnresponse_t **structp);
  36 .ad
  37 .sp
  38 .na
  39 lwres_result_t
  40 lwres_getnamebyaddr(lwres_context_t *ctx, lwres_uint32_t addrtype, lwres_uint16_t addrlen, const unsigned char *addr, lwres_gnbaresponse_t **structp);
  41 .ad
  42 \fR.SH "DESCRIPTION"
  43 .PP
  44 \fBlwres_string_parse()\fR retrieves a DNS-encoded
  45 string starting the current pointer of lightweight resolver buffer
  46 \fIb\fR: i.e. b->current.
  47 When the function returns, the address of the first byte of the
  48 encoded string is returned via \fI*c\fR and the
  49 length of that string is given by \fI*len\fR. The
  50 buffer's current pointer is advanced to point at the character
  51 following the string length, the encoded string, and the trailing
  52 \fBNULL\fR character.
  53 .PP
  54 \fBlwres_addr_parse()\fR extracts an address from the
  55 buffer \fIb\fR. The buffer's current pointer
  56 b->current is presumed to point at an encoded
  57 address: the address preceded by a 32-bit protocol family identifier
  58 and a 16-bit length field. The encoded address is copied to
  59 addr->address and
  60 addr->length indicates the size in bytes of
  61 the address that was copied. b->current is
  62 advanced to point at the next byte of available data in the buffer
  63 following the encoded address.
  64 .PP
  65 \fBlwres_getaddrsbyname()\fR
  66 and
  67 \fBlwres_getnamebyaddr()\fR
  68 use the
  69 \fBlwres_gnbaresponse_t\fR
  70 structure defined below:
  71 .sp
  72 .nf
  73 typedef struct {
  74         lwres_uint32_t          flags;
  75         lwres_uint16_t          naliases;
  76         lwres_uint16_t          naddrs;
  77         char                   *realname;
  78         char                  **aliases;
  79         lwres_uint16_t          realnamelen;
  80         lwres_uint16_t         *aliaslen;
  81         lwres_addrlist_t        addrs;
  82         void                   *base;
  83         size_t                  baselen;
  84 } lwres_gabnresponse_t;
  85 .sp
  86 .fi
  87 The contents of this structure are not manipulated directly but
  88 they are controlled through the
  89 \fBlwres_gabn\fR(3)
  90 functions.
  91 .PP
  92 The lightweight resolver uses
  93 \fBlwres_getaddrsbyname()\fR to perform foward lookups.
  94 Hostname \fIname\fR is looked up using the resolver
  95 context \fIctx\fR for memory allocation.
  96 \fIaddrtypes\fR is a bitmask indicating which type of
  97 addresses are to be looked up. Current values for this bitmask are
  98 \fBLWRES_ADDRTYPE_V4\fR for IPv4 addresses and
  99 \fBLWRES_ADDRTYPE_V6\fR for IPv6 addresses. Results of the
 100 lookup are returned in \fI*structp\fR.
 101 .PP
 102 \fBlwres_getnamebyaddr()\fR performs reverse lookups.
 103 Resolver context \fIctx\fR is used for memory
 104 allocation. The address type is indicated by
 105 \fIaddrtype\fR: \fBLWRES_ADDRTYPE_V4\fR or
 106 \fBLWRES_ADDRTYPE_V6\fR. The address to be looked up is given
 107 by \fIaddr\fR and its length is
 108 \fIaddrlen\fR bytes. The result of the function call
 109 is made available through \fI*structp\fR.
 110 .SH "RETURN VALUES"
 111 .PP
 112 Successful calls to
 113 \fBlwres_string_parse()\fR
 114 and
 115 \fBlwres_addr_parse()\fR
 116 return
 117 LWRES_R_SUCCESS.
 118 Both functions return
 119 LWRES_R_FAILURE
 120 if the buffer is corrupt or
 121 LWRES_R_UNEXPECTEDEND
 122 if the buffer has less space than expected for the components of the
 123 encoded string or address.
 124 .PP
 125 \fBlwres_getaddrsbyname()\fR
 126 returns
 127 LWRES_R_SUCCESS
 128 on success and it returns
 129 LWRES_R_NOTFOUND
 130 if the hostname
 131 \fIname\fR
 132 could not be found.
 133 .PP
 134 LWRES_R_SUCCESS
 135 is returned by a successful call to
 136 \fBlwres_getnamebyaddr()\fR.
 137 .PP
 138 Both
 139 \fBlwres_getaddrsbyname()\fR
 140 and
 141 \fBlwres_getnamebyaddr()\fR
 142 return
 143 LWRES_R_NOMEMORY
 144 when memory allocation requests fail and
 145 LWRES_R_UNEXPECTEDEND
 146 if the buffers used for sending queries and receiving replies are too
 147 small.
 148 .SH "SEE ALSO"
 149 .PP
 150 \fBlwres_buffer\fR(3),
 151 \fBlwres_gabn\fR(3).