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LWRES_RESUTIL(3) BIND9 LWRES_RESUTIL(3)
NAME
lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr -
lightweight resolver utility functions
SYNOPSIS
#include <lwres/lwres.h>
lwres_result_t lwres_string_parse(lwres_buffer_t *b, char **c, lwres_uint16_t *len);
lwres_result_t lwres_addr_parse(lwres_buffer_t *b, lwres_addr_t *addr);
lwres_result_t lwres_getaddrsbyname(lwres_context_t *ctx, const char *name,
lwres_uint32_t addrtypes,
lwres_gabnresponse_t **structp);
lwres_result_t lwres_getnamebyaddr(lwres_context_t *ctx, lwres_uint32_t addrtype,
lwres_uint16_t addrlen, const unsigned char *addr,
lwres_gnbaresponse_t **structp);
DESCRIPTION
lwres_string_parse() retrieves a DNS-encoded string starting the current pointer of
lightweight resolver buffer b: i.e. b->current. When the function returns, the address of
the first byte of the encoded string is returned via *c and the length of that string is
given by *len. The buffer's current pointer is advanced to point at the character
following the string length, the encoded string, and the trailing NULL character.
lwres_addr_parse() extracts an address from the buffer b. The buffer's current pointer
b->current is presumed to point at an encoded address: the address preceded by a 32-bit
protocol family identifier and a 16-bit length field. The encoded address is copied to
addr->address and addr->length indicates the size in bytes of the address that was copied.
b->current is advanced to point at the next byte of available data in the buffer following
the encoded address.
lwres_getaddrsbyname() and lwres_getnamebyaddr() use the lwres_gnbaresponse_t structure
defined below:
typedef struct {
lwres_uint32_t flags;
lwres_uint16_t naliases;
lwres_uint16_t naddrs;
char *realname;
char **aliases;
lwres_uint16_t realnamelen;
lwres_uint16_t *aliaslen;
lwres_addrlist_t addrs;
void *base;
size_t baselen;
} lwres_gabnresponse_t;
The contents of this structure are not manipulated directly but they are controlled
through the lwres_gabn(3) functions.
The lightweight resolver uses lwres_getaddrsbyname() to perform forward lookups. Hostname
name is looked up using the resolver context ctx for memory allocation. addrtypes is a
bitmask indicating which type of addresses are to be looked up. Current values for this
bitmask are LWRES_ADDRTYPE_V4 for IPv4 addresses and LWRES_ADDRTYPE_V6 for IPv6 addresses.
Results of the lookup are returned in *structp.
lwres_getnamebyaddr() performs reverse lookups. Resolver context ctx is used for memory
allocation. The address type is indicated by addrtype: LWRES_ADDRTYPE_V4 or
LWRES_ADDRTYPE_V6. The address to be looked up is given by addr and its length is addrlen
bytes. The result of the function call is made available through *structp.
RETURN VALUES
Successful calls to lwres_string_parse() and lwres_addr_parse() return LWRES_R_SUCCESS.
Both functions return LWRES_R_FAILURE if the buffer is corrupt or LWRES_R_UNEXPECTEDEND if
the buffer has less space than expected for the components of the encoded string or
address.
lwres_getaddrsbyname() returns LWRES_R_SUCCESS on success and it returns LWRES_R_NOTFOUND
if the hostname name could not be found.
LWRES_R_SUCCESS is returned by a successful call to lwres_getnamebyaddr().
Both lwres_getaddrsbyname() and lwres_getnamebyaddr() return LWRES_R_NOMEMORY when memory
allocation requests fail and LWRES_R_UNEXPECTEDEND if the buffers used for sending queries
and receiving replies are too small.
SEE ALSO
lwres_buffer(3), lwres_gabn(3).
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright (C) 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018 Internet Systems Consortium,
Inc. ("ISC")
ISC 2007-06-18 LWRES_RESUTIL(3)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2024-04-19 01:10 @18.219.22.169 CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)