1LWRES_RESUTIL(3)                     BIND9                    LWRES_RESUTIL(3)
2
3
4

NAME

6       lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname,
7       lwres_getnamebyaddr - lightweight resolver utility functions
8

SYNOPSIS

10       #include <lwres/lwres.h>
11
12       lwres_result_t lwres_string_parse(lwres_buffer_t *b, char **c,
13                                         lwres_uint16_t *len);
14
15       lwres_result_t lwres_addr_parse(lwres_buffer_t *b, lwres_addr_t *addr);
16
17       lwres_result_t lwres_getaddrsbyname(lwres_context_t *ctx,
18                                           const char *name,
19                                           lwres_uint32_t addrtypes,
20                                           lwres_gabnresponse_t **structp);
21
22       lwres_result_t lwres_getnamebyaddr(lwres_context_t *ctx,
23                                          lwres_uint32_t addrtype,
24                                          lwres_uint16_t addrlen,
25                                          const unsigned char *addr,
26                                          lwres_gnbaresponse_t **structp);
27

DESCRIPTION

29       lwres_string_parse() retrieves a DNS-encoded string starting the
30       current pointer of lightweight resolver buffer b: i.e.  b->current.
31       When the function returns, the address of the first byte of the encoded
32       string is returned via *c and the length of that string is given by
33       *len. The buffer's current pointer is advanced to point at the
34       character following the string length, the encoded string, and the
35       trailing NULL character.
36
37       lwres_addr_parse() extracts an address from the buffer b. The buffer's
38       current pointer b->current is presumed to point at an encoded address:
39       the address preceded by a 32-bit protocol family identifier and a
40       16-bit length field. The encoded address is copied to addr->address and
41       addr->length indicates the size in bytes of the address that was
42       copied.  b->current is advanced to point at the next byte of available
43       data in the buffer following the encoded address.
44
45       lwres_getaddrsbyname() and lwres_getnamebyaddr() use the
46       lwres_gnbaresponse_t structure defined below:
47
48           typedef struct {
49                   lwres_uint32_t          flags;
50                   lwres_uint16_t          naliases;
51                   lwres_uint16_t          naddrs;
52                   char                   *realname;
53                   char                  **aliases;
54                   lwres_uint16_t          realnamelen;
55                   lwres_uint16_t         *aliaslen;
56                   lwres_addrlist_t        addrs;
57                   void                   *base;
58                   size_t                  baselen;
59           } lwres_gabnresponse_t;
60
61       The contents of this structure are not manipulated directly but they
62       are controlled through the lwres_gabn(3) functions.
63
64       The lightweight resolver uses lwres_getaddrsbyname() to perform forward
65       lookups. Hostname name is looked up using the resolver context ctx for
66       memory allocation.  addrtypes is a bitmask indicating which type of
67       addresses are to be looked up. Current values for this bitmask are
68       LWRES_ADDRTYPE_V4 for IPv4 addresses and LWRES_ADDRTYPE_V6 for IPv6
69       addresses. Results of the lookup are returned in *structp.
70
71       lwres_getnamebyaddr() performs reverse lookups. Resolver context ctx is
72       used for memory allocation. The address type is indicated by addrtype:
73       LWRES_ADDRTYPE_V4 or LWRES_ADDRTYPE_V6. The address to be looked up is
74       given by addr and its length is addrlen bytes. The result of the
75       function call is made available through *structp.
76

RETURN VALUES

78       Successful calls to lwres_string_parse() and lwres_addr_parse() return
79       LWRES_R_SUCCESS.  Both functions return LWRES_R_FAILURE if the buffer
80       is corrupt or LWRES_R_UNEXPECTEDEND if the buffer has less space than
81       expected for the components of the encoded string or address.
82
83       lwres_getaddrsbyname() returns LWRES_R_SUCCESS on success and it
84       returns LWRES_R_NOTFOUND if the hostname name could not be found.
85
86       LWRES_R_SUCCESS is returned by a successful call to
87       lwres_getnamebyaddr().
88
89       Both lwres_getaddrsbyname() and lwres_getnamebyaddr() return
90       LWRES_R_NOMEMORY when memory allocation requests fail and
91       LWRES_R_UNEXPECTEDEND if the buffers used for sending queries and
92       receiving replies are too small.
93

SEE ALSO

95       lwres_buffer(3), lwres_gabn(3).
96

AUTHOR

98       Internet Systems Consortium, Inc.
99
101       Copyright © 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018 Internet
102       Systems Consortium, Inc. ("ISC")
103
104
105
106ISC                               2007-06-18                  LWRES_RESUTIL(3)
Impressum