1LWRES_RESUTIL(3) BIND9 LWRES_RESUTIL(3)
2
6 lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname,
7 lwres_getnamebyaddr - lightweight resolver utility functions
8
10 #include <lwres/lwres.h>
11 lwres_result_t lwres_string_parse(lwres_buffer_t *b, char **c,
13 uint16_t *len);
14 lwres_result_t lwres_addr_parse(lwres_buffer_t *b, lwres_addr_t *addr);
16 lwres_result_t lwres_getaddrsbyname(lwres_context_t *ctx,
18 const char *name,
19 uint32_t addrtypes,
20 lwres_gabnresponse_t **structp);
21 lwres_result_t lwres_getnamebyaddr(lwres_context_t *ctx,
23 uint32_t addrtype, uint16_t addrlen,
24 const unsigned char *addr,
25 lwres_gnbaresponse_t **structp);
26
28 lwres_string_parse() retrieves a DNS-encoded string starting the
29 current pointer of lightweight resolver buffer b: i.e. b->current.
30 When the function returns, the address of the first byte of the encoded
31 string is returned via *c and the length of that string is given by
32 *len. The buffer's current pointer is advanced to point at the
33 character following the string length, the encoded string, and the
34 trailing NULL character.
35 lwres_addr_parse() extracts an address from the buffer b. The buffer's
37 current pointer b->current is presumed to point at an encoded address:
38 the address preceded by a 32-bit protocol family identifier and a
39 16-bit length field. The encoded address is copied to addr->address and
40 addr->length indicates the size in bytes of the address that was
41 copied. b->current is advanced to point at the next byte of available
42 data in the buffer following the encoded address.
43 lwres_getaddrsbyname() and lwres_getnamebyaddr() use the
45 lwres_gnbaresponse_t structure defined below:
46 typedef struct {
48 uint32_t flags;
49 uint16_t naliases;
50 uint16_t naddrs;
51 char *realname;
52 char **aliases;
53 uint16_t realnamelen;
54 uint16_t *aliaslen;
55 lwres_addrlist_t addrs;
56 void *base;
57 size_t baselen;
58 } lwres_gabnresponse_t;
59 The contents of this structure are not manipulated directly but they
61 are controlled through the lwres_gabn(3) functions.
62 The lightweight resolver uses lwres_getaddrsbyname() to perform forward
64 lookups. Hostname name is looked up using the resolver context ctx for
65 memory allocation. addrtypes is a bitmask indicating which type of
66 addresses are to be looked up. Current values for this bitmask are
67 LWRES_ADDRTYPE_V4 for IPv4 addresses and LWRES_ADDRTYPE_V6 for IPv6
68 addresses. Results of the lookup are returned in *structp.
69 lwres_getnamebyaddr() performs reverse lookups. Resolver context ctx is
71 used for memory allocation. The address type is indicated by addrtype:
72 LWRES_ADDRTYPE_V4 or LWRES_ADDRTYPE_V6. The address to be looked up is
73 given by addr and its length is addrlen bytes. The result of the
74 function call is made available through *structp.
75
77 Successful calls to lwres_string_parse() and lwres_addr_parse() return
78 LWRES_R_SUCCESS. Both functions return LWRES_R_FAILURE if the buffer
79 is corrupt or LWRES_R_UNEXPECTEDEND if the buffer has less space than
80 expected for the components of the encoded string or address.
81 lwres_getaddrsbyname() returns LWRES_R_SUCCESS on success and it
83 returns LWRES_R_NOTFOUND if the hostname name could not be found.
84 LWRES_R_SUCCESS is returned by a successful call to
86 lwres_getnamebyaddr().
87 Both lwres_getaddrsbyname() and lwres_getnamebyaddr() return
89 LWRES_R_NOMEMORY when memory allocation requests fail and
90 LWRES_R_UNEXPECTEDEND if the buffers used for sending queries and
91 receiving replies are too small.
92
94 lwres_buffer(3), lwres_gabn(3).
95
97 Internet Systems Consortium, Inc.
98
100 Copyright © 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018, 2019
101 Internet Systems Consortium, Inc. ("ISC")
102ISC 2007-06-18 LWRES_RESUTIL(3)