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 foward
       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).

COPYRIGHT

       Copyright © 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
       Copyright © 2000, 2001 Internet Software Consortium.