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.