2007-06-18 ISC Internet Systems Consortium, Inc. lwres_resutil 3 BIND9 2000 2001 2004 2005 2007 2014 2015 2016 2018 2019 Internet Systems Consortium, Inc. ("ISC") lwres_string_parse lwres_addr_parse lwres_getaddrsbyname lwres_getnamebyaddr lightweight resolver utility functions #include <lwres/lwres.h> lwres_result_t lwres_string_parse lwres_buffer_t *b char **c 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 uint32_t addrtypes lwres_gabnresponse_t **structp lwres_result_t lwres_getnamebyaddr lwres_context_t *ctx uint32_t addrtype uint16_t addrlen const unsigned char *addr lwres_gnbaresponse_t **structp 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 { uint32_t flags; uint16_t naliases; uint16_t naddrs; char *realname; char **aliases; uint16_t realnamelen; 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_gabn3 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. 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. lwres_buffer3 , lwres_gabn3 .