lwres_resutil (3) - Linux Manuals

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.

COPYRIGHT