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$Id: lwres_resutil.3,v 1.5 2001/01/09 21:50:21 bwelling Exp $
.Dd Jun 30, 2000 .Dt LWRES_RESUTIL 3 .Os BIND9 9 .Sh NAME .Nm lwres_string_parse , .Nm lwres_addr_parse , .Nm lwres_getaddrsbyname , .Nm lwres_getnamebyaddr .Nd lightweight resolver utility functions .Sh SYNOPSIS .Fd #include <lwres/lwres.h> .Fd .Ft lwres_result_t .Fo lwres_string_parse .Fa "lwres_buffer_t *b" .Fa "char **c" .Fa "lwres_uint16_t *len" .Fc .Ft lwres_result_t .Fo lwres_addr_parse .Fa "lwres_buffer_t *b" .Fa "lwres_addr_t *addr" .Fc .Ft lwres_result_t .Fo lwres_getaddrsbyname .Fa "lwres_context_t *ctx" .Fa "const char *name" .Fa "lwres_uint32_t addrtypes" .Fa "lwres_gabnresponse_t **structp" .Fc .Ft lwres_result_t .Fo lwres_getnamebyaddr .Fa "lwres_context_t *ctx" .Fa "lwres_uint32_t addrtype" .Fa "lwres_uint16_t addrlen" .Fa "const unsigned char *addr" .Fa "lwres_gnbaresponse_t **structp" .Fc .Sh DESCRIPTION .Fn lwres_string_parse retrieves a DNS-encoded string starting the current pointer of lightweight resolver buffer .Fa b : i.e. .Li b->current . When the function returns, the address of the first byte of the encoded string is returned via .Fa *c and the length of that string is given by .Fa *len . The buffer's current pointer is advanced to point at the character following the string length, the encoded string, and the trailing .Dv NULL character. .Fn lwres_string_parse has an assertion check that .Fa b is not .Dv NULL .
p .Fn lwres_addr_parse extracts an address from the buffer .Fa b . It checks that .Fa addr is not null. The buffer's current pointer .Li 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 .Li addr->address and .Li addr->length indicates the size in bytes of the address that was copied. .Li b->current is advanced to point at the next byte of available data in the buffer following the encoded address.
p .Fn lwres_getaddrsbyname and .Fn lwres_getnamebyaddr use the .Dv "lwres_gnbaresponse_t" structure defined below: d -literal -offset indent 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; .Ed The contents of this structure are not manipulated directly but they are controlled through the .Xr lwres_gabn 3 functions.
p The lightweight resolver uses .Fn lwres_getaddrsbyname to perform foward lookups. Hostname .Fa name is looked up using the resolver context .Fa ctx for memory allocation. .Fa addrtypes is a bitmask indicating which type of addresses are to be looked up. Current values for this bitmask are .Dv LWRES_ADDRTYPE_V4 for IPv4 addresses and .Dv LWRES_ADDRTYPE_V6 for IPv6 addresses. Results of the lookup are returned in .Fa *structp . .Fn lwres_getaddrsbyname checks that its pointer arguments are not .Dv NULL and that .Fa addrtypes is non-zero.
p .Fn lwres_getnamebyaddr performs reverse lookups. Resolver context .Fa ctx is used for memory allocation. The address type is indicated by .Fa addrtype : .Dv LWRES_ADDRTYPE_V4 or .Dv LWRES_ADDRTYPE_V6 . The address to be looked up is given by .Fa addr and its length is .Fa addrlen bytes. The result of the function call is made available through .Fa *structp . Like .Fn lwres_getaddrsbyname , .Fn lwres_getnamebyaddr uses assertion checking to ensure its pointer arguments are not .Dv NULL and .Fa addrtype is not zero. .Fn lwres_getaddrsbyname also checks that .Fa addrlen is non-zero. .Sh RETURN VALUES Successful calls to .Fn lwres_string_parse and .Fn lwres_addr_parse return .Er LWRES_R_SUCCESS. Both functions return .Er LWRES_R_FAILURE if the buffer is corrupt or .Er LWRES_R_UNEXPECTEDEND if the buffer has less space than expected for the components of the encoded string or address.
p .Fn lwres_getaddrsbyname returns .Er LWRES_R_SUCCESS on success and it returns .Er LWRES_R_NOTFOUND if the hostname .Fa name could not be found.
p .Er LWRES_R_SUCCESS is returned by a successful call to .Fn lwres_getnamebyaddr .
p Both .Fn lwres_getaddrsbyname and .Fn lwres_getnamebyaddr return .Er LWRES_R_NOMEMORY when memory allocation requests fail and .Er LWRES_R_UNEXPECTEDEND if the buffers used for sending queries and receiving replies are too small. .Sh SEE ALSO .Xr lwres_buffer 3 , .Xr lwres_gabn 3 .