resparse(3)

NAME
res_parse, res_copy, res_print, res_free - parse and manipulate DNS resolver responses

SYNOPSIS
#include rr.h
res_response * res_parse(msg)
char *msg; res_response * res_copy(resp)
res_response *resp; res_print(resp)
res_response *resp; res_free(resp)
res_response *resp;

DESCRIPTION
These routines are used for parsing the response from a call to the DNS resolver routines into a C structure suitable for programmer use, and to manipulate such structures.

Res_parse takes the result of a call to res_query or res_search. This is then parsed into an appropriate structure, and domain names unpacked into standard null-terminated C strings. It then returns a pointer to this structure.

Res_copy takes a pointer to a res_response structure, makes a copy of it and returns a pointer to the copy.

Res_print prints out the specified res_response structure, using a similar style to nslookup.

Res_free takes a pointer to a res_response structure, frees all memory allocated to it and clears the counts of the number of records of each type present.

DATA STRUCTURES
The structures used are as follows:
res_response {
HEADER header;
The header as defined in <arpa/nameser.h>.
s_question **question;
Pointer to an array of question records.
s_rr **answer;
Pointer to an array of answer resource records.
s_rr **authority;
Pointer to an array of nameserver resource records.
s_rr **additional;
Pointer to an array of additional resource records (the addresses of the authoritative nameservers).
} s_question {
char *qname;
The name that the query was sent for.
u_short qtype
u_short qclass
The type and class of query, as defined in <arpa/nameser.h>.
} s_rr {
char *name;
The name of the resource record.
u_short type
u_short class
The type and class of the record, as defined in <arpa/nameser.h>.
u_long ttl
How long (in seconds) this record may be cached.
u_long dlen;
The length of the type-specific data.
This need not be the same as the size of the unpacked data - particularly for domain names.
union u_rdata rdata;
The type-specific data (see rr.h for details).
}

RETURN VALUES
Res_parse and res_copy will return a pointer to the new structure, or a NULL pointer in case of errors.
Res_print and res_free do not return anything.

WARNINGS
Res_parse now returns a pointer to a dynamically assigned area, (previous releases used a static area which which would be overwritten by subsequent calls).
The pointer returned by res_parse should be freed using res_free (contrary to the instructions with earlier releases of this library). If res_print is called with a pointer that has been freed, it will (probably) print out an "empty" header.
This is a Bad Thing to do anyway!

FILES
/usr/local/lib/libresparse.a

SEE ALSO
resolver(3), gethostbyname(3)
DNS and BIND

AUTHOR
Dave Shield    <D.T.Shield@csc.liv.ac.uk>