GETRRSETBYNAME(3)

NAME
getrrsetbyname - retrieve DNS records

SYNOPSIS
#include <netdb.h>
int
getrrsetbyname(const char *hostname, unsigned int rdclass, unsigned int rdtype, unsigned int flags, struct rrsetinfo **res);
int
freerrset(struct rrsetinfo **rrset);

DESCRIPTION
getrrsetbyname() gets a set of resource records associated with a hostname, class and type. hostname is a pointer a to null-terminated string. The flags field is currently unused and must be zero.

After a successful call to getrrsetbyname(), *res is a pointer to an rrsetinfo structure, containing a list of one or more rdatainfo structures containing resource records and potentially another list of rdatainfo structures containing SIG resource records associated with those records. The members rri_rdclass and rri_rdtype are copied from the parameters. rri_ttl and rri_name are properties of the obtained rrset. The resource records contained in rri_rdatas and rri_sigs are in uncompressed DNS wire format. Properties of the rdataset are represented in the rri_flags bitfield. If the RRSET_VALIDATED bit is set, the data has been DNSSEC validated and the signatures verified.

The following structures are used:

    struct  rdatainfo {
            unsigned int            rdi_length;     /* length of data */
            unsigned char           *rdi_data;      /* record data */
    };
    struct  rrsetinfo {
            unsigned int            rri_flags;      /* RRSET_VALIDATED ... */
            unsigned int            rri_rdclass;    /* class number */
            unsigned int            rri_rdtype;     /* RR type number */
            unsigned int            rri_ttl;        /* time to live */
            unsigned int            rri_nrdatas;    /* size of rdatas array */
            unsigned int            rri_nsigs;      /* size of sigs array */
            char                    *rri_name;      /* canonical name */
            struct rdatainfo        *rri_rdatas;    /* individual records */
            struct rdatainfo        *rri_sigs;      /* individual signatures */
    };

All of the information returned by getrrsetbyname() is dynamically allocated: the rrsetinfo and rdatainfo structures, and the canonical host name strings pointed to by the rrsetinfostructure. Memory allocated for the dynamically allocated structures created by a successful call to getrrsetbyname() is released by freerrset(). rrset is a pointer to a struct rrset created by a call to getrrsetbyname().

If the EDNS0 option is activated in resolv.conf(3), getrrsetbyname() will request DNSSEC authentication using the EDNS0 DNSSEC OK (DO) bit.

RETURN VALUES
getrrsetbyname() returns zero on success, and one of the following error codes if an error occurred:

ERRSET_NONAME
    the name does not exist
ERRSET_NODATA
    the name exists, but does not have data of the desired type
ERRSET_NOMEMORY
    memory could not be allocated
ERRSET_INVAL
    a parameter is invalid
ERRSET_FAIL
    other failure

SEE ALSO
resolver(3), resolv.conf(5), named(8)

AUTHORS
Jakob Schlyter <jakob@openbsd.org>

HISTORY
getrrsetbyname() first appeared in OpenBSD 3.0. The API first appeared in ISC BIND version 9.

BUGS
The data in *rdi_data should be returned in uncompressed wire format. Currently, the data is in compressed format and the caller can't uncompress since it doesn't have the full message.

CAVEATS
The RRSET_VALIDATED flag in rri_flags is set if the AD (autenticated data) bit in the DNS answer is set. This flag should not be trusted unless the transport between the nameserver and the resolver is secure (e.g. IPsec, trusted network, loopback communication).