dnsquery

NAME

dnsquery - query domain name servers using resolver

SYNOPSIS

dnsquery [-dsv] [-c class] [-n nameserver]
		 [-p period] [-r retry] [-t type] host

The dnsquery(1) program is a general interface to nameservers through BIND resolver library calls. The program supports queries to the nameserver with an opcode of QUERY. This program is intended to be a replacement or supplement to programs like nstest, nsquery and nslookup. All arguments except for host and nameserver are treated without case-sensitivity.

OPTIONS

-nnameserver

The nameserver to be used in the query. Nameservers can appear as either Internet addresses of the form w.x.y.z or can appear as domain names. (Default: as specified in /etc/resolv.conf.)

-ttype

The type of resource record of interest. Types include:

Aa: A address
NS: Nameserver
CNAME: Canonical name
PTR: Domain name pointer
SOA: Start of authority
WKS: Well-known service
HINFO: Host information
MINFO: Mailbox information
MX: Mail exchange
RP: Responsible person
MG: Mail group member
AFSDB: DCE or AFS server
ANY: Wildcard

Note that any case may be used. (Default: ANY.)

-cclass

The class of resource records of interest. Classes include:

IN: Internet
HS: Hesiod
CHAOS: Chaos
ANY: Wildcard

Note that any case may be used. (Default: IN.)

-rretry

The number of times to retry if the nameserver is not responding. (Default: 4.)

-pperiod

Period to wait before timing out. (Default: RES_TIMEOUT.)

-d

Turn on debugging. This sets the RES_DEBUG bit of the resolver's options field. (Default: no debugging.)

-s

Use a stream rather than a packet. This uses a Transmission Control Protocol (TCP) stream connection with the nameserver rather than a User Datagram Protocol (UDP) datagram. This sets the RES_USEVC bit of the resolver's options field. (Default: UDP datagram.)

-v

Synonym for the -s flag.

host

The name of the host (or domain) of interest.

FILES

/etc/resolv.conf: To get the default ns and search lists
<arpa/nameser.h>: List of usable RR types and classes
<resolv.h>: List of resolver flags

DIAGNOSTICS

If the resolver fails to answer the query and debugging has not been turned on, dnsquery(1) will simply print a message like:

Query failed (rc = 1): Unknown host

The value of the return code is supplied by h_errno.

BUGS

Queries of a class other than IN can have interesting results since ordinarily a nameserver only has a list of root nameservers for class IN resource records.

The dnsquery(1) utility uses a call to inet_addr(3) to determine whether the argument for the -n option is a valid Internet address. Unfortunately, inet_addr(3) seems to cause a segmentation fault with some (bad) IP addresses (such as 1.2.3.4.5

AUTHOR

Bryan Beecher