NAME
delv - DNS lookup and validation utility
SYNOPSIS
delv
[@server] [ -4] [-6] [-a anchor-file]
[ -b address] [-c class]
[-d level] [-i] [-m]
[-p port#] [-q name]
[-t type] [-x addr]
[name] [type] [class] [queryopt...]
delv
[-h]
delv
[-v]
delv
[queryopt...] [query...]
DESCRIPTION
delv (Domain Entity Lookup & Validation) is a tool for sending DNS
queries and validating the results, using the the same internal resolver and
validator logic as
named.
delv will send to a specified name server all queries needed to fetch and
validate the requested data; this includes the original requested query,
subsequent queries to follow CNAME or DNAME chains, and queries for DNSKEY, DS
and DLV records to establish a chain of trust for DNSSEC validation. It does
not perform iterative resolution, but simulates the behavior of a name server
configured for DNSSEC validating and forwarding.
By default, responses are validated using built-in DNSSEC trust anchors for the
root zone (".") and for the ISC DNSSEC lookaside validation zone
("dlv.isc.org"). Records returned by
delv are either fully
validated or were not signed. If validation fails, an explanation of the
failure is included in the output; the validation process can be traced in
detail. Because
delv does not rely on an external server to carry out
validation, it can be used to check the validity of DNS responses in
environments where local name servers may not be trustworthy.
Unless it is told to query a specific name server,
delv will try each of
the servers listed in /etc/resolv.conf. If no usable server addresses are
found,
delv will send queries to the localhost addresses (127.0.0.1 for
IPv4, ::1 for IPv6).
When no command line arguments or options are given,
delv will perform an
NS query for "." (the root zone).
SIMPLE USAGE
A typical invocation of
delv looks like:
where:
server
is the name or IP address of the name server
to query. This can be an IPv4 address in dotted-decimal notation or an IPv6
address in colon-delimited notation. When the supplied
server argument
is a hostname,
delv resolves that name before querying that name server
(note, however, that this initial lookup is
not validated by DNSSEC).
If no
server argument is provided,
delv consults /etc/resolv.conf;
if an address is found there, it queries the name server at that address. If
either of the
-4 or
-6 options are in use, then only addresses
for the corresponding transport will be tried. If no usable addresses are
found,
delv will send queries to the localhost addresses (127.0.0.1 for
IPv4, ::1 for IPv6).
name
is the domain name to be looked up.
type
indicates what type of query is required
— ANY, A, MX, etc. type can be any valid query type. If no
type argument is supplied, delv will perform a lookup for an A
record.
OPTIONS
-a
anchor-file
Specifies a file from which to read DNSSEC
trust anchors. The default is /etc/bind.keys, which is included with BIND 9
and contains trust anchors for the root zone (".") and for the ISC
DNSSEC lookaside validation zone ("dlv.isc.org").
Keys that do not match the root or DLV trust-anchor names are ignored; these key
names can be overridden using the
+dlv=NAME or
+root=NAME
options.
Note: When reading the trust anchor file,
delv treats
managed-keys
statements and
trusted-keys statements identically. That is, for a
managed key, it is the
initial key that is trusted; RFC 5011 key
management is not supported.
delv will not consult the managed-keys
database maintained by
named. This means that if either of the keys in
/etc/bind.keys is revoked and rolled over, it will be necessary to update
/etc/bind.keys to use DNSSEC validation in
delv.
-b
address
Sets the source IP address of the query to
address. This must be a valid address on one of the host's network
interfaces or "0.0.0.0" or "::". An optional source port
may be specified by appending "#<port>"
-c
class
Sets the query class for the requested data.
Currently, only class "IN" is supported in delv and any other
value is ignored.
-d
level
Set the systemwide debug level to
level. The allowed range is from 0 to 99. The default is 0 (no
debugging). Debugging traces from delv become more verbose as the debug
level increases. See the +mtrace, +rtrace, and +vtrace
options below for additional debugging details.
-h
Display the delv help usage output and
exit.
-i
Insecure mode. This disables internal DNSSEC
validation. (Note, however, this does not set the CD bit on upstream queries.
If the server being queried is performing DNSSEC validation, then it will not
return invalid data; this can cause delv to time out. When it is
necessary to examine invalid data to debug a DNSSEC problem, use dig
+cd.)
-m
Enables memory usage debugging.
-p
port#
Specifies a destination port to use for
queries instead of the standard DNS port number 53. This option would be used
with a name server that has been configured to listen for queries on a
non-standard port number.
-q
name
Sets the query name to name. While the
query name can be specified without using the -q, it is sometimes
necessary to disambiguate names from types or classes (for example, when
looking up the name "ns", which could be misinterpreted as the type
NS, or "ch", which could be misinterpreted as class CH).
-t
type
Sets the query type to
type, which can
be any valid query type supported in BIND 9 except for zone transfer types
AXFR and IXFR. As with
-q, this is useful to distinguish query name
type or class when they are ambiguous. it is sometimes necessary to
disambiguate names from types.
The default query type is "A", unless the
-x option is supplied
to indicate a reverse lookup, in which case it is "PTR".
-v
Print the delv version and exit.
-x
addr
Performs a reverse lookup, mapping an
addresses to a name. addr is an IPv4 address in dotted-decimal
notation, or a colon-delimited IPv6 address. When -x is used, there is
no need to provide the name or type arguments. delv
automatically performs a lookup for a name like 11.12.13.10.in-addr.arpa and
sets the query type to PTR. IPv6 addresses are looked up using nibble format
under the IP6.ARPA domain.
-4
Forces delv to only use IPv4.
-6
Forces delv to only use IPv6.
QUERY OPTIONS
delv provides a number of query options which affect the way results are
displayed, and in some cases the way lookups are performed.
Each query option is identified by a keyword preceded by a plus sign (+). Some
keywords set or reset an option. These may be preceded by the string no to
negate the meaning of that keyword. Other keywords assign values to options
like the timeout interval. They have the form
+keyword=value. The query
options are:
+[no]cdflag
Controls whether to set the CD (checking
disabled) bit in queries sent by delv. This may be useful when
troubleshooting DNSSEC problems from behind a validating resolver. A
validating resolver will block invalid responses, making it difficult to
retrieve them for analysis. Setting the CD flag on queries will cause the
resolver to return invalid responses, which delv can then validate
internally and report the errors in detail.
+[no]class
Controls whether to display the CLASS when
printing a record. The default is to display the CLASS.
+[no]ttl
Controls whether to display the TTL when
printing a record. The default is to display the TTL.
+[no]rtrace
Toggle resolver fetch logging. This reports
the name and type of each query sent by
delv in the process of carrying
out the resolution and validation process: this includes including the
original query and all subsequent queries to follow CNAMEs and to establish a
chain of trust for DNSSEC validation.
This is equivalent to setting the debug level to 1 in the "resolver"
logging category. Setting the systemwide debug level to 1 using the
-d
option will product the same output (but will affect other logging categories
as well).
+[no]mtrace
Toggle message logging. This produces a
detailed dump of the responses received by
delv in the process of
carrying out the resolution and validation process.
This is equivalent to setting the debug level to 10 for the the
"packets" module of the "resolver" logging category.
Setting the systemwide debug level to 10 using the
-d option will
produce the same output (but will affect other logging categories as
well).
+[no]vtrace
Toggle validation logging. This shows the
internal process of the validator as it determines whether an answer is
validly signed, unsigned, or invalid.
This is equivalent to setting the debug level to 3 for the the
"validator" module of the "dnssec" logging category.
Setting the systemwide debug level to 3 using the
-d option will
produce the same output (but will affect other logging categories as
well).
+[no]short
Provide a terse answer. The default is to
print the answer in a verbose form.
+[no]comments
Toggle the display of comment lines in the
output. The default is to print comments.
+[no]rrcomments
Toggle the display of per-record comments in
the output (for example, human-readable key information about DNSKEY records).
The default is to print per-record comments.
+[no]crypto
Toggle the display of cryptographic fields in
DNSSEC records. The contents of these field are unnecessary to debug most
DNSSEC validation failures and removing them makes it easier to see the common
failures. The default is to display the fields. When omitted they are replaced
by the string "[omitted]" or in the DNSKEY case the key id is
displayed as the replacement, e.g. "[ key id = value ]".
+[no]trust
Controls whether to display the trust level
when printing a record. The default is to display the trust level.
+[no]split[=W]
Split long hex- or base64-formatted fields in
resource records into chunks of W characters (where W is rounded
up to the nearest multiple of 4). +nosplit or +split=0 causes
fields not to be split at all. The default is 56 characters, or 44 characters
when multiline mode is active.
+[no]all
Set or clear the display options
+[no]comments, +[no]rrcomments, and +[no]trust as a
group.
+[no]multiline
Print long records (such as RRSIG, DNSKEY, and
SOA records) in a verbose multi-line format with human-readable comments. The
default is to print each record on a single line, to facilitate machine
parsing of the delv output.
+[no]dnssec
Indicates whether to display RRSIG records in
the delv output. The default is to do so. Note that (unlike in
dig) this does not control whether to request DNSSEC records or
whether to validate them. DNSSEC records are always requested, and validation
will always occur unless suppressed by the use of -i or +noroot
and +nodlv.
+[no]root[=ROOT]
Indicates whether to perform conventional
(non-lookaside) DNSSEC validation, and if so, specifies the name of a trust
anchor. The default is to validate using a trust anchor of "." (the
root zone), for which there is a built-in key. If specifying a different trust
anchor, then -a must be used to specify a file containing the
key.
+[no]dlv[=DLV]
Indicates whether to perform DNSSEC lookaside
validation, and if so, specifies the name of the DLV trust anchor. The default
is to perform lookaside validation using a trust anchor of
"dlv.isc.org", for which there is a built-in key. If specifying a
different name, then -a must be used to specify a file containing the
DLV key.
FILES
/etc/bind.keys
/etc/resolv.conf
SEE ALSO
dig(1),
named(8), RFC4034, RFC4035, RFC4431, RFC5074, RFC5155.
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright © 2014-2016 Internet Systems Consortium, Inc. ("ISC")