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 is a tool for sending DNS queries and validating the
results, using 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
anchor for the root zone ("."). 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 one
or more trust anchors for the root zone (".").
Keys that do not match the root zone name are ignored. An
alternate key name can be specified using the +root=NAME options.
DNSSEC Lookaside Validation can also be turned on by using the
+dlv=NAME to specify the name of a zone containing DLV records.
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
"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
"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 -a option
must also be used to specify a file containing the DLV key.
+[no]tcp
Controls whether to use TCP when sending queries. The
default is to use UDP unless a truncated response has been received.
+[no]unknownformat
Print all RDATA in unknown RR type presentation format
(RFC 3597). The default is to print RDATA for known types in the type's
presentation format.
FILES¶
/etc/bind.keys
/etc/resolv.conf
AUTHOR¶
Internet Systems Consortium, Inc.
COPYRIGHT¶
Copyright © 2014-2020 Internet Systems Consortium, Inc.
("ISC")
