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377 lines
15 KiB
ReStructuredText
377 lines
15 KiB
ReStructuredText
:tocdepth: 3
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base/protocols/dns/main.zeek
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============================
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.. zeek:namespace:: DNS
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Base DNS analysis script which tracks and logs DNS queries along with
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their responses.
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:Namespace: DNS
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:Imports: :doc:`base/protocols/conn/removal-hooks.zeek </scripts/base/protocols/conn/removal-hooks.zeek>`, :doc:`base/protocols/dns/consts.zeek </scripts/base/protocols/dns/consts.zeek>`, :doc:`base/utils/queue.zeek </scripts/base/utils/queue.zeek>`
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Summary
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~~~~~~~
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Runtime Options
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###############
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============================================================================= =======================================================================
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:zeek:id:`DNS::max_pending_msgs`: :zeek:type:`count` :zeek:attr:`&redef` Give up trying to match pending DNS queries or replies for a given
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query/transaction ID once this number of unmatched queries or replies
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is reached (this shouldn't happen unless either the DNS server/resolver
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is broken, Zeek is not seeing all the DNS traffic, or an AXFR query
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response is ongoing).
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:zeek:id:`DNS::max_pending_query_ids`: :zeek:type:`count` :zeek:attr:`&redef` Give up trying to match pending DNS queries or replies across all
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query/transaction IDs once there is at least one unmatched query or
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reply across this number of different query IDs.
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============================================================================= =======================================================================
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Types
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#####
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===================================================== ================================================================
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:zeek:type:`DNS::Info`: :zeek:type:`record` The record type which contains the column fields of the DNS log.
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:zeek:type:`DNS::PendingMessages`: :zeek:type:`table` Yields a queue of :zeek:see:`DNS::Info` objects for a given
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DNS message query/transaction ID.
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:zeek:type:`DNS::State`: :zeek:type:`record` A record type which tracks the status of DNS queries for a given
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:zeek:type:`connection`.
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===================================================== ================================================================
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Redefinitions
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#############
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==================================================================== ===========================================================
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:zeek:type:`Log::ID`: :zeek:type:`enum` The DNS logging stream identifier.
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* :zeek:enum:`DNS::LOG`
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:zeek:type:`connection`: :zeek:type:`record`
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:New Fields: :zeek:type:`connection`
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dns: :zeek:type:`DNS::Info` :zeek:attr:`&optional`
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dns_state: :zeek:type:`DNS::State` :zeek:attr:`&optional`
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:zeek:id:`likely_server_ports`: :zeek:type:`set` :zeek:attr:`&redef`
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==================================================================== ===========================================================
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Events
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######
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=========================================== =================================================================
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:zeek:id:`DNS::log_dns`: :zeek:type:`event` An event that can be handled to access the :zeek:type:`DNS::Info`
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record as it is sent to the logging framework.
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=========================================== =================================================================
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Hooks
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#####
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============================================================ =================================================================
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:zeek:id:`DNS::do_reply`: :zeek:type:`hook` This is called by the specific dns_*_reply events with a "reply"
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which may not represent the full data available from the resource
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record, but it's generally considered a summarization of the
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responses.
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:zeek:id:`DNS::finalize_dns`: :zeek:type:`Conn::RemovalHook` DNS finalization hook.
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:zeek:id:`DNS::log_policy`: :zeek:type:`Log::PolicyHook` A default logging policy hook for the stream.
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:zeek:id:`DNS::set_session`: :zeek:type:`hook` A hook that is called whenever a session is being set.
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============================================================ =================================================================
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Detailed Interface
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~~~~~~~~~~~~~~~~~~
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Runtime Options
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###############
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.. zeek:id:: DNS::max_pending_msgs
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:source-code: base/protocols/dns/main.zeek 126 126
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:Type: :zeek:type:`count`
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:Attributes: :zeek:attr:`&redef`
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:Default: ``50``
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Give up trying to match pending DNS queries or replies for a given
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query/transaction ID once this number of unmatched queries or replies
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is reached (this shouldn't happen unless either the DNS server/resolver
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is broken, Zeek is not seeing all the DNS traffic, or an AXFR query
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response is ongoing).
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.. zeek:id:: DNS::max_pending_query_ids
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:source-code: base/protocols/dns/main.zeek 131 131
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:Type: :zeek:type:`count`
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:Attributes: :zeek:attr:`&redef`
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:Default: ``50``
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Give up trying to match pending DNS queries or replies across all
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query/transaction IDs once there is at least one unmatched query or
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reply across this number of different query IDs.
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Types
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#####
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.. zeek:type:: DNS::Info
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:source-code: base/protocols/dns/main.zeek 18 86
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:Type: :zeek:type:`record`
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.. zeek:field:: ts :zeek:type:`time` :zeek:attr:`&log`
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The earliest time at which a DNS protocol message over the
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associated connection is observed.
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.. zeek:field:: uid :zeek:type:`string` :zeek:attr:`&log`
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A unique identifier of the connection over which DNS messages
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are being transferred.
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.. zeek:field:: id :zeek:type:`conn_id` :zeek:attr:`&log`
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The connection's 4-tuple of endpoint addresses/ports.
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.. zeek:field:: proto :zeek:type:`transport_proto` :zeek:attr:`&log`
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The transport layer protocol of the connection.
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.. zeek:field:: trans_id :zeek:type:`count` :zeek:attr:`&log` :zeek:attr:`&optional`
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A 16-bit identifier assigned by the program that generated
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the DNS query. Also used in responses to match up replies to
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outstanding queries.
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.. zeek:field:: rtt :zeek:type:`interval` :zeek:attr:`&log` :zeek:attr:`&optional`
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Round trip time for the query and response. This indicates
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the delay between when the request was seen until the
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answer started.
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.. zeek:field:: query :zeek:type:`string` :zeek:attr:`&log` :zeek:attr:`&optional`
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The domain name that is the subject of the DNS query.
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.. zeek:field:: qclass :zeek:type:`count` :zeek:attr:`&log` :zeek:attr:`&optional`
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The QCLASS value specifying the class of the query.
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.. zeek:field:: qclass_name :zeek:type:`string` :zeek:attr:`&log` :zeek:attr:`&optional`
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A descriptive name for the class of the query.
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.. zeek:field:: qtype :zeek:type:`count` :zeek:attr:`&log` :zeek:attr:`&optional`
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A QTYPE value specifying the type of the query.
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.. zeek:field:: qtype_name :zeek:type:`string` :zeek:attr:`&log` :zeek:attr:`&optional`
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A descriptive name for the type of the query.
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.. zeek:field:: rcode :zeek:type:`count` :zeek:attr:`&log` :zeek:attr:`&optional`
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The response code value in DNS response messages.
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.. zeek:field:: rcode_name :zeek:type:`string` :zeek:attr:`&log` :zeek:attr:`&optional`
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A descriptive name for the response code value.
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.. zeek:field:: AA :zeek:type:`bool` :zeek:attr:`&log` :zeek:attr:`&default` = ``F`` :zeek:attr:`&optional`
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The Authoritative Answer bit for response messages specifies
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that the responding name server is an authority for the
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domain name in the question section.
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.. zeek:field:: TC :zeek:type:`bool` :zeek:attr:`&log` :zeek:attr:`&default` = ``F`` :zeek:attr:`&optional`
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The Truncation bit specifies that the message was truncated.
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.. zeek:field:: RD :zeek:type:`bool` :zeek:attr:`&log` :zeek:attr:`&default` = ``F`` :zeek:attr:`&optional`
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The Recursion Desired bit in a request message indicates that
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the client wants recursive service for this query.
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.. zeek:field:: RA :zeek:type:`bool` :zeek:attr:`&log` :zeek:attr:`&default` = ``F`` :zeek:attr:`&optional`
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The Recursion Available bit in a response message indicates
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that the name server supports recursive queries.
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.. zeek:field:: Z :zeek:type:`count` :zeek:attr:`&log` :zeek:attr:`&default` = ``0`` :zeek:attr:`&optional`
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A reserved field that is zero in queries and responses unless
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using DNSSEC. This field represents the 3-bit Z field using
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the specification from RFC 1035.
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.. zeek:field:: answers :zeek:type:`vector` of :zeek:type:`string` :zeek:attr:`&log` :zeek:attr:`&optional`
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The set of resource descriptions in the query answer.
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.. zeek:field:: TTLs :zeek:type:`vector` of :zeek:type:`interval` :zeek:attr:`&log` :zeek:attr:`&optional`
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The caching intervals of the associated RRs described by the
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*answers* field.
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.. zeek:field:: rejected :zeek:type:`bool` :zeek:attr:`&log` :zeek:attr:`&default` = ``F`` :zeek:attr:`&optional`
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The DNS query was rejected by the server.
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.. zeek:field:: total_answers :zeek:type:`count` :zeek:attr:`&optional`
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The total number of resource records in a reply message's
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answer section.
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.. zeek:field:: total_replies :zeek:type:`count` :zeek:attr:`&optional`
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The total number of resource records in a reply message's
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answer, authority, and additional sections.
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.. zeek:field:: saw_query :zeek:type:`bool` :zeek:attr:`&default` = ``F`` :zeek:attr:`&optional`
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Whether the full DNS query has been seen.
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.. zeek:field:: saw_reply :zeek:type:`bool` :zeek:attr:`&default` = ``F`` :zeek:attr:`&optional`
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Whether the full DNS reply has been seen.
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.. zeek:field:: auth :zeek:type:`set` [:zeek:type:`string`] :zeek:attr:`&log` :zeek:attr:`&optional`
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(present if :doc:`/scripts/policy/protocols/dns/auth-addl.zeek` is loaded)
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Authoritative responses for the query.
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.. zeek:field:: addl :zeek:type:`set` [:zeek:type:`string`] :zeek:attr:`&log` :zeek:attr:`&optional`
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(present if :doc:`/scripts/policy/protocols/dns/auth-addl.zeek` is loaded)
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Additional responses for the query.
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.. zeek:field:: original_query :zeek:type:`string` :zeek:attr:`&log` :zeek:attr:`&optional`
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(present if :doc:`/scripts/policy/protocols/dns/log-original-query-case.zeek` is loaded)
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Query with original letter casing
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The record type which contains the column fields of the DNS log.
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.. zeek:type:: DNS::PendingMessages
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:source-code: base/protocols/dns/main.zeek 119 119
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:Type: :zeek:type:`table` [:zeek:type:`count`] of :zeek:type:`Queue::Queue`
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Yields a queue of :zeek:see:`DNS::Info` objects for a given
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DNS message query/transaction ID.
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.. zeek:type:: DNS::State
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:source-code: base/protocols/dns/main.zeek 135 150
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:Type: :zeek:type:`record`
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.. zeek:field:: pending_query :zeek:type:`DNS::Info` :zeek:attr:`&optional`
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A single query that hasn't been matched with a response yet.
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Note this is maintained separate from the *pending_queries*
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field solely for performance reasons -- it's possible that
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*pending_queries* contains further queries for which a response
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has not yet been seen, even for the same transaction ID.
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.. zeek:field:: pending_queries :zeek:type:`DNS::PendingMessages` :zeek:attr:`&optional`
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Indexed by query id, returns Info record corresponding to
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queries that haven't been matched with a response yet.
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.. zeek:field:: pending_replies :zeek:type:`DNS::PendingMessages` :zeek:attr:`&optional`
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Indexed by query id, returns Info record corresponding to
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replies that haven't been matched with a query yet.
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A record type which tracks the status of DNS queries for a given
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:zeek:type:`connection`.
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Events
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######
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.. zeek:id:: DNS::log_dns
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:source-code: base/protocols/dns/main.zeek 90 90
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:Type: :zeek:type:`event` (rec: :zeek:type:`DNS::Info`)
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An event that can be handled to access the :zeek:type:`DNS::Info`
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record as it is sent to the logging framework.
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Hooks
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#####
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.. zeek:id:: DNS::do_reply
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:source-code: base/protocols/dns/main.zeek 104 104
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:Type: :zeek:type:`hook` (c: :zeek:type:`connection`, msg: :zeek:type:`dns_msg`, ans: :zeek:type:`dns_answer`, reply: :zeek:type:`string`) : :zeek:type:`bool`
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This is called by the specific dns_*_reply events with a "reply"
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which may not represent the full data available from the resource
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record, but it's generally considered a summarization of the
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responses.
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:param c: The connection record for which to fill in DNS reply data.
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:param msg: The DNS message header information for the response.
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:param ans: The general information of a RR response.
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:param reply: The specific response information according to RR type/class.
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.. zeek:id:: DNS::finalize_dns
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:source-code: base/protocols/dns/main.zeek 643 658
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:Type: :zeek:type:`Conn::RemovalHook`
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DNS finalization hook. Remaining DNS info may get logged when it's called.
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.. zeek:id:: DNS::log_policy
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:source-code: base/protocols/dns/main.zeek 15 15
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:Type: :zeek:type:`Log::PolicyHook`
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A default logging policy hook for the stream.
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.. zeek:id:: DNS::set_session
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:source-code: base/protocols/dns/main.zeek 238 346
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:Type: :zeek:type:`hook` (c: :zeek:type:`connection`, msg: :zeek:type:`dns_msg`, is_query: :zeek:type:`bool`) : :zeek:type:`bool`
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A hook that is called whenever a session is being set.
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This can be used if additional initialization logic needs to happen
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when creating a new session value.
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:param c: The connection involved in the new session.
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:param msg: The DNS message header information.
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:param is_query: Indicator for if this is being called for a query or a response.
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