draft-ietf-dnsop-extended-error-04.txt		draft-ietf-dnsop-extended-error-05.txt
	Network Working Group W. Kumari		Network Working Group W. Kumari
	Internet-Draft Google		Internet-Draft Google
	Intended status: Standards Track E. Hunt		Intended status: Standards Track E. Hunt
	Expires: July 11, 2019 ISC		Expires: September 12, 2019 ISC
	R. Arends		R. Arends
	ICANN		ICANN
	W. Hardaker		W. Hardaker
	USC/ISI		USC/ISI
	D. Lawrence		D. Lawrence
	Oracle + Dyn		Oracle + Dyn
	January 07, 2019		March 11, 2019
	Extended DNS Errors		Extended DNS Errors
	draft-ietf-dnsop-extended-error-04		draft-ietf-dnsop-extended-error-05
	Abstract		Abstract
	This document defines an extensible method to return additional		This document defines an extensible method to return additional
	information about the cause of DNS errors. Though created primarily		information about the cause of DNS errors. Though created primarily
	to extend SERVFAIL to provide additional information about the cause		to extend SERVFAIL to provide additional information about the cause
	of DNS and DNSSEC failures, the Extended DNS Errors option defined in		of DNS and DNSSEC failures, the Extended DNS Errors option defined in
	this document allows all response types to contain extended error		this document allows all response types to contain extended error
	information.		information.
	skipping to change at page 1, line 42 ¶		skipping to change at page 1, line 42 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on July 11, 2019.		This Internet-Draft will expire on September 12, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction and background . . . . . . . . . . . . . . . . . 3		1. Introduction and background . . . . . . . . . . . . . . . . . 3
	1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3		1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4
	2. Extended Error EDNS0 option format . . . . . . . . . . . . . 3		2. Extended Error EDNS0 option format . . . . . . . . . . . . . 4
	3. Use of the Extended DNS Error option . . . . . . . . . . . . 4		3. Use of the Extended DNS Error option . . . . . . . . . . . . 5
	3.1. The R (Retry) flag . . . . . . . . . . . . . . . . . . . 5		3.1. The R (Retry) flag . . . . . . . . . . . . . . . . . . . 5
	3.2. The RESPONSE-CODE field . . . . . . . . . . . . . . . . . 5		3.2. The RESPONSE-CODE field . . . . . . . . . . . . . . . . . 5
	3.3. The INFO-CODE field . . . . . . . . . . . . . . . . . . . 5		3.3. The INFO-CODE field . . . . . . . . . . . . . . . . . . . 6
	3.4. The EXTRA-TEXT field . . . . . . . . . . . . . . . . . . 5		3.4. The EXTRA-TEXT field . . . . . . . . . . . . . . . . . . 6
	4. Defined Extended DNS Errors . . . . . . . . . . . . . . . . . 5		4. Defined Extended DNS Errors . . . . . . . . . . . . . . . . . 6
	4.1. INFO-CODEs for use with RESPONSE-CODE: NOERROR(0) . . . . 6		4.1. INFO-CODEs for use with RESPONSE-CODE: NOERROR(0) . . . . 6
	4.1.1. NOERROR Extended DNS Error Code 1 - Unsupported		4.1.1. NOERROR Extended DNS Error Code 1 - Unsupported
	DNSKEY Algorithm . . . . . . . . . . . . . . . . . . 6		DNSKEY Algorithm . . . . . . . . . . . . . . . . . . 6
	4.1.2. NOERROR Extended DNS Error Code 2 - Unsupported		4.1.2. NOERROR Extended DNS Error Code 2 - Unsupported
	DS Algorithm . . . . . . . . . . . . . . . . . . . . 6		DS Algorithm . . . . . . . . . . . . . . . . . . . . 6
	4.2. INFO-CODEs for use with RESPONSE-CODE: SERVFAIL(2) . . . 6		4.1.3. INFO-CODEs for use with RESPONSE-CODE: NOERROR(3) . . 6
	4.2.1. SERVFAIL Extended DNS Error Code 1 - DNSSEC Bogus . . 6		4.1.4. NOERROR Extended DNS Error Code 4 - Forged answer . . 7
	4.2.2. SERVFAIL Extended DNS Error Code 2 - DNSSEC		4.1.5. SERVFAIL Extended DNS Error Code 5 - DNSSEC
	Indeterminate . . . . . . . . . . . . . . . . . . . . 6		Indeterminate . . . . . . . . . . . . . . . . . . . . 7
	4.2.3. SERVFAIL Extended DNS Error Code 3 - Signature		4.2. INFO-CODEs for use with RESPONSE-CODE: SERVFAIL(2) . . . 7
	Expired . . . . . . . . . . . . . . . . . . . . . . . 6		4.2.1. SERVFAIL Extended DNS Error Code 1 - DNSSEC Bogus . . 7
	4.2.4. SERVFAIL Extended DNS Error Code 4 - Signature Not		4.2.2. SERVFAIL Extended DNS Error Code 2 - Signature
	Yet Valid . . . . . . . . . . . . . . . . . . . . . . 6		Expired . . . . . . . . . . . . . . . . . . . . . . . 7
	4.2.5. SERVFAIL Extended DNS Error Code 5 - DNSKEY missing . 6		4.2.3. SERVFAIL Extended DNS Error Code 3 - Signature Not
	4.2.6. SERVFAIL Extended DNS Error Code 6 - RRSIGs missing . 7		Yet Valid . . . . . . . . . . . . . . . . . . . . . . 7
	4.2.7. SERVFAIL Extended DNS Error Code 7 - No Zone Key Bit		4.2.4. SERVFAIL Extended DNS Error Code 4 - DNSKEY missing . 7
	Set . . . . . . . . . . . . . . . . . . . . . . . . . 7		4.2.5. SERVFAIL Extended DNS Error Code 5 - RRSIGs missing . 7
	4.3. INFO-CODEs for use with RESPONSE-CODE: REFUSED(5) . . . . 7		4.2.6. SERVFAIL Extended DNS Error Code 6 - No Zone Key Bit
	4.3.1. REFUSED Extended DNS Error Code 1 - Lame . . . . . . 7		Set . . . . . . . . . . . . . . . . . . . . . . . . . 8
	4.3.2. REFUSED Extended DNS Error Code 2 - Prohibited . . . 7		4.2.7. SERVFAIL Extended DNS Error Code 7 - No
	4.4. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) . . . 7		Reachable Authority . . . . . . . . . . . . . . . . . 8
	4.4.1. NXDOMAIN Extended DNS Error Code 1 - Blocked . . . . 7		4.2.8. SERVFAIL Extended DNS Error Code 8 - NSEC Missing . . 8
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7		4.2.9. SERVFAIL Extended DNS Error Code 9 - Cached Error . . 8
	5.1. new Extended Error Code EDNS Option . . . . . . . . . . . 7		4.2.10. SERVFAIL Extended DNS Error Code 10 - Not Ready . . . 8
	5.2. New Extended Error Code EDNS Option . . . . . . . . . . . 8		4.3. INFO-CODEs for use with RESPONSE-CODE: NOTIMP(4) . . . . 8
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 9		4.3.1. NOTIMP Extended DNS Error Code 1 - Deprecated . . . . 8
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10		4.4. INFO-CODEs for use with RESPONSE-CODE: REFUSED(5) . . . . 8
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10		4.4.1. REFUSED Extended DNS Error Code 1 - Lame . . . . . . 8
	8.1. Normative References . . . . . . . . . . . . . . . . . . 10		4.4.2. REFUSED Extended DNS Error Code 2 - Prohibited . . . 9
	8.2. Informative References . . . . . . . . . . . . . . . . . 10		4.5. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) . . . 9
	Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 11		4.5.1. NXDOMAIN Extended DNS Error Code 1 - Blocked . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11		4.6. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) . . . 9
			4.6.1. NXDOMAIN Extended DNS Error Code 2 - Censored . . . . 9
			4.7. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) . . . 9
			4.7.1. NXDOMAIN Extended DNS Error Code 3 - Stale Answer . . 9
			5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
			5.1. A New Extended Error Code EDNS Option . . . . . . . . . . 9
			5.2. New Double-Index Registry Table for Extended Error Codes 10
			6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
			7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
			8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
			8.1. Normative References . . . . . . . . . . . . . . . . . . 13
			8.2. Informative References . . . . . . . . . . . . . . . . . 13
			Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 14
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
	1. Introduction and background		1. Introduction and background
	There are many reasons that a DNS query may fail, some of them		There are many reasons that a DNS query may fail, some of them
	transient, some permanent; some can be resolved by querying another		transient, some permanent; some can be resolved by querying another
	server, some are likely best handled by stopping resolution.		server, some are likely best handled by stopping resolution.
	Unfortunately, the error signals that a DNS server can return are		Unfortunately, the error signals that a DNS server can return are
	very limited, and are not very expressive. This means that		very limited, and are not very expressive. This means that
	applications and resolvers often have to "guess" at what the issue is		applications and resolvers often have to "guess" at what the issue is
	- e.g. was the answer marked REFUSED because of a lame delegation, or		- e.g. was the answer marked REFUSED because of a lame delegation, or
	skipping to change at page 3, line 41 ¶		skipping to change at page 4, line 7 ¶
	returned again, and the user gets an (largely) incomprehensible error		returned again, and the user gets an (largely) incomprehensible error
	message; or the next resolver is not a validating resolver, and the		message; or the next resolver is not a validating resolver, and the
	user is returned a potentially harmful result.		user is returned a potentially harmful result.
	This document specifies a mechanism to extend (or annotate) DNS		This document specifies a mechanism to extend (or annotate) DNS
	errors to provide additional information about the cause of the		errors to provide additional information about the cause of the
	error. When properly authenticated, this information can be used by		error. When properly authenticated, this information can be used by
	the resolver to make a decision regarding whether or not to retry or		the resolver to make a decision regarding whether or not to retry or
	it can be used or by technical users attempting to debug issues.		it can be used or by technical users attempting to debug issues.
			These extended error codes are specially useful when received by
			resolvers, to return to stub resolvers or to downstream resolvers.
			Authoritative servers MAY parse and use them, but most error codes
			would make no sense for them. Authoritative servers may need to
			generate extended error codes though.
	1.1. Requirements notation		1.1. Requirements notation
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Extended Error EDNS0 option format		2. Extended Error EDNS0 option format
	This draft uses an EDNS0 ([RFC2671]) option to include Extended DNS		This draft uses an EDNS0 ([RFC2671]) option to include Extended DNS
	Error (EDE) information in DNS messages. The option is structured as		Error (EDE) information in DNS messages. The option is structured as
	skipping to change at page 4, line 31 ¶		skipping to change at page 4, line 51 ¶
	o OPTION-CODE, 2 octets (defined in [RFC6891]), for EDE is TBD.		o OPTION-CODE, 2 octets (defined in [RFC6891]), for EDE is TBD.
	[RFC Editor: change TBD to the proper code once assigned by IANA.]		[RFC Editor: change TBD to the proper code once assigned by IANA.]
	o OPTION-LENGTH, 2 octets ((defined in [RFC6891]) contains the		o OPTION-LENGTH, 2 octets ((defined in [RFC6891]) contains the
	length of the payload (everything after OPTION-LENGTH) in octets		length of the payload (everything after OPTION-LENGTH) in octets
	and should be 4 plus the length of the EXTRA-TEXT section (which		and should be 4 plus the length of the EXTRA-TEXT section (which
	may be a zero-length string).		may be a zero-length string).
	o The RETRY flag, 1 bit; the RETRY bit (R) indicates a flag defined		o The RETRY flag, 1 bit; the RETRY bit (R) indicates a flag defined
	for use in this specification.		for use in this specification.
	o The RESERVED bits, 15 bits: these bits are reserved for future		o The RESERVED bits, 15 bits: these bits are reserved for future
	use, potentially as additional flags. The RESERVED bits MUST be		use, potentially as additional flags. The RESERVED bits MUST be
	set to 0 by the sender and SHOULD be ignored by the receiver.		set to 0 by the sender and MUST be ignored by the receiver.
	o RESPONSE-CODE, 4 bits.		o RESPONSE-CODE, 4 bits.
	o INFO-CODE, 12-bits.		o INFO-CODE, 12-bits.
	o EXTRA-TEXT, a variable length, UTF-8 encoded, text field that may		o EXTRA-TEXT, a variable length, UTF-8 encoded, text field that may
	hold additional textual information.		hold additional textual information.
	3. Use of the Extended DNS Error option		3. Use of the Extended DNS Error option
	The Extended DNS Error (EDE) is an EDNS option. It can be included		The Extended DNS Error (EDE) is an EDNS option. It can be included
	in any response (SERVFAIL, NXDOMAIN, REFUSED, etc) to a query that		in any response (SERVFAIL, NXDOMAIN, REFUSED, etc) to a query that
	includes an EDNS option. This document includes a set of initial		includes OPT Pseudo-RR [RFC6891]. This document includes a set of
	codepoints (and requests to the IANA to add them to the registry),		initial codepoints (and requests to the IANA to add them to the
	but is extensible via the IANA registry to allow additional error and		registry), but is extensible via the IANA registry to allow
	information codes to be defined in the future.		additional error and information codes to be defined in the future.
	The fields of the Extended DNS Error option are defined further in		The fields of the Extended DNS Error option are defined further in
	the following sub-sections.		the following sub-sections.
	3.1. The R (Retry) flag		3.1. The R (Retry) flag
	The R (Retry) flag provides a hint as to what the receiver may want		The R (Retry) flag provides a hint as to what the receiver may want
	to do with this annotated error. Specifically, the R (or Retry) flag		to do with this annotated error. Specifically, the R (or Retry) flag
	provides a hint to the receiver that it should retry the query to		provides a hint to the receiver that it should retry the query to
	another server. If the R bit is set (1), the sender believes that		another server. If the R bit is set (1), the sender believes that
	retrying the query may provide a successful answer next time; if the		retrying the query may provide a successful answer next time; if the
	R bit is clear (0), the sender believes that the resolver should not		R bit is clear (0), the sender believes that the resolver should not
	ask another server.		ask another server.
	The mechanism is specifically designed to be extensible, and so		The mechanism is specifically designed to be extensible, and so
	implementations may receive EDE codes that it does not understand.		implementations may receive EDE codes that it does not understand.
	The R flag allows implementations to make a decision as to what to do		The R flag allows implementations to make a decision as to what to do
	if it receives a response with an unknown code - retry or drop the		if it receives a response with an unknown code - retry or drop the
	query. Note that this flag is only a suggestion. Unless a		query. Note that this flag is only a suggestion. Unless a
	protective transport mechanism (like TSIG [RFC2845] or TLS [RFC8094])		protective transport mechanism (like TSIG [RFC2845] or (D)TLS xref
	is used, the bit's value could have have been altered by a person-in-		target="RFC7858"/>, [RFC8094]) is used, the bit's value could have
	the-middle. Receivers can choose to ignore this hint. See the		have been altered by a person-in-the-middle. Receivers can choose to
	security considerations for additional considerations.		ignore this hint. See the security considerations for additional
			considerations.
	3.2. The RESPONSE-CODE field		3.2. The RESPONSE-CODE field
	This 4-bit value SHOULD be a copy of the RCODE from the primary DNS		This 4-bit value SHOULD be a copy of the RCODE from the primary DNS
	packet. Multiple EDNS0/EDE records may be included in the response.		packet. RESPONSE-CODEs MAY use a different RCODE to provide
	When including multiple EDNS0/EDE records in a response in order to		additional or better information. For example, multiple EDNS0/EDE
	provide additional error information, other RESPONSE-CODEs MAY use a		records may be included in the response and the supplemental EDNS0/
	different RCODE.		EDE records may wish to include other RESPONSE-CODE values based on
			communication results with other DNS servers.
	3.3. The INFO-CODE field		3.3. The INFO-CODE field
	This 12-bit value provides the additional context for the RESPONSE-		This 12-bit value provides the additional context for the RESPONSE-
	CODE value. This combination of the RESPONSE-CODE and the INFO-CODE		CODE value. This combination of the RESPONSE-CODE and the INFO-CODE
	serve as a joint-index into the IANA "Extended DNS Errors" registry.		serve as a joint-index into the IANA "Extended DNS Errors" registry.
			Note to implementers: the combination of the RESPONSE-CODE and INFO-
			CODE fits within a 16-bit field, allowing implementers the choice of
			treating the combination as either two separate values, as defined in
			this document, or as a single 16-bit integer as long as the results
			are deterministic.
	3.4. The EXTRA-TEXT field		3.4. The EXTRA-TEXT field
	The UTF-8-encoded, EXTRA-TEXT field may be zero-length, or may hold		The UTF-8-encoded, EXTRA-TEXT field may be zero-length, or may hold
	additional information useful to network operators.		additional information useful to network operators.
	4. Defined Extended DNS Errors		4. Defined Extended DNS Errors
	This document defines some initial EDE codes. The mechanism is		This document defines some initial EDE codes. The mechanism is
	intended to be extensible, and additional code-points can be		intended to be extensible, and additional code-points can be
	registered in the "Extended DNS Errors" registry. This document		registered in the "Extended DNS Errors" registry. This document
	skipping to change at page 6, line 22 ¶		skipping to change at page 6, line 47 ¶
	4.1.1. NOERROR Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm		4.1.1. NOERROR Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm
	The resolver attempted to perform DNSSEC validation, but a DNSKEY		The resolver attempted to perform DNSSEC validation, but a DNSKEY
	RRSET contained only unknown algorithms. The R flag should be set.		RRSET contained only unknown algorithms. The R flag should be set.
	4.1.2. NOERROR Extended DNS Error Code 2 - Unsupported DS Algorithm		4.1.2. NOERROR Extended DNS Error Code 2 - Unsupported DS Algorithm
	The resolver attempted to perform DNSSEC validation, but a DS RRSET		The resolver attempted to perform DNSSEC validation, but a DS RRSET
	contained only unknown algorithms. The R flag should be set.		contained only unknown algorithms. The R flag should be set.
	4.2. INFO-CODEs for use with RESPONSE-CODE: SERVFAIL(2)		4.1.3. INFO-CODEs for use with RESPONSE-CODE: NOERROR(3)
			4.1.3.1. NOERROR Extended DNS Error Code 3 - Stale Answer
	4.2.1. SERVFAIL Extended DNS Error Code 1 - DNSSEC Bogus		The resolver was unable to resolve answer within its time limits and
			decided to answer with a previously cached data instead of answering
			with an error. This is typically caused by problems on authoritative
			side, possibly as result of a DoS attack. The R flag should not be
			set, since retrying is likely to create additional load without
			yielding a more fresh answer.
	The resolver attempted to perform DNSSEC validation, but validation		4.1.4. NOERROR Extended DNS Error Code 4 - Forged answer
	ended in the Bogus state. The R flag should not be set.
	4.2.2. SERVFAIL Extended DNS Error Code 2 - DNSSEC Indeterminate		For policy reasons (legal obligation, or malware filtering, for
			instance), an answer was forged. The R flag should not be set.
			4.1.5. SERVFAIL Extended DNS Error Code 5 - DNSSEC Indeterminate
	The resolver attempted to perform DNSSEC validation, but validation		The resolver attempted to perform DNSSEC validation, but validation
	ended in the Indeterminate state. The R flag should not be set.		ended in the Indeterminate state. The R flag should not be set.
	4.2.3. SERVFAIL Extended DNS Error Code 3 - Signature Expired		4.2. INFO-CODEs for use with RESPONSE-CODE: SERVFAIL(2)
	The resolver attempted to perform DNSSEC validation, but the		4.2.1. SERVFAIL Extended DNS Error Code 1 - DNSSEC Bogus
	signature was expired. The R flag should not be set.
	4.2.4. SERVFAIL Extended DNS Error Code 4 - Signature Not Yet Valid		The resolver attempted to perform DNSSEC validation, but validation
			ended in the Bogus state. The R flag should not be set.
			4.2.2. SERVFAIL Extended DNS Error Code 2 - Signature Expired
			The resolver attempted to perform DNSSEC validation, a signature in
			the validation chain was expired. The R flag should not be set.
			4.2.3. SERVFAIL Extended DNS Error Code 3 - Signature Not Yet Valid
	The resolver attempted to perform DNSSEC validation, but the		The resolver attempted to perform DNSSEC validation, but the
	signatures received were not yet valid. The R flag should not be		signatures received were not yet valid. The R flag should not be
	set.		set.
	4.2.5. SERVFAIL Extended DNS Error Code 5 - DNSKEY missing		4.2.4. SERVFAIL Extended DNS Error Code 4 - DNSKEY missing
	A DS record existed at a parent, but no DNSKEY record could be found		A DS record existed at a parent, but no supported matching DNSKEY
	for the child. The R flag should not be set.		record could be found for the child. The R flag should not be set.
	4.2.6. SERVFAIL Extended DNS Error Code 6 - RRSIGs missing		4.2.5. SERVFAIL Extended DNS Error Code 5 - RRSIGs missing
	The resolver attempted to perform DNSSEC validation, but no RRSIGs		The resolver attempted to perform DNSSEC validation, but no RRSIGs
	could be found for at least one RRset where RRSIGs were expected.		could be found for at least one RRset where RRSIGs were expected.
	4.2.7. SERVFAIL Extended DNS Error Code 7 - No Zone Key Bit Set		4.2.6. SERVFAIL Extended DNS Error Code 6 - No Zone Key Bit Set
	The resolver attempted to perform DNSSEC validation, but no Zone Key		The resolver attempted to perform DNSSEC validation, but no Zone Key
	Bit was set in a DNSKEY.		Bit was set in a DNSKEY.
	4.3. INFO-CODEs for use with RESPONSE-CODE: REFUSED(5)		4.2.7. SERVFAIL Extended DNS Error Code 7 - No Reachable Authority
	4.3.1. REFUSED Extended DNS Error Code 1 - Lame		The resolver could not reach any of the authoritative name servers
			(or they refused to reply). The R flag should be set.
	An authoritative resolver that receives a query (with the RD bit		4.2.8. SERVFAIL Extended DNS Error Code 8 - NSEC Missing
	clear) for a domain for which it is not authoritative SHOULD include
	this EDE code in the REFUSED response. Implementations should set
	the R flag in this case (another nameserver might not be lame).
	4.3.2. REFUSED Extended DNS Error Code 2 - Prohibited		The resolver attempted to perform DNSSEC validation, but the
			requested data was missing and a covering NSEC or NSEC3 was not
			provided. The R flag should be set.
			4.2.9. SERVFAIL Extended DNS Error Code 9 - Cached Error
			The resolver has cached SERVFAIL for this query without additional
			information. Th R flag should be set.
			4.2.10. SERVFAIL Extended DNS Error Code 10 - Not Ready
			The server is unable to answer the query as it is not fully up and
			functional yet.
			4.3. INFO-CODEs for use with RESPONSE-CODE: NOTIMP(4)
			4.3.1. NOTIMP Extended DNS Error Code 1 - Deprecated
			The requested operation or query is not supported as its use has been
			deprecated. Implementations should not set the R flag. (Retrying
			request elsewhere is unlikely to yield any other results.)
			4.4. INFO-CODEs for use with RESPONSE-CODE: REFUSED(5)
			4.4.1. REFUSED Extended DNS Error Code 1 - Lame
			An authoritative server that receives a query (with the RD bit clear)
			for a domain for which it is not authoritative SHOULD include this
			EDE code in the SERVFAIL response. A resolver that receives a query
			(with the RD bit clear) SHOULD include this EDE code in the REFUSED
			response. Implementations should set the R flag in this case
			(another nameserver or resolver might not be lame).
			4.4.2. REFUSED Extended DNS Error Code 2 - Prohibited
	An authoritative or recursive resolver that receives a query from an		An authoritative or recursive resolver that receives a query from an
	"unauthorized" client can annotate its REFUSED message with this		"unauthorized" client can annotate its REFUSED message with this
	code. Examples of "unauthorized" clients are recursive queries from		code. Examples of "unauthorized" clients are recursive queries from
	IP addresses outside the network, blacklisted IP addresses, local		IP addresses outside the network, blacklisted IP addresses, local
	policy, etc.		policy, etc.
	Implementations SHOULD allow operators to define what to set the R		Implementations SHOULD allow operators to define what to set the R
	flag to in this case.		flag to in this case.
	4.4. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3)		4.5. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3)
	4.4.1. NXDOMAIN Extended DNS Error Code 1 - Blocked		4.5.1. NXDOMAIN Extended DNS Error Code 1 - Blocked
	The resolver attempted to perfom a DNS query but the domain is		The resolver attempted to perfom a DNS query but the domain is
	blacklisted due to a security policy. The R flag should not be set.		blacklisted due to a security policy implemented on the server being
			directly talked to. The R flag should be set.
			4.6. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3)
			4.6.1. NXDOMAIN Extended DNS Error Code 2 - Censored
			The resolver attempted to perfom a DNS query but the domain was
			blacklisted by a security policy imposed upon the server being talked
			to. Note that how the imposed policy is applied is irrelevant (in-
			band DNS somehow, court order, etc). The R flag should be set.
			4.7. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3)
			4.7.1. NXDOMAIN Extended DNS Error Code 3 - Stale Answer
			The resolver was unable to resolve answer within its time limits and
			decided to answer with a previously cached NXDOMAIN answer instead of
			answering with an error. This is typically caused by problems on
			authoritative side, possibly as result of a DoS attack. The R flag
			should not be set, since retrying is likely to create additional load
			without yielding a more fresh answer.
	5. IANA Considerations		5. IANA Considerations
	5.1. new Extended Error Code EDNS Option		5.1. A New Extended Error Code EDNS Option
	This document defines a new EDNS(0) option, entitled "Extended DNS		This document defines a new EDNS(0) option, entitled "Extended DNS
	Error", assigned a value of TBD1 from the "DNS EDNS0 Option Codes		Error", assigned a value of TBD1 from the "DNS EDNS0 Option Codes
	(OPT)" registry [to be removed upon publication:		(OPT)" registry [to be removed upon publication:
	[http://www.iana.org/assignments/dns-parameters/dns-		[http://www.iana.org/assignments/dns-parameters/dns-
	parameters.xhtml#dns-parameters-11]		parameters.xhtml#dns-parameters-11]
	Value Name Status Reference		Value Name Status Reference
	----- ---------------- ------ ------------------		----- ---------------- ------ ------------------
	TBD Extended DNS Error TBD [ This document ]		TBD Extended DNS Error TBD [ This document ]
	5.2. New Extended Error Code EDNS Option		5.2. New Double-Index Registry Table for Extended Error Codes
	This document defines a new double-index IANA registry table, where		This document defines a new double-index IANA registry table, where
	the first index value is the RCODE value and the second index value		the first index value is the RCODE value and the second index value
	is the INFO-CODE from the Extended DNS Error EDNS option defined in		is the INFO-CODE from the Extended DNS Error EDNS option defined in
	this document. The IANA is requested to create and maintain this		this document. The IANA is requested to create and maintain this
	"Extended DNS Error codes" registry. The codepoint space for each		"Extended DNS Error codes" registry. The codepoint space for each
	INFO-CODE index is to be broken into 3 ranges:		INFO-CODE index is to be broken into 3 ranges:
	o 0 - 3583: Specification required.		o 0 - 3583: Specification required.
	o 3584 - 3839: First Come First Served.		o 3584 - 3839: First Come First Served.
	skipping to change at page 8, line 34 ¶		skipping to change at page 10, line 34 ¶
	RESPONSE-CODE: 0 (NOERROR)		RESPONSE-CODE: 0 (NOERROR)
	INFO-CODE: 1		INFO-CODE: 1
	Purpose: Unsupported DNSKEY		Purpose: Unsupported DNSKEY
	Reference: Section 4.1.1		Reference: Section 4.1.1
	RESPONSE-CODE: 0 (NOERROR)		RESPONSE-CODE: 0 (NOERROR)
	INFO-CODE: 2		INFO-CODE: 2
	Purpose: Unsupported DS Algorithm		Purpose: Unsupported DS Algorithm
	Reference: Section 4.1.2		Reference: Section 4.1.2
			RESPONSE-CODE: 3 (NOERROR)
			INFO-CODE: 3
			Purpose: Answering with stale/cached data
			Reference: Section 4.1.3.1
			RESPONSE-CODE: 0 (NOERROR)
			INFO-CODE: 4
			Purpose: Forged answer
			Reference: Section 4.1.4
			RESPONSE-CODE: 0 (NOERROR)
			INFO-CODE: 5
			Purpose: DNSSEC Indeterminate
			Reference: Section 4.1.5
	RESPONSE-CODE: 2 (SERVFAIL)		RESPONSE-CODE: 2 (SERVFAIL)
	INFO-CODE: 1		INFO-CODE: 1
	Purpose: DNSSEC Bogus		Purpose: DNSSEC Bogus
	Reference: Section 4.2.1		Reference: Section 4.2.1
	RESPONSE-CODE: 2 (SERVFAIL)		RESPONSE-CODE: 2 (SERVFAIL)
	INFO-CODE: 2		INFO-CODE: 2
	Purpose: DNSSEC Indeterminate		Purpose: Signature Expired
	Reference: Section 4.2.2		Reference: Section 4.2.2
	RESPONSE-CODE: 2 (SERVFAIL)		RESPONSE-CODE: 2 (SERVFAIL)
	INFO-CODE: 3		INFO-CODE: 3
	Purpose: Signature Expired		Purpose: Signature Not Yet Valid
	Reference: Section 4.2.3		Reference: Section 4.2.3
	RESPONSE-CODE: 2 (SERVFAIL)		RESPONSE-CODE: 2 (SERVFAIL)
	INFO-CODE: 4		INFO-CODE: 4
	Purpose: Signature Not Yet Valid		Purpose: DNSKEY missing
	Reference: Section 4.2.4		Reference: Section 4.2.4
	RESPONSE-CODE: 2 (SERVFAIL)		RESPONSE-CODE: 2 (SERVFAIL)
	INFO-CODE: 5		INFO-CODE: 5
	Purpose: DNSKEY missing		Purpose: RRSIGs missing
	Reference: Section 4.2.5		Reference: Section 4.2.5
	RESPONSE-CODE: 2 (SERVFAIL)		RESPONSE-CODE: 2 (SERVFAIL)
	INFO-CODE: 6		INFO-CODE: 6
	Purpose: RRSIGs missing		Purpose: No Zone Key Bit Set
	Reference: Section 4.2.6		Reference: Section 4.2.6
	RESPONSE-CODE: 2 (SERVFAIL)		RESPONSE-CODE: 2 (SERVFAIL)
	INFO-CODE: 7		INFO-CODE: 7
	Purpose: No Zone Key Bit Set		Purpose: No NSEC records could be obtained
	Reference: Section 4.2.7		Reference: Section 4.2.8
			RESPONSE-CODE: 2 (SERVFAIL)
			INFO-CODE: 9
			Purpose: The SERVFAIL error comes from the cache
			Reference: Section 4.2.9
			RESPONSE-CODE: 2 (SERVFAIL)
			INFO-CODE: 10
			Purpose: Not Ready.
			Reference: Section 4.2.10
	RESPONSE-CODE: 3 (NXDOMAIN)		RESPONSE-CODE: 3 (NXDOMAIN)
	INFO-CODE: 1		INFO-CODE: 1
	Purpose: Blocked		Purpose: Blocked
	Reference: Section 4.4.1		Reference: Section 4.5.1
			RESPONSE-CODE: 3 (NXDOMAIN)
			INFO-CODE: 2
			Purpose: Censored
			Reference: Section 4.6.1
			RESPONSE-CODE: 3 (NXDOMAIN)
			INFO-CODE: 3
			Purpose: Answering with stale/cached NXDOMAIN data
			Reference: Section 4.7.1
			RESPONSE-CODE: 4 (NOTIMP)
			INFO-CODE: 1
			Purpose:
			Reference: Section 4.4.2
	RESPONSE-CODE: 5 (REFUSED)		RESPONSE-CODE: 5 (REFUSED)
	INFO-CODE: 1		INFO-CODE: 1
	Purpose: Lame		Purpose: Lame
	Reference: Section 4.3.1		Reference: Section 4.4.1
	RESPONSE-CODE: 5 (REFUSED)		RESPONSE-CODE: 5 (REFUSED)
	INFO-CODE: 2		INFO-CODE: 2
	Purpose: Prohibited		Purpose: Prohibited
	Reference: Section 4.3.2		Reference: Section 4.4.2
	6. Security Considerations		6. Security Considerations
	Though DNSSEC continues to be deployed, unfortunately a significant		Though DNSSEC continues to be deployed, unfortunately a significant
	number of clients (~11% according to [GeoffValidation]) that receive		number of clients (~11% according to [GeoffValidation]) that receive
	a SERVFAIL from a validating resolver because of a DNSSEC validaion		a SERVFAIL from a validating resolver because of a DNSSEC validaion
	issue will simply ask the next (potentially non-validating) resolver		issue will simply ask the next (potentially non-validating) resolver
	in their list, and thus don't get any of the protections which DNSSEC		in their list, and thus don't get any of the protections which DNSSEC
	should provide. This is very similar to a kid asking his mother if		should provide. This is very similar to a kid asking his mother if
	he can have another cookie. When the mother says "No, it will ruin		he can have another cookie. When the mother says "No, it will ruin
	skipping to change at page 10, line 15 ¶		skipping to change at page 13, line 7 ¶
	mechanisms, there are some tradeoffs. As an example, an attacker who		mechanisms, there are some tradeoffs. As an example, an attacker who
	is able to insert the DNSSEC Bogus Extended Error into a packet could		is able to insert the DNSSEC Bogus Extended Error into a packet could
	instead simply reply with a fictitious address (A or AAAA) record.		instead simply reply with a fictitious address (A or AAAA) record.
	The R bit hint and extended error information are informational -		The R bit hint and extended error information are informational -
	implementations can choose how much to trust this information and		implementations can choose how much to trust this information and
	validating resolvers / stubs may choose to put a different weight on		validating resolvers / stubs may choose to put a different weight on
	it.		it.
	7. Acknowledgements		7. Acknowledgements
	The authors wish to thank Joe Abley, Mark Andrews, Vladimir Cunat,		The authors wish to thank Joe Abley, Mark Andrews, Stephane
	Peter DeVries, Peter van Dijk, Donald Eastlake, Bob Harold, Evan		Bortzmeyer, Vladimir Cunat, Peter DeVries, Peter van Dijk, Donald
	Hunt, Geoff Huston, Shane Kerr, Edward Lewis, Carlos M. Martinez,		Eastlake, Bob Harold, Evan Hunt, Geoff Huston, Shane Kerr, Edward
	George Michelson, Petr Spacek, Ondrej Sury, Loganaden Velvindron, and		Lewis, Carlos M. Martinez, George Michelson, Michael Sheldon, Petr
	Paul Vixie. They also vaguely remember discussing this with a number		Spacek, Ondrej Sury, Loganaden Velvindron, and Paul Vixie. They also
	of people over the years, but have forgotten who all they were -- if		vaguely remember discussing this with a number of people over the
	you were one of them, and are not listed, please let us know and		years, but have forgotten who all they were -- if you were one of
	we'll acknowledge you.		them, and are not listed, please let us know and we'll acknowledge
			you.
	I also want to thank the band "Infected Mushroom" for providing a		I also want to thank the band "Infected Mushroom" for providing a
	good background soundtrack (and to see if I can get away with this!)		good background soundtrack (and to see if I can get away with this!)
	Another author would like to thank the band "Mushroom Infectors".		Another author would like to thank the band "Mushroom Infectors".
	This was funny at the time we wrote it, but I cannot remember why...		This was funny at the time we wrote it, but I cannot remember why...
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997, <https://www.rfc-		DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
	editor.org/info/rfc2119>.		editor.org/info/rfc2119>.
			[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
			for DNS (EDNS(0))", STD 75, RFC 6891,
			DOI 10.17487/RFC6891, April 2013, <https://www.rfc-
			editor.org/info/rfc6891>.
	8.2. Informative References		8.2. Informative References
	[GeoffValidation]		[GeoffValidation]
	IANA, "A quick review of DNSSEC Validation in today's		IANA, "A quick review of DNSSEC Validation in today's
	Internet", June 2016, <http://www.potaroo.net/		Internet", June 2016, <http://www.potaroo.net/
	presentations/2016-06-27-dnssec.pdf>.		presentations/2016-06-27-dnssec.pdf>.
	[RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.		[RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
	Wellington, "Secret Key Transaction Authentication for DNS		Wellington, "Secret Key Transaction Authentication for DNS
	(TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,		(TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,
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