--- 1/draft-ietf-dnsop-no-response-issue-09.txt 2018-07-20 12:13:08.198312122 -0700 +++ 2/draft-ietf-dnsop-no-response-issue-10.txt 2018-07-20 12:13:08.246313286 -0700 @@ -1,18 +1,18 @@ Network Working Group M. Andrews -Internet-Draft ISC -Intended status: Best Current Practice July 18, 2018 -Expires: January 19, 2019 +Internet-Draft R. Bellis +Intended status: Best Current Practice ISC +Expires: January 21, 2019 July 20, 2018 A Common Operational Problem in DNS Servers - Failure To Respond. - draft-ietf-dnsop-no-response-issue-09 + draft-ietf-dnsop-no-response-issue-10 Abstract The DNS is a query / response protocol. Failing to respond to queries, or responding incorrectly, causes both immediate operational problems and long term problems with protocol development. This document identifies a number of common kinds of queries to which some servers either fail to respond or else respond incorrectly. This document also suggests procedures for TLD and other zone @@ -29,21 +29,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on January 19, 2019. + This Internet-Draft will expire on January 21, 2019. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -70,50 +70,50 @@ 3.2.2. EDNS Queries - Version Specific . . . . . . . . . . . 7 3.2.3. EDNS Options . . . . . . . . . . . . . . . . . . . . 7 3.2.4. EDNS Flags . . . . . . . . . . . . . . . . . . . . . 7 3.2.5. Truncated EDNS Responses . . . . . . . . . . . . . . 8 3.2.6. DO Bit Handling . . . . . . . . . . . . . . . . . . . 8 3.2.7. EDNS over TCP . . . . . . . . . . . . . . . . . . . . 8 4. Firewalls and Load Balancers . . . . . . . . . . . . . . . . 8 5. Scrubbing Services . . . . . . . . . . . . . . . . . . . . . 9 6. Whole Answer Caches . . . . . . . . . . . . . . . . . . . . . 10 7. Response Code Selection . . . . . . . . . . . . . . . . . . . 10 - 8. Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 + 8. Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.1. Testing - Basic DNS . . . . . . . . . . . . . . . . . . . 11 8.1.1. Is The Server Configured For The Zone? . . . . . . . 11 - 8.1.2. Testing Unknown Types . . . . . . . . . . . . . . . . 12 + 8.1.2. Testing Unknown Types . . . . . . . . . . . . . . . . 11 8.1.3. Testing Header Bits . . . . . . . . . . . . . . . . . 12 - 8.1.4. Testing Unknown Opcodes . . . . . . . . . . . . . . . 14 - 8.1.5. Testing Recursive Queries . . . . . . . . . . . . . . 15 - 8.1.6. Testing TCP . . . . . . . . . . . . . . . . . . . . . 15 - 8.2. Testing - Extended DNS . . . . . . . . . . . . . . . . . 16 - 8.2.1. Testing Minimal EDNS . . . . . . . . . . . . . . . . 16 + 8.1.4. Testing Unknown Opcodes . . . . . . . . . . . . . . . 13 + 8.1.5. Testing Recursive Queries . . . . . . . . . . . . . . 14 + 8.1.6. Testing TCP . . . . . . . . . . . . . . . . . . . . . 14 + 8.2. Testing - Extended DNS . . . . . . . . . . . . . . . . . 15 + 8.2.1. Testing Minimal EDNS . . . . . . . . . . . . . . . . 15 8.2.2. Testing EDNS Version Negotiation . . . . . . . . . . 16 - 8.2.3. Testing Unknown EDNS Options . . . . . . . . . . . . 17 - 8.2.4. Testing Unknown EDNS Flags . . . . . . . . . . . . . 18 + 8.2.3. Testing Unknown EDNS Options . . . . . . . . . . . . 16 + 8.2.4. Testing Unknown EDNS Flags . . . . . . . . . . . . . 17 8.2.5. Testing EDNS Version Negotiation With Unknown EDNS Flags . . . . . . . . . . . . . . . . . . . . . . . . 18 8.2.6. Testing EDNS Version Negotiation With Unknown EDNS - Options . . . . . . . . . . . . . . . . . . . . . . . 19 + Options . . . . . . . . . . . . . . . . . . . . . . . 18 - 8.2.7. Testing Truncated Responses . . . . . . . . . . . . . 20 - 8.2.8. Testing DNSSEC Queries . . . . . . . . . . . . . . . 20 - 8.2.9. Testing EDNS Version Negotiation With DNSSEC . . . . 21 - 8.2.10. Testing With Multiple Defined EDNS Options . . . . . 22 - 8.3. When EDNS Is Not Supported . . . . . . . . . . . . . . . 22 + 8.2.7. Testing Truncated Responses . . . . . . . . . . . . . 19 + 8.2.8. Testing DNSSEC Queries . . . . . . . . . . . . . . . 19 + 8.2.9. Testing EDNS Version Negotiation With DNSSEC . . . . 20 + 8.2.10. Testing With Multiple Defined EDNS Options . . . . . 21 + 8.3. When EDNS Is Not Supported . . . . . . . . . . . . . . . 21 9. Remediation . . . . . . . . . . . . . . . . . . . . . . . . . 22 - 10. Security Considerations . . . . . . . . . . . . . . . . . . . 24 - 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 - 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 - 12.1. Normative References . . . . . . . . . . . . . . . . . . 24 - 12.2. Informative References . . . . . . . . . . . . . . . . . 25 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 25 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 23 + 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 + 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 + 12.1. Normative References . . . . . . . . . . . . . . . . . . 23 + 12.2. Informative References . . . . . . . . . . . . . . . . . 24 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 1. Introduction The DNS [RFC1034], [RFC1035] is a query / response protocol. Failing to respond to queries, or responding incorrectly, causes both immediate operational problems and long term problems with protocol development. Failure to respond to a query is indistinguishable from packet loss without doing an analysis of query-response patterns. Additionally @@ -217,24 +217,21 @@ They are: EDNS queries with and without extensions; queries for unknown (unallocated) or unsupported types; and filtering of TCP queries. 3.1. Basic DNS Queries 3.1.1. Zone Existence Initially, to test existence of the zone, an SOA query should be made. If the SOA record is not returned but some other response is - returned, this is a indication of a bad delegation. If the tester - fails to get a response to a SOA query, the Operator should make an A - query for the zone, as some nameservers fail to respond to SOA - queries but will respond to A queries. + returned, this is an indication of a bad delegation. 3.1.2. Unknown / Unsupported Type Queries Identifying servers that fail to respond to unknown or unsupported types can be done by making an initial DNS query for an A record, making a number of queries for an unallocated type, then making a query for an A record again. IANA maintains a registry of allocated types. If the server responds to the first and last queries but fails to @@ -420,188 +417,162 @@ Scrubbing services, unlike firewalls, are also turned on and off in response to denial of service attacks. One needs to take care when choosing a scrubbing service. Ideally, Operators should run these tests against a scrubbing service to ensure that these tests are not seen as attack vectors. 6. Whole Answer Caches Whole answer caches take a previously constructed answer and return - it to a subsequent query for the same qname, qtype and qclass, just - updating the query id field and possibly the qname to match the - incoming query to avoid constructing each response individually. - - Whole answer caches can return the wrong response to a query if they - do not take all of the attributes of the query into account, rather - than just some of them e.g. qname, qtype and qclass. This has - implications when testing and with overall protocol compliance. - - Two current examples are: - - o Whole answer caches that ignore the EDNS version field which - results in incorrect answers to non EDNS version 0 queries being - returned if they were preceded by a EDNS version 0 query for the - same name and type. + it to a subsequent query for the same question. However, they can + return the wrong response if they do not take all of the relevant + attributes of the query into account. - o Whole answer caches that ignore the EDNS options in the query - resulting in options only working some of the time and/or options - being returned when not requested. + In addition to the standard tuple of a non- + exhaustive set of attributes that must be considered include: RD, AD, + CD, OPT record, DO, EDNS buffer size, EDNS version, EDNS options, and + transport. 7. Response Code Selection Choosing the correct response code when responding to DNS queries is - important. Just because a DNS qtype is not implemented does not mean - that NOTIMP is the correct response code to return. Response codes - should be chosen considering how clients will handle them. + important. Response codes should be chosen considering how clients + will handle them. For unimplemented opcodes NOTIMP is the expected response code. For example, a new opcode could change the message format by extending - the header or changing the structure of the records etc. This may - result in FORMERR being returned though NOTIMP would be more correct. + the header or changing the structure of the records etc. - Unimplemented type codes, Name Error (NXDOMAIN) and NOERROR (no data) - are the expected response codes. A server is not supposed to serve a - zone which contains unsupported types ([RFC1034]) so the only thing - left is return if the QNAME exists or not. NOTIMP and REFUSED are - not useful responses as they force the clients to try the other - authoritative servers for a zone looking for a server which will - answer the query. + For unimplemented type codes, and in the absence of other errors, the + only valid response is NoError if the qname exists, and NameError + (NXDOMAIN) otherwise. For Meta-RRs NOTIMP may be returned + instead.
 - Meta queries may be the exception but these need to be thought about - on a case by case basis. + If a zone cannot be loaded because it contains unimplemented type + codes that are not encoded as unknown record types according to + [RFC3597] then the expected response is SERVFAIL. If the server supports EDNS and receives a query with an unsupported EDNS version, the correct response is BADVERS [RFC6891]. If the server does not support EDNS at all, FORMERR and NOTIMP are the expected error codes. That said a minimal EDNS server implementation requires parsing the OPT records and responding with an empty OPT record. There is no need to interpret any EDNS options present in the request as unsupported EDNS options are expected to be ignored [RFC6891]. 8. Testing - Testing is divided into two sections. Basic DNS which all servers - should meet and Extended DNS which should be met by all servers that - support EDNS (a server is deemed to support EDNS if it gives a valid - EDNS response to any EDNS query). If a server does not support EDNS - it should still respond to all the tests. + Testing is divided into two sections. "Basic DNS", which all servers + should meet, and "Extended DNS", which should be met by all servers + that support EDNS (a server is deemed to support EDNS if it gives a + valid EDNS response to any EDNS query). If a server does not support + EDNS it should still respond to all the tests. It is advisable to run all of the tests below in parallel so as to minimise the delays due to multiple timeouts when the servers do not - respond. There are 16 queries directed to each nameserver assuming - no packet loss testing different aspects of Basic DNS and EDNS. + respond. There are 16 queries directed to each nameserver (assuming + no packet loss) testing different aspects of Basic DNS and Extended + DNS. The tests below use dig from BIND 9.11.0. 8.1. Testing - Basic DNS This first set of tests cover basic DNS server behaviour and all servers should pass these tests. 8.1.1. Is The Server Configured For The Zone? Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set and without EDNS. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be set in the response, RA may also be set [RFC1034]. We do not expect - a OPT record to be returned [RFC6891]. + an OPT record to be returned [RFC6891]. Verify the server is configured for the zone: dig +noedns +noad +norec soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section expect: flag: aa to be present expect: flag: rd to NOT be present expect: flag: ad to NOT be present expect: the OPT record to NOT be present 8.1.2. Testing Unknown Types Ask for the TYPE1000 record at the zone's name. This query is made with no DNS flag bits set and without EDNS. TYPE1000 has been chosen for this purpose as IANA is unlikely to allocate this type in the - near future and it is not in type space reserved for end user - allocation. + near future and it is not in a range reserved for private use + [RFC6895]. - We don't expect any records to be returned in the answer section with - the rcode set to NOERROR and the AA and QR bits to be set in the - response, RA may also be set [RFC1034]. We do not expect a OPT + We expect no records to be returned in the answer section with the + rcode set to NOERROR and the AA and QR bits to be set in the + response. RA may also be set [RFC1034]. We do not expect an OPT record to be returned [RFC6891]. Check that queries for an unknown type work: dig +noedns +noad +norec type1000 $zone @$server expect: status: NOERROR expect: an empty answer section. expect: flag: aa to be present expect: flag: rd to NOT be present expect: flag: ad to NOT be present expect: the OPT record to NOT be present - That new types are to be expected is specified in Section 3.6, - [RFC1035]. Servers that don't support a new type are expected to - reject a zone that contains a unsupported type as per Section 5.2, - [RFC1035]. This means that a server that does load a zone can answer - questions for unknown types with NOERROR or NXDOMAIN as per - Section 4.3.2, [RFC1034]. [RFC6895] later reserved distinct ranges - for meta and data types which allows servers to be definitive about - whether a query should be answerable from zone content or not. - 8.1.3. Testing Header Bits 8.1.3.1. Testing CD=1 Queries Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with only the CD DNS flag bit set and all other DNS bits clear and without EDNS. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be - set in the response. We do not expect a OPT record to be returned. + set in the response. We do not expect an OPT record to be returned. If the server supports DNSSEC, CD should be set in the response [RFC4035] otherwise CD should be clear [RFC1034]. Check that queries with CD=1 work: dig +noedns +noad +norec +cd soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section expect: flag: aa to be present expect: flag: rd to NOT be present expect: flag: ad to NOT be present expect: the OPT record to NOT be present - CD use in queries is defined in [RFC4035]. - 8.1.3.2. Testing AD=1 Queries Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with only the AD DNS flag bit set and all other DNS bits clear and without EDNS. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be - set in the response. We do not expect a OPT record to be returned. - - If the server supports DNSSEC, AD may be set in the response - [RFC6840] otherwise AD should be clear [RFC1034]. + set in the response. We do not expect an OPT record to be returned. + The purpose of this query is to detect blocking of queries with the + AD bit present, not the specific value of AD in the response. Check that queries with AD=1 work: dig +noedns +norec +ad soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section expect: flag: aa to be present expect: flag: rd to NOT be present expect: the OPT record to NOT be present @@ -610,74 +581,68 @@ 8.1.3.3. Testing Reserved Bit Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with only the final reserved DNS flag bit set and all other DNS bits clear and without EDNS. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be set in the response, RA may be set. The final reserved bit must not - be set [RFC1034]. We do not expect a OPT record to be returned + be set [RFC1034]. We do not expect an OPT record to be returned [RFC6891]. Check that queries with the last unassigned DNS header flag work and that the flag bit is not copied to the response: dig +noedns +noad +norec +zflag soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section - expect: MBZ to NOT be in the response + expect: MBZ to NOT be in the response (see below) expect: flag: aa to be present expect: flag: rd to NOT be present expect: flag: ad to NOT be present expect: the OPT record to NOT be present - MBZ (Must Be Zero) presence indicates the flag bit has been - incorrectly copied. See Section 4.1.1, [RFC1035] "Z Reserved for - future use. Must be zero in all queries and responses." + MBZ (Must Be Zero) is a dig-specific indication that the flag bit has + been incorrectly copied. See Section 4.1.1, [RFC1035] "Z Reserved + for future use. Must be zero in all queries and responses." 8.1.4. Testing Unknown Opcodes Construct a DNS message that consists of only a DNS header with opcode set to 15 (currently not allocated), no DNS header bits set and empty question, answer, authority and additional sections. Check that new opcodes are handled: dig +noedns +noad +opcode=15 +norec +header-only @$server expect: status: NOTIMP - expect: SOA record to NOT be present + expect: opcode: 15 + expect: all sections to be empty expect: flag: aa to NOT be present expect: flag: rd to NOT be present expect: flag: ad to NOT be present expect: the OPT record to NOT be present - As unknown opcodes have no definition, including packet format other - than there must be a DNS header present (QR, OPCODE and RCODE are the - only header fields that need to be common across all opcodes, - everything else in the header can potentially be redefined), there is - only one possible rcode that make sense to return to a request with a - unknown opcode and that is NOTIMP. - 8.1.5. Testing Recursive Queries Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with only the RD DNS flag bit set and without EDNS. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA, QR and RD bits to be set in the response, RA may also be set [RFC1034]. We do not - expect a OPT record to be returned [RFC6891]. + expect an OPT record to be returned [RFC6891]. Check that recursive queries work: dig +noedns +noad +rec soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section expect: flag: aa to be present expect: flag: rd to be present expect: flag: ad to NOT be present @@ -685,21 +650,21 @@ 8.1.6. Testing TCP Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set and without EDNS. This query is to be sent using TCP. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be set in the response, RA may also be set [RFC1034]. We do not expect - a OPT record to be returned [RFC6891]. + an OPT record to be returned [RFC6891]. Check that TCP queries work: dig +noedns +noad +norec +tcp soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section expect: flag: aa to be present expect: flag: rd to NOT be present expect: flag: ad to NOT be present @@ -716,209 +681,209 @@ EDNS support. 8.2.1. Testing Minimal EDNS Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 0 is used without any EDNS options or EDNS flags set. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be - set in the response, RA may also be set [RFC1034]. We expect a OPT + set in the response, RA may also be set [RFC1034]. We expect an OPT record to be returned. There should be no EDNS flags present in the response. The EDNS version field should be zero and there should be no EDNS options present [RFC6891]. Check that plain EDNS queries work: dig +nocookie +edns=0 +noad +norec soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: EDNS Version 0 in response expect: flag: aa to be present expect: flag: ad to NOT be present +nocookie disables sending a EDNS COOKIE option in which is on by default in BIND 9.11.0. 8.2.2. Testing EDNS Version Negotiation Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 1 is used without any EDNS options or EDNS flags set. We expect the SOA record for the zone to NOT be returned in the answer section with the extended rcode set to BADVERS and the QR bit - to be set in the response, RA may also be set [RFC1034]. We expect a - OPT record to be returned. There should be no EDNS flags present in - the response. The EDNS version field should be zero as EDNS versions - other than 0 are yet to be specified and there should be no EDNS - options present [RFC6891]. + to be set in the response, RA may also be set [RFC1034]. We expect + an OPT record to be returned. There should be no EDNS flags present + in the response. The EDNS version field should be zero as EDNS + versions other than 0 are yet to be specified and there should be no + EDNS options present [RFC6891]. Check that EDNS version 1 queries work (EDNS supported): dig +nocookie +edns=1 +noednsneg +noad +norec soa $zone @$server expect: status: BADVERS expect: the SOA record to NOT be present in the answer section - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: EDNS Version 0 in response expect: flag: aa to NOT be present expect: flag: ad to NOT be present Only EDNS Version 0 is currently defined so the response should always be a 0 version. This will change when EDNS version 1 is defined. BADVERS is the expected rcode if EDNS is supported as per Section 6.1.3, [RFC6891]. 8.2.3. Testing Unknown EDNS Options Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 0 is used without any EDNS flags. A EDNS option is present with a value from the yet to be assigned range. The unassigned value chosen is 100 and will need to be adjusted when IANA assigns this value formally. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be - set in the response, RA may also be set [RFC1034]. We expect a OPT + set in the response, RA may also be set [RFC1034]. We expect an OPT record to be returned. There should be no EDNS flags present in the response. The EDNS version field should be zero as EDNS versions other than 0 are yet to be specified and there should be no EDNS options present as unknown EDNS options are supposed to be ignored by the server [RFC6891]. Check that EDNS queries with an unknown option work (EDNS supported): dig +nocookie +edns=0 +noad +norec +ednsopt=100 soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: OPT=100 to NOT be present expect: EDNS Version 0 in response expect: flag: aa to be present expect: flag: ad to NOT be present Unknown EDNS options are supposed to be ignored, Section 6.1.2, [RFC6891]. 8.2.4. Testing Unknown EDNS Flags Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 0 is used without any EDNS options. A unassigned EDNS flag bit is set (0x40 in this case). We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be - set in the response, RA may also be set [RFC1034]. We expect a OPT + set in the response, RA may also be set [RFC1034]. We expect an OPT record to be returned. There should be no EDNS flags present in the response as unknown EDNS flags are supposed to be ignored. The EDNS version field should be zero and there should be no EDNS options present [RFC6891]. Check that EDNS queries with unknown flags work (EDNS supported): dig +nocookie +edns=0 +noad +norec +ednsflags=0x40 soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: MBZ not to be present expect: EDNS Version 0 in response expect: flag: aa to be present expect: flag: ad to NOT be present MBZ (Must Be Zero) presence indicates the flag bit has been incorrectly copied as per Section 6.1.4, [RFC6891]. 8.2.5. Testing EDNS Version Negotiation With Unknown EDNS Flags Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 1 is used without any EDNS options. A unassigned EDNS flag bit is set (0x40 in this case). We expect the SOA record for the zone to NOT be returned in the answer section with the extended rcode set to BADVERS and the QR bit - to be set in the response, RA may also be set [RFC1034]. We expect a - OPT record to be returned. There should be no EDNS flags present in - the response as unknown EDNS flags are supposed to be ignored. The - EDNS version field should be zero as EDNS versions other than 0 are - yet to be specified and there should be no EDNS options present + to be set in the response, RA may also be set [RFC1034]. We expect + an OPT record to be returned. There should be no EDNS flags present + in the response as unknown EDNS flags are supposed to be ignored. + The EDNS version field should be zero as EDNS versions other than 0 + are yet to be specified and there should be no EDNS options present [RFC6891]. Check that EDNS version 1 queries with unknown flags work (EDNS supported): dig +nocookie +edns=1 +noednsneg +noad +norec +ednsflags=0x40 soa \ $zone @$server expect: status: BADVERS expect: SOA record to NOT be present - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: MBZ not to be present expect: EDNS Version 0 in response expect: flag: aa to NOT be present expect: flag: ad to NOT be present +noednsneg disables EDNS version negotiation in DiG; MBZ (Must Be Zero) presence indicates the flag bit has been incorrectly copied. 8.2.6. Testing EDNS Version Negotiation With Unknown EDNS Options Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 1 is used. A unknown EDNS option is present (option code 100 has been chosen). We expect the SOA record for the zone to NOT be returned in the answer section with the extended rcode set to BADVERS and the QR bit - to be set in the response, RA may also be set [RFC1034]. We expect a - OPT record to be returned. There should be no EDNS flags present in - the response. The EDNS version field should be zero as EDNS versions - other than 0 are yet to be specified and there should be no EDNS - options present [RFC6891]. + to be set in the response, RA may also be set [RFC1034]. We expect + an OPT record to be returned. There should be no EDNS flags present + in the response. The EDNS version field should be zero as EDNS + versions other than 0 are yet to be specified and there should be no + EDNS options present [RFC6891]. Check that EDNS version 1 queries with unknown options work (EDNS supported): dig +nocookie +edns=1 +noednsneg +noad +norec +ednsopt=100 soa \ $zone @$server expect: status: BADVERS expect: SOA record to NOT be present - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: OPT=100 to NOT be present expect: EDNS Version 0 in response expect: flag: aa to be present expect: flag: ad to NOT be present +noednsneg disables EDNS version negotiation in DiG. 8.2.7. Testing Truncated Responses Ask for the DNSKEY records of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 0 is used without any EDNS options. The only EDNS flag set is DO. The EDNS UDP buffer size is set to 512. The intention of this query is elicit a truncated response from the server. Most signed DNSKEY responses are bigger than 512 bytes. We expect a response with the rcode set to NOERROR and the AA and QR bits to be set, AD may be set in the response if the server supports DNSSEC otherwise it should be clear. TC and RA may also be set - [RFC1034]. We expect a OPT record to be present in the response. + [RFC1034]. We expect an OPT record to be present in the response. There should be no EDNS flags other than DO present in the response. The EDNS version field should be zero and there should be no EDNS options present [RFC6891]. If TC is not set it is not possible to confirm that the server correctly adds the OPT record to the truncated responses or not. dig +norec +dnssec +bufsize=512 +ignore dnskey $zone @$server expect: NOERROR expect: OPT record with version set to 0 @@ -927,94 +892,94 @@ Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 0 is used without any EDNS options. The only EDNS flag set is DO. We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be set in the response, AD may be set in the response if the server supports DNSSEC otherwise it should be clear. RA may also be set - [RFC1034]. We expect a OPT record to be returned. There should be + [RFC1034]. We expect an OPT record to be returned. There should be no EDNS flags other than DO present in the response which should be present if the server supports DNSSEC. The EDNS version field should be zero and there should be no EDNS options present [RFC6891]. Check that a DNSSEC queries work (EDNS supported): dig +nocookie +edns=0 +noad +norec +dnssec soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: DO=1 to be present if a RRSIG is in the response expect: EDNS Version 0 in response expect: flag: aa to be present DO=1 should be present if RRSIGs are returned as they indicate that the server supports DNSSEC. Servers that support DNSSEC are supposed to copy the DO bit from the request to the response as per [RFC3225]. 8.2.9. Testing EDNS Version Negotiation With DNSSEC Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 1 is used without any EDNS options. The only EDNS flag set is DO. We expect the SOA record for the zone to NOT be returned in the answer section with the rcode set to BADVERS and the only the QR bit - and possibly the RA bit to be set [RFC1034]. We expect a OPT record + and possibly the RA bit to be set [RFC1034]. We expect an OPT record to be returned. There should be no EDNS flags other than DO present in the response which should be present if the server supports DNSSEC. The EDNS version field should be zero and there should be no EDNS options present [RFC6891]. Check that EDNS version 1 DNSSEC queries work (EDNS supported): dig +nocookie +edns=1 +noednsneg +noad +norec +dnssec soa \ $zone @$server expect: status: BADVERS expect: SOA record to NOT be present - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: DO=1 to be present if the EDNS version 0 DNSSEC query test returned DO=1 expect: EDNS Version 0 in response expect: flag: aa to NOT be present +noednsneg disables EDNS version negotiation in DiG. 8.2.10. Testing With Multiple Defined EDNS Options Ask for the SOA record of the zone the server is nominally configured to serve. This query is made with no DNS flag bits set. EDNS version 0 is used. A number of defined EDNS options are present (NSID [RFC5001], DNS COOKIE [RFC7873], EDNS Client Subnet [RFC7871] and EDNS Expire [RFC7314]). We expect the SOA record for the zone to be returned in the answer section with the rcode set to NOERROR and the AA and QR bits to be - set in the response, RA may also be set [RFC1034]. We expect a OPT + set in the response, RA may also be set [RFC1034]. We expect an OPT record to be returned. There should be no EDNS flags present in the response. The EDNS version field should be zero. Any of the requested EDNS options supported by the server and permitted server configuration may be returned [RFC6891]. Check that EDNS queries with multiple defined EDNS options work: dig +edns=0 +noad +norec +cookie +nsid +expire +subnet=0.0.0.0/0 \ soa $zone @$server expect: status: NOERROR expect: the SOA record to be present in the answer section - expect: a OPT record to be present in the additional section + expect: an OPT record to be present in the additional section expect: EDNS Version 0 in response expect: flag: aa to be present expect: flag: ad to NOT be present 8.3. When EDNS Is Not Supported If EDNS is not supported by the nameserver, we expect a response to all the above queries. That response may be a FORMERR or NOTIMP error response or the OPT record may just be ignored. @@ -1141,36 +1106,48 @@ D. Wessels, "DNS Transport over TCP - Implementation Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016, . 12.2. Informative References [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, DOI 10.17487/RFC2671, August 1999, . + [RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record + (RR) Types", RFC 3597, DOI 10.17487/RFC3597, September + 2003, . + [RFC5001] Austein, R., "DNS Name Server Identifier (NSID) Option", RFC 5001, DOI 10.17487/RFC5001, August 2007, . [RFC7314] Andrews, M., "Extension Mechanisms for DNS (EDNS) EXPIRE Option", RFC 7314, DOI 10.17487/RFC7314, July 2014, . [RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W. Kumari, "Client Subnet in DNS Queries", RFC 7871, DOI 10.17487/RFC7871, May 2016, . [RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS) Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016, . -Author's Address +Authors' Addresses M. Andrews Internet Systems Consortium 950 Charter Street Redwood City, CA 94063 US Email: marka@isc.org + + Ray Bellis + Internet Systems Consortium + 950 Charter Street + Redwood City, CA 94063 + US + + Email: ray@isc.org