Can someone from Amazon please answer.

Jared Mauch jared at puck.nether.net
Sat Aug 27 00:12:44 UTC 2016


My personal favorite broken domain is New York State Thruway folks.

https://ednscomp.isc.org/ednscomp/cb652bc112

If you ask for AAAA of www.thruway.ny.gov it is a CNAME to www.wip.thruway.ny.gov and that
breaks a number of DNS servers and load balancers, eg:

$ host -t aaaa www.wip.thruway.ny.gov
;; reply from unexpected source: 2001:558:100e:4:69:252:66:215#53, expected 2001:558:feed::1#53
;; reply from unexpected source: 2001:558:100e:4:69:252:66:215#53, expected 2001:558:feed::1#53

Waiting for the timeouts to occur or trying to get a robust response via TCP is problematic at best.

DNS works really well despite much of the damage from firewall vendors and ill informed consultants.

- Jared

> On Aug 26, 2016, at 7:54 PM, Josh Reynolds <josh at kyneticwifi.com> wrote:
> 
> Excellent info, thank you Mark.
> 
> On Aug 26, 2016 6:53 PM, "Mark Andrews" <marka at isc.org> wrote:
> 
>> 
>> In message <[email protected]
>> mail.gmail.com>, Josh Reynolds writes:
>>> 
>>> Just looking at the RFC...
>>> -----
>>> VERSION Indicates the implementation level of the setter. Full
>> conformance
>>> with this specification is indicated by version '0'. Requestors are
>>> encouraged to set this to the lowest implemented level capable of
>>> expressing a transaction, to minimise the responder and network load of
>>> discovering the greatest common implementation level between requestor
>> and
>>> responder. A requestor's version numbering strategy MAY ideally be a
>>> run-time configuration option. If a responder does not implement the
>>> VERSION level of the request, then it MUST respond with RCODE=BADVERS.
>> All
>>> responses MUST be limited in format to the VERSION level of the request,
>>> but the VERSION of each response SHOULD be the highest implementation
>> level
>>> of the responder. In this way, a requestor will learn the implementation
>>> level of a responder as a side effect of every response, including error
>>> responses and including RCODE=BADVERS.
>>> -----
>>> What am I missing, based on your output?
>> 
>> The servers do not RESPOND to EDNS version != 0 queries.  The following
>> sends a EDNS version 1 query and tells dig not to complete the EDNS version
>> negotiation so you can see the BADVERS response.
>> 
>> % dig lostoncampus.com.au. @205.251.195.156 +edns=1 +noednsneg soa
>> 
>> ; <<>> DiG 9.11.0rc1 <<>> lostoncampus.com.au. @205.251.195.156 +edns=1
>> +noednsneg soa
>> ;; global options: +cmd
>> ;; connection timed out; no servers could be reached
>> %
>> 
>> A EDNS version 0 query to show reachability and that EDNS is supported.
>> 
>> % dig lostoncampus.com.au. @205.251.195.156 +edns=0 +noednsneg soa
>> 
>> ; <<>> DiG 9.11.0rc1 <<>> lostoncampus.com.au. @205.251.195.156 +edns=0
>> +noednsneg soa
>> ;; global options: +cmd
>> ;; Got answer:
>> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 63224
>> ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 1
>> ;; WARNING: recursion requested but not available
>> 
>> ;; OPT PSEUDOSECTION:
>> ; EDNS: version: 0, flags:; udp: 4096
>> ;; QUESTION SECTION:
>> ;lostoncampus.com.au.           IN      SOA
>> 
>> ;; ANSWER SECTION:
>> lostoncampus.com.au.    900     IN      SOA     ns-1222.awsdns-24.org.
>> awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
>> 
>> ;; AUTHORITY SECTION:
>> lostoncampus.com.au.    172800  IN      NS      ns-1222.awsdns-24.org.
>> lostoncampus.com.au.    172800  IN      NS      ns-1812.awsdns-34.co.uk.
>> lostoncampus.com.au.    172800  IN      NS      ns-78.awsdns-09.com.
>> lostoncampus.com.au.    172800  IN      NS      ns-924.awsdns-51.net.
>> 
>> ;; Query time: 126 msec
>> ;; SERVER: 205.251.195.156#53(205.251.195.156)
>> ;; WHEN: Sat Aug 27 09:40:29 EST 2016
>> ;; MSG SIZE  rcvd: 248
>> 
>> %
>> 
>> What you should see is something like the following.  Note the
>> version field is zero (0) and the rcode (status) field is BADVERS.
>> This response does show a protocol error: AD should not be set in
>> this response as there is no authenticated data.
>> 
>> % dig . @a.root-servers.net +edns=1 +noednsneg soa
>> 
>> ; <<>> DiG 9.11.0rc1 <<>> . @a.root-servers.net +edns=1 +noednsneg soa
>> ;; global options: +cmd
>> ;; Got answer:
>> ;; ->>HEADER<<- opcode: QUERY, status: BADVERS, id: 22570
>> ;; flags: qr rd ad; QUERY: 0, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
>> ;; WARNING: recursion requested but not available
>> 
>> ;; OPT PSEUDOSECTION:
>> ; EDNS: version: 0, flags:; udp: 1232
>> ;; Query time: 438 msec
>> ;; SERVER: 2001:503:ba3e::2:30#53(2001:503:ba3e::2:30)
>> ;; WHEN: Sat Aug 27 09:34:32 EST 2016
>> ;; MSG SIZE  rcvd: 23
>> 
>> %
>> 
>> Amazon are not alone here (about 20% of servers fail to respond to
>> EDNS version 1 queries) but they are big player so they should be
>> doing things correctly.  See
>> https://ednscomp.isc.org/compliance/alexa-report.html for others
>> serving the Alexa top 1000 that get things wrong there are a lot
>> of you out there.  There are also reports for the bottom 1000, .GOV,
>> .AU and the root zone at https://ednscomp.isc.org along with a
>> online compliance checker so others can test their servers.  You
>> just need to name a zone and it will work out the rest or you can
>> target individual servers even those not listed in the NS RRset.
>> 
>> There is also a whole series of graphs showing failure trends for
>> different EDNS compliance tests at
>> https://ednscomp.isc.org/compliance/summary.html
>> 
>> Mark
>> 
>>> On Aug 23, 2016 6:43 PM, "Mark Andrews" <marka at isc.org> wrote:
>>> 
>>>> 
>>>> I'm curious.  What are you trying to achieve by blocking EDNS version
>>>> negotiation?  Is it really too hard to return BADVERS to a EDNS
>>>> query with version != 0 along with the version of EDNS you support
>>>> in the version field?  Are you deliberately trying to prevent the
>>>> IETF from deciding to bump the EDNS version in the future?  Do you
>>>> have firewalls that have this behaviour hard coded?  Do you even
>>>> test for RFC compliance?
>>>> 
>>>> Mark
>>>> 
>>>> lostoncampus.com.au. @205.251.195.156 (ns-924.awsdns-51.net.): dns=ok
>>>> edns=ok edns1=timeout edns at 512=ok ednsopt=ok edns1opt=timeout do=ok
>>>> ednsflags=ok optlist=ok,nsid,subnet signed=ok ednstcp=ok
>>>> lostoncampus.com.au. @205.251.192.78 (ns-78.awsdns-09.com.): dns=ok
>>>> edns=ok edns1=timeout edns at 512=ok ednsopt=ok edns1opt=timeout do=ok
>>>> ednsflags=ok optlist=ok,nsid,subnet signed=ok ednstcp=ok
>>>> lostoncampus.com.au. @205.251.196.198 (ns-1222.awsdns-24.org.): dns=ok
>>>> edns=ok edns1=timeout edns at 512=ok ednsopt=ok edns1opt=timeout do=ok
>>>> ednsflags=ok optlist=ok,nsid,subnet signed=ok ednstcp=ok
>>>> lostoncampus.com.au. @205.251.199.20 (ns-1812.awsdns-34.co.uk.):
>> dns=ok
>>>> edns=ok edns1=timeout edns at 512=ok ednsopt=ok edns1opt=timeout do=ok
>>>> ednsflags=ok optlist=ok,nsid,subnet signed=ok ednstcp=ok
>>>> 
>>>> --
>>>> Mark Andrews, ISC
>>>> 1 Seymour St., Dundas Valley, NSW 2117, Australia
>>>> PHONE:  +61 2 9871 4742                         INTERNET:
>> marka at isc.org
>>>> 
>>> 
>> --
>> Mark Andrews, ISC
>> 1 Seymour St., Dundas Valley, NSW 2117, Australia
>> PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org
>> 




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