Disabling EDNS0 options in 8.3.1 queries

[Mark_Andrews at isc.org]

> We recently upgraded our name servers to 8.3.1, and are having
> problems resolving some names at yahoo.com, e.g. biz.yahoo.com,
> weather.yahoo.com, etc.  Bind 8.3.1 appears to be adding an
> EDNS0 option to the query, and yahoo's name servers are just
> dropping the query, instead of responding with NOTIMPL or FORMERR
> (sp?).  I've read a bit about this on the mailing lists, groups,
> faqs, etc., and it seems that some commercial Bind implementations

	Perhaps you ment "some commercial DNS implementations".

> have this bad behavior and some load balancers will also drop the
> queries.

	These servers don't drop EDNS0 queries.  Perhaps you have some
	other piece of equipment (firwall/nat perhaps) that is blocking
	these queries / reponses.  The "+bufsize=512" causes a EDNS0
	query to be generated.

	Mark

; <<>> DiG 9.2.1 <<>> +bufsize=512 biz.yahoo.com @NS1.YAHOO.COM
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2231
;; flags: qr rd; QUERY: 1, ANSWER: 1, AUTHORITY: 13, ADDITIONAL: 13

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;biz.yahoo.com.			IN	A

;; ANSWER SECTION:
biz.yahoo.com.		1800	IN	CNAME	biz.finance.yahoo.akadns.net.

;; AUTHORITY SECTION:
net.			68466	IN	NS	A.GTLD-SERVERS.net.
net.			68466	IN	NS	G.GTLD-SERVERS.net.
net.			68466	IN	NS	H.GTLD-SERVERS.net.
net.			68466	IN	NS	C.GTLD-SERVERS.net.
net.			68466	IN	NS	I.GTLD-SERVERS.net.
net.			68466	IN	NS	B.GTLD-SERVERS.net.
net.			68466	IN	NS	D.GTLD-SERVERS.net.
net.			68466	IN	NS	L.GTLD-SERVERS.net.
net.			68466	IN	NS	F.GTLD-SERVERS.net.
net.			68466	IN	NS	J.GTLD-SERVERS.net.
net.			68466	IN	NS	K.GTLD-SERVERS.net.
net.			68466	IN	NS	E.GTLD-SERVERS.net.
net.			68466	IN	NS	M.GTLD-SERVERS.net.

;; ADDITIONAL SECTION:
A.GTLD-SERVERS.net.	241243	IN	A	192.5.6.30
G.GTLD-SERVERS.net.	241243	IN	A	192.42.93.30
H.GTLD-SERVERS.net.	241243	IN	A	192.54.112.30
C.GTLD-SERVERS.net.	241243	IN	A	192.26.92.30
I.GTLD-SERVERS.net.	241243	IN	A	192.43.172.30
B.GTLD-SERVERS.net.	241243	IN	A	192.33.14.30
D.GTLD-SERVERS.net.	241243	IN	A	192.31.80.30
L.GTLD-SERVERS.net.	241243	IN	A	192.41.162.30
F.GTLD-SERVERS.net.	241243	IN	A	192.35.51.30
J.GTLD-SERVERS.net.	241243	IN	A	210.132.100.101
K.GTLD-SERVERS.net.	414045	IN	A	192.52.178.30
E.GTLD-SERVERS.net.	241243	IN	A	192.12.94.30

;; Query time: 267 msec
;; SERVER: 66.218.71.63#53(NS1.YAHOO.COM)
;; WHEN: Thu May 23 09:57:37 2002
;; MSG SIZE  rcvd: 497


; <<>> DiG 9.2.1 <<>> +bufsize=512 biz.finance.yahoo.akadns.net @zg.akadns.net
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: FORMERR, id: 56716
;; flags: qr rd; QUERY: 0, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; Query time: 260 msec
;; SERVER: 204.248.36.131#53(zg.akadns.net)
;; WHEN: Thu May 23 09:58:56 2002
;; MSG SIZE  rcvd: 12

> 
> SO....How do I stop 8.3.1 from sending them out in the first
> place?  I see nothing in the documentation about this, no options,
> etc.  The code shows an 'edns0' option in the resolv.conf that will
> turn it *on*, but I see no options to turn it off.  I've tried commenting 
> out RES_USE_EDNS0 in lib/resolv.h, which should remove lots of #ifdef'd code,
> to no effect.
> 
> Thanks,
> 
> - Darren
> 
--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at isc.org