[dns-operations] Mozilla Firefox and ANY queries

[Fred Morris]

On Wed, 4 Mar 2015, Bob Harold wrote:
> Can someone be more specific on what "overwhelm"s the os cache?  I
> assume all the names still need to be looked up in te os and thus get
> in the os cache.  Is it cache hits that are too many - that sounds
> unlikely.  Or is it entries with very low ttl that you are caching
> longer in the browser to avoid lookups?

I didn't understand this either. So I did some cursory playing with BIND
9.9.2.

* ANY always returns a TTL of 5 seconds.
* Unless RD is turned off, named re-issues the request to the
authoritative nameservers, iff it has nothing whatsoever in cache.

If overwhelming cache was a key consideration, one would think that this
would be surfaced in testing. I haven't looked over on the BIND lists.

--

Fred Morris

--

[Edited for brevity. brian* are names which are not explicitly defined for
the zone, which is wildcarded.]

** BIND fetches it into cache when it wasn't there previously. Note the
TTLs (all of them). **

;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;brian.m3047.net.		IN	ANY

;; ANSWER SECTION:
brian.m3047.net.	5	IN	A	209.221.140.128

;; AUTHORITY SECTION:
m3047.net.		5049	IN	NS	ns2.distributedns.com.
m3047.net.		5049	IN	NS	ns1.distributedns.com.

;; ADDITIONAL SECTION:
ns1.distributedns.com.	22104	IN	A	50.194.52.65
ns2.distributedns.com.	22104	IN	A	50.194.52.67

;; Query time: 115 msec
;; SERVER: 10.0.0.220#53(10.0.0.220)
;; WHEN: Tue Mar  3 11:36:48 2015
;; MSG SIZE  rcvd: 134

** RD is disabled. **

m3047 at flame:~> dig brian2.m3047.net any +norecurse

;; flags: qr ra; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;brian2.m3047.net.		IN	ANY

;; AUTHORITY SECTION:
m3047.net.		5023	IN	NS	ns1.distributedns.com.
m3047.net.		5023	IN	NS	ns2.distributedns.com.

;; ADDITIONAL SECTION:
ns1.distributedns.com.	22078	IN	A	50.194.52.65
ns2.distributedns.com.	22078	IN	A	50.194.52.67

** Let's query specifically for the (synthesized) A record and load it
into cache... Notice the TTL. **

;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;brian2.m3047.net.		IN	A

;; ANSWER SECTION:
brian2.m3047.net.	86400	IN	A	209.221.140.128

;; AUTHORITY SECTION:
m3047.net.		4966	IN	NS	ns1.distributedns.com.
m3047.net.		4966	IN	NS	ns2.distributedns.com.

;; ADDITIONAL SECTION:
ns1.distributedns.com.	22021	IN	A	50.194.52.65
ns2.distributedns.com.	22021	IN	A	50.194.52.67

** Let's see what ANY says. Notice the TTL. Notice all of the TTLs. **

;; flags: qr ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;brian2.m3047.net.		IN	ANY

;; ANSWER SECTION:
brian2.m3047.net.	5	IN	A	209.221.140.128

;; AUTHORITY SECTION:
m3047.net.		4962	IN	NS	ns2.distributedns.com.
m3047.net.		4962	IN	NS	ns1.distributedns.com.

;; ADDITIONAL SECTION:
ns1.distributedns.com.	22017	IN	A	50.194.52.65
ns2.distributedns.com.	22017	IN	A	50.194.52.67

** TTL is still 5 seconds for our qname, but the rest of the TTLs are
counting down... **

;; flags: qr ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;brian2.m3047.net.		IN	ANY

;; ANSWER SECTION:
brian2.m3047.net.	5	IN	A	209.221.140.128

;; AUTHORITY SECTION:
m3047.net.		4789	IN	NS	ns1.distributedns.com.
m3047.net.		4789	IN	NS	ns2.distributedns.com.

;; ADDITIONAL SECTION:
ns1.distributedns.com.	21844	IN	A	50.194.52.65
ns2.distributedns.com.	21844	IN	A	50.194.52.67

** Hopefully you get the idea... **

;; flags: qr ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;brian2.m3047.net.		IN	A

;; ANSWER SECTION:
brian2.m3047.net.	86214	IN	A	209.221.140.128

;; AUTHORITY SECTION:
m3047.net.		4780	IN	NS	ns1.distributedns.com.
m3047.net.		4780	IN	NS	ns2.distributedns.com.

;; ADDITIONAL SECTION:
ns1.distributedns.com.	21835	IN	A	50.194.52.65
ns2.distributedns.com.	21835	IN	A	50.194.52.67