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Author Topic: DNS Relay  (Read 11218 times)

YukiS

  • Level 1 Member
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  • Posts: 2
DNS Relay
« on: October 09, 2010, 04:40:43 PM »

As of 1.34EUb05, the DNS relay feature of the router still only supports DNS queries over UDP. DNS queries over TCP should be allowed as they may well be required as the size of zone records grow with the coming move to IPv6.

TCP queries are implemented as part of the standard and are the fallback to be used when the response is too long for UDP and would otherwise be truncated. Some sites already rely on this functionality, for example SixXS uses it to distribute large TXT records containing a list of tunnel brokers.
To check for this yourself, try running the command "dig @192.168.0.1 _aiccu.sixxs.net txt" if you have a Unix-based OS, or "nslookup -q=txt _aiccu.sixxs.net 192.168.0.1" on Windows. You will see that you do not get a satisfactory response:

Code: [Select]
>dig @192.168.0.1 _aiccu.sixxs.net txt
;; Truncated, retrying in TCP mode.
;; Connection to 192.168.0.1#53(192.168.0.1) for _aiccu.sixxs.net failed: connec
tion refused.

Now compare this to querying a DNS server directly:

Code: [Select]
dig @8.8.8.8 _aiccu.sixxs.net txt
;; Truncated, retrying in TCP mode.

; <<>> DiG 9.3.2 <<>> @8.8.8.8 _aiccu.sixxs.net txt
; (1 server found)
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2011
;; flags: qr rd ra; QUERY: 1, ANSWER: 10, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;_aiccu.sixxs.net. IN TXT

;; ANSWER SECTION:
_aiccu.sixxs.net. 2436 IN TXT "# AICCU TIC/TSP Servers"
_aiccu.sixxs.net. 2436 IN TXT "# http://www.sixxs.net/tools/ai
ccu/brokers/"
_aiccu.sixxs.net. 2436 IN TXT "# <name> | <url> | website | tl
d's"
_aiccu.sixxs.net. 2436 IN TXT "SixXS" "tic://tic.sixxs.net" "h
ttp://www.sixxs.net" "be de ee fi gb ie it nl nz pl pt si se us"
_aiccu.sixxs.net. 2436 IN TXT "ACADEMIA Sinica Computing Centr
e" "tsp://tb2.ipv6.ascc.net" "http://tb2.ipv6.ascc.net" "tw"
_aiccu.sixxs.net. 2436 IN TXT "Hexago / Freenet6" "tsp://broke
r.freenet6.net" "http://www.freenet6.net" "ca"
_aiccu.sixxs.net. 2436 IN TXT "AARNet" "tsp://broker.aarnet.ne
t.au" "http://broker.aarnet.net.au" "au"
_aiccu.sixxs.net. 2436 IN TXT "ECS Southampton" "tsp://broker.
ecs.soton.ac.uk" "http://broker.ecs.soton.ac.uk" "gb"
_aiccu.sixxs.net. 2436 IN TXT "UKERNA" "tsp://broker.ipv6.ac.u
k" "http://www.broker.ipv6.ac.uk" "gb"
_aiccu.sixxs.net. 2436 IN TXT "Wanadoo France" "tsp://ts.ipv6.
wanadoo.fr" "http://www.ipv6.wanadoo.fr" "fr"

;; Query time: 33 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Tue Oct 05 14:02:57 2010
;; MSG SIZE rcvd: 778

At the moment I have disabled DNS relay to get proper responses to these queries, but I also experience intermittent issues with the router not handing out the DNS IPs in this mode.

Both problems really need to be addressed, but moreso the second one as it's affecting the basic functionality of the router.
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