Maintained by: NLnet Labs

[Unbound-users] Disable "OPT UDPsize" in queries

Denis
Wed Jul 23 16:17:48 CEST 2014


I use unbound as local caching server.
When query goes from my local unbound to provider with "OPT UDPsize=512" -
there is no any response from provider. I tried to set different values for
"edns-buffer-size" but it does not helped.

I found that unbound tries to send queries with this option. After several
attempts it send queries without this option and that it gets response from
the provider. This leads to the significant delay in resolving.

Is there and way to make unbound send queries without this option?

This is example from tcpdump:
----
    192.168.1.75.31273 > 85.21.192.3.53: [udp sum ok] 21532+% [1au] A? ya.ru.
ar: . OPT UDPsize=512 OK (34)
17:23:25.336577 IP (tos 0x0, ttl 64, id 45283, offset 0, flags [none],
proto UDP (17), length 62)
    192.168.1.75.23166 > 85.21.192.3.53: [udp sum ok] 57209+% [1au] A? ya.ru.
ar: . OPT UDPsize=512 OK (34)
17:23:26.884201 IP (tos 0x0, ttl 64, id 45285, offset 0, flags [none],
proto UDP (17), length 62)
    192.168.1.75.58082 > 213.234.192.8.53: [udp sum ok] 20104+% [1au] A?
ya.ru. ar: . OPT UDPsize=512 OK (34)
17:23:29.938285 IP (tos 0x0, ttl 64, id 45286, offset 0, flags [none],
proto UDP (17), length 62)
    192.168.1.75.54667 > 213.234.192.8.53: [udp sum ok] 18401+% [1au] A?
ya.ru. ar: . OPT UDPsize=512 OK (34)
17:23:32.992060 IP (tos 0x0, ttl 64, id 45289, offset 0, flags [none],
proto UDP (17), length 62)
    192.168.1.75.60379 > 85.21.192.3.53: [udp sum ok] 16464+% [1au] A? ya.ru.
ar: . OPT UDPsize=512 OK (34)
17:23:36.045801 IP (tos 0x0, ttl 64, id 45290, offset 0, flags [none],
proto UDP (17), length 62)
    192.168.1.75.39746 > 85.21.192.3.53: [udp sum ok] 38011+% [1au] A? ya.ru.
ar: . OPT UDPsize=512 OK (34)
17:23:39.095634 IP (tos 0x0, ttl 64, id 45291, offset 0, flags [none],
proto UDP (17), length 51)
    192.168.1.75.26679 > 85.21.192.3.53: [udp sum ok] 3546+ A? ya.ru. (23)
17:23:39.099508 IP (tos 0x68, ttl 56, id 50151, offset 0, flags [none],
proto UDP (17), length 99)
    85.21.192.3.53 > 192.168.1.75.26679: [udp sum ok] 3546 q: A? ya.ru.
3/0/0 ya.ru. A 93.158.134.3, ya.ru. A 213.180.204.3,ya.ru. A 213.180.193.3
(71)
---

As soon as query was sent without this option (at 17:23:39.099508) - I get
the response.

Best regards,
Denis
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