bind-9.7.2 not forward CNAMEDed domain names

Tue Feb 22 13:07:31 UTC 2011

2011/2/22 Florian Weimer <fweimer at bfk.de>:
> * Drunkard Zhang:
>
>> My capture command: tcpdump -s 0 -nnnvvv -w 360.cn-`date +%Y%m%d`.pcap
>> udp port 53
>>
>> 17:59:36 ~ $ dig +nocmd speedtest.360.cn @211.161.192.1 +multiline
>> +noall +answer
>> speedtest.360.cn.     215 IN CNAME speedtest.360.cn.cloudcdn.net.
>> speedtest.360.cn.cloudcdn.net. 325 IN CNAME cloud010005.cachecn.com.
>> cloud010005.cachecn.com. 368 IN       A 61.155.141.28
>>
>> but bind just resolved cloud010005.cachecn.com again.
>
> With a cold cache, I see this:
>
> [1au] A? speedtest.360.cn. ar: . OPT UDPsize=4096 OK (45)
> [1au] A? speedtest.360.cn.cloudcdn.net. ar: . OPT UDPsize=4096 OK (58)
> [1au] A? cloud010005.cachecn.com. ar: . OPT UDPsize=4096 OK (52)
>
> I suspect that the middle CNAME is still in cache in your case.
>
I don't think so. I started named with: "named -u named -n1 -g -d 3"
on a test machine, then "tcpdump -s 0 -nnnvvv udp port 53" in another
window, and "dig +nocmd speedtest.360.cn @211.161.192.146 +multiline
+noall +answer" in another window. I did the test as clean as
possible.

Below is all got by tcpdump, pretty similar with pcap file in first mail.
[Added blank lines between packets by hand]

 ~ # tcpdump -s 0 -nnnvvv udp port 53
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size
65535 bytes
20:43:08.393967 IP (tos 0x0, ttl 47, id 1482, offset 0, flags [none],
proto UDP (17), length 62) 58.41.157.204.59988 > 211.161.192.146.53:
[udp sum ok] 6096+ A? speedtest.360.cn. (34)

20:43:08.396078 IP (tos 0x0, ttl 64, id 45821, offset 0, flags [none],
proto UDP (17), length 73) 211.161.192.146.14231 > 211.161.192.1.53:
[bad udp cksum 6d1a!] 49635+ [1au] A? speedtest.360.cn. ar: . OPT
UDPsize=4096 OK (45)

20:43:08.396380 IP (tos 0x0, ttl 64, id 39052, offset 0, flags [none],
proto UDP (17), length 56) 211.161.192.146.50308 > 192.228.79.201.53:
[bad udp cksum 2cca!] 37786 [1au] NS? . ar: . OPT UDPsize=4096 OK (28)

20:43:08.398608 IP (tos 0x0, ttl 58, id 44814, offset 0, flags [none],
proto UDP (17), length 377) 211.161.192.1.53 > 211.161.192.146.14231:
[udp sum ok] 49635 q: A? speedtest.360.cn. 3/8/5 speedtest.360.cn.
CNAME speedtest.360.cn.cloudcdn.net., speedtest.360.cn.cloudcdn.net.
CNAME cloud010005.cachecn.com., cloud010005.cachecn.com. A
61.155.141.28 ns: cachecn.com. NS ns8.cachecn.com., cachecn.com. NS
ns4.cachecn.com., cachecn.com. NS ns7.cachecn.com., cachecn.com. NS
ns1.cachecn.com., cachecn.com. NS ns5.cachecn.com., cachecn.com. NS
ns3.cachecn.com., cachecn.com. NS ns6.cachecn.com., cachecn.com. NS
ns2.cachecn.com. ar: ns5.cachecn.com. A 211.100.19.162,
ns6.cachecn.com. A 202.106.196.105, ns7.cachecn.com. A 222.73.28.254,
ns8.cachecn.com. A 122.226.213.156, . OPT UDPsize=4096 OK (349)

20:43:08.399516 IP (tos 0x0, ttl 64, id 6525, offset 0, flags [none],
proto UDP (17), length 80) 211.161.192.146.31420 > 192.203.230.10.53:
[bad udp cksum a4ab!] 43801 [1au] A? cloud010005.cachecn.com. ar: .
OPT UDPsize=4096 OK (52)

20:43:08.688506 IP (tos 0x0, ttl 43, id 32537, offset 0, flags [none],
proto UDP (17), length 753) 192.203.230.10.53 > 211.161.192.146.31420:
[udp sum ok] 43801- q: A? cloud010005.cachecn.com. 0/15/16 ns: com. NS
b.gtld-servers.net., com. NS c.gtld-servers.net., com. NS
a.gtld-servers.net., com. NS k.gtld-servers.net., com. NS
l.gtld-servers.net., com. NS j.gtld-servers.net., com. NS
m.gtld-servers.net., com. NS i.gtld-servers.net., com. NS
g.gtld-servers.net., com. NS f.gtld-servers.net., com. NS
e.gtld-servers.net., com. NS d.gtld-servers.net., com. NS
h.gtld-servers.net., com. NSEC, com. RRSIG ar: a.gtld-servers.net. A
192.5.6.30, a.gtld-servers.net. AAAA 2001:503:a83e::2:30,
b.gtld-servers.net. A 192.33.14.30, b.gtld-servers.net. AAAA
2001:503:231d::2:30, c.gtld-servers.net. A 192.26.92.30,
d.gtld-servers.net. A 192.31.80.30, e.gtld-servers.net. A
192.12.94.30, f.gtld-servers.net. A 192.35.51.30, g.gtld-servers.net.
A 192.42.93.30, h.gtld-servers.net. A 192.54.112.30,
i.gtld-servers.net. A 192.43.172.30, j.gtld-servers.net. A
192.48.79.30, k.gtld-servers.net. A 192.52.178.30, l.gtld-servers.net.
A 192.41.162.30, m.gtld-servers.net. A 192.55.83.30, . OPT
UDPsize=4096 OK (725)

20:43:08.689155 IP (tos 0x0, ttl 64, id 4592, offset 0, flags [none],
proto UDP (17), length 80) 211.161.192.146.56785 > 192.35.51.30.53:
[bad udp cksum 7b72!] 59478 [1au] A? cloud010005.cachecn.com. ar: .
OPT UDPsize=4096 OK (52)

20:43:08.741174 IP (tos 0x0, ttl 43, id 13825, offset 0, flags [none],
proto UDP (17), length 857) 192.228.79.201.53 > 211.161.192.146.50308:
[udp sum ok] 37786*- q: NS? . 14/0/22 . NS a.root-servers.net., . NS
i.root-servers.net., . NS m.root-servers.net., . NS
l.root-servers.net., . NS d.root-servers.net., . NS
e.root-servers.net., . NS g.root-servers.net., . NS
b.root-servers.net., . NS c.root-servers.net., . NS
f.root-servers.net., . NS j.root-servers.net., . NS
k.root-servers.net., . NS h.root-servers.net., . RRSIG ar:
a.root-servers.net. A 198.41.0.4, b.root-servers.net. A
192.228.79.201, c.root-servers.net. A 192.33.4.12, d.root-servers.net.
A 128.8.10.90, e.root-servers.net. A 192.203.230.10,
f.root-servers.net. A 192.5.5.241, g.root-servers.net. A 192.112.36.4,
h.root-servers.net. A 128.63.2.53, i.root-servers.net. A
192.36.148.17, j.root-servers.net. A 192.58.128.30,
k.root-servers.net. A 193.0.14.129, l.root-servers.net. A 199.7.83.42,
m.root-servers.net. A 202.12.27.33, a.root-servers.net. AAAA
2001:503:ba3e::2:30, f.root-servers.net. AAAA 2001:500:2f::f,
h.root-servers.net. AAAA 2001:500:1::803f:235, i.root-servers.net.
AAAA 2001:7fe::53, j.root-servers.net. AAAA 2001:503:c27::2:30,
k.root-servers.net. AAAA 2001:7fd::1, l.root-servers.net. AAAA
2001:500:3::42, m.root-servers.net. AAAA 2001:dc3::35, . OPT
UDPsize=4096 OK (829)

20:43:09.188375 IP (tos 0x0, ttl 42, id 57476, offset 0, flags [none],
proto UDP (17), length 216) 192.35.51.30.53 > 211.161.192.146.56785:
[udp sum ok] 59478- q: A? cloud010005.cachecn.com. 0/4/5 ns:
cachecn.com. NS ns1.cachecn.com., cachecn.com. NS ns2.cachecn.com.,
cachecn.com. NS ns4.cachecn.com., cachecn.com. NS ns3.cachecn.com. ar:
ns1.cachecn.com. A 211.100.19.166, ns2.cachecn.com. A 61.152.94.167,
ns4.cachecn.com. A 60.31.215.206, ns3.cachecn.com. A 210.75.240.15, .
OPT UDPsize=512 OK (188)

20:43:09.188756 IP (tos 0x0, ttl 64, id 11374, offset 0, flags [none],
proto UDP (17), length 80) 211.161.192.146.43751 > 211.100.19.166.53:
[bad udp cksum 1a67!] 16144 [1au] A? cloud010005.cachecn.com. ar: .
OPT UDPsize=4096 OK (52)

20:43:09.229260 IP (tos 0x0, ttl 48, id 65156, offset 0, flags [none],
proto UDP (17), length 368) 211.100.19.166.53 > 211.161.192.146.43751:
[udp sum ok] 16144*- q: A? cloud010005.cachecn.com. 1/8/9
cloud010005.cachecn.com. A 112.90.216.14 ns: cachecn.com. NS
ns5.cachecn.com., cachecn.com. NS ns2.cachecn.com., cachecn.com. NS
ns4.cachecn.com., cachecn.com. NS ns6.cachecn.com., cachecn.com. NS
ns7.cachecn.com., cachecn.com. NS ns3.cachecn.com., cachecn.com. NS
ns1.cachecn.com., cachecn.com. NS ns8.cachecn.com. ar:
ns1.cachecn.com. A 211.100.19.166, ns2.cachecn.com. A 61.152.94.167,
ns3.cachecn.com. A 210.75.240.15, ns4.cachecn.com. A 60.31.215.206,
ns5.cachecn.com. A 211.100.19.162, ns6.cachecn.com. A 202.106.196.105,
ns7.cachecn.com. A 222.73.28.254, ns8.cachecn.com. A 122.226.213.156,
. OPT UDPsize=4096 OK (340)

20:43:09.229694 IP (tos 0x0, ttl 64, id 62111, offset 0, flags [none],
proto UDP (17), length 366) 211.161.192.146.53 > 58.41.157.204.59988:
[bad udp cksum 1f39!] 6096 q: A? speedtest.360.cn. 3/8/4
speedtest.360.cn. CNAME speedtest.360.cn.cloudcdn.net.,
speedtest.360.cn.cloudcdn.net. CNAME cloud010005.cachecn.com.,
cloud010005.cachecn.com. A 112.90.216.14 ns: cachecn.com. NS
ns3.cachecn.com., cachecn.com. NS ns4.cachecn.com., cachecn.com. NS
ns5.cachecn.com., cachecn.com. NS ns6.cachecn.com., cachecn.com. NS
ns7.cachecn.com., cachecn.com. NS ns8.cachecn.com., cachecn.com. NS
ns1.cachecn.com., cachecn.com. NS ns2.cachecn.com. ar:
ns5.cachecn.com. A 211.100.19.162, ns6.cachecn.com. A 202.106.196.105,
ns7.cachecn.com. A 222.73.28.254, ns8.cachecn.com. A 122.226.213.156
(338)
^C
12 packets captured
12 packets received by filter
0 packets dropped by kernel
 ~ # named -v
BIND 9.7.2-P3
 ~ #

And the dig result:
20:50:22 ~ $ dig +nocmd speedtest.360.cn @211.161.192.146 +multiline
+noall +answer
speedtest.360.cn.	1098 IN	CNAME speedtest.360.cn.cloudcdn.net.
speedtest.360.cn.cloudcdn.net. 55 IN CNAME cloud010005.cachecn.com.
cloud010005.cachecn.com. 600 IN	A 112.90.216.14

TTL in first two lines isn't orginal value, so these should be from
upstream DNS 211.161.192.1 .