bind-9.7.2 not forward CNAMEDed domain names

[Drunkard Zhang]

>>>> The upstream DNS server 211.161.192.1 did responsed correctly, by
>>>> analysis via tcpdump.  But why bind didn't use THE RESPONSE, but
>>>> resolves again from root-servers.
>>>
>>> Unfortunately, the information provided by 211.161.192.1 must be
>>> discarded because that is server is not authoritative for cachecn.com.
>>> From your resolver's perspective, it is a totally unrelated domain
>>> name.
>>>
>> Thanks! So bind can accept second hand answer, but won't accept third
>> hand (or more) answer?
>
> It shouldn't accept the second CNAME, either.  Are you sure that it
> does?  It's probably the same globally, so it's not visible from the
> cache contents.
>
Yes, from the capture it just didn't accept the last CNAME.

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.