On 28/11/12 03:45, 石骁毅 wrote:
Hi all,
When using a public DNS, there is huge catch for not playing so well with
CDN.
Is there a way to preserve the CDN by asking dnsmasq to send multiple
resolve
request to a few server instead of one, and return the IP with shorter
route path.
It doesn't have to return immediately, but query the second one in another
thread
(just saying,) and after the other is proved nearer then update the entry
in the
cache. So that the client will get a better resolve result when the cache
expires.
I knew this could be done by using `--server` option to assign DNS server
for a list
of domains, but when there are thousands of domains need to be set this is
a little
painful. So I'm seeking for a better solution.
Thanks,
Xiaoyi
PS:
I don't have much options other than using a public DNS, since internet
in China
is highly censored, domains like google.com, twitter.com will be
hijacked using
ISP provided DNS. For example:
root@OpenWrt:~# nslookup twitter.com 202.106.196.115
Server: 202.106.196.115
Address 1: 202.106.196.115 linedns.bta.net.cn
Name: twitter.com
Address 1: 59.24.3.173
root@OpenWrt:~# nslookup twitter.com 8.8.8.8
Server: 8.8.8.8
Address 1: 8.8.8.8 google-public-dns-a.google.com
Name: twitter.com
Address 1: 199.59.150.7 r-199-59-150-7.twttr.com
Address 2: 199.59.149.230 www4.twitter.com
Address 3: 199.59.150.39 r-199-59-150-39.twttr.com
It's an interesting problem, but I'm not sure in dnsmasq is the best
place to do it, or even the DNS. I tried your twitter example, and
Google DNS always returns answers, but on each query it returns three
different addresses from a much bigger pool. Trying to second-guess the
Google servers is going to be difficult if you can't even find all the
possible twitter servers in one query.
Simon.
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