判断dns支持不支持edns

pip install clientsubnetoption (works for both Python2 & Python3)
Import clientsubnetoption and dependancies you\'ll need:
```
import dns
import clientsubnetoption
```

Setup your ClientSubnetOption with the information you want:

cso = clientsubnetoption.ClientSubnetOption(\'1.2.3.4\')

Create your DNS packet:

message = dns.message.make_query(\'google.com\', \'A\')

Add the edns option:
```
message.use_edns(options=[cso])
```
Use message to make your query:
```
r = dns.query.udp(message, \'8.8.8.8\')
```
Option information is now at r.options and there can be multiple, so you may need to iterate through them to find the ClientSubnetOption object.
```
for options in r.options:
    if isinstance(options, ClientSubnetOption):
        # do stuff here
        pass
```

ip_list = []
        cname_probe = "dl.3366.com"
        # ip = "27.40.1.34"
        # ip = "218.61.196.242"
        ip = "218.61.196.242"
        cso = clientsubnetoption.ClientSubnetOption(ip, 32)
        msg = dns.message.make_query(cname_probe, \'A\')
        msg.use_edns(edns=True, ednsflags=0, options=[cso])
        msg.use_edns(options=[cso])
        # dns_serv = "218.61.196.242"
        # dns_serv = "119.6.103.36"
        dns_serv = "119.29.29.29"
        res = dns.query.udp(msg, dns_serv)
        print res.options
        for options in res.options:
            if isinstance(options, clientsubnetoption.ClientSubnetOption):
                # do stuff here
                print "yes"
            else:
                print "not type"
        

        if not res.answer:
            print res.answer
            raise Exception("edns no answer")
        rrset_a = res.answer[-1]
        for rdata in rrset_a:
            ip_list.append(str(rdata.to_text()))
        return ip_list