告诉urllib2使用自定义DNS

Question

我想告诉urllib2.urlopen(或自定义开启者)使用127.0.0.1(或::1)来解析地址.但是,我不会改变我的/etc/resolv.conf.

一种可能的解决方案是使用类似dnspython查询地址和httplib构建自定义URL开启工具的工具.我更喜欢告诉urlopen使用自定义名称服务器.有什么建议？

Answer 1

看起来名称解析最终由处理socket.create_connection.

-> urllib2.urlopen
-> httplib.HTTPConnection
-> socket.create_connection

虽然设置了"Host:"标头后,您可以解析主机并将IP地址传递到开启器.

我建议你进行子类化httplib.HTTPConnection,并在传递之前将connect方法包装起来进行修改.self.hostsocket.create_connection

然后子类HTTPHandler(和HTTPSHandler)将http_open方法替换为传递你的方法HTTPConnection而不是httplib自己的方法do_open.

像这样:

import urllib2
import httplib
import socket

def MyResolver(host):
  if host == 'news.bbc.co.uk':
    return '66.102.9.104' # Google IP
  else:
    return host

class MyHTTPConnection(httplib.HTTPConnection):
  def connect(self):
    self.sock = socket.create_connection((MyResolver(self.host),self.port),self.timeout)
class MyHTTPSConnection(httplib.HTTPSConnection):
  def connect(self):
    sock = socket.create_connection((MyResolver(self.host), self.port), self.timeout)
    self.sock = ssl.wrap_socket(sock, self.key_file, self.cert_file)

class MyHTTPHandler(urllib2.HTTPHandler):
  def http_open(self,req):
    return self.do_open(MyHTTPConnection,req)

class MyHTTPSHandler(urllib2.HTTPSHandler):
  def https_open(self,req):
    return self.do_open(MyHTTPSConnection,req)

opener = urllib2.build_opener(MyHTTPHandler,MyHTTPSHandler)
urllib2.install_opener(opener)

f = urllib2.urlopen('http://news.bbc.co.uk')
data = f.read()
from lxml import etree
doc = etree.HTML(data)

>>> print doc.xpath('//title/text()')
['Google']

如果您使用HTTPS,显然存在证书问题,您需要填写MyResolver ...

Answer 2

另一种(脏)方式是猴子修补socket.getaddrinfo.

例如,此代码为dns查找添加(无限制)缓存.

import socket
prv_getaddrinfo = socket.getaddrinfo
dns_cache = {}  # or a weakref.WeakValueDictionary()
def new_getaddrinfo(*args):
    try:
        return dns_cache[args]
    except KeyError:
        res = prv_getaddrinfo(*args)
        dns_cache[args] = res
        return res
socket.getaddrinfo = new_getaddrinfo