#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright 2014-2015 clowwindy
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
from __future__ import absolute_import, division, print_function, \
with_statement
import os
import socket
import struct
import re
import logging
from shadowsocks import common, lru_cache, eventloop, shell
CACHE_SWEEP_INTERVAL = 30
VALID_HOSTNAME = re.compile(br"(?!-)[A-Z\d\-_]{1,63}(? 63:
return None
results.append(common.chr(l))#一个字节
results.append(label)
results.append(b'\0')
return b''.join(results)
def build_request(address, qtype):#构造一个请求数据包
request_id = os.urandom(2)#2byte租房因此高压包
header = struct.pack('!BBHHHH', 1, 0, 1, 0, 0, 0)#112222字节 0 QR查询 0000 opcode标准查询 0 响应报文有效果 0 不截断 1可以迭代查询 0相应 000保留取0 0000返回码 无错误 1个问题 0回答 权威服务器条目数 额外信息条目数
#提问只打包了一个题目
addr = build_address(address)#打标签
qtype_qclass = struct.pack('!HH', qtype, QCLASS_IN) #各两个字节
return request_id + header + addr + qtype_qclass
#构造的都是迭代查询
# 分析ip数据包，返回一个ip地址，点分格式
def parse_ip(addrtype, data, length, offset):
if addrtype == QTYPE_A:
return socket.inet_ntop(socket.AF_INET, data[offset:offset + length])
elif addrtype == QTYPE_AAAA:
return socket.inet_ntop(socket.AF_INET6, data[offset:offset + length])
elif addrtype in [QTYPE_CNAME, QTYPE_NS]:#包里回复报文解析出来的 权威
return parse_name(data, offset)[1]#cnmae返回cnmae记录值
else:
return data[offset:offset + length]#SOA直接返回数据 不解析了
def parse_name(data, offset):#返回一个元组（整个记录的长度，别名b'www.google.com'）的二进制流 answer的长度和question的长度一致 故可以一直用
p = offset
labels = []
l = common.ord(data[p])
while l > 0:
if (l & (128 + 64)) == (128 + 64):#递归了
# pointer
pointer = struct.unpack('!H', data[p:p + 2])[0]
pointer &= 0x3FFF#取出递归的偏移位置
r = parse_name(data, pointer)
labels.append(r[1])
p += 2#指针就是最后了 直接返回
# pointer is the end
return p - offset, b'.'.join(labels)#返回的是www.google.com这样
else:
labels.append(data[p + 1:p + 1 + l])#从偏移处取出标签
p += 1 + l#更改偏移
l = common.ord(data[p])#取下一个的长度 结束为0
return p - offset + 1, b'.'.join(labels)#一个是直接返回 一个是递归返回
# rfc1035
# record
# 1 1 1 1 1 1
# 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | |
# / /
# / NAME /
# | |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | TYPE |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | CLASS |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | TTL |
# | |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | RDLENGTH |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
# / RDATA /
# / /
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
def parse_record(data, offset, question=False):#nlen 是名字的长度
nlen, name = parse_name(data, offset)
if not question:
record_type, record_class, record_ttl, record_rdlength = struct.unpack(
'!HHiH', data[offset + nlen:offset + nlen + 10]
)
ip = parse_ip(record_type, data, record_rdlength, offset + nlen + 10)#从offset + nlen + 10开始 加上record_rdlength ns记录返回了元组（长度，域名）
return nlen + 10 + record_rdlength, \
(name, ip, record_type, record_class, record_ttl) #一条记录的长度，以及一个元组
else:
record_type, record_class = struct.unpack(#这是提问的 没有
'!HH', data[offset + nlen:offset + nlen + 4]#问题的名字还在 没有RDLENGTH和RDATA
)
return nlen + 4, (name, None, record_type, record_class, None, None)
def parse_header(data):
if len(data) >= 12:
header = struct.unpack('!HBBHHHH', data[:12])
res_id = header[0]
res_qr = header[1] & 128#10000000 最高位
res_tc = header[1] & 2#10 RD位 1期望递归
res_ra = header[2] & 128#RA位 1 递归可用
res_rcode = header[2] & 15#Rcode位
# assert res_tc == 0
# assert res_rcode in [0, 3]
res_qdcount = header[3]
res_ancount = header[4]
res_nscount = header[5]
res_arcount = header[6]
return (res_id, res_qr, res_tc, res_ra, res_rcode, res_qdcount,
res_ancount, res_nscount, res_arcount)
return None
def parse_response(data):
try:
if len(data) >= 12:
header = parse_header(data)
if not header:
return None
res_id, res_qr, res_tc, res_ra, res_rcode, res_qdcount, \
res_ancount, res_nscount, res_arcount = header
qds = []
ans = []
offset = 12#去头
for i in range(0, res_qdcount):
l, r = parse_record(data, offset, True)
offset += l#parse_record返回的是字段长度 所以offset要累加 非常漂亮
if r:
qds.append(r)
for i in range(0, res_ancount):
l, r = parse_record(data, offset)#回答 跨过一条
offset += l
if r:
ans.append(r)#回答加入元组
for i in range(0, res_nscount):
l, r = parse_record(data, offset)#名字长度+头长度10+记录长度
offset += l
for i in range(0, res_arcount):
l, r = parse_record(data, offset)
offset += l
response = DNSResponse()#一个类
if qds:
response.hostname = qds[0][0]#www.baidu.com
for an in qds:
response.questions.append((an[1], an[2], an[3]))#None, record_type, record_class 只取这些record_ttl不要了
for an in ans:
response.answers.append((an[1], an[2], an[3]))#ip, record_type, record_class
return response
except Exception as e:
shell.print_exception(e)
return None
def is_valid_hostname(hostname):
if len(hostname) > 255:
return False
if hostname[-1] == b'.':
hostname = hostname[:-1]
return all(VALID_HOSTNAME.match(x) for x in hostname.split(b'.'))
class DNSResponse(object): #调用str方法
def __init__(self):
self.hostname = None
self.questions = [] # each: (addr, type, class)
self.answers = [] # each: (addr, type, class)
def __str__(self):
return '%s: %s' % (self.hostname, str(self.answers)) #字符串表示
STATUS_FIRST = 0
STATUS_SECOND = 1
class DNSResolver(object):
def __init__(self, server_list=None, prefer_ipv6=False):
self._loop = None
self._hosts = {}
self._hostname_status = {}
self._hostname_to_cb = {}
self._cb_to_hostname = {}
self._cache = lru_cache.LRUCache(timeout=300)#没有指定删除时的 对各个值的回调函数
self._sock = None
if server_list is None:
self._servers = None #一个包含DNS的列表
self._parse_resolv()
else:
self._servers = server_list
if prefer_ipv6:
self._QTYPES = [QTYPE_AAAA, QTYPE_A]
else:
self._QTYPES = [QTYPE_A, QTYPE_AAAA]
self._parse_hosts()
# TODO monitor hosts change and reload hosts
# TODO parse /etc/gai.conf and follow its rules
def _parse_resolv(self):
self._servers = []
try:
with open('/etc/resolv.conf', 'rb') as f:#从/etc/resolv.conf找dns服务器
content = f.readlines()
for line in content:
line = line.strip()
if not (line and line.startswith(b'nameserver')):
continue
parts = line.split()
if len(parts)