1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
|
module EventMachine
module DNS
class Resolver
def self.windows?
if RUBY_PLATFORM =~ /mswin32|cygwin|mingw|bccwin/
require 'win32/resolv'
true
else
false
end
end
HOSTS_FILE = windows? ? Win32::Resolv.get_hosts_path : '/etc/hosts'
@hosts = nil
@nameservers = nil
@socket = nil
def self.resolve(hostname)
Request.new(socket, hostname)
end
def self.socket
if @socket && @socket.error?
@socket = Socket.open
else
@socket ||= Socket.open
end
end
def self.nameservers=(ns)
@nameservers = ns
end
def self.nameservers
return @nameservers if @nameservers
if windows?
_, ns = Win32::Resolv.get_resolv_info
return @nameservers = ns || []
end
@nameservers = []
IO.readlines('/etc/resolv.conf').each do |line|
if line =~ /^nameserver (.+)$/
@nameservers << $1.split(/\s+/).first
end
end
@nameservers
rescue
@nameservers = []
end
def self.nameserver
nameservers.shuffle.first
end
def self.hosts
return @hosts if @hosts
@hosts = {}
IO.readlines(HOSTS_FILE).each do |line|
next if line =~ /^#/
addr, host = line.split(/\s+/)
next unless addr && host
@hosts[host] ||= []
@hosts[host] << addr
end
@hosts
rescue
@hosts = {}
end
end
class RequestIdAlreadyUsed < RuntimeError; end
class Socket < EventMachine::Connection
def self.open
EventMachine::open_datagram_socket('0.0.0.0', 0, self)
end
def initialize
@nameserver = nil
end
def post_init
@requests = {}
end
def start_timer
@timer ||= EM.add_periodic_timer(0.1, &method(:tick))
end
def stop_timer
EM.cancel_timer(@timer)
@timer = nil
end
def unbind
end
def tick
@requests.each do |id,req|
req.tick
end
end
def register_request(id, req)
if @requests.has_key?(id)
raise RequestIdAlreadyUsed
else
@requests[id] = req
end
start_timer
end
def deregister_request(id, req)
@requests.delete(id)
stop_timer if @requests.length == 0
end
def send_packet(pkt)
send_datagram(pkt, nameserver, 53)
end
def nameserver=(ns)
@nameserver = ns
end
def nameserver
@nameserver || Resolver.nameserver
end
# Decodes the packet, looks for the request and passes the
# response over to the requester
def receive_data(data)
msg = nil
begin
msg = Resolv::DNS::Message.decode data
rescue
else
req = @requests[msg.id]
if req
@requests.delete(msg.id)
stop_timer if @requests.length == 0
req.receive_answer(msg)
end
end
end
end
class Request
include Deferrable
attr_accessor :retry_interval, :max_tries
def initialize(socket, hostname)
@socket = socket
@hostname = hostname
@tries = 0
@last_send = Time.at(0)
@retry_interval = 3
@max_tries = 5
if addrs = Resolver.hosts[hostname]
succeed addrs
else
EM.next_tick { tick }
end
end
def tick
# Break early if nothing to do
return if @last_send + @retry_interval > Time.now
if @tries < @max_tries
send
else
@socket.deregister_request(@id, self)
fail 'retries exceeded'
end
end
def receive_answer(msg)
addrs = []
msg.each_answer do |name,ttl,data|
if data.kind_of?(Resolv::DNS::Resource::IN::A) ||
data.kind_of?(Resolv::DNS::Resource::IN::AAAA)
addrs << data.address.to_s
end
end
if addrs.empty?
fail "rcode=#{msg.rcode}"
else
succeed addrs
end
end
private
def send
@tries += 1
@last_send = Time.now
@socket.send_packet(packet.encode)
end
def id
begin
@id = rand(65535)
@socket.register_request(@id, self)
rescue RequestIdAlreadyUsed
retry
end unless defined?(@id)
@id
end
def packet
msg = Resolv::DNS::Message.new
msg.id = id
msg.rd = 1
msg.add_question @hostname, Resolv::DNS::Resource::IN::A
msg
end
end
end
end
|
