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588 lines
15 KiB
Python
Executable file
588 lines
15 KiB
Python
Executable file
# Domain Name Server (DNS) interface
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#
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# See RFC 1035:
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# ------------------------------------------------------------------------
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# Network Working Group P. Mockapetris
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# Request for Comments: 1035 ISI
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# November 1987
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# Obsoletes: RFCs 882, 883, 973
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#
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# DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION
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# ------------------------------------------------------------------------
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import string
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import dnstype
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import dnsclass
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import dnsopcode
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# Low-level 16 and 32 bit integer packing and unpacking
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def pack16bit(n):
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return chr((n>>8)&0xFF) + chr(n&0xFF)
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def pack32bit(n):
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return chr((n>>24)&0xFF) + chr((n>>16)&0xFF) \
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+ chr((n>>8)&0xFF) + chr(n&0xFF)
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def unpack16bit(s):
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return (ord(s[0])<<8) | ord(s[1])
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def unpack32bit(s):
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return (ord(s[0])<<24) | (ord(s[1])<<16) \
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| (ord(s[2])<<8) | ord(s[3])
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def addr2bin(addr):
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if type(addr) == type(0):
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return addr
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bytes = string.splitfields(addr, '.')
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if len(bytes) != 4: raise ValueError, 'bad IP address'
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n = 0
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for byte in bytes: n = n<<8 | string.atoi(byte)
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return n
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def bin2addr(n):
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return '%d.%d.%d.%d' % ((n>>24)&0xFF, (n>>16)&0xFF,
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(n>>8)&0xFF, n&0xFF)
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# Packing class
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class Packer:
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def __init__(self):
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self.buf = ''
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self.index = {}
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def getbuf(self):
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return self.buf
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def addbyte(self, c):
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if len(c) != 1: raise TypeError, 'one character expected'
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self.buf = self.buf + c
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def addbytes(self, bytes):
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self.buf = self.buf + bytes
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def add16bit(self, n):
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self.buf = self.buf + pack16bit(n)
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def add32bit(self, n):
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self.buf = self.buf + pack32bit(n)
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def addaddr(self, addr):
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n = addr2bin(addr)
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self.buf = self.buf + pack32bit(n)
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def addstring(self, s):
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self.addbyte(chr(len(s)))
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self.addbytes(s)
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def addname(self, name):
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# Domain name packing (section 4.1.4)
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# Add a domain name to the buffer, possibly using pointers.
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# The case of the first occurrence of a name is preserved.
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# Redundant dots are ignored.
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list = []
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for label in string.splitfields(name, '.'):
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if label:
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if len(label) > 63:
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raise PackError, 'label too long'
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list.append(label)
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keys = []
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for i in range(len(list)):
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key = string.upper(string.joinfields(list[i:], '.'))
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keys.append(key)
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if self.index.has_key(key):
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pointer = self.index[key]
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break
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else:
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i = len(list)
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pointer = None
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# Do it into temporaries first so exceptions don't
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# mess up self.index and self.buf
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buf = ''
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offset = len(self.buf)
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index = []
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for j in range(i):
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label = list[j]
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n = len(label)
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if offset + len(buf) < 0x3FFF:
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index.append( (keys[j], offset + len(buf)) )
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else:
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print 'dnslib.Packer.addname:',
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print 'warning: pointer too big'
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buf = buf + (chr(n) + label)
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if pointer:
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buf = buf + pack16bit(pointer | 0xC000)
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else:
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buf = buf + '\0'
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self.buf = self.buf + buf
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for key, value in index:
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self.index[key] = value
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def dump(self):
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keys = self.index.keys()
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keys.sort()
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print '-'*40
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for key in keys:
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print '%20s %3d' % (key, self.index[key])
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print '-'*40
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space = 1
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for i in range(0, len(self.buf)+1, 2):
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if self.buf[i:i+2] == '**':
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if not space: print
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space = 1
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continue
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space = 0
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print '%4d' % i,
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for c in self.buf[i:i+2]:
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if ' ' < c < '\177':
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print ' %c' % c,
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else:
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print '%2d' % ord(c),
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print
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print '-'*40
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# Unpacking class
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UnpackError = 'dnslib.UnpackError' # Exception
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class Unpacker:
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def __init__(self, buf):
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self.buf = buf
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self.offset = 0
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def getbyte(self):
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c = self.buf[self.offset]
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self.offset = self.offset + 1
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return c
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def getbytes(self, n):
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s = self.buf[self.offset : self.offset + n]
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if len(s) != n: raise UnpackError, 'not enough data left'
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self.offset = self.offset + n
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return s
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def get16bit(self):
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return unpack16bit(self.getbytes(2))
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def get32bit(self):
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return unpack32bit(self.getbytes(4))
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def getaddr(self):
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return bin2addr(self.get32bit())
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def getstring(self):
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return self.getbytes(ord(self.getbyte()))
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def getname(self):
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# Domain name unpacking (section 4.1.4)
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c = self.getbyte()
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i = ord(c)
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if i & 0xC0 == 0xC0:
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d = self.getbyte()
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j = ord(d)
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pointer = ((i<<8) | j) & ~0xC000
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save_offset = self.offset
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try:
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self.offset = pointer
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domain = self.getname()
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finally:
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self.offset = save_offset
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return domain
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if i == 0:
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return ''
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domain = self.getbytes(i)
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remains = self.getname()
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if not remains:
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return domain
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else:
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return domain + '.' + remains
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# Test program for packin/unpacking (section 4.1.4)
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def testpacker():
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N = 25
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R = range(N)
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import timing
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# See section 4.1.4 of RFC 1035
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timing.start()
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for i in R:
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p = Packer()
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p.addbytes('*' * 20)
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p.addname('f.ISI.ARPA')
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p.addbytes('*' * 8)
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p.addname('Foo.F.isi.arpa')
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p.addbytes('*' * 18)
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p.addname('arpa')
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p.addbytes('*' * 26)
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p.addname('')
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timing.finish()
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print round(timing.milli() * 0.001 / N, 3), 'seconds per packing'
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p.dump()
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u = Unpacker(p.buf)
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u.getbytes(20)
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u.getname()
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u.getbytes(8)
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u.getname()
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u.getbytes(18)
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u.getname()
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u.getbytes(26)
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u.getname()
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timing.start()
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for i in R:
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u = Unpacker(p.buf)
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res = (u.getbytes(20),
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u.getname(),
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u.getbytes(8),
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u.getname(),
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u.getbytes(18),
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u.getname(),
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u.getbytes(26),
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u.getname())
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timing.finish()
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print round(timing.milli() * 0.001 / N, 3), 'seconds per unpacking'
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for item in res: print item
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# Pack/unpack RR toplevel format (section 3.2.1)
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class RRpacker(Packer):
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def __init__(self):
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Packer.__init__(self)
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self.rdstart = None
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def addRRheader(self, name, type, klass, ttl, *rest):
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self.addname(name)
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self.add16bit(type)
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self.add16bit(klass)
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self.add32bit(ttl)
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if rest:
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if res[1:]: raise TypeError, 'too many args'
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rdlength = rest[0]
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else:
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rdlength = 0
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self.add16bit(rdlength)
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self.rdstart = len(self.buf)
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def patchrdlength(self):
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rdlength = unpack16bit(self.buf[self.rdstart-2:self.rdstart])
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if rdlength == len(self.buf) - self.rdstart:
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return
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rdata = self.buf[self.rdstart:]
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save_buf = self.buf
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ok = 0
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try:
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self.buf = self.buf[:self.rdstart-2]
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self.add16bit(len(rdata))
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self.buf = self.buf + rdata
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ok = 1
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finally:
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if not ok: self.buf = save_buf
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def endRR(self):
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if self.rdstart is not None:
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self.patchrdlength()
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self.rdstart = None
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def getbuf(self):
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if self.rdstart is not None: self.patchrdlenth()
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return Packer.getbuf(self)
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# Standard RRs (section 3.3)
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def addCNAME(self, name, klass, ttl, cname):
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self.addRRheader(name, dnstype.CNAME, klass, ttl)
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self.addname(cname)
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self.endRR()
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def addHINFO(self, name, klass, ttl, cpu, os):
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self.addRRheader(name, dnstype.HINFO, klass, ttl)
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self.addstring(cpu)
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self.addstring(os)
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self.endRR()
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def addMX(self, name, klass, ttl, preference, exchange):
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self.addRRheader(name, dnstype.MX, klass, ttl)
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self.add16bit(preference)
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self.addname(exchange)
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self.endRR()
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def addNS(self, name, klass, ttl, nsdname):
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self.addRRheader(name, dnstype.NS, klass, ttl)
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self.addname(nsdname)
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self.endRR()
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def addPTR(self, name, klass, ttl, ptrdname):
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self.addRRheader(name, dnstype.PTR, klass, ttl)
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self.addname(ptrdname)
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self.endRR()
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def addSOA(self, name, klass, ttl,
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mname, rname, serial, refresh, retry, expire, minimum):
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self.addRRheader(name, dnstype.SOA, klass, ttl)
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self.addname(mname)
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self.addname(rname)
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self.add32bit(serial)
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self.add32bit(refresh)
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self.add32bit(retry)
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self.add32bit(expire)
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self.add32bit(minimum)
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self.endRR()
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def addTXT(self, name, klass, ttl, list):
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self.addRRheader(name, dnstype.TXT, klass, ttl)
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for txtdata in list:
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self.addstring(txtdata)
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self.endRR()
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# Internet specific RRs (section 3.4) -- class = IN
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def addA(self, name, ttl, address):
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self.addRRheader(name, dnstype.A, dnsclass.IN, ttl)
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self.addaddr(address)
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self.endRR()
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def addWKS(self, name, ttl, address, protocol, bitmap):
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self.addRRheader(name, dnstype.WKS, dnsclass.IN, ttl)
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self.addaddr(address)
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self.addbyte(chr(protocol))
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self.addbytes(bitmap)
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self.endRR()
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class RRunpacker(Unpacker):
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def __init__(self, buf):
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Unpacker.__init__(self, buf)
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self.rdend = None
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def getRRheader(self):
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name = self.getname()
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type = self.get16bit()
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klass = self.get16bit()
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ttl = self.get32bit()
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rdlength = self.get16bit()
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self.rdend = self.offset + rdlength
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return (name, type, klass, ttl, rdlength)
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def endRR(self):
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if self.offset != self.rdend:
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raise UnpackError, 'end of RR not reached'
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def getCNAMEdata(self):
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return self.getname()
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def getHINFOdata(self):
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return self.getstring(), self.getstring()
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def getMXdata(self):
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return self.get16bit(), self.getname()
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def getNSdata(self):
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return self.getname()
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def getPTRdata(self):
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return self.getname()
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def getSOAdata(self):
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return self.getname(), \
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self.getname(), \
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self.get32bit(), \
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self.get32bit(), \
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self.get32bit(), \
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self.get32bit(), \
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self.get32bit()
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def getTXTdata(self):
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list = []
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while self.offset != self.rdend:
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list.append(self.getstring())
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return list
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def getAdata(self):
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return self.getaddr()
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def getWKSdata(self):
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address = self.getaddr()
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protocol = ord(self.getbyte())
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bitmap = self.getbytes(self.rdend - self.offset)
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return address, protocol, bitmap
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# Pack/unpack Message Header (section 4.1)
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class Hpacker(Packer):
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def addHeader(self, id, qr, opcode, aa, tc, rd, ra, z, rcode,
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qdcount, ancount, nscount, arcount):
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self.add16bit(id)
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self.add16bit((qr&1)<<15 | (opcode*0xF)<<11 | (aa&1)<<10
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| (tc&1)<<9 | (rd&1)<<8 | (ra&1)<<7
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| (z&7)<<4 | (rcode&0xF))
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self.add16bit(qdcount)
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self.add16bit(ancount)
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self.add16bit(nscount)
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self.add16bit(arcount)
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class Hunpacker(Unpacker):
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def getHeader(self):
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id = self.get16bit()
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flags = self.get16bit()
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qr, opcode, aa, tc, rd, ra, z, rcode = (
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(flags>>15)&1,
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(flags>>11)&0xF,
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(flags>>10)&1,
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(flags>>9)&1,
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(flags>>8)&1,
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(flags>>7)&1,
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(flags>>4)&7,
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(flags>>0)&0xF)
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qdcount = self.get16bit()
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ancount = self.get16bit()
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nscount = self.get16bit()
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arcount = self.get16bit()
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return (id, qr, opcode, aa, tc, rd, ra, z, rcode,
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qdcount, ancount, nscount, arcount)
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# Pack/unpack Question (section 4.1.2)
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class Qpacker(Packer):
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def addQuestion(self, qname, qtype, qclass):
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self.addname(qname)
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self.add16bit(qtype)
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self.add16bit(qclass)
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class Qunpacker(Unpacker):
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def getQuestion(self):
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return self.getname(), self.get16bit(), self.get16bit()
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# Pack/unpack Message(section 4)
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# NB the order of the base classes is important for __init__()!
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class Mpacker(RRpacker, Qpacker, Hpacker):
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pass
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class Munpacker(RRunpacker, Qunpacker, Hunpacker):
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pass
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# Routines to print an unpacker to stdout, for debugging.
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# These affect the unpacker's current position!
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def dumpM(u):
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print 'HEADER:',
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(id, qr, opcode, aa, tc, rd, ra, z, rcode,
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qdcount, ancount, nscount, arcount) = u.getHeader()
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print 'id=%d,' % id,
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print 'qr=%d, opcode=%d, aa=%d, tc=%d, rd=%d, ra=%d, z=%d, rcode=%d,' \
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% (qr, opcode, aa, tc, rd, ra, z, rcode)
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if tc: print '*** response truncated! ***'
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if rcode: print '*** nonzero error code! (%d) ***' % rcode
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print ' qdcount=%d, ancount=%d, nscount=%d, arcount=%d' \
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% (qdcount, ancount, nscount, arcount)
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for i in range(qdcount):
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print 'QUESTION %d:' % i,
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dumpQ(u)
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for i in range(ancount):
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print 'ANSWER %d:' % i,
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dumpRR(u)
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for i in range(nscount):
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print 'AUTHORITY RECORD %d:' % i,
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dumpRR(u)
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for i in range(arcount):
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print 'ADDITIONAL RECORD %d:' % i,
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dumpRR(u)
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def dumpQ(u):
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qname, qtype, qclass = u.getQuestion()
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print 'qname=%s, qtype=%d(%s), qclass=%d(%s)' \
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% (qname,
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qtype, dnstype.typestr(qtype),
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qclass, dnsclass.classstr(qclass))
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def dumpRR(u):
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name, type, klass, ttl, rdlength = u.getRRheader()
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typename = dnstype.typestr(type)
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print 'name=%s, type=%d(%s), class=%d(%s), ttl=%d' \
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% (name,
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type, typename,
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klass, dnsclass.classstr(klass),
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ttl)
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mname = 'get%sdata' % typename
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if hasattr(u, mname):
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print ' formatted rdata:', getattr(u, mname)()
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else:
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print ' binary rdata:', u.getbytes(rdlength)
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# Test program
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def test():
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import sys
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import getopt
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import socket
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protocol = 'udp'
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server = 'cnri.reston.va.us' # XXX adapt this to your local
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port = 53
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opcode = dnsopcode.QUERY
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rd = 0
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qtype = dnstype.MX
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qname = 'cwi.nl'
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try:
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opts, args = getopt.getopt(sys.argv[1:], 'Trs:tu')
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if len(args) > 2: raise getopt.error, 'too many arguments'
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except getopt.error, msg:
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print msg
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print 'Usage: python dnslib.py',
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print '[-T] [-r] [-s server] [-t] [-u]',
|
|
print '[qtype [qname]]'
|
|
print '-T: run testpacker() and exit'
|
|
print '-r: recursion desired (default not)'
|
|
print '-s server: use server (default %s)' % server
|
|
print '-t: use TCP protocol'
|
|
print '-u: use UDP protocol (default)'
|
|
print 'qtype: query type (default %s)' % \
|
|
dnstype.typestr(qtype)
|
|
print 'qname: query name (default %s)' % qname
|
|
print 'Recognized qtype values:'
|
|
qtypes = dnstype.typemap.keys()
|
|
qtypes.sort()
|
|
n = 0
|
|
for qtype in qtypes:
|
|
n = n+1
|
|
if n >= 8: n = 1; print
|
|
print '%s = %d' % (dnstype.typemap[qtype], qtype),
|
|
print
|
|
sys.exit(2)
|
|
for o, a in opts:
|
|
if o == '-T': testpacker(); return
|
|
if o == '-t': protocol = 'tcp'
|
|
if o == '-u': protocol = 'udp'
|
|
if o == '-s': server = a
|
|
if o == '-r': rd = 1
|
|
if args[0:]:
|
|
try:
|
|
qtype = eval(string.upper(args[0]), dnstype.__dict__)
|
|
except (NameError, SyntaxError):
|
|
print 'bad query type:', `args[0]`
|
|
sys.exit(2)
|
|
if args[1:]:
|
|
qname = args[1]
|
|
if qtype == dnstype.AXFR:
|
|
print 'Query type AXFR, protocol forced to TCP'
|
|
protocol = 'tcp'
|
|
print 'QTYPE %d(%s)' % (qtype, dnstype.typestr(qtype))
|
|
m = Mpacker()
|
|
m.addHeader(0,
|
|
0, opcode, 0, 0, rd, 0, 0, 0,
|
|
1, 0, 0, 0)
|
|
m.addQuestion(qname, qtype, dnsclass.IN)
|
|
request = m.getbuf()
|
|
if protocol == 'udp':
|
|
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
|
|
s.connect((server, port))
|
|
s.send(request)
|
|
reply = s.recv(1024)
|
|
else:
|
|
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
|
|
s.connect((server, port))
|
|
s.send(pack16bit(len(request)) + request)
|
|
s.shutdown(1)
|
|
f = s.makefile('r')
|
|
header = f.read(2)
|
|
if len(header) < 2:
|
|
print '*** EOF ***'
|
|
return
|
|
count = unpack16bit(header)
|
|
reply = f.read(count)
|
|
if len(reply) != count:
|
|
print '*** Incomplete reply ***'
|
|
return
|
|
u = Munpacker(reply)
|
|
dumpM(u)
|
|
if protocol == 'tcp' and qtype == dnstype.AXFR:
|
|
while 1:
|
|
header = f.read(2)
|
|
if len(header) < 2:
|
|
print '========== EOF =========='
|
|
break
|
|
count = unpack16bit(header)
|
|
if not count:
|
|
print '========== ZERO COUNT =========='
|
|
break
|
|
print '========== NEXT =========='
|
|
reply = f.read(count)
|
|
if len(reply) != count:
|
|
print '*** Incomplete reply ***'
|
|
break
|
|
u = Munpacker(reply)
|
|
dumpM(u)
|
|
|
|
|
|
# Run test program when called as a script
|
|
|
|
if __name__ == '__main__':
|
|
test()
|