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jblitzar
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github-python-corpus

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def dns_ptr(self, i):
"""Get a list of domain names for an IP address."""
return self.dns('%s.%s.arpa'%(reverse_dots(i),self.v), 'PTR')
# We have to be careful which additional DNS RRs we cache. For
# instance, PTR records are controlled by the connecting IP, and they
# could poison our local cache with bogus A and MX records.
SAFE2CACHE = {
('MX','A'): None,
('MX','MX'): None,
('CNAME','A'): None,
('A','A'): None,
('AAAA','AAAA'): None,
('PTR','PTR'): None,
('TXT','TXT'): None,
('SPF','SPF'): None
}
# FIXME: move to anydns
#
# All types return a list of values. TXT/SPF values are
# in turn a list of strings (as bytes), as DNS supports long
# strings as shorter strings which must be concatenated.
#
def dns(self, name, qtype, cnames=None, ignore_void=False):
"""DNS query.
If the result is in cache, return that. Otherwise pull the
result from DNS, and cache ALL answers, so additional info
is available for further queries later.
CNAMEs are followed.
If there is no data, [] is returned.
pre: qtype in ['A', 'AAAA', 'MX', 'PTR', 'TXT', 'SPF']
post: isinstance(__return__, types.ListType)
Examples:
>>> c = query(s='strong-bad@email.example.com',
... h='parallel.kitterman.org',i='192.0.2.123')
>>> "".join( chr(x) for x in bytearray(c.dns('parallel.kitterman.org', 'TXT')[0][0]) )
'v=spf1 include:long.kitterman.org include:cname.kitterman.org -all'
"""
if not name:
raise Exception('Invalid query')
name = str(name)
if name.endswith('.'): name = name[:-1]
if not reduce(lambda x, y: x and 0 < len(y) < 64, name.split('.'), True):
return [] # invalid DNS name (too long or empty)
name = name.lower()
result = self.cache.get( (name, qtype), [])
if result: return result
cnamek = (name,'CNAME')
cname = self.cache.get( cnamek )
debug = self.verbose # and name.startswith('cname.')
if cname:
cname = cname[0]
else:
safe2cache = query.SAFE2CACHE
if self.querytime < 0:
raise TempError('DNS Error: exceeded max query lookup time')
if self.querytime < self.timeout and self.querytime > 0:
timeout = self.querytime
else:
timeout = self.timeout
timethen = time.time()
for k, v in DNSLookup(name, qtype, self.strict, timeout):
if debug: print('result=',k,v)
# Force case insensitivity in cache, DNS servers often
# return random case in domain part of answers.
k = (k[0].lower(), k[1])
if k == cnamek:
cname = v
result = self.cache.get( (cname, qtype), [])
if result: break
if k[1] == 'CNAME' or (qtype,k[1]) in safe2cache:
if debug: print('addcache=',k,v)
self.cache.setdefault(k, []).append(v)
#if ans and qtype == k[1]:
# self.cache.setdefault((name,qtype), []).append(v)
result = self.cache.get( (name, qtype), [])
if self.querytime > 0:
self.querytime = self.querytime - (time.time()-timethen)
if not result and cname:
if not cnames:
cnames = {}
elif len(cnames) >= MAX_CNAME:
#return result # if too many == NX_DOMAIN
raise PermError('Length of CNAME chain exceeds %d' % MAX_CNAME)
cnames[name] = cname
if cname.lower().rstrip('.') in cnames:
if self.strict > 1: raise AmbiguityWarning('CNAME loop', cname)
else:
result = self.dns(cname, qtype, cnames=cnames)
if result:
self.cache[(name,qtype)] = result