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# -*- test-case-name: twisted.names.test.test_hosts -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
hosts(5) support.
"""
from twisted.internet import defer
from twisted.internet.abstract import isIPAddress, isIPv6Address
from twisted.names import common, dns
from twisted.python import failure
from twisted.python.compat import nativeString
from twisted.python.filepath import FilePath
def searchFileForAll(hostsFile, name):
"""
Search the given file, which is in hosts(5) standard format, for addresses
associated with a given name.
@param hostsFile: The name of the hosts(5)-format file to search.
@type hostsFile: L{FilePath}
@param name: The name to search for.
@type name: C{bytes}
@return: L{None} if the name is not found in the file, otherwise a
C{str} giving the address in the file associated with the name.
"""
results = []
try:
lines = hostsFile.getContent().splitlines()
except BaseException:
return results
name = name.lower()
for line in lines:
idx = line.find(b"#")
if idx != -1:
line = line[:idx]
if not line:
continue
parts = line.split()
if name.lower() in [s.lower() for s in parts[1:]]:
try:
maybeIP = nativeString(parts[0])
except ValueError: # Not ASCII.
continue
if isIPAddress(maybeIP) or isIPv6Address(maybeIP):
results.append(maybeIP)
return results
def searchFileFor(file, name):
"""
Grep given file, which is in hosts(5) standard format, for an address
entry with a given name.
@param file: The name of the hosts(5)-format file to search.
@type file: C{str} or C{bytes}
@param name: The name to search for.
@type name: C{bytes}
@return: L{None} if the name is not found in the file, otherwise a
C{str} giving the first address in the file associated with
the name.
"""
addresses = searchFileForAll(FilePath(file), name)
if addresses:
return addresses[0]
return None
class Resolver(common.ResolverBase):
"""
A resolver that services hosts(5) format files.
"""
def __init__(self, file=b"/etc/hosts", ttl=60 * 60):
common.ResolverBase.__init__(self)
self.file = file
self.ttl = ttl
def _aRecords(self, name):
"""
Return a tuple of L{dns.RRHeader} instances for all of the IPv4
addresses in the hosts file.
"""
return tuple(
dns.RRHeader(name, dns.A, dns.IN, self.ttl, dns.Record_A(addr, self.ttl))
for addr in searchFileForAll(FilePath(self.file), name)
if isIPAddress(addr)
)
def _aaaaRecords(self, name):
"""
Return a tuple of L{dns.RRHeader} instances for all of the IPv6
addresses in the hosts file.
"""
return tuple(
dns.RRHeader(
name, dns.AAAA, dns.IN, self.ttl, dns.Record_AAAA(addr, self.ttl)
)
for addr in searchFileForAll(FilePath(self.file), name)
if isIPv6Address(addr)
)
def _respond(self, name, records):
"""
Generate a response for the given name containing the given result
records, or a failure if there are no result records.
@param name: The DNS name the response is for.
@type name: C{str}
@param records: A tuple of L{dns.RRHeader} instances giving the results
that will go into the response.
@return: A L{Deferred} which will fire with a three-tuple of result
records, authority records, and additional records, or which will
fail with L{dns.DomainError} if there are no result records.
"""
if records:
return defer.succeed((records, (), ()))
return defer.fail(failure.Failure(dns.DomainError(name)))
def lookupAddress(self, name, timeout=None):
"""
Read any IPv4 addresses from C{self.file} and return them as
L{Record_A} instances.
"""
name = dns.domainString(name)
return self._respond(name, self._aRecords(name))
def lookupIPV6Address(self, name, timeout=None):
"""
Read any IPv6 addresses from C{self.file} and return them as
L{Record_AAAA} instances.
"""
name = dns.domainString(name)
return self._respond(name, self._aaaaRecords(name))
# Someday this should include IPv6 addresses too, but that will cause
# problems if users of the API (mainly via getHostByName) aren't updated to
# know about IPv6 first.
# FIXME - getHostByName knows about IPv6 now.
lookupAllRecords = lookupAddress
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