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#--
#Copyright 2007 Nominet UK
#
#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.
#++
## This class implements a cache.
# It stores data under qname-qclass-qtype tuples.
# Each tuple indexes a CacheData object (which
# stores a Message, and an expiration).
# If a new Message is stored to a tuple, it will
# overwrite the previous Message.
# When a Message is retrieved from the cache, the header
# and ttls will be "fixed" - i.e. AA cleared, etc.
#@TODO@ Max size for cache?
module Dnsruby
class Cache # :nodoc: all
def initialize()
@cache = Hash.new
@mutex = Mutex.new
end
def cache
@cache
end
def clear()
@mutex.synchronize {
@cache = Hash.new
}
end
def length
return @cache.length
end
def add(message)
q = message.question[0]
key = CacheKey.new(q.qname, q.qtype, q.qclass).to_s
data = CacheData.new(message)
@mutex.synchronize {
if (@cache[key])
TheLog.debug("CACHE REPLACE : #{q.qname}, #{q.qtype}\n")
else
TheLog.debug("CACHE ADD : #{q.qname}, #{q.qtype}\n")
end
@cache[key] = data
}
end
# This method "fixes up" the response, so that the header and ttls are OK
# The resolver will still need to copy the flags and ID across from the query
def find(qname, qtype, qclass = Classes.IN)
# print "CACHE find : #{qname}, #{qtype}\n"
qn = Name.create(qname)
qn.absolute = true
key = CacheKey.new(qn, qtype, qclass).to_s
@mutex.synchronize {
data = @cache[key]
if (!data)
# print "CACHE lookup failed\n"
return nil
end
if (data.expiration <= Time.now.to_i)
@cache.delete(key)
TheLog.debug("CACHE lookup stale\n")
return nil
end
m = data.message
TheLog.debug("CACHE found\n")
return m
}
end
def Cache.delete(qname, qtype, qclass = Classes.IN)
key = CacheKey.new(qname, qtype, qclass)
@mutex.synchronize {
@cache.delete(key)
}
end
class CacheKey # :nodoc: all
attr_accessor :qname, :qtype, :qclass
def initialize(*args)
self.qclass = Classes.IN
if (args.length > 0)
self.qname = Name.create(args[0])
self.qname.absolute = true
if (args.length > 1)
self.qtype = Types.new(args[1])
if (args.length > 2)
self.qclass = Classes.new(args[2])
end
end
end
end
def to_s
return "#{qname.inspect.downcase} #{qclass} #{qtype}"
end
end
class CacheData # :nodoc: all
attr_reader :expiration
def message=(m)
@expiration = get_expiration(m)
@message = Message.decode(m.encode)
@message.cached = true
end
def message
m = Message.decode(@message.encode)
m.cached = true
# @TODO@ What do we do about answerfrom, answersize, etc.?
m.header.aa = false # Anything else to do here?
# Fix up TTLs!!
offset = (Time.now - @time_stored).to_i
m.each_resource {|rr|
next if rr.type == Types::OPT
rr.ttl = rr.ttl - offset
}
return m
end
def get_expiration(m)
# Find the minimum ttl of any of the rrsets
min_ttl = 9999999
m.each_section {|section|
section.rrsets.each {|rrset|
if (rrset.ttl < min_ttl)
min_ttl = rrset.ttl
end
}
}
if (min_ttl == 9999999)
return 0
end
return (Time.now.to_i + min_ttl)
end
def initialize(*args)
@expiration = 0
@time_stored = Time.now.to_i
self.message=(args[0])
end
def to_s
return "#{self.message}"
end
end
end
end
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