commit 304e792dcea0a469441117ac6a9b8764477eb14d
Author: Damian Johnson <atagar(a)torproject.org>
Date: Fri Oct 18 11:58:00 2013 -0700
Dropping hostnames module
In an earlier version we supported hostname resolution, but this leaked tor
connecion information to our DNS resolver (very, very bad). Since then we've
had the util for performing lookups but it's unused by the codebase.
I'd love to add a capability like this back in when we can do so safely, but
there's little point in keeping an unused module.
---
arm/starter.py | 3 -
arm/util/__init__.py | 2 +-
arm/util/hostnames.py | 394 -------------------------------------------------
armrc.sample | 16 --
4 files changed, 1 insertion(+), 414 deletions(-)
diff --git a/arm/starter.py b/arm/starter.py
index d7c68f9..94bfa6c 100644
--- a/arm/starter.py
+++ b/arm/starter.py
@@ -19,7 +19,6 @@ import arm
import arm.controller
import arm.logPanel
import arm.util.connections
-import arm.util.hostnames
import arm.util.panel
import arm.util.sysTools
import arm.util.torConfig
@@ -288,8 +287,6 @@ def _shutdown_daemons():
# joins on utility daemon threads - this might take a moment since the
# internal threadpools being joined might be sleeping
- arm.util.hostnames.stop()
-
resourceTrackers = arm.util.sysTools.RESOURCE_TRACKERS.values()
resolver = arm.util.connections.get_resolver() if arm.util.connections.get_resolver().is_alive() else None
diff --git a/arm/util/__init__.py b/arm/util/__init__.py
index 33897a1..9fa96e6 100644
--- a/arm/util/__init__.py
+++ b/arm/util/__init__.py
@@ -4,5 +4,5 @@ application's status, making cross platform system calls, parsing tor data,
and safely working with curses (hiding some of the gory details).
"""
-__all__ = ["connections", "hostnames", "panel", "sysTools", "textInput", "torConfig", "torTools", "uiTools"]
+__all__ = ["connections", "panel", "sysTools", "textInput", "torConfig", "torTools", "uiTools"]
diff --git a/arm/util/hostnames.py b/arm/util/hostnames.py
deleted file mode 100644
index a829f9f..0000000
--- a/arm/util/hostnames.py
+++ /dev/null
@@ -1,394 +0,0 @@
-"""
-Service providing hostname resolution via reverse DNS lookups. This provides
-both resolution via a thread pool (looking up several addresses at a time) and
-caching of the results. If used, it's advisable that this service is stopped
-when it's no longer needed. All calls are both non-blocking and thread safe.
-
-Be aware that this relies on querying the system's DNS servers, possibly
-leaking the requested addresses to third parties.
-"""
-
-# The only points of concern in terms of concurrent calls are the RESOLVER and
-# RESOLVER.resolvedCache. This services provides (mostly) non-locking thread
-# safety via the following invariants:
-# - Resolver and cache instances are non-destructible
-# Nothing can be removed or invalidated. Rather, halting resolvers and
-# trimming the cache are done via reassignment (pointing the RESOLVER or
-# RESOLVER.resolvedCache to another copy).
-# - Functions create and use local references to the resolver and its cache
-# This is for consistency (ie, all operations are done on the same resolver
-# or cache instance regardless of concurrent assignments). Usually it's
-# assigned to a local variable called 'resolverRef' or 'cacheRef'.
-# - Locks aren't necessary, but used to help in the following cases:
-# - When assigning to the RESOLVER (to avoid orphaned instances with
-# running thread pools).
-# - When adding/removing from the cache (prevents workers from updating
-# an outdated cache reference).
-
-import time
-import socket
-import threading
-import itertools
-import Queue
-import distutils.sysconfig
-
-from stem.util import conf, log, system
-
-RESOLVER = None # hostname resolver (service is stopped if None)
-RESOLVER_LOCK = threading.RLock() # regulates assignment to the RESOLVER
-RESOLVER_COUNTER = itertools.count() # atomic counter, providing the age for new entries (for trimming)
-DNS_ERROR_CODES = ("1(FORMERR)", "2(SERVFAIL)", "3(NXDOMAIN)", "4(NOTIMP)", "5(REFUSED)", "6(YXDOMAIN)",
- "7(YXRRSET)", "8(NXRRSET)", "9(NOTAUTH)", "10(NOTZONE)", "16(BADVERS)")
-
-def conf_handler(key, value):
- if key == "queries.hostnames.poolSize":
- return max(1, value)
- elif key == "cache.hostnames.size":
- return max(100, value)
- elif key == "cache.hostnames.trimSize":
- return max(10, value)
- elif key == "cache.hostnames.trimSize":
- return min(value, CONFIG["cache.hostnames.size"] / 2)
-
-CONFIG = conf.config_dict("arm", {
- "queries.hostnames.poolSize": 5,
- "queries.hostnames.useSocketModule": False,
- "cache.hostnames.size": 700000,
- "cache.hostnames.trimSize": 200000,
-}, conf_handler)
-
-def start():
- """
- Primes the service to start resolving addresses. Calling this explicitly is
- not necessary since resolving any address will start the service if it isn't
- already running.
- """
-
- global RESOLVER
- RESOLVER_LOCK.acquire()
- if not isRunning(): RESOLVER = _Resolver()
- RESOLVER_LOCK.release()
-
-def stop():
- """
- Halts further resolutions and stops the service. This joins on the resolver's
- thread pool and clears its lookup cache.
- """
-
- global RESOLVER
- RESOLVER_LOCK.acquire()
- if isRunning():
- # Releases resolver instance. This is done first so concurrent calls to the
- # service won't try to use it. However, using a halted instance is fine and
- # all calls currently in progress can still proceed on the RESOLVER's local
- # references.
- resolverRef, RESOLVER = RESOLVER, None
-
- # joins on its worker thread pool
- resolverRef.stop()
- for t in resolverRef.threadPool: t.join()
- RESOLVER_LOCK.release()
-
-def setPaused(isPause):
- """
- Allows or prevents further hostname resolutions (resolutions still make use of
- cached entries if available). This starts the service if it isn't already
- running.
-
- Arguments:
- isPause - puts a freeze on further resolutions if true, allows them to
- continue otherwise
- """
-
- # makes sure a running resolver is set with the pausing setting
- RESOLVER_LOCK.acquire()
- start()
- RESOLVER.isPaused = isPause
- RESOLVER_LOCK.release()
-
-def isRunning():
- """
- Returns True if the service is currently running, False otherwise.
- """
-
- return bool(RESOLVER)
-
-def isPaused():
- """
- Returns True if the resolver is paused, False otherwise.
- """
-
- resolverRef = RESOLVER
- if resolverRef: return resolverRef.isPaused
- else: return False
-
-def isResolving():
- """
- Returns True if addresses are currently waiting to be resolved, False
- otherwise.
- """
-
- resolverRef = RESOLVER
- if resolverRef: return not resolverRef.unresolvedQueue.empty()
- else: return False
-
-def resolve(ipAddr, timeout = 0, suppressIOExc = True):
- """
- Provides the hostname associated with a given IP address. By default this is
- a non-blocking call, fetching cached results if available and queuing the
- lookup if not. This provides None if the lookup fails (with a suppressed
- exception) or timeout is reached without resolution. This starts the service
- if it isn't already running.
-
- If paused this simply returns the cached reply (no request is queued and
- returns immediately regardless of the timeout argument).
-
- Requests may raise the following exceptions:
- - ValueError - address was unresolvable (includes the DNS error response)
- - IOError - lookup failed due to os or network issues (suppressed by default)
-
- Arguments:
- ipAddr - ip address to be resolved
- timeout - maximum duration to wait for a resolution (blocks to
- completion if None)
- suppressIOExc - suppresses lookup errors and re-runs failed calls if true,
- raises otherwise
- """
-
- # starts the service if it isn't already running (making sure we have an
- # instance in a thread safe fashion before continuing)
- resolverRef = RESOLVER
- if resolverRef == None:
- RESOLVER_LOCK.acquire()
- start()
- resolverRef = RESOLVER
- RESOLVER_LOCK.release()
-
- if resolverRef.isPaused:
- # get cache entry, raising if an exception and returning if a hostname
- cacheRef = resolverRef.resolvedCache
-
- if ipAddr in cacheRef:
- entry = cacheRef[ipAddr][0]
- if suppressIOExc and type(entry) == IOError: return None
- elif isinstance(entry, Exception): raise entry
- else: return entry
- else: return None
- elif suppressIOExc:
- # if resolver has cached an IOError then flush the entry (this defaults to
- # suppression since these error may be transient)
- cacheRef = resolverRef.resolvedCache
- flush = ipAddr in cacheRef and type(cacheRef[ipAddr]) == IOError
-
- try: return resolverRef.getHostname(ipAddr, timeout, flush)
- except IOError: return None
- else: return resolverRef.getHostname(ipAddr, timeout)
-
-def getPendingCount():
- """
- Provides an approximate count of the number of addresses still pending
- resolution.
- """
-
- resolverRef = RESOLVER
- if resolverRef: return resolverRef.unresolvedQueue.qsize()
- else: return 0
-
-def getRequestCount():
- """
- Provides the number of resolutions requested since starting the service.
- """
-
- resolverRef = RESOLVER
- if resolverRef: return resolverRef.totalResolves
- else: return 0
-
-def _resolveViaSocket(ipAddr):
- """
- Performs hostname lookup via the socket module's gethostbyaddr function. This
- raises an IOError if the lookup fails (network issue) and a ValueError in
- case of DNS errors (address unresolvable).
-
- Arguments:
- ipAddr - ip address to be resolved
- """
-
- try:
- # provides tuple like: ('localhost', [], ['127.0.0.1'])
- return socket.gethostbyaddr(ipAddr)[0]
- except socket.herror, exc:
- if exc[0] == 2: raise IOError(exc[1]) # "Host name lookup failure"
- else: raise ValueError(exc[1]) # usually "Unknown host"
- except socket.error, exc: raise ValueError(exc[1])
-
-def _resolveViaHost(ipAddr):
- """
- Performs a host lookup for the given IP, returning the resolved hostname.
- This raises an IOError if the lookup fails (os or network issue), and a
- ValueError in the case of DNS errors (address is unresolvable).
-
- Arguments:
- ipAddr - ip address to be resolved
- """
-
- hostname = system.call("host %s" % ipAddr)[0].split()[-1:][0]
-
- if hostname == "reached":
- # got message: ";; connection timed out; no servers could be reached"
- raise IOError("lookup timed out")
- elif hostname in DNS_ERROR_CODES:
- # got error response (can't do resolution on address)
- raise ValueError("address is unresolvable: %s" % hostname)
- else:
- # strips off ending period and returns hostname
- return hostname[:-1]
-
-class _Resolver():
- """
- Performs reverse DNS resolutions. Lookups are a network bound operation so
- this spawns a pool of worker threads to do several at a time in parallel.
- """
-
- def __init__(self):
- # IP Address => (hostname/error, age), resolution failures result in a
- # ValueError with the lookup's status
- self.resolvedCache = {}
-
- self.resolvedLock = threading.RLock() # governs concurrent access when modifying resolvedCache
- self.unresolvedQueue = Queue.Queue() # unprocessed lookup requests
- self.recentQueries = [] # recent resolution requests to prevent duplicate requests
- self.threadPool = [] # worker threads that process requests
- self.totalResolves = 0 # counter for the total number of addresses queried to be resolved
- self.isPaused = False # prevents further resolutions if true
- self.halt = False # if true, tells workers to stop
- self.cond = threading.Condition() # used for pausing threads
-
- # Determines if resolutions are made using os 'host' calls or python's
- # 'socket.gethostbyaddr'. The following checks if the system has the
- # gethostbyname_r function, which determines if python resolutions can be
- # done in parallel or not. If so, this is preferable.
- isSocketResolutionParallel = distutils.sysconfig.get_config_var("HAVE_GETHOSTBYNAME_R")
- self.useSocketResolution = CONFIG["queries.hostnames.useSocketModule"] and isSocketResolutionParallel
-
- for _ in range(CONFIG["queries.hostnames.poolSize"]):
- t = threading.Thread(target = self._workerLoop)
- t.setDaemon(True)
- t.start()
- self.threadPool.append(t)
-
- def getHostname(self, ipAddr, timeout, flushCache = False):
- """
- Provides the hostname, queuing the request and returning None if the
- timeout is reached before resolution. If a problem's encountered then this
- either raises an IOError (for os and network issues) or ValueError (for DNS
- resolution errors).
-
- Arguments:
- ipAddr - ip address to be resolved
- timeout - maximum duration to wait for a resolution (blocks to
- completion if None)
- flushCache - if true the cache is skipped and address re-resolved
- """
-
- # if outstanding requests are done then clear recentQueries to allow
- # entries removed from the cache to be re-run
- if self.unresolvedQueue.empty(): self.recentQueries = []
-
- # copies reference cache (this is important in case the cache is trimmed
- # during this call)
- cacheRef = self.resolvedCache
-
- if not flushCache and ipAddr in cacheRef:
- # cached response is available - raise if an error, return if a hostname
- response = cacheRef[ipAddr][0]
- if isinstance(response, Exception): raise response
- else: return response
- elif flushCache or ipAddr not in self.recentQueries:
- # new request - queue for resolution
- self.totalResolves += 1
- self.recentQueries.append(ipAddr)
- self.unresolvedQueue.put(ipAddr)
-
- # periodically check cache if requester is willing to wait
- if timeout == None or timeout > 0:
- startTime = time.time()
-
- while timeout == None or time.time() - startTime < timeout:
- if ipAddr in cacheRef:
- # address was resolved - raise if an error, return if a hostname
- response = cacheRef[ipAddr][0]
- if isinstance(response, Exception): raise response
- else: return response
- else: time.sleep(0.1)
-
- return None # timeout reached without resolution
-
- def stop(self):
- """
- Halts further resolutions and terminates the thread.
- """
-
- self.cond.acquire()
- self.halt = True
- self.cond.notifyAll()
- self.cond.release()
-
- def _workerLoop(self):
- """
- Simple producer-consumer loop followed by worker threads. This takes
- addresses from the unresolvedQueue, attempts to look up its hostname, and
- adds its results or the error to the resolved cache. Resolver reference
- provides shared resources used by the thread pool.
- """
-
- while not self.halt:
- # if resolver is paused then put a hold on further resolutions
- if self.isPaused:
- self.cond.acquire()
- if not self.halt: self.cond.wait(1)
- self.cond.release()
- continue
-
- # snags next available ip, timeout is because queue can't be woken up
- # when 'halt' is set
- try: ipAddr = self.unresolvedQueue.get_nowait()
- except Queue.Empty:
- # no elements ready, wait a little while and try again
- self.cond.acquire()
- if not self.halt: self.cond.wait(1)
- self.cond.release()
- continue
- if self.halt: break
-
- try:
- if self.useSocketResolution: result = _resolveViaSocket(ipAddr)
- else: result = _resolveViaHost(ipAddr)
- except IOError, exc: result = exc # lookup failed
- except ValueError, exc: result = exc # dns error
-
- self.resolvedLock.acquire()
- self.resolvedCache[ipAddr] = (result, RESOLVER_COUNTER.next())
-
- # trim cache if excessively large (clearing out oldest entries)
- if len(self.resolvedCache) > CONFIG["cache.hostnames.size"]:
- # Providing for concurrent, non-blocking calls require that entries are
- # never removed from the cache, so this creates a new, trimmed version
- # instead.
-
- # determines minimum age of entries to be kept
- currentCount = RESOLVER_COUNTER.next()
- newCacheSize = CONFIG["cache.hostnames.size"] - CONFIG["cache.hostnames.trimSize"]
- threshold = currentCount - newCacheSize
- newCache = {}
-
- msg = "trimming hostname cache from %i entries to %i" % (len(self.resolvedCache), newCacheSize)
- log.info(msg)
-
- # checks age of each entry, adding to toDelete if too old
- for ipAddr, entry in self.resolvedCache.iteritems():
- if entry[1] >= threshold: newCache[ipAddr] = entry
-
- self.resolvedCache = newCache
-
- self.resolvedLock.release()
-
diff --git a/armrc.sample b/armrc.sample
index 37e4bd4..682db5e 100644
--- a/armrc.sample
+++ b/armrc.sample
@@ -250,23 +250,7 @@ features.connection.showColumn.nickname true
features.connection.showColumn.destination true
features.connection.showColumn.expandedIp true
-# Thread pool size for hostname resolutions
-# Determines the maximum number of concurrent requests. Upping this to around
-# thirty or so seems to be problematic, causing intermittently seizing.
-
-queries.hostnames.poolSize 5
-
-# Method of resolving hostnames
-# If true, uses python's internal "socket.gethostbyaddr" to resolve addresses
-# rather than the host command. This is ignored if the system's unable to make
-# parallel requests. Resolving this way seems to be much slower than host calls
-# in practice.
-
-queries.hostnames.useSocketModule false
-
# Caching parameters
-cache.hostnames.size 700000
-cache.hostnames.trimSize 200000
cache.logPanel.size 1000
cache.armLog.size 1000
cache.armLog.trimSize 200
