MatrixSynapse/synapse/http/endpoint.py

364 lines
12 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket Ltd
#
# 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.
import collections
import logging
import random
import re
import time
from twisted.internet import defer
from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
from twisted.internet.error import ConnectError
from twisted.names import client, dns
from twisted.names.error import DNSNameError, DomainError
logger = logging.getLogger(__name__)
SERVER_CACHE = {}
# our record of an individual server which can be tried to reach a destination.
#
# "host" is the hostname acquired from the SRV record. Except when there's
# no SRV record, in which case it is the original hostname.
_Server = collections.namedtuple(
"_Server", "priority weight host port expires"
)
def parse_server_name(server_name):
"""Split a server name into host/port parts.
Args:
server_name (str): server name to parse
Returns:
Tuple[str, int|None]: host/port parts.
Raises:
ValueError if the server name could not be parsed.
"""
try:
if server_name[-1] == ']':
# ipv6 literal, hopefully
return server_name, None
domain_port = server_name.rsplit(":", 1)
domain = domain_port[0]
port = int(domain_port[1]) if domain_port[1:] else None
return domain, port
except Exception:
raise ValueError("Invalid server name '%s'" % server_name)
VALID_HOST_REGEX = re.compile(
"\\A[0-9a-zA-Z.-]+\\Z",
)
def parse_and_validate_server_name(server_name):
"""Split a server name into host/port parts and do some basic validation.
Args:
server_name (str): server name to parse
Returns:
Tuple[str, int|None]: host/port parts.
Raises:
ValueError if the server name could not be parsed.
"""
host, port = parse_server_name(server_name)
# these tests don't need to be bulletproof as we'll find out soon enough
# if somebody is giving us invalid data. What we *do* need is to be sure
# that nobody is sneaking IP literals in that look like hostnames, etc.
# look for ipv6 literals
if host[0] == '[':
if host[-1] != ']':
raise ValueError("Mismatched [...] in server name '%s'" % (
server_name,
))
return host, port
# otherwise it should only be alphanumerics.
if not VALID_HOST_REGEX.match(host):
raise ValueError("Server name '%s' contains invalid characters" % (
server_name,
))
return host, port
def matrix_federation_endpoint(reactor, destination, tls_client_options_factory=None,
timeout=None):
"""Construct an endpoint for the given matrix destination.
Args:
reactor: Twisted reactor.
destination (unicode): The name of the server to connect to.
tls_client_options_factory
(synapse.crypto.context_factory.ClientTLSOptionsFactory):
Factory which generates TLS options for client connections.
timeout (int): connection timeout in seconds
"""
domain, port = parse_server_name(destination)
endpoint_kw_args = {}
if timeout is not None:
endpoint_kw_args.update(timeout=timeout)
if tls_client_options_factory is None:
transport_endpoint = HostnameEndpoint
default_port = 8008
else:
# the SNI string should be the same as the Host header, minus the port.
# as per https://github.com/matrix-org/synapse/issues/2525#issuecomment-336896777,
# the Host header and SNI should therefore be the server_name of the remote
# server.
tls_options = tls_client_options_factory.get_options(domain)
def transport_endpoint(reactor, host, port, timeout):
return wrapClientTLS(
tls_options,
HostnameEndpoint(reactor, host, port, timeout=timeout),
)
default_port = 8448
if port is None:
return _WrappingEndpointFac(SRVClientEndpoint(
reactor, "matrix", domain, protocol="tcp",
default_port=default_port, endpoint=transport_endpoint,
endpoint_kw_args=endpoint_kw_args
), reactor)
else:
return _WrappingEndpointFac(transport_endpoint(
reactor, domain, port, **endpoint_kw_args
), reactor)
class _WrappingEndpointFac(object):
def __init__(self, endpoint_fac, reactor):
self.endpoint_fac = endpoint_fac
self.reactor = reactor
@defer.inlineCallbacks
def connect(self, protocolFactory):
conn = yield self.endpoint_fac.connect(protocolFactory)
conn = _WrappedConnection(conn, self.reactor)
defer.returnValue(conn)
class _WrappedConnection(object):
"""Wraps a connection and calls abort on it if it hasn't seen any action
for 2.5-3 minutes.
"""
__slots__ = ["conn", "last_request"]
def __init__(self, conn, reactor):
object.__setattr__(self, "conn", conn)
object.__setattr__(self, "last_request", time.time())
self._reactor = reactor
def __getattr__(self, name):
return getattr(self.conn, name)
def __setattr__(self, name, value):
setattr(self.conn, name, value)
def _time_things_out_maybe(self):
# We use a slightly shorter timeout here just in case the callLater is
# triggered early. Paranoia ftw.
# TODO: Cancel the previous callLater rather than comparing time.time()?
if time.time() - self.last_request >= 2.5 * 60:
self.abort()
# Abort the underlying TLS connection. The abort() method calls
# loseConnection() on the TLS connection which tries to
# shutdown the connection cleanly. We call abortConnection()
# since that will promptly close the TLS connection.
#
# In Twisted >18.4; the TLS connection will be None if it has closed
# which will make abortConnection() throw. Check that the TLS connection
# is not None before trying to close it.
if self.transport.getHandle() is not None:
self.transport.abortConnection()
def request(self, request):
self.last_request = time.time()
# Time this connection out if we haven't send a request in the last
# N minutes
# TODO: Cancel the previous callLater?
self._reactor.callLater(3 * 60, self._time_things_out_maybe)
d = self.conn.request(request)
def update_request_time(res):
self.last_request = time.time()
# TODO: Cancel the previous callLater?
self._reactor.callLater(3 * 60, self._time_things_out_maybe)
return res
d.addCallback(update_request_time)
return d
class SRVClientEndpoint(object):
"""An endpoint which looks up SRV records for a service.
Cycles through the list of servers starting with each call to connect
picking the next server.
Implements twisted.internet.interfaces.IStreamClientEndpoint.
"""
def __init__(self, reactor, service, domain, protocol="tcp",
default_port=None, endpoint=HostnameEndpoint,
endpoint_kw_args={}):
self.reactor = reactor
self.service_name = "_%s._%s.%s" % (service, protocol, domain)
if default_port is not None:
self.default_server = _Server(
host=domain,
port=default_port,
priority=0,
weight=0,
expires=0,
)
else:
self.default_server = None
self.endpoint = endpoint
self.endpoint_kw_args = endpoint_kw_args
self.servers = None
self.used_servers = None
@defer.inlineCallbacks
def fetch_servers(self):
self.used_servers = []
self.servers = yield resolve_service(self.service_name)
def pick_server(self):
if not self.servers:
if self.used_servers:
self.servers = self.used_servers
self.used_servers = []
self.servers.sort()
elif self.default_server:
return self.default_server
else:
raise ConnectError(
"No server available for %s" % self.service_name
)
# look for all servers with the same priority
min_priority = self.servers[0].priority
weight_indexes = list(
(index, server.weight + 1)
for index, server in enumerate(self.servers)
if server.priority == min_priority
)
total_weight = sum(weight for index, weight in weight_indexes)
target_weight = random.randint(0, total_weight)
for index, weight in weight_indexes:
target_weight -= weight
if target_weight <= 0:
server = self.servers[index]
# XXX: this looks totally dubious:
#
# (a) we never reuse a server until we have been through
# all of the servers at the same priority, so if the
# weights are A: 100, B:1, we always do ABABAB instead of
# AAAA...AAAB (approximately).
#
# (b) After using all the servers at the lowest priority,
# we move onto the next priority. We should only use the
# second priority if servers at the top priority are
# unreachable.
#
del self.servers[index]
self.used_servers.append(server)
return server
@defer.inlineCallbacks
def connect(self, protocolFactory):
if self.servers is None:
yield self.fetch_servers()
server = self.pick_server()
logger.info("Connecting to %s:%s", server.host, server.port)
endpoint = self.endpoint(
self.reactor, server.host, server.port, **self.endpoint_kw_args
)
connection = yield endpoint.connect(protocolFactory)
defer.returnValue(connection)
@defer.inlineCallbacks
def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=time):
cache_entry = cache.get(service_name, None)
if cache_entry:
if all(s.expires > int(clock.time()) for s in cache_entry):
servers = list(cache_entry)
defer.returnValue(servers)
servers = []
try:
try:
answers, _, _ = yield dns_client.lookupService(service_name)
except DNSNameError:
defer.returnValue([])
if (len(answers) == 1
and answers[0].type == dns.SRV
and answers[0].payload
and answers[0].payload.target == dns.Name(b'.')):
raise ConnectError("Service %s unavailable" % service_name)
for answer in answers:
if answer.type != dns.SRV or not answer.payload:
continue
payload = answer.payload
servers.append(_Server(
host=str(payload.target),
port=int(payload.port),
priority=int(payload.priority),
weight=int(payload.weight),
expires=int(clock.time()) + answer.ttl,
))
servers.sort()
cache[service_name] = list(servers)
except DomainError as e:
# We failed to resolve the name (other than a NameError)
# Try something in the cache, else rereaise
cache_entry = cache.get(service_name, None)
if cache_entry:
logger.warn(
"Failed to resolve %r, falling back to cache. %r",
service_name, e
)
servers = list(cache_entry)
else:
raise e
defer.returnValue(servers)