mirror of
https://mau.dev/maunium/synapse.git
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228 lines
7.6 KiB
Python
228 lines
7.6 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014-2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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import random
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import re
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from twisted.internet import defer
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from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
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from twisted.internet.error import ConnectError
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from synapse.http.federation.srv_resolver import Server, resolve_service
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logger = logging.getLogger(__name__)
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def parse_server_name(server_name):
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"""Split a server name into host/port parts.
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Args:
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server_name (str): server name to parse
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Returns:
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Tuple[str, int|None]: host/port parts.
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Raises:
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ValueError if the server name could not be parsed.
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"""
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try:
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if server_name[-1] == ']':
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# ipv6 literal, hopefully
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return server_name, None
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domain_port = server_name.rsplit(":", 1)
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domain = domain_port[0]
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port = int(domain_port[1]) if domain_port[1:] else None
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return domain, port
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except Exception:
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raise ValueError("Invalid server name '%s'" % server_name)
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VALID_HOST_REGEX = re.compile(
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"\\A[0-9a-zA-Z.-]+\\Z",
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)
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def parse_and_validate_server_name(server_name):
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"""Split a server name into host/port parts and do some basic validation.
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Args:
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server_name (str): server name to parse
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Returns:
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Tuple[str, int|None]: host/port parts.
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Raises:
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ValueError if the server name could not be parsed.
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"""
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host, port = parse_server_name(server_name)
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# these tests don't need to be bulletproof as we'll find out soon enough
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# if somebody is giving us invalid data. What we *do* need is to be sure
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# that nobody is sneaking IP literals in that look like hostnames, etc.
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# look for ipv6 literals
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if host[0] == '[':
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if host[-1] != ']':
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raise ValueError("Mismatched [...] in server name '%s'" % (
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server_name,
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))
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return host, port
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# otherwise it should only be alphanumerics.
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if not VALID_HOST_REGEX.match(host):
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raise ValueError("Server name '%s' contains invalid characters" % (
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server_name,
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))
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return host, port
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def matrix_federation_endpoint(reactor, destination, tls_client_options_factory=None,
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timeout=None):
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"""Construct an endpoint for the given matrix destination.
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Args:
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reactor: Twisted reactor.
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destination (unicode): The name of the server to connect to.
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tls_client_options_factory
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(synapse.crypto.context_factory.ClientTLSOptionsFactory):
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Factory which generates TLS options for client connections.
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timeout (int): connection timeout in seconds
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"""
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domain, port = parse_server_name(destination)
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endpoint_kw_args = {}
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if timeout is not None:
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endpoint_kw_args.update(timeout=timeout)
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if tls_client_options_factory is None:
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transport_endpoint = HostnameEndpoint
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default_port = 8008
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else:
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# the SNI string should be the same as the Host header, minus the port.
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# as per https://github.com/matrix-org/synapse/issues/2525#issuecomment-336896777,
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# the Host header and SNI should therefore be the server_name of the remote
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# server.
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tls_options = tls_client_options_factory.get_options(domain)
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def transport_endpoint(reactor, host, port, timeout):
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return wrapClientTLS(
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tls_options,
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HostnameEndpoint(reactor, host, port, timeout=timeout),
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)
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default_port = 8448
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if port is None:
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return SRVClientEndpoint(
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reactor, "matrix", domain, protocol="tcp",
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default_port=default_port, endpoint=transport_endpoint,
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endpoint_kw_args=endpoint_kw_args
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)
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else:
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return transport_endpoint(
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reactor, domain, port, **endpoint_kw_args
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)
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class SRVClientEndpoint(object):
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"""An endpoint which looks up SRV records for a service.
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Cycles through the list of servers starting with each call to connect
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picking the next server.
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Implements twisted.internet.interfaces.IStreamClientEndpoint.
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"""
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def __init__(self, reactor, service, domain, protocol="tcp",
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default_port=None, endpoint=HostnameEndpoint,
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endpoint_kw_args={}):
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self.reactor = reactor
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self.service_name = "_%s._%s.%s" % (service, protocol, domain)
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if default_port is not None:
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self.default_server = Server(
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host=domain,
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port=default_port,
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)
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else:
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self.default_server = None
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self.endpoint = endpoint
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self.endpoint_kw_args = endpoint_kw_args
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self.servers = None
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self.used_servers = None
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@defer.inlineCallbacks
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def fetch_servers(self):
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self.used_servers = []
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self.servers = yield resolve_service(self.service_name)
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def pick_server(self):
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if not self.servers:
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if self.used_servers:
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self.servers = self.used_servers
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self.used_servers = []
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self.servers.sort()
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elif self.default_server:
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return self.default_server
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else:
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raise ConnectError(
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"No server available for %s" % self.service_name
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)
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# look for all servers with the same priority
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min_priority = self.servers[0].priority
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weight_indexes = list(
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(index, server.weight + 1)
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for index, server in enumerate(self.servers)
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if server.priority == min_priority
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)
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total_weight = sum(weight for index, weight in weight_indexes)
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target_weight = random.randint(0, total_weight)
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for index, weight in weight_indexes:
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target_weight -= weight
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if target_weight <= 0:
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server = self.servers[index]
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# XXX: this looks totally dubious:
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#
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# (a) we never reuse a server until we have been through
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# all of the servers at the same priority, so if the
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# weights are A: 100, B:1, we always do ABABAB instead of
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# AAAA...AAAB (approximately).
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#
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# (b) After using all the servers at the lowest priority,
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# we move onto the next priority. We should only use the
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# second priority if servers at the top priority are
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# unreachable.
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#
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del self.servers[index]
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self.used_servers.append(server)
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return server
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@defer.inlineCallbacks
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def connect(self, protocolFactory):
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if self.servers is None:
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yield self.fetch_servers()
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server = self.pick_server()
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logger.info("Connecting to %s:%s", server.host, server.port)
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endpoint = self.endpoint(
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self.reactor, server.host, server.port, **self.endpoint_kw_args
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)
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connection = yield endpoint.connect(protocolFactory)
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defer.returnValue(connection)
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