Improve proxy handling

Have a background proxy detection loop; removes need to check
specific peers at startup.
Consider proxy down once attempts to use it fail 3 times in a row.
Regularly attempt to rediscover a proxy if it is down.

lib/socks.py

@@ -137,44 +137,101 @@ class Socks(util.LoggedClass):
 class SocksProxy(util.LoggedClass):
 
     def __init__(self, host, port, loop=None):
-        '''Host can be an IPv4 address, IPv6 address, or a host name.'''
+        '''Host can be an IPv4 address, IPv6 address, or a host name.
+        Port can be None, in which case one is auto-detected.'''
         super().__init__()
+        # Host and port of the proxy
         self.host = host
-        self.port = port
+        self.try_ports = [port, 9050, 9150, 1080]
+        self.errors = 0
         self.ip_addr = None
+        self.lost_event = asyncio.Event()
         self.loop = loop or asyncio.get_event_loop()
+        self.set_lost()
+
+    async def auto_detect_loop(self):
+        '''Try to detect a proxy at regular intervals until one is found.
+        If one is found, do nothing until one is lost.'''
+        while True:
+            await self.lost_event.wait()
+            self.lost_event.clear()
+            tries = 0
+            while True:
+                tries += 1
+                log_failure = tries % 10 == 1
+                await self.detect_proxy(log_failure=log_failure)
+                if self.is_up():
+                    break
+                await asyncio.sleep(600)
+
+    def is_up(self):
+        '''Returns True if we have a good proxy.'''
+        return self.port is not None
+
+    def set_lost(self):
+        '''Called when the proxy appears lost/down.'''
+        self.port = None
+        self.lost_event.set()
+
+    async def connect_via_proxy(self, host, port, proxy_address=None):
+        '''Connect to a (host, port) pair via the proxy.  Returns the
+        connected socket on success.'''
+        proxy_address = proxy_address or (self.host, self.port)
+        sock = socket.socket()
+        sock.setblocking(False)
+        try:
+            await self.loop.sock_connect(sock, proxy_address)
+            socks = Socks(self.loop, sock, host, port)
+            await socks.handshake()
+            return sock
+        except Exception:
+            sock.close()
+            raise
+
+    async def detect_proxy(self, host='www.google.com', port=80,
+                           log_failure=True):
+        '''Attempt to detect a proxy by establishing a connection through it
+        to the given target host / port pair.
+        '''
+        if self.is_up():
+            return
+
+        sock = None
+        for proxy_port in self.try_ports:
+            if proxy_port is None:
+                continue
+            paddress = (self.host, proxy_port)
+            try:
+                sock = await self.connect_via_proxy(host, port, paddress)
+                break
+            except Exception as e:
+                if log_failure:
+                    self.logger.info('failed to detect proxy at {}: {}'
+                                     .format(util.address_string(paddress), e))
+
+        # Failed all ports?
+        if sock is None:
+            return
+
+        peername = sock.getpeername()
+        sock.close()
+        self.ip_addr = peername[0]
+        self.port = proxy_port
+        self.errors = 0
+        self.logger.info('detected proxy at {} ({})'
+                         .format(util.address_string(paddress), self.ip_addr))
 
     async def create_connection(self, protocol_factory, host, port, ssl=None):
         '''All arguments are as to asyncio's create_connection method.'''
-        if self.port is None:
+        try:
-            proxy_ports = [9050, 9150, 1080]
+            sock = await self.connect_via_proxy(host, port)
-        else:
+            self.errors = 0
-            proxy_ports = [self.port]
+        except Exception:
-
+            self.errors += 1
-        for proxy_port in proxy_ports:
+            # If we have 3 consecutive errors, consider the proxy undetected
-            address = (self.host, proxy_port)
+            if self.errors == 3:
-            sock = socket.socket()
+                self.set_lost()
-            sock.setblocking(False)
+            raise
-            try:
-                await self.loop.sock_connect(sock, address)
-            except OSError as e:
-                if proxy_port == proxy_ports[-1]:
-                    raise
-                continue
-
-            socks = Socks(self.loop, sock, host, port)
-            try:
-                await socks.handshake()
-                if self.port is None:
-                    self.ip_addr = sock.getpeername()[0]
-                    self.port = proxy_port
-                    self.logger.info('detected proxy at {} ({})'
-                                     .format(util.address_string(address),
-                                             self.ip_addr))
-                break
-            except Exception as e:
-                sock.close()
-                raise
 
         hostname = host if ssl else None
         return await self.loop.create_connection(

server/peers.py

@@ -230,7 +230,6 @@ class PeerManager(util.LoggedClass):
         self.peers = set()
         self.onion_peers = []
         self.permit_onion_peer_time = time.time()
-        self.last_tor_retry_time = 0
         self.tor_proxy = SocksProxy(env.tor_proxy_host, env.tor_proxy_port,
                                     loop=self.loop)
         self.import_peers()
@@ -463,6 +462,7 @@ class PeerManager(util.LoggedClass):
           2) Verifying connectivity of new peers.
           3) Retrying old peers at regular intervals.
         '''
+        self.ensure_future(self.tor_proxy.auto_detect_loop())
         self.connect_to_irc()
         if not self.env.peer_discovery:
             self.logger.info('peer discovery is disabled')
@@ -492,10 +492,6 @@ class PeerManager(util.LoggedClass):
         nearly_stale_time = (now - STALE_SECS) + WAKEUP_SECS * 2
 
         def should_retry(peer):
-            # Try some Tor at startup to determine the proxy so we can
-            # serve the right banner file
-            if self.tor_proxy.port is None and self.is_coin_onion_peer(peer):
-                return True
             # Retry a peer whose ports might have updated
             if peer.other_port_pairs:
                 return True
@@ -507,14 +503,6 @@ class PeerManager(util.LoggedClass):
 
         peers = [peer for peer in self.peers if should_retry(peer)]
 
-        # If we don't have a tor proxy drop tor peers, but retry
-        # occasionally
-        if self.tor_proxy.port is None:
-            if now < self.last_tor_retry_time + 3600:
-                peers = [peer for peer in peers if not peer.is_tor]
-            elif any(peer.is_tor for peer in peers):
-                self.last_tor_retry_time = now
-
         for peer in peers:
             peer.try_count += 1
             pairs = peer.connection_port_pairs()
@@ -529,6 +517,9 @@ class PeerManager(util.LoggedClass):
         sslc = ssl.SSLContext(ssl.PROTOCOL_TLS) if kind == 'SSL' else None
 
         if peer.is_tor:
+            # Don't attempt an onion connection if we don't have a tor proxy
+            if not self.tor_proxy.is_up():
+                return
             create_connection = self.tor_proxy.create_connection
         else:
             create_connection = self.loop.create_connection