Permit HOST to be a comma-separated list.

Update documentation to match.

docs/ENVIRONMENT.rst

@@ -85,8 +85,11 @@ These environment variables are optional:
 
 * **HOST**
 
-  The host that the TCP and SSL servers will use.  Defaults to
+  The host or IP address that the TCP and SSL servers will use when
-  `localhost`.  Set to blank to listen on all addresses (IPv4 and IPv6).
+  binding listening sockets.  Defaults to `localhost`.  To listen on
+  multiple specific addresses specify a comma-separated list.  Set to
+  an empty string to listen on all available interfaces (likely both
+  IPv4 and IPv6).
 
 * **TCP_PORT**
 

server/controller.py

@@ -305,12 +305,13 @@ class Controller(util.LoggedClass):
         self.state = self.LISTENING
 
         env = self.env
+        host = env.cs_host()
         if env.tcp_port is not None:
-            await self.start_server('TCP', env.host, env.tcp_port)
+            await self.start_server('TCP', host, env.tcp_port)
         if env.ssl_port is not None:
             sslc = ssl.SSLContext(ssl.PROTOCOL_TLS)
             sslc.load_cert_chain(env.ssl_certfile, keyfile=env.ssl_keyfile)
-            await self.start_server('SSL', env.host, env.ssl_port, ssl=sslc)
+            await self.start_server('SSL', host, env.ssl_port, ssl=sslc)
 
     async def notify(self):
         '''Notify sessions about height changes and touched addresses.'''

server/env.py

@@ -183,3 +183,12 @@ class Env(lib_util.LoggedClass):
             import uvloop
             return uvloop.EventLoopPolicy()
         raise self.Error('unknown event loop policy "{}"'.format(policy))
+
+    def cs_host(self):
+        '''Returns the 'host' argument to pass to asyncio's create_server
+        call.  The result can be a single host name string, a list of
+        host name strings, or an empty string to bind to all interfaces.'''
+        result = self.host.split(',')
+        if len(result) == 1:
+            result = result[0]
+        return result

server/peers.py

@@ -562,7 +562,12 @@ class PeerManager(util.LoggedClass):
         else:
             create_connection = self.loop.create_connection
 
-        local_addr = (self.env.host, None) if self.env.host else None
+        # Use our listening Host/IP for outgoing connections so our
+        # peers see the correct source.
+        host = self.env.cs_host()
+        if isinstance(host, list):
+            host = host[0]
+        local_addr = (host, None) if host else None
 
         protocol_factory = partial(PeerSession, peer, self, kind)
         coro = create_connection(protocol_factory, peer.host, port, ssl=sslc,

tests/server/test_env.py

@@ -94,6 +94,12 @@ def test_CACHE_MB():
 
 def test_HOST():
     assert_default('HOST', 'host', 'localhost')
+    os.environ['HOST'] = ''
+    e = Env()
+    assert e.cs_host() == ''
+    os.environ['HOST'] = '192.168.0.1,23.45.67.89'
+    e = Env()
+    assert e.cs_host() == ['192.168.0.1', '23.45.67.89']
 
 def test_REORG_LIMIT():
     assert_integer('REORG_LIMIT', 'reorg_limit', lib_coins.Bitcoin.REORG_LIMIT)