simplify Server.sni, fix #4547 (#4660)

mitmproxy/addons/tlsconfig.py

@@ -171,7 +171,7 @@ class TlsConfig:
         else:
             verify = net_tls.Verify.VERIFY_PEER
 
-        if server.sni is True:
+        if server.sni is None:
             server.sni = client.sni or server.address[0]
 
         if not server.alpn_offers:

mitmproxy/connection.py

@@ -2,7 +2,7 @@ import uuid
 import warnings
 from abc import ABCMeta
 from enum import Flag
-from typing import Literal, Optional, Sequence, Tuple, Union
+from typing import Optional, Sequence, Tuple
 
 from mitmproxy import certs
 from mitmproxy.coretypes import serializable
@@ -85,10 +85,9 @@ class Connection(serializable.Serializable, metaclass=ABCMeta):
     """Ciphers accepted by the proxy server on this connection."""
     tls_version: Optional[str] = None
     """The active TLS version."""
-    sni: Union[str, Literal[True], None]
+    sni: Optional[str] = None
     """
     The [Server Name Indication (SNI)](https://en.wikipedia.org/wiki/Server_Name_Indication) sent in the ClientHello.
-    For server connections, this value may also be set to `True`, which means "use `Server.address`".
     """
 
     timestamp_start: Optional[float]
@@ -144,8 +143,6 @@ class Client(Connection):
     """
     The certificate used by mitmproxy to establish TLS with the client.
     """
-    sni: Union[str, None] = None
-    """The Server Name Indication sent by the client."""
 
     timestamp_start: float
     """*Timestamp:* TCP SYN received"""
@@ -272,7 +269,6 @@ class Server(Connection):
     timestamp_tcp_setup: Optional[float] = None
     """*Timestamp:* TCP ACK received."""
 
-    sni: Union[str, Literal[True], None] = True
     via: Optional[server_spec.ServerSpec] = None
     """An optional proxy server specification via which the connection should be established."""