Updated NETCONF framing protocol detection to check both client & server capabilities

src/Renci.SshNet/Netconf/NetConfSession.cs

@@ -150,7 +150,13 @@ protected override void OnDataReceived(byte[] data)
                 var nsMgr = new XmlNamespaceManager(ServerCapabilities.NameTable);
                 nsMgr.AddNamespace("nc", "urn:ietf:params:xml:ns:netconf:base:1.0");
 
-                _usingFramingProtocol = ServerCapabilities.SelectSingleNode("/nc:hello/nc:capabilities/nc:capability[text()='urn:ietf:params:netconf:base:1.1']", nsMgr) != null;
+                const string xpath = "/nc:hello/nc:capabilities/nc:capability[text()='urn:ietf:params:netconf:base:1.1']";
+
+                // This will currently evaluate to false since we (the client) do not advertise 1.1 capability.
+                // Despite some code existing for the 1.1 framing protocol, it is thought to be incorrect or
+                // incomplete. The NETCONF code is practically untested at the time of writing.
+                _usingFramingProtocol = ServerCapabilities.SelectSingleNode(xpath, nsMgr) != null
+                    && ClientCapabilities.SelectSingleNode(xpath, nsMgr) != null;
 
                 _ = _serverCapabilitiesConfirmed.Set();
             }