Enable splice for freedom outbound (downlink only)

- Add outbound name
- Add outbound conn in ctx
- Refactor splice: it can be turn on from all inbounds and outbounds
- Refactor splice: Add splice copy to vless inbound
- Fix http error test
- Add freedom splice toggle via env var
- Populate outbound obj in context
- Use CanSpliceCopy to mark a connection
- Turn off splice by default

proxy/socks/server.go

@@ -63,11 +63,11 @@ func (s *Server) Network() []net.Network {
 
 // Process implements proxy.Inbound.
 func (s *Server) Process(ctx context.Context, network net.Network, conn stat.Connection, dispatcher routing.Dispatcher) error {
-	if inbound := session.InboundFromContext(ctx); inbound != nil {
-		inbound.Name = "socks"
-		inbound.User = &protocol.MemoryUser{
-			Level: s.config.UserLevel,
-		}
+	inbound := session.InboundFromContext(ctx)
+	inbound.Name = "socks"
+	inbound.SetCanSpliceCopy(2)
+	inbound.User = &protocol.MemoryUser{
+		Level: s.config.UserLevel,
 	}
 
 	switch network {