Outbound: Add outbound sendThrough origin behavior (#4349)

* added support of sending through origin for outbounds

* added strings package import

* usage of net.SplitHostPort instead of manual splitting

---------

Co-authored-by: poly <poly@>

app/proxyman/outbound/handler.go

@@ -273,7 +273,16 @@ func (h *Handler) Dial(ctx context.Context, dest net.Destination) (stat.Connecti
 			outbounds := session.OutboundsFromContext(ctx)
 			ob := outbounds[len(outbounds)-1]
 			if h.senderSettings.ViaCidr == "" {
+				if h.senderSettings.Via.AsAddress().Family().IsDomain() && h.senderSettings.Via.AsAddress().Domain() == "origin" {
+					if inbound := session.InboundFromContext(ctx); inbound != nil {
+						origin, _, err := net.SplitHostPort(inbound.Conn.LocalAddr().String())
+						if err == nil {
+							ob.Gateway = net.ParseAddress(origin)
+						}
+					}
+				} else {
 					ob.Gateway = h.senderSettings.Via.AsAddress()
+				}
 			} else { //Get a random address.
 				ob.Gateway = ParseRandomIPv6(h.senderSettings.Via.AsAddress(), h.senderSettings.ViaCidr)
 			}

infra/conf/xray.go

@@ -292,9 +292,11 @@ func (c *OutboundDetourConfig) Build() (*core.OutboundHandlerConfig, error) {
 			senderSettings.ViaCidr = strings.Split(*c.SendThrough, "/")[1]
 		} else {
 			if address.Family().IsDomain() {
+				if address.Address.Domain() != "origin" {
 					return nil, errors.New("unable to send through: " + address.String())
 				}
 			}
+		}
 		senderSettings.Via = address.Build()
 	}