XHTTP server: Forbid Mux.Cool except pure XUDP (#4128)

https://github.com/XTLS/Xray-core/discussions/4113#discussioncomment-11491701

app/proxyman/inbound/inbound.go

@@ -7,6 +7,7 @@ import (
 	"github.com/xtls/xray-core/app/proxyman"
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/errors"
+	"github.com/xtls/xray-core/common/net"
 	"github.com/xtls/xray-core/common/serial"
 	"github.com/xtls/xray-core/common/session"
 	"github.com/xtls/xray-core/core"
@@ -158,6 +159,9 @@ func NewHandler(ctx context.Context, config *core.InboundHandlerConfig) (inbound
 			Mark: streamSettings.SocketSettings.Mark,
 		})
 	}
+	if streamSettings != nil && streamSettings.ProtocolName == "splithttp" {
+		ctx = session.ContextWithAllowedNetwork(ctx, net.Network_UDP)
+	}
 
 	allocStrategy := receiverSettings.AllocationStrategy
 	if allocStrategy == nil || allocStrategy.Type == proxyman.AllocationStrategy_Always {