only build for linux

proxy/dokodemo/sockopt_linux.go

@@ -0,0 +1,30 @@
+// +build linux
+
+package dokodemo
+
+import (
+	"syscall"
+
+	"github.com/v2ray/v2ray-core/common/log"
+	v2net "github.com/v2ray/v2ray-core/common/net"
+	"github.com/v2ray/v2ray-core/transport/hub"
+)
+
+const SO_ORIGINAL_DST = 80
+
+func GetOriginalDestination(conn *hub.Connection) v2net.Destination {
+	fd, err := conn.SysFd()
+	if err != nil {
+		log.Info("Dokodemo: Failed to get original destination: ", err)
+		return nil
+	}
+
+	addr, err := syscall.GetsockoptIPv6Mreq(fd, syscall.IPPROTO_IP, SO_ORIGINAL_DST)
+	if err != nil {
+		log.Info("Dokodemo: Failed to call getsockopt: ", err)
+		return nil
+	}
+	ip := v2net.IPAddress(addr.Multiaddr[4:8])
+	port := uint16(addr.Multiaddr[2])<<8 + uint16(addr.Multiaddr[3])
+	return v2net.TCPDestination(ip, v2net.Port(port))
+}