Feature: add TCP TPROXY support (#1049)

proxy/redir/tproxy_linux.go

@@ -0,0 +1,40 @@
+// +build linux
+
+package redir
+
+import (
+	"net"
+	"syscall"
+)
+
+func setsockopt(rc syscall.RawConn, addr string) error {
+	isIPv6 := true
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		return err
+	}
+	ip := net.ParseIP(host)
+	if ip != nil && ip.To4() != nil {
+		isIPv6 = false
+	}
+
+	rc.Control(func(fd uintptr) {
+		err = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
+
+		if err == nil {
+			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_TRANSPARENT, 1)
+		}
+		if err == nil && isIPv6 {
+			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, IPV6_TRANSPARENT, 1)
+		}
+
+		if err == nil {
+			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_RECVORIGDSTADDR, 1)
+		}
+		if err == nil && isIPv6 {
+			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, IPV6_RECVORIGDSTADDR, 1)
+		}
+	})
+
+	return err
+}