diff --git a/main.c b/main.c
index d452985..e4f7356 100644
--- a/main.c
+++ b/main.c
@@ -51,6 +51,7 @@
   printf("-6 [IPv6 address]\n");
   printf("-m [socket mark]\n");
   printf("-t [tun file descriptor number]\n");
+  printf("-w [write socket descriptor number]\n");
 }
 
 /* function: main
@@ -60,11 +61,11 @@
   struct tun_data tunnel;
   int opt;
   char *uplink_interface = NULL, *plat_prefix = NULL, *mark_str = NULL;
-  char *v4_addr = NULL, *v6_addr = NULL, *tunfd_str = NULL;
+  char *v4_addr = NULL, *v6_addr = NULL, *tunfd_str = NULL, *write_sock_str = NULL;
   uint32_t mark   = MARK_UNSET;
   unsigned len;
 
-  while ((opt = getopt(argc, argv, "i:p:4:6:m:t:h")) != -1) {
+  while ((opt = getopt(argc, argv, "i:p:4:6:m:t:w:h")) != -1) {
     switch (opt) {
       case 'i':
         uplink_interface = optarg;
@@ -84,6 +85,9 @@
       case 't':
         tunfd_str = optarg;
         break;
+      case 'w':
+        write_sock_str = optarg;
+        break;
       case 'h':
         print_help();
         exit(0);
@@ -112,6 +116,15 @@
     exit(1);
   }
 
+  if (write_sock_str != NULL && !parse_int(write_sock_str, &tunnel.write_fd6)) {
+    logmsg(ANDROID_LOG_FATAL, "invalid sock_write %s", write_sock_str);
+    exit(1);
+  }
+  if (!tunnel.write_fd6) {
+    logmsg(ANDROID_LOG_FATAL, "no write_fd6 specified on commandline.");
+    exit(1);
+  }
+
   len = snprintf(tunnel.device4, sizeof(tunnel.device4), "%s%s", DEVICEPREFIX, uplink_interface);
   if (len >= sizeof(tunnel.device4)) {
     logmsg(ANDROID_LOG_FATAL, "interface name too long '%s'", tunnel.device4);
@@ -124,7 +137,7 @@
          v6_addr ? v6_addr : "(none)");
 
   // open our raw sockets before dropping privs
-  open_sockets(&tunnel, mark);
+  open_sockets(&tunnel);
 
   configure_interface(uplink_interface, plat_prefix, v4_addr, v6_addr, &tunnel, mark);