tproxy patch for netcat v1.10 GNU commutiy version

nc_tproxy.patch

--- a/netcat.c  2018-01-11 22:13:14.000000000 +0000
+++ b/netcat.c  2020-04-04 01:24:53.000042333 +0000
@@ -81,6 +81,10 @@
 #include <fcntl.h>             /* O_WRONLY et al */
 #include <unistd.h>

+/* quick hack to make it working without patched kernel source,
+   for https://sourceforge.net/projects/nc110/files/community%20releases/ */
+#define IP_TRANSPARENT 19
+
 /* handy stuff: */
 #define SA struct sockaddr     /* socket overgeneralization braindeath */
 #define SAI struct sockaddr_in /* ... whoever came up with this model */
@@ -196,6 +199,7 @@
 USHORT o_random = 0;
 USHORT o_udpmode = 0;
 USHORT o_verbose = 0;
+USHORT o_transparent = 0;
 USHORT o_holler_stderr = 1;
 unsigned int o_wait = 0;
 USHORT o_zero = 0;
@@ -814,6 +818,13 @@
   if (rr == -1)
     holler ("nnetfd reuseport failed");                /* ??? */
 #endif
+  if (o_transparent) {
+    x = 1;
+    rr = setsockopt(nnetfd, SOL_IP, IP_TRANSPARENT, &x, sizeof(x));
+    if (rr == -1) {
+      holler("nnetfd set transparent failed");
+    }
+  }
 #if 0
 /* If you want to screw with RCVBUF/SNDBUF, do it here.  Liudvikas Bukys at
    Rochester sent this example, which would involve YET MORE options and is
@@ -1832,6 +1843,7 @@
        -t                      answer TELNET negotiation");
 #endif
   holler ("\
+       -T                      set IP_TRANSPARENT for the socket\n\
        -u                      UDP mode\n\
        -v                      verbose [use twice to be more verbose]\n\
        -w secs                 timeout for connects and final net reads\n\
@@ -1974,7 +1986,7 @@

 /* If your shitbox doesn't have getopt, step into the nineties already. */
 /* optarg, optind = next-argv-component [i.e. flag arg]; optopt = last-char */
-  while ((x = getopt (argc, argv, "46abc:e:g:G:hi:lno:p:q:rs:tuvw:z")) != EOF) {
+  while ((x = getopt (argc, argv, "46abc:e:g:G:hi:lno:p:q:rs:tTuvw:z")) != EOF) {
 /* Debug (("in go: x now %c, optarg %x optind %d", x, optarg, optind)) */
     switch (x) {
 #ifdef INET6
@@ -2029,6 +2041,8 @@
        if (! o_interval)
          bail ("invalid interval time %s", optarg);
        break;
+      case 'T':                                /* numeric-only, no DNS lookups */
+       o_transparent = 1; break;
       case 'l':                                /* listen mode */
        o_listen++; break;
       case 'n':                                /* numeric-only, no DNS lookups */

Orignial Patch can be found at the related kernel doc page.
This one is for the nc source code in https://sourceforge.net/projects/nc110/files/community%20releases/ .