[patch] Fix closing socket twice bug in netcat program

[Nan Xiao]

Hi tech@,

Before netcat program exits, it will check whether s is -1, and close
socket if s is not -1:

        if (s != -1)
                close(s);

The following patch fixes the issue that netcat will close socket twice
if it works as a server:

Index: netcat.c
===================================================================
RCS file: /cvs/src/usr.bin/nc/netcat.c,v
retrieving revision 1.192
diff -u -p -r1.192 netcat.c
--- netcat.c    10 Aug 2018 17:15:22 -0000      1.192
+++ netcat.c    4 Sep 2018 04:51:55 -0000
@@ -622,9 +622,10 @@ main(int argc, char *argv[])
                                }
                                close(connfd);
                        }
-                       if (family != AF_UNIX)
+                       if (family != AF_UNIX) {
                                close(s);
-                       else if (uflag) {
+                               s = -1;
+                       } else if (uflag) {
                                if (connect(s, NULL, 0) < 0)
                                        err(1, "connect");
                        }

Thanks!
-- 
Best Regards
Nan Xiao