ztcp should not pick fd 0

[Greg Klanderman <gak@klanderman.net>]

I'm using ztcp to connect to a server; when the connection is lost and
needs to be re-opened from within the completion system (compctl),
calling 'ztcp <host> <port>' will actually choose fd 0 for the socket
file descriptor which is hosing other parts of my program (calling out
to a python process specifically).  I can work around this problem by
requesting the previous fd with the '-d' option (I suppose that's not
100% safe because after closing the original socket that fd might get
reallocated in the intervening time), but it would be really nice if
ztcp could be made to never choose fds 0 through 2.  This is also a
problem because if you try to close fd 0 with ztcp you'll get the
error '0 is an invalid argument to -c'.

The obvious patch below does not work because movefd() marks the fd as
FDT_INTERNAL, and that causes the fd to get closed when external
programs are exec'd.  This calls into question the other use of movefd
in tcp.c as well.

Suggestions welcome..

Greg


Index: Src/Modules/tcp.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Modules/tcp.c,v
retrieving revision 1.51
diff -u -r1.51 tcp.c
--- Src/Modules/tcp.c	22 Sep 2009 16:04:16 -0000	1.51
+++ Src/Modules/tcp.c	11 Aug 2010 15:34:42 -0000
@@ -668,6 +668,16 @@
 		    return 1;
 		}
 	    }
+            else {
+                /* if fd is < 10, move it up to be >= 10 */
+                int oldfd = sess->fd;
+                sess->fd = movefd(sess->fd);
+		if (sess->fd < 0) {
+		    zerrnam(nam, "could not move socket fd %d: %e", oldfd, errno);
+		    return 1;
+		}
+            }
+
 
 	    setiparam("REPLY", sess->fd);