From f6c5727ba2ff8f1e107e721f591c0068711c57fa Mon Sep 17 00:00:00 2001
From: tb <>
Date: Sun, 18 Dec 2022 12:51:10 +0000
Subject: nc: do not test the connection in non-interactive mode

The connection test writes four X to the socket, which corrupts data
that we may want to pipe into nc. So don't do that if stdin is not a
tty but still do it in scan mode, this is needed according to chris.

based on a diff by and ok mpf
---
 src/usr.bin/nc/netcat.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/usr.bin/nc/netcat.c b/src/usr.bin/nc/netcat.c
index e945ba6e8f..dc60158749 100644
--- a/src/usr.bin/nc/netcat.c
+++ b/src/usr.bin/nc/netcat.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: netcat.c,v 1.222 2022/12/18 12:48:28 tb Exp $ */
+/* $OpenBSD: netcat.c,v 1.223 2022/12/18 12:51:10 tb Exp $ */
 /*
  * Copyright (c) 2001 Eric Jackson <ericj@monkey.org>
  * Copyright (c) 2015 Bob Beck.  All rights reserved.
@@ -1510,6 +1510,10 @@ udptest(int s)
 {
 	int i, ret;
 
+	/* Only write to the socket in scan mode or interactive mode. */
+	if (!zflag && !isatty(STDIN_FILENO))
+		return 0;
+
 	for (i = 0; i <= 3; i++) {
 		if (write(s, "X", 1) == 1)
 			ret = 1;
-- 
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