From 09df948871d740f8f9071d4246f856b04e2d4772 Mon Sep 17 00:00:00 2001
From: XANTRONIX Development <dev@xantronix.com>
Date: Thu, 30 Jul 2020 01:34:43 -0400
Subject: [PATCH] Only set use tcsetattr() on TTYs for KISS TNCs

Fix patty_kiss_tnc_new_fd() to only attempt tcgetattr()/tcsetattr() on
file descriptors for whom isatty() is true, allowing files and sockets
to once again be used
---
 src/kiss.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/kiss.c b/src/kiss.c
index 61cf3cf..a3945bb 100644
--- a/src/kiss.c
+++ b/src/kiss.c
@@ -52,16 +52,18 @@ patty_kiss_tnc *patty_kiss_tnc_new_fd(int fd) {
         goto error_malloc_buf;
     }
 
-    if (tcgetattr(fd, &tnc->attrs) < 0) {
-        goto error_tcgetattr;
-    }
+    if (isatty(fd)) {
+        if (tcgetattr(fd, &tnc->attrs) < 0) {
+            goto error_tcgetattr;
+        }
 
-    memcpy(&tnc->attrs_old, &tnc->attrs, sizeof(tnc->attrs_old));
+        memcpy(&tnc->attrs_old, &tnc->attrs, sizeof(tnc->attrs_old));
 
-    cfmakeraw(&tnc->attrs);
+        cfmakeraw(&tnc->attrs);
 
-    if (tcsetattr(fd, TCSANOW, &tnc->attrs) < 0) {
-        goto error_tcsetattr;
+        if (tcsetattr(fd, TCSANOW, &tnc->attrs) < 0) {
+            goto error_tcsetattr;
+        }
     }
 
     tnc->fd      =  fd;