From d266058ad4b92590a1e4a19ada3a1831457686f0 Mon Sep 17 00:00:00 2001
From: XANTRONIX Development <dev@xantronix.com>
Date: Fri, 29 May 2020 00:11:54 -0400
Subject: [PATCH] Fix patty_kiss_tnc_recv() issues

Fix patty_kiss_tnc_recv() issues with small buffers (~330 bytes) by
more properly detecting EOF being the condition at which the current
decoder offset in the buffer is equal to the last buffer read size; the
offset can never be the number of bytes read, and the initial read
length is -1, so early EOF conditions are avoided
---
 src/kiss.c | 31 ++++++++-----------------------
 1 file changed, 8 insertions(+), 23 deletions(-)

diff --git a/src/kiss.c b/src/kiss.c
index 1ac8b58..838b42f 100644
--- a/src/kiss.c
+++ b/src/kiss.c
@@ -27,10 +27,7 @@ struct _patty_kiss_tnc {
            offset,
            dropped;
 
-    ssize_t readlen,
-            left;
-
-    int eof;
+    ssize_t readlen;
 };
 
 patty_kiss_tnc *patty_kiss_tnc_open_fd(int fd) {
@@ -45,12 +42,10 @@ patty_kiss_tnc *patty_kiss_tnc_open_fd(int fd) {
     }
 
     tnc->fd      = fd;
-    tnc->bufsz   = PATTY_KISS_BUFSZ;
-    tnc->offset  = 0;
-    tnc->dropped = 0;
-    tnc->readlen = 0;
-    tnc->left    = 0;
-    tnc->eof     = 0;
+    tnc->bufsz   =  PATTY_KISS_BUFSZ;
+    tnc->offset  =  0;
+    tnc->dropped =  0;
+    tnc->readlen = -1;
 
     return tnc;
 
@@ -93,10 +88,8 @@ void patty_kiss_tnc_close(patty_kiss_tnc *tnc) {
 }
 
 static void tnc_drop(patty_kiss_tnc *tnc) {
-    tnc->offset  = 0;
-    tnc->readlen = 0;
-    tnc->left    = 0;
-    tnc->eof     = 0;
+    tnc->offset  =  0;
+    tnc->readlen = -1;
     tnc->dropped++;
 }
 
@@ -113,7 +106,7 @@ ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
 
     enum kiss_flags flags = KISS_NONE;
 
-    if (tnc->eof) {
+    if (tnc->offset == tnc->readlen) {
         return 0;
     }
 
@@ -139,8 +132,6 @@ ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
 
                 goto done;
             }
-
-            tnc->left = tnc->readlen;
         }
 
         c = ((uint8_t *)tnc->buf)[tnc->offset++];
@@ -220,12 +211,6 @@ done:
         return 0;
     }
 
-    tnc->left -= r;
-
-    if (tnc->readlen < tnc->bufsz && tnc->left == 0) {
-        tnc->eof = 1;
-    }
-
     return (ssize_t)w;
 
 error_io: