From d44889121e7d620da31737d2f9315eda787cc76d Mon Sep 17 00:00:00 2001
From: XANTRONIX Development <dev@xantronix.com>
Date: Wed, 27 May 2020 19:11:25 -0400
Subject: [PATCH] Do not decode KISS frames into internal buffer

Changes:

    * Modify patty_kiss_tnc_recv() to accept a pointer to a read buffer,
      and a maximum length argument, to receive one packet

    * Modify src/decode.c to use the new patty_kiss_tnc_recv() calling
      form
---
 include/patty/kiss.h |  5 +++--
 src/decode.c         | 23 +++++++++++++++++------
 src/kiss.c           | 23 ++++++-----------------
 3 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/include/patty/kiss.h b/include/patty/kiss.h
index eab42bf..059e169 100644
--- a/include/patty/kiss.h
+++ b/include/patty/kiss.h
@@ -40,11 +40,12 @@ void patty_kiss_tnc_close(patty_kiss_tnc *tnc);
 size_t patty_kiss_tnc_dropped(patty_kiss_tnc *tnc);
 
 ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
-                            void **frame,
+                            void *buf,
+                            size_t len,
                             int *port);
 
 ssize_t patty_kiss_tnc_send(patty_kiss_tnc *tnc,
-                            const void *frame,
+                            const void *buf,
                             size_t len,
                             int port);
 
diff --git a/src/decode.c b/src/decode.c
index c44cddf..3cadf79 100644
--- a/src/decode.c
+++ b/src/decode.c
@@ -142,7 +142,7 @@ error_io:
 
 int main(int argc, char **argv) {
     patty_kiss_tnc *tnc;
-    void *data;
+    void *buf;
     int port;
 
     if (argc != 2) {
@@ -155,38 +155,49 @@ int main(int argc, char **argv) {
         goto error_kiss_tnc_open;
     }
 
+    if ((buf = malloc(PATTY_KISS_BUFSZ)) == NULL) {
+        perror("malloc()");
+
+        goto error_malloc_buf;
+    }
+
     while (1) {
         ssize_t len;
         patty_ax25_frame frame;
 
-        if ((len = patty_kiss_tnc_recv(tnc, &data, &port)) < 0) {
+        if ((len = patty_kiss_tnc_recv(tnc, buf, PATTY_KISS_BUFSZ, &port)) < 0) {
             perror("Unable to read frame");
 
-            goto error_ax25_frame_read;
+            goto error_kiss_tnc_recv;
         } else if (len == 0) {
             break;
         }
 
-        if (patty_ax25_frame_decode(&frame, data, len) < 0) {
+        if (patty_ax25_frame_decode(&frame, buf, len) < 0) {
             perror("Unable to decode frame");
 
             goto error_ax25_frame_decode;
         }
 
-        if (frame_fprint(stdout, &frame, data, len) < 0) {
+        if (frame_fprint(stdout, &frame, buf, len) < 0) {
             perror("Unable to print frame");
 
             goto error_frame_fprint;
         }
     }
 
+    free(buf);
+
     patty_kiss_tnc_close(tnc);
 
     return 0;
 
 error_frame_fprint:
 error_ax25_frame_decode:
-error_ax25_frame_read:
+error_kiss_tnc_recv:
+    free(buf);
+
+error_malloc_buf:
     patty_kiss_tnc_close(tnc);
 
 error_kiss_tnc_open:
diff --git a/src/kiss.c b/src/kiss.c
index 6351ecb..105d94a 100644
--- a/src/kiss.c
+++ b/src/kiss.c
@@ -39,10 +39,6 @@ patty_kiss_tnc *patty_kiss_tnc_open_fd(int fd, size_t bufsz) {
         goto error_malloc_buf;
     }
 
-    if ((tnc->frame = malloc(bufsz)) == NULL) {
-        goto error_malloc_frame;
-    }
-
     tnc->fd      = fd;
     tnc->bufsz   = bufsz;
     tnc->buflen  = 0;
@@ -50,9 +46,6 @@ patty_kiss_tnc *patty_kiss_tnc_open_fd(int fd, size_t bufsz) {
 
     return tnc;
 
-error_malloc_frame:
-    free(tnc->buf);
-
 error_malloc_buf:
     free(tnc);
 
@@ -87,7 +80,6 @@ int patty_kiss_tnc_fd_unix(patty_kiss_tnc *tnc) {
 
 void patty_kiss_tnc_close(patty_kiss_tnc *tnc) {
     close(tnc->fd);
-     free(tnc->frame);
      free(tnc->buf);
      free(tnc);
 }
@@ -130,7 +122,8 @@ size_t patty_kiss_tnc_dropped(patty_kiss_tnc *tnc) {
 }
 
 ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
-                            void **frame,
+                            void *buf,
+                            size_t len,
                             int *port) {
     size_t i = 0,
            b = 0;
@@ -141,7 +134,7 @@ ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
         goto error_io;
     }
 
-    while (i < tnc->buflen) {
+    while (i < tnc->buflen && b < len) {
         uint8_t c = ((uint8_t *)tnc->buf)[i++];
 
         if (!(flags & KISS_FRAME)) {
@@ -189,12 +182,12 @@ ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
         } else {
             switch (c) {
                 case PATTY_KISS_TFEND:
-                    ((uint8_t *)tnc->frame)[b++] = PATTY_KISS_FEND;
+                    ((uint8_t *)buf)[b++] = PATTY_KISS_FEND;
                     flags &= ~KISS_ESCAPE;
                     continue;
 
                 case PATTY_KISS_TFESC:
-                    ((uint8_t *)tnc->frame)[b++] = PATTY_KISS_FESC;
+                    ((uint8_t *)buf)[b++] = PATTY_KISS_FESC;
                     flags &= ~KISS_ESCAPE;
                     continue;
 
@@ -205,18 +198,14 @@ ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
             }
         }
 
-        ((uint8_t *)tnc->frame)[b++] = c;
+        ((uint8_t *)buf)[b++] = c;
     }
 
 done:
     if (flags & KISS_FRAME) {
         tnc_drop(tnc);
-
-        *frame = NULL;
     } else {
         tnc_flush(tnc, i);
-
-        *frame = tnc->frame;
     }
 
     return (ssize_t)b;