From 905d5b117c9e3b23a57efe950bbad79dd08a0cb6 Mon Sep 17 00:00:00 2001
From: XANTRONIX Development <dev@xantronix.com>
Date: Sun, 12 Jul 2020 22:14:58 -0400
Subject: [PATCH] Better handle read()s of multiple frames from TNC

Implement better handling of situations when read() captures multiple
TNC frames; ensure each frame is handled in src/server.c, function
handle_iface(), to ensure packets aren't ignored before the next
select() call
---
 include/patty/ax25/if.h |  2 ++
 include/patty/kiss.h    |  2 ++
 src/if.c                |  7 +++++++
 src/kiss.c              | 12 ++++++++++++
 src/server.c            | 20 +++++++++++---------
 5 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/include/patty/ax25/if.h b/include/patty/ax25/if.h
index a3c6c1a..e8313d7 100644
--- a/include/patty/ax25/if.h
+++ b/include/patty/ax25/if.h
@@ -82,6 +82,8 @@ int patty_ax25_if_promisc_add(patty_ax25_if *iface,
 int patty_ax25_if_promisc_delete(patty_ax25_if *iface,
                                  int fd);
 
+ssize_t patty_ax25_if_pending(patty_ax25_if *iface);
+
 ssize_t patty_ax25_if_recv(patty_ax25_if *iface,
                            void **buf);
 
diff --git a/include/patty/kiss.h b/include/patty/kiss.h
index 090bfbf..2fb34bc 100644
--- a/include/patty/kiss.h
+++ b/include/patty/kiss.h
@@ -39,6 +39,8 @@ void patty_kiss_tnc_destroy(patty_kiss_tnc *tnc);
 
 size_t patty_kiss_tnc_dropped(patty_kiss_tnc *tnc);
 
+ssize_t patty_kiss_tnc_pending(patty_kiss_tnc *tnc);
+
 ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
                             void *buf,
                             size_t len,
diff --git a/src/if.c b/src/if.c
index 46e67b0..61e56c0 100644
--- a/src/if.c
+++ b/src/if.c
@@ -336,6 +336,10 @@ static int handle_promisc_frame(uint32_t key,
     return patty_kiss_tnc_send(tnc, frame->buf, frame->len, 0);
 }
 
+ssize_t patty_ax25_if_pending(patty_ax25_if *iface) {
+    return patty_kiss_tnc_pending(iface->tnc);
+}
+
 ssize_t patty_ax25_if_recv(patty_ax25_if *iface,
                            void **buf) {
     ssize_t readlen;
@@ -347,6 +351,8 @@ ssize_t patty_ax25_if_recv(patty_ax25_if *iface,
                                        iface->rx_bufsz,
                                        &port)) < 0) {
         goto error_kiss_tnc_recv;
+    } else if (readlen == 0) {
+        goto done;
     }
 
     *buf = iface->rx_buf;
@@ -364,6 +370,7 @@ ssize_t patty_ax25_if_recv(patty_ax25_if *iface,
         goto error_handle_promisc_frame;
     }
 
+done:
     return readlen;
 
 error_handle_promisc_frame:
diff --git a/src/kiss.c b/src/kiss.c
index cb4d895..0f734e2 100644
--- a/src/kiss.c
+++ b/src/kiss.c
@@ -109,6 +109,18 @@ size_t patty_kiss_tnc_dropped(patty_kiss_tnc *tnc) {
     return tnc->dropped;
 }
 
+ssize_t patty_kiss_tnc_pending(patty_kiss_tnc *tnc) {
+    if (tnc->readlen < 0) {
+        return -1;
+    }
+
+    if (tnc->offset == 0) {
+        return 0;
+    }
+
+    return tnc->readlen - tnc->offset;
+}
+
 ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
                             void *buf,
                             size_t len,
diff --git a/src/server.c b/src/server.c
index 482f05e..a456ca8 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1342,17 +1342,19 @@ static int handle_iface(patty_ax25_server *server, patty_ax25_if *iface) {
         goto done;
     }
 
-    if ((readlen = patty_ax25_if_recv(iface, &buf)) < 0) {
-        goto error_io;
-    } else if (readlen == 0) {
-        fd_clear(server, fd);
+    do {
+        if ((readlen = patty_ax25_if_recv(iface, &buf)) < 0) {
+            goto error_io;
+        } else if (readlen == 0) {
+            fd_clear(server, fd);
 
-        goto done;
-    }
+            goto done;
+        }
 
-    if (handle_frame(server, iface, buf, readlen) < 0) {
-        goto error_io;
-    }
+        if (handle_frame(server, iface, buf, readlen) < 0) {
+            goto error_io;
+        }
+    } while (patty_ax25_if_pending(iface));
 
 done:
     return 0;