From cb38337c2b6f28cf56b29ffc2519012b7d342e61 Mon Sep 17 00:00:00 2001
From: Vincent Bernat <vincent@bernat.ch>
Date: Fri, 24 Apr 2020 19:09:42 +0200
Subject: [PATCH] lib: stricly-prevent use of a connection used to watch events

The protocol cannot handle received events mixed with regular
messages. Once the connection is dedicated to a watch, prevent its
regular use.
---
 src/lib/atom.c       | 7 ++++++-
 src/lib/atom.h       | 1 +
 src/lib/connection.c | 3 ++-
 src/lib/lldpctl.h    | 6 ++++--
 4 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/lib/atom.c b/src/lib/atom.c
index f81d3bbc..54e94ae6 100644
--- a/src/lib/atom.c
+++ b/src/lib/atom.c
@@ -314,6 +314,10 @@ _lldpctl_do_something(lldpctl_conn_t *conn,
 {
 	ssize_t rc;
 
+	if (conn->state == CONN_STATE_WATCHING)
+		/* The connection cannot be used anymore. */
+		return SET_ERROR(conn, LLDPCTL_ERR_INVALID_STATE);
+
 	if (conn->state == CONN_STATE_IDLE) {
 		/* We need to build the message to send, then send
 		 * it. */
@@ -371,6 +375,7 @@ lldpctl_watch_callback(lldpctl_conn_t *conn,
 	if (rc == 0) {
 		conn->watch_cb = cb;
 		conn->watch_data = data;
+		conn->state = CONN_STATE_WATCHING;
 	}
 	return rc;
 }
@@ -382,7 +387,7 @@ lldpctl_watch(lldpctl_conn_t *conn)
 
 	RESET_ERROR(conn);
 
-	if (conn->state != CONN_STATE_IDLE)
+	if (conn->state != CONN_STATE_WATCHING)
 		return SET_ERROR(conn, LLDPCTL_ERR_INVALID_STATE);
 
 	conn->watch_triggered = 0;
diff --git a/src/lib/atom.h b/src/lib/atom.h
index a818f7ac..d6ae218f 100644
--- a/src/lib/atom.h
+++ b/src/lib/atom.h
@@ -54,6 +54,7 @@ struct lldpctl_conn_t {
 #define CONN_STATE_GET_CHASSIS_RECV	14
 #define CONN_STATE_GET_DEFAULT_PORT_SEND 15
 #define CONN_STATE_GET_DEFAULT_PORT_RECV 16
+#define CONN_STATE_WATCHING		17
 	int state;		/* Current state */
 	/* Data attached to the state. It is used to check that we are using the
 	 * same data as a previous call until the state machine goes to
diff --git a/src/lib/connection.c b/src/lib/connection.c
index aa88dadf..191d7c6a 100644
--- a/src/lib/connection.c
+++ b/src/lib/connection.c
@@ -262,7 +262,8 @@ lldpctl_recv(lldpctl_conn_t *conn, const uint8_t *data, size_t length)
 	return conn->input_buffer_len;
 }
 
-int lldpctl_process_conn_buffer(lldpctl_conn_t *conn)
+int
+lldpctl_process_conn_buffer(lldpctl_conn_t *conn)
 {
 	int rc;
 
diff --git a/src/lib/lldpctl.h b/src/lib/lldpctl.h
index c9f4d474..2369bf20 100644
--- a/src/lib/lldpctl.h
+++ b/src/lib/lldpctl.h
@@ -471,7 +471,8 @@ typedef enum {
  * reference to it, be sure to increment the reference count in the callback.
  *
  * @warning The provided connection should not be used at all. Do not use @c
- * lldpctl_atom_set_*() functions on @c interface or @c neighbor either.
+ * lldpctl_atom_set_*() functions on @c interface or @c neighbor either. If you
+ * do, you will get a @c LLDPCTL_ERR_INVALID_STATE error.
  *
  * @see lldpctl_watch_callback
  */
@@ -494,7 +495,8 @@ typedef void (*lldpctl_change_callback)(lldpctl_conn_t *conn,
  * LLDPCTL_ERR_WOULDBLOCK.
  *
  * @warning Once a callback is registered, the connection shouldn't be used for
- * anything else than receiving notifications.
+ * anything else than receiving notifications. If you do, you will get a @c
+ * LLDPCTL_ERR_INVALID_STATE error.
  */
 int lldpctl_watch_callback(lldpctl_conn_t *conn,
     lldpctl_change_callback cb,
-- 
2.39.2