TT#26513 Delete the kernel forwarding table on startup

If we are creating the kernel forwarding table, we have to make sure it
has been deleted already, otherwise we can get into collisions with the
already setup forwardings, and the subsequent add will fail anyway.

Change-Id: I2601c602543ff3e3493bae296d263dde545ff352
(cherry picked from commit fd3c1d2519)

daemon/kernel.c

@@ -28,7 +28,7 @@ struct kernel_interface kernel;
 
 
 
-static int kernel_create_table(unsigned int id) {
+static int kernel_action_table(const char *action, unsigned int id) {
 	char str[64];
 	int fd;
 	int i;
@@ -36,7 +36,9 @@ static int kernel_create_table(unsigned int id) {
 	fd = open(PREFIX "/control", O_WRONLY | O_TRUNC);
 	if (fd == -1)
 		return -1;
-	sprintf(str, "add %u\n", id);
+	i = snprintf(str, sizeof(str), "%s %u\n", action, id);
+	if (i >= sizeof(str))
+		goto fail;
 	i = write(fd, str, strlen(str));
 	if (i == -1)
 		goto fail;
@@ -49,6 +51,14 @@ fail:
 	return -1;
 }
 
+static int kernel_create_table(unsigned int id) {
+	return kernel_action_table("add", id);
+}
+
+static int kernel_delete_table(unsigned int id) {
+	return kernel_action_table("del", id);
+}
+
 static int kernel_open_table(unsigned int id) {
 	char str[64];
 	int fd;
@@ -79,6 +89,11 @@ int kernel_setup_table(unsigned int id) {
 
 	kernel.is_wanted = 1;
 
+	if (kernel_delete_table(id) && errno != ENOENT) {
+		ilog(LOG_ERR, "FAILED TO DELETE KERNEL TABLE %i (%s), KERNEL FORWARDING DISABLED",
+				id, strerror(errno));
+		return -1;
+	}
 	if (kernel_create_table(id)) {
 		ilog(LOG_ERR, "FAILED TO CREATE KERNEL TABLE %i (%s), KERNEL FORWARDING DISABLED",
 				id, strerror(errno));

debian/ngcp-rtpengine-daemon.init

@@ -182,9 +182,6 @@ case "$1" in
 			ip6tables -D rtpengine -p udp -j RTPENGINE --id "$TABLE" 2>/dev/null
 			ip6tables -I rtpengine -p udp -j RTPENGINE --id "$TABLE"
 		fi
-		if [ -e /proc/rtpengine/control ]; then
-			echo "del $TABLE" > /proc/rtpengine/control 2>/dev/null
-		fi
 	fi
 	set -e
 	log_daemon_msg "Starting $DESC" "$NAME"