[PATCH ustp] ubus: create bridge config on demand in bridge_state

[Tao Gong]

The kernel runs /sbin/bridge-stp as soon as a bridge is created with STP
enabled, which calls ustp's bridge_state. netifd sends the bridge's config
in a stp_init notification just before creating the bridge, but ustpd only
receives that if it is already subscribed to network.device - and it polls
for that object once per second.

If the bridge is created inside that polling gap, bridge_state has no config
for it and returns NOT_FOUND. When the userspace helper fails, the kernel
falls back to in-kernel legacy 802.1D STP and transmits Version 0 Config
BPDUs onto the wire, permanently causing connected RSTP switches to downgrade
to legacy STP.

Create the config instead of refusing. A fresh config is zeroed, so all its
set_* flags are false and the bridge operates with ustpd's default RSTP
parameters; netifd's real values arrive moments later via stp_init.

Link: https://github.com/openwrt/ustp/issues/8
Signed-off-by: Tao Gong <gongtao0607 at gmail.com>
---
 ubus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ubus.c b/ubus.c
index 201761c..9dd5bb3 100644
--- a/ubus.c
+++ b/ubus.c
@@ -135,7 +135,7 @@ ubus_bridge_state(struct ubus_context *ctx, struct ubus_object *obj,
 		return UBUS_STATUS_NOT_FOUND;
 
 	if (blobmsg_get_bool(tb[BRIDGE_STATE_ENABLED])) {
-		cfg = bridge_config_get(bridge_name, false);
+		cfg = bridge_config_get(bridge_name, true);
 		if (!cfg)
 			return UBUS_STATUS_NOT_FOUND;
 
-- 
2.55.0