Commit 30843315 authored by Vivien Didelot's avatar Vivien Didelot Committed by David S. Miller
Browse files

net: bridge: add helper to call /sbin/bridge-stp 



If /sbin/bridge-stp is available on the system, bridge tries to execute
it instead of the kernel implementation when starting/stopping STP.

If anything goes wrong with /sbin/bridge-stp, bridge silently falls back
to kernel STP, making hard to debug userspace STP.

This patch adds a br_stp_call_user helper to start/stop userspace STP
and debug errors from the program: abnormal exit status is stored in the
lower byte and normal exit status is stored in higher byte.

Below is a simple example on a kernel with dynamic debug enabled:

    # ln -s /bin/false /sbin/bridge-stp
    # brctl stp br0 on
    br0: failed to start userspace STP (256)
    # dmesg
    br0: /sbin/bridge-stp exited with code 1
    br0: failed to start userspace STP (256)
    br0: using kernel STP

Signed-off-by: default avatarVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4c73195e

net/bridge/br_stp_if.c

+31 −12
Original line number Diff line number Diff line
@@ -134,17 +134,36 @@ void br_stp_disable_port(struct net_bridge_port *p) 
		br_become_root_bridge(br);

}



static void br_stp_start(struct net_bridge *br)

static int br_stp_call_user(struct net_bridge *br, char *arg)

{

	int r;

	char *argv[] = { BR_STP_PROG, br->dev->name, "start", NULL };

	char *argv[] = { BR_STP_PROG, br->dev->name, arg, NULL };

	char *envp[] = { NULL };

	int rc;



	/* call userspace STP and report program errors */

	rc = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);

	if (rc > 0) {

		if (rc & 0xff)

			br_debug(br, BR_STP_PROG " received signal %d\n",

				 rc & 0x7f);

		else

			br_debug(br, BR_STP_PROG " exited with code %d\n",

				 (rc >> 8) & 0xff);

	}



	return rc;

}



static void br_stp_start(struct net_bridge *br)

{

	struct net_bridge_port *p;

	int err = -ENOENT;



	if (net_eq(dev_net(br->dev), &init_net))

		r = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);

	else

		r = -ENOENT;

		err = br_stp_call_user(br, "start");



	if (err && err != -ENOENT)

		br_err(br, "failed to start userspace STP (%d)\n", err);



	spin_lock_bh(&br->lock);
@@ -153,9 +172,10 @@ static void br_stp_start(struct net_bridge *br) 
	else if (br->bridge_forward_delay > BR_MAX_FORWARD_DELAY)

		__br_set_forward_delay(br, BR_MAX_FORWARD_DELAY);



	if (r == 0) {

	if (!err) {

		br->stp_enabled = BR_USER_STP;

		br_debug(br, "userspace STP started\n");



		/* Stop hello and hold timers */

		del_timer(&br->hello_timer);

		list_for_each_entry(p, &br->port_list, list)
@@ -173,14 +193,13 @@ static void br_stp_start(struct net_bridge *br) 


static void br_stp_stop(struct net_bridge *br)

{

	int r;

	char *argv[] = { BR_STP_PROG, br->dev->name, "stop", NULL };

	char *envp[] = { NULL };

	struct net_bridge_port *p;

	int err;



	if (br->stp_enabled == BR_USER_STP) {

		r = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);

		br_info(br, "userspace STP stopped, return code %d\n", r);

		err = br_stp_call_user(br, "stop");

		if (err)

			br_err(br, "failed to stop userspace STP (%d)\n", err);



		/* To start timers on any ports left in blocking */

		mod_timer(&br->hello_timer, jiffies + br->hello_time);

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