[PATCH net-next] net: bridge: add helper to call /sbin/bridge-stp
From: Vivien Didelot
Date: Thu Sep 08 2016 - 12:51:17 EST
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: Vivien Didelot <vivien.didelot@xxxxxxxxxxxxxxxxxxxx>
---
net/bridge/br_stp_if.c | 43 +++++++++++++++++++++++++++++++------------
1 file changed, 31 insertions(+), 12 deletions(-)
diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 341caa0..d8ad73b 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -134,17 +134,36 @@ void br_stp_disable_port(struct net_bridge_port *p)
br_become_root_bridge(br);
}
+static int br_stp_call_user(struct net_bridge *br, char *arg)
+{
+ 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)
{
- int r;
- char *argv[] = { BR_STP_PROG, br->dev->name, "start", NULL };
- char *envp[] = { NULL };
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);
--
2.9.3