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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: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vivien Didelot 2016-09-08 12:50:43 -04:00 committed by David S. Miller
parent 4c73195edb
commit 308433155a
1 changed files with 31 additions and 12 deletions
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43
net/bridge/br_stp_if.c
View File

@ -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);