bridge: range check STP parameters

Apply restrictions on STP parameters based 802.1D 1998 standard.
   * Fixes missing locking in set path cost ioctl
   * Uses common code for both ioctl and sysfs

This is based on an earlier patch Sasikanth V but with overhaul.

Note:
1. It does NOT enforce the restriction on the relationship max_age and
   forward delay or hello time because in existing implementation these are
   set as independant operations.

2. If STP is disabled, there is no restriction on forward delay

3. No restriction on holding time because users use Linux code to act
   as hub or be sticky.

4. Although standard allow 0-255, Linux only allows 0-63 for port priority
   because more bits are reserved for port number.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 48 insertions, 0 deletions

diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index 7370d14f634d..bb4383e84de9 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -484,3 +484,51 @@ void br_received_tcn_bpdu(struct net_bridge_port *p)
                 br_topology_change_acknowledge(p);
         }
 }
+
+/* Change bridge STP parameter */
+int br_set_hello_time(struct net_bridge *br, unsigned long val)
+{
+        unsigned long t = clock_t_to_jiffies(val);
+
+        if (t < BR_MIN_HELLO_TIME || t > BR_MAX_HELLO_TIME)
+                return -ERANGE;
+
+        spin_lock_bh(&br->lock);
+        br->bridge_hello_time = t;
+        if (br_is_root_bridge(br))
+                br->hello_time = br->bridge_hello_time;
+        spin_unlock_bh(&br->lock);
+        return 0;
+}
+
+int br_set_max_age(struct net_bridge *br, unsigned long val)
+{
+        unsigned long t = clock_t_to_jiffies(val);
+
+        if (t < BR_MIN_MAX_AGE || t > BR_MAX_MAX_AGE)
+                return -ERANGE;
+
+        spin_lock_bh(&br->lock);
+        br->bridge_max_age = t;
+        if (br_is_root_bridge(br))
+                br->max_age = br->bridge_max_age;
+        spin_unlock_bh(&br->lock);
+        return 0;
+
+}
+
+int br_set_forward_delay(struct net_bridge *br, unsigned long val)
+{
+        unsigned long t = clock_t_to_jiffies(val);
+
+        if (br->stp_enabled != BR_NO_STP &&
+            (t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
+                return -ERANGE;
+
+        spin_lock_bh(&br->lock);
+        br->bridge_forward_delay = t;
+        if (br_is_root_bridge(br))
+                br->forward_delay = br->bridge_forward_delay;
+        spin_unlock_bh(&br->lock);
+        return 0;
+}