bridge: control carrier based on ports online

This makes the bridge device behave like a physical device.
In earlier releases the bridge always asserted carrier. This
changes the behavior so that bridge device carrier is on only
if one or more ports are in the forwarding state. This
should help IPv6 autoconfiguration, DHCP, and routing daemons.

I did brief testing with Network and Virt manager and they
seem fine, but since this changes behavior of bridge, it should
wait until net-next (2.6.39).

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Reviewed-by: Nicolas de Pesloüan <nicolas.2p.debian@free.fr>
Tested-By: Adam Majer <adamm@zombino.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 13 deletions

diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index 57186d84d2bd..a5badd0f8226 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -397,28 +397,37 @@ static void br_make_forwarding(struct net_bridge_port *p)
 void br_port_state_selection(struct net_bridge *br)
 {
         struct net_bridge_port *p;
+        unsigned int liveports = 0;
 
         /* Don't change port states if userspace is handling STP */
         if (br->stp_enabled == BR_USER_STP)
                 return;
 
         list_for_each_entry(p, &br->port_list, list) {
-                if (p->state != BR_STATE_DISABLED) {
-                        if (p->port_no == br->root_port) {
-                                p->config_pending = 0;
-                                p->topology_change_ack = 0;
-                                br_make_forwarding(p);
-                        } else if (br_is_designated_port(p)) {
-                                del_timer(&p->message_age_timer);
-                                br_make_forwarding(p);
-                        } else {
-                                p->config_pending = 0;
-                                p->topology_change_ack = 0;
-                                br_make_blocking(p);
-                        }
+                if (p->state == BR_STATE_DISABLED)
+                        continue;
+
+                if (p->port_no == br->root_port) {
+                        p->config_pending = 0;
+                        p->topology_change_ack = 0;
+                        br_make_forwarding(p);
+                } else if (br_is_designated_port(p)) {
+                        del_timer(&p->message_age_timer);
+                        br_make_forwarding(p);
+                } else {
+                        p->config_pending = 0;
+                        p->topology_change_ack = 0;
+                        br_make_blocking(p);
                 }
 
+                if (p->state == BR_STATE_FORWARDING)
+                        ++liveports;
         }
+
+        if (liveports == 0)
+                netif_carrier_off(br->dev);
+        else
+                netif_carrier_on(br->dev);
 }
 
 /* called under bridge lock */