bridge: set priority of STP packets

[ Upstream commit 547b4e71 ]

Spanning Tree Protocol packets should have always been marked as
control packets, this causes them to get queued in the high prirority
FIFO. As Radia Perlman mentioned in her LCA talk, STP dies if bridge
gets overloaded and can't communicate. This is a long-standing bug back
to the first versions of Linux bridge.
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/bridge/br_stp_bpdu.c

@@ -16,6 +16,7 @@
 #include <linux/etherdevice.h>
 #include <linux/llc.h>
 #include <linux/slab.h>
+#include <linux/pkt_sched.h>
 #include <net/net_namespace.h>
 #include <net/llc.h>
 #include <net/llc_pdu.h>
@@ -40,6 +41,7 @@ static void br_send_bpdu(struct net_bridge_port *p,
 
 	skb->dev = p->dev;
 	skb->protocol = htons(ETH_P_802_2);
+	skb->priority = TC_PRIO_CONTROL;
 
 	skb_reserve(skb, LLC_RESERVE);
 	memcpy(__skb_put(skb, length), data, length);