bridge: reduce size of input cb to 16 bytes

Reduce size of br_input_skb_cb from 24 to 16 bytes by
using bitfield for those values that can only be 0 or 1.

igmp is the igmp type value, so it needs to be at least u8.

Furthermore, the bridge currently relies on step-by-step initialization
of br_input_skb_cb fields as the skb passes through the stack.

Explicitly zero out the bridge input cb instead, this avoids having to
review/validate that no BR_INPUT_SKB_CB(skb)->foo test can see a
'random' value from previous protocol cb.

AFAICS all current fields are always set up before they are read again,
so this is not a bug fix.

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 7946aa3..e7110a6 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -425,15 +425,13 @@ struct br_input_skb_cb {
 	struct net_device *brdev;
 
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
-	int igmp;
-	int mrouters_only;
+	u8 igmp;
+	u8 mrouters_only:1;
 #endif
-
-	bool proxyarp_replied;
-	bool src_port_isolated;
-
+	u8 proxyarp_replied:1;
+	u8 src_port_isolated:1;
 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
-	bool vlan_filtered;
+	u8 vlan_filtered:1;
 #endif
 
 #ifdef CONFIG_NET_SWITCHDEV