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 <[email protected]>
Acked-by: David S. Miller <[email protected]>
Acked-by: Nikolay Aleksandrov <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

Author: Florian Westphal

net/bridge/br_arp_nd_proxy.c

@@ -131,7 +131,7 @@ void br_do_proxy_suppress_arp(struct sk_buff *skb, struct net_bridge *br,
 	u8 *arpptr, *sha;
 	__be32 sip, tip;
 
-	BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;
+	BR_INPUT_SKB_CB(skb)->proxyarp_replied = 0;
 
 	if ((dev->flags & IFF_NOARP) ||
 	    !pskb_may_pull(skb, arp_hdr_len(dev)))
@@ -161,7 +161,7 @@ void br_do_proxy_suppress_arp(struct sk_buff *skb, struct net_bridge *br,
 			return;
 		if (ipv4_is_zeronet(sip) || sip == tip) {
 			/* prevent flooding to neigh suppress ports */
-			BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
+			BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
 			return;
 		}
 	}
@@ -181,7 +181,7 @@ void br_do_proxy_suppress_arp(struct sk_buff *skb, struct net_bridge *br,
 		/* its our local ip, so don't proxy reply
 		 * and don't forward to neigh suppress ports
 		 */
-		BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
+		BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
 		return;
 	}
 
@@ -217,7 +217,7 @@ void br_do_proxy_suppress_arp(struct sk_buff *skb, struct net_bridge *br,
 			 */
 			if (replied ||
 			    br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED))
-				BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
+				BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
 		}
 
 		neigh_release(n);
@@ -393,15 +393,15 @@ void br_do_suppress_nd(struct sk_buff *skb, struct net_bridge *br,
 	struct ipv6hdr *iphdr;
 	struct neighbour *n;
 
-	BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;
+	BR_INPUT_SKB_CB(skb)->proxyarp_replied = 0;
 
 	if (p && (p->flags & BR_NEIGH_SUPPRESS))
 		return;
 
 	if (msg->icmph.icmp6_type == NDISC_NEIGHBOUR_ADVERTISEMENT &&
 	    !msg->icmph.icmp6_solicited) {
 		/* prevent flooding to neigh suppress ports */
-		BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
+		BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
 		return;
 	}
 
@@ -414,7 +414,7 @@ void br_do_suppress_nd(struct sk_buff *skb, struct net_bridge *br,
 
 	if (ipv6_addr_any(saddr) || !ipv6_addr_cmp(saddr, daddr)) {
 		/* prevent flooding to neigh suppress ports */
-		BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
+		BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
 		return;
 	}
 
@@ -432,7 +432,7 @@ void br_do_suppress_nd(struct sk_buff *skb, struct net_bridge *br,
 		/* its our own ip, so don't proxy reply
 		 * and don't forward to arp suppress ports
 		 */
-		BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
+		BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
 		return;
 	}
 
@@ -465,7 +465,7 @@ void br_do_suppress_nd(struct sk_buff *skb, struct net_bridge *br,
 			 */
 			if (replied ||
 			    br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED))
-				BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
+				BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
 		}
 		neigh_release(n);
 	}

net/bridge/br_input.c

@@ -227,6 +227,8 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 	if (!skb)
 		return RX_HANDLER_CONSUMED;
 
+	memset(skb->cb, 0, sizeof(struct br_input_skb_cb));
+
 	p = br_port_get_rcu(skb->dev);
 	if (p->flags & BR_VLAN_TUNNEL) {
 		if (br_handle_ingress_vlan_tunnel(skb, p,

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