net: bridge: add skb drop reasons to the most common drop points

The bridge input code may drop frames for various reasons and at various
points in the ingress handling logic. Currently kfree_skb() is used
everywhere, and therefore no drop reason is specified. Add drop reasons
to the most common drop points.

Drop reasons are not added exhaustively to the entire bridge code. The
intention is to incrementally add drop reasons to the rest of the bridge
code in follow up patches.

Signed-off-by: Radu Rendec <[email protected]>
Reviewed-by: Ido Schimmel <[email protected]>
Acked-by: Nikolay Aleksandrov <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: rrendec

include/net/dropreason-core.h

@@ -111,6 +111,8 @@
 	FN(TUNNEL_TXINFO)		\
 	FN(LOCAL_MAC)			\
 	FN(ARP_PVLAN_DISABLE)		\
+	FN(MAC_IEEE_MAC_CONTROL)	\
+	FN(BRIDGE_INGRESS_STP_STATE)	\
 	FNe(MAX)
 
 /**
@@ -520,6 +522,16 @@ enum skb_drop_reason {
 	 * enabled.
 	 */
 	SKB_DROP_REASON_ARP_PVLAN_DISABLE,
+	/**
+	 * @SKB_DROP_REASON_MAC_IEEE_MAC_CONTROL: the destination MAC address
+	 * is an IEEE MAC Control address.
+	 */
+	SKB_DROP_REASON_MAC_IEEE_MAC_CONTROL,
+	/**
+	 * @SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE: the STP state of the
+	 * ingress bridge port does not allow frames to be forwarded.
+	 */
+	SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE,
 	/**
 	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
 	 * shouldn't be used as a real 'reason' - only for tracing code gen

net/bridge/br_forward.c

@@ -201,6 +201,7 @@ void br_flood(struct net_bridge *br, struct sk_buff *skb,
 	      enum br_pkt_type pkt_type, bool local_rcv, bool local_orig,
 	      u16 vid)
 {
+	enum skb_drop_reason reason = SKB_DROP_REASON_NO_TX_TARGET;
 	struct net_bridge_port *prev = NULL;
 	struct net_bridge_port *p;
 
@@ -234,8 +235,11 @@ void br_flood(struct net_bridge *br, struct sk_buff *skb,
 			continue;
 
 		prev = maybe_deliver(prev, p, skb, local_orig);
-		if (IS_ERR(prev))
+		if (IS_ERR(prev)) {
+			reason = PTR_ERR(prev) == -ENOMEM ? SKB_DROP_REASON_NOMEM :
+				 SKB_DROP_REASON_NOT_SPECIFIED;
 			goto out;
+		}
 	}
 
 	if (!prev)
@@ -249,7 +253,7 @@ void br_flood(struct net_bridge *br, struct sk_buff *skb,
 
 out:
 	if (!local_rcv)
-		kfree_skb(skb);
+		kfree_skb_reason(skb, reason);
 }
 
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
@@ -289,6 +293,7 @@ void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
 			struct net_bridge_mcast *brmctx,
 			bool local_rcv, bool local_orig)
 {
+	enum skb_drop_reason reason = SKB_DROP_REASON_NO_TX_TARGET;
 	struct net_bridge_port *prev = NULL;
 	struct net_bridge_port_group *p;
 	bool allow_mode_include = true;
@@ -329,8 +334,11 @@ void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
 		}
 
 		prev = maybe_deliver(prev, port, skb, local_orig);
-		if (IS_ERR(prev))
+		if (IS_ERR(prev)) {
+			reason = PTR_ERR(prev) == -ENOMEM ? SKB_DROP_REASON_NOMEM :
+				 SKB_DROP_REASON_NOT_SPECIFIED;
 			goto out;
+		}
 delivered:
 		if ((unsigned long)lport >= (unsigned long)port)
 			p = rcu_dereference(p->next);
@@ -349,6 +357,6 @@ void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
 
 out:
 	if (!local_rcv)
-		kfree_skb(skb);
+		kfree_skb_reason(skb, reason);
 }
 #endif

net/bridge/br_input.c

@@ -75,6 +75,7 @@ static int br_pass_frame_up(struct sk_buff *skb, bool promisc)
 /* note: already called with rcu_read_lock */
 int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
+	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 	enum br_pkt_type pkt_type = BR_PKT_UNICAST;
 	struct net_bridge_fdb_entry *dst = NULL;
@@ -96,8 +97,10 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 	if (br_mst_is_enabled(br)) {
 		state = BR_STATE_FORWARDING;
 	} else {
-		if (p->state == BR_STATE_DISABLED)
+		if (p->state == BR_STATE_DISABLED) {
+			reason = SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE;
 			goto drop;
+		}
 
 		state = p->state;
 	}
@@ -155,8 +158,10 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 		}
 	}
 
-	if (state == BR_STATE_LEARNING)
+	if (state == BR_STATE_LEARNING) {
+		reason = SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE;
 		goto drop;
+	}
 
 	BR_INPUT_SKB_CB(skb)->brdev = br->dev;
 	BR_INPUT_SKB_CB(skb)->src_port_isolated = !!(p->flags & BR_ISOLATED);
@@ -223,7 +228,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 out:
 	return 0;
 drop:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, reason);
 	goto out;
 }
 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
@@ -324,15 +329,18 @@ static int br_process_frame_type(struct net_bridge_port *p,
  */
 static rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 {
+	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	struct net_bridge_port *p;
 	struct sk_buff *skb = *pskb;
 	const unsigned char *dest = eth_hdr(skb)->h_dest;
 
 	if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 		return RX_HANDLER_PASS;
 
-	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
+	if (!is_valid_ether_addr(eth_hdr(skb)->h_source)) {
+		reason = SKB_DROP_REASON_MAC_INVALID_SOURCE;
 		goto drop;
+	}
 
 	skb = skb_share_check(skb, GFP_ATOMIC);
 	if (!skb)
@@ -374,6 +382,7 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 			return RX_HANDLER_PASS;
 
 		case 0x01:	/* IEEE MAC (Pause) */
+			reason = SKB_DROP_REASON_MAC_IEEE_MAC_CONTROL;
 			goto drop;
 
 		case 0x0E:	/* 802.1AB LLDP */
@@ -423,8 +432,9 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 
 		return nf_hook_bridge_pre(skb, pskb);
 	default:
+		reason = SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE;
 drop:
-		kfree_skb(skb);
+		kfree_skb_reason(skb, reason);
 	}
 	return RX_HANDLER_CONSUMED;
 }