bpf, devmap: Exclude XDP broadcast to master device

If the ingress device is bond slave, do not broadcast back through it or
the bond master.
Signed-off-by: Jussi Maki <joamaki@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210731055738.16820-5-joamaki@gmail.com

kernel/bpf/devmap.c

@@ -534,10 +534,9 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
 	return __xdp_enqueue(dev, xdp, dev_rx, dst->xdp_prog);
 }
 
-static bool is_valid_dst(struct bpf_dtab_netdev *obj, struct xdp_buff *xdp,
-			 int exclude_ifindex)
+static bool is_valid_dst(struct bpf_dtab_netdev *obj, struct xdp_buff *xdp)
 {
-	if (!obj || obj->dev->ifindex == exclude_ifindex ||
+	if (!obj ||
 	    !obj->dev->netdev_ops->ndo_xdp_xmit)
 		return false;
 
@@ -562,17 +561,48 @@ static int dev_map_enqueue_clone(struct bpf_dtab_netdev *obj,
 	return 0;
 }
 
+static inline bool is_ifindex_excluded(int *excluded, int num_excluded, int ifindex)
+{
+	while (num_excluded--) {
+		if (ifindex == excluded[num_excluded])
+			return true;
+	}
+	return false;
+}
+
+/* Get ifindex of each upper device. 'indexes' must be able to hold at
+ * least MAX_NEST_DEV elements.
+ * Returns the number of ifindexes added.
+ */
+static int get_upper_ifindexes(struct net_device *dev, int *indexes)
+{
+	struct net_device *upper;
+	struct list_head *iter;
+	int n = 0;
+
+	netdev_for_each_upper_dev_rcu(dev, upper, iter) {
+		indexes[n++] = upper->ifindex;
+	}
+	return n;
+}
+
 int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
 			  struct bpf_map *map, bool exclude_ingress)
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
-	int exclude_ifindex = exclude_ingress ? dev_rx->ifindex : 0;
 	struct bpf_dtab_netdev *dst, *last_dst = NULL;
+	int excluded_devices[1+MAX_NEST_DEV];
 	struct hlist_head *head;
 	struct xdp_frame *xdpf;
+	int num_excluded = 0;
 	unsigned int i;
 	int err;
 
+	if (exclude_ingress) {
+		num_excluded = get_upper_ifindexes(dev_rx, excluded_devices);
+		excluded_devices[num_excluded++] = dev_rx->ifindex;
+	}
+
 	xdpf = xdp_convert_buff_to_frame(xdp);
 	if (unlikely(!xdpf))
 		return -EOVERFLOW;
@@ -581,7 +611,10 @@ int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
 		for (i = 0; i < map->max_entries; i++) {
 			dst = rcu_dereference_check(dtab->netdev_map[i],
 						    rcu_read_lock_bh_held());
-			if (!is_valid_dst(dst, xdp, exclude_ifindex))
+			if (!is_valid_dst(dst, xdp))
+				continue;
+
+			if (is_ifindex_excluded(excluded_devices, num_excluded, dst->dev->ifindex))
 				continue;
 
 			/* we only need n-1 clones; last_dst enqueued below */
@@ -601,7 +634,11 @@ int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
 			head = dev_map_index_hash(dtab, i);
 			hlist_for_each_entry_rcu(dst, head, index_hlist,
 						 lockdep_is_held(&dtab->index_lock)) {
-				if (!is_valid_dst(dst, xdp, exclude_ifindex))
+				if (!is_valid_dst(dst, xdp))
+					continue;
+
+				if (is_ifindex_excluded(excluded_devices, num_excluded,
+							dst->dev->ifindex))
 					continue;
 
 				/* we only need n-1 clones; last_dst enqueued below */
@@ -675,18 +712,27 @@ int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
 			   bool exclude_ingress)
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
-	int exclude_ifindex = exclude_ingress ? dev->ifindex : 0;
 	struct bpf_dtab_netdev *dst, *last_dst = NULL;
+	int excluded_devices[1+MAX_NEST_DEV];
 	struct hlist_head *head;
 	struct hlist_node *next;
+	int num_excluded = 0;
 	unsigned int i;
 	int err;
 
+	if (exclude_ingress) {
+		num_excluded = get_upper_ifindexes(dev, excluded_devices);
+		excluded_devices[num_excluded++] = dev->ifindex;
+	}
+
 	if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
 		for (i = 0; i < map->max_entries; i++) {
 			dst = rcu_dereference_check(dtab->netdev_map[i],
 						    rcu_read_lock_bh_held());
-			if (!dst || dst->dev->ifindex == exclude_ifindex)
+			if (!dst)
+				continue;
+
+			if (is_ifindex_excluded(excluded_devices, num_excluded, dst->dev->ifindex))
 				continue;
 
 			/* we only need n-1 clones; last_dst enqueued below */
@@ -700,12 +746,17 @@ int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
 				return err;
 
 			last_dst = dst;
+
 		}
 	} else { /* BPF_MAP_TYPE_DEVMAP_HASH */
 		for (i = 0; i < dtab->n_buckets; i++) {
 			head = dev_map_index_hash(dtab, i);
 			hlist_for_each_entry_safe(dst, next, head, index_hlist) {
-				if (!dst || dst->dev->ifindex == exclude_ifindex)
+				if (!dst)
+					continue;
+
+				if (is_ifindex_excluded(excluded_devices, num_excluded,
+							dst->dev->ifindex))
 					continue;
 
 				/* we only need n-1 clones; last_dst enqueued below */