xdp: Extend xdp_redirect_map with broadcast support

This patch adds two flags BPF_F_BROADCAST and BPF_F_EXCLUDE_INGRESS to
extend xdp_redirect_map for broadcast support.

With BPF_F_BROADCAST the packet will be broadcasted to all the interfaces
in the map. with BPF_F_EXCLUDE_INGRESS the ingress interface will be
excluded when do broadcasting.

When getting the devices in dev hash map via dev_map_hash_get_next_key(),
there is a possibility that we fall back to the first key when a device
was removed. This will duplicate packets on some interfaces. So just walk
the whole buckets to avoid this issue. For dev array map, we also walk the
whole map to find valid interfaces.

Function bpf_clear_redirect_map() was removed in
commit ee75aef ("bpf, xdp: Restructure redirect actions").
Add it back as we need to use ri->map again.

With test topology:
  +-------------------+             +-------------------+
  | Host A (i40e 10G) |  ---------- | eno1(i40e 10G)    |
  +-------------------+             |                   |
                                    |   Host B          |
  +-------------------+             |                   |
  | Host C (i40e 10G) |  ---------- | eno2(i40e 10G)    |
  +-------------------+             |                   |
                                    |          +------+ |
                                    | veth0 -- | Peer | |
                                    | veth1 -- |      | |
                                    | veth2 -- |  NS  | |
                                    |          +------+ |
                                    +-------------------+

On Host A:
 # pktgen/pktgen_sample03_burst_single_flow.sh -i eno1 -d $dst_ip -m $dst_mac -s 64

On Host B(Intel(R) Xeon(R) CPU E5-2690 v3 @ 2.60GHz, 128G Memory):
Use xdp_redirect_map and xdp_redirect_map_multi in samples/bpf for testing.
All the veth peers in the NS have a XDP_DROP program loaded. The
forward_map max_entries in xdp_redirect_map_multi is modify to 4.

Testing the performance impact on the regular xdp_redirect path with and
without patch (to check impact of additional check for broadcast mode):

5.12 rc4         | redirect_map        i40e->i40e      |    2.0M |  9.7M
5.12 rc4         | redirect_map        i40e->veth      |    1.7M | 11.8M
5.12 rc4 + patch | redirect_map        i40e->i40e      |    2.0M |  9.6M
5.12 rc4 + patch | redirect_map        i40e->veth      |    1.7M | 11.7M

Testing the performance when cloning packets with the redirect_map_multi
test, using a redirect map size of 4, filled with 1-3 devices:

5.12 rc4 + patch | redirect_map multi  i40e->veth (x1) |    1.7M | 11.4M
5.12 rc4 + patch | redirect_map multi  i40e->veth (x2) |    1.1M |  4.3M
5.12 rc4 + patch | redirect_map multi  i40e->veth (x3) |    0.8M |  2.6M

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Link: https://lore.kernel.org/bpf/20210519090747.1655268-3-liuhangbin@gmail.com

include/linux/bpf.h

@@ -1501,8 +1501,13 @@ int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
 		    struct net_device *dev_rx);
 int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
 		    struct net_device *dev_rx);
+int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
+			  struct bpf_map *map, bool exclude_ingress);
 int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
 			     struct bpf_prog *xdp_prog);
+int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
+			   struct bpf_prog *xdp_prog, struct bpf_map *map,
+			   bool exclude_ingress);
 bool dev_map_can_have_prog(struct bpf_map *map);
 
 void __cpu_map_flush(void);
@@ -1670,6 +1675,13 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
 	return 0;
 }
 
+static inline
+int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
+			  struct bpf_map *map, bool exclude_ingress)
+{
+	return 0;
+}
+
 struct sk_buff;
 
 static inline int dev_map_generic_redirect(struct bpf_dtab_netdev *dst,
@@ -1679,6 +1691,14 @@ static inline int dev_map_generic_redirect(struct bpf_dtab_netdev *dst,
 	return 0;
 }
 
+static inline
+int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
+			   struct bpf_prog *xdp_prog, struct bpf_map *map,
+			   bool exclude_ingress)
+{
+	return 0;
+}
+
 static inline void __cpu_map_flush(void)
 {
 }

include/linux/filter.h

@@ -646,6 +646,7 @@ struct bpf_redirect_info {
 	u32 flags;
 	u32 tgt_index;
 	void *tgt_value;
+	struct bpf_map *map;
 	u32 map_id;
 	enum bpf_map_type map_type;
 	u32 kern_flags;
@@ -1464,31 +1465,41 @@ static inline bool bpf_sk_lookup_run_v6(struct net *net, int protocol,
 }
 #endif /* IS_ENABLED(CONFIG_IPV6) */
 
-static __always_inline int __bpf_xdp_redirect_map(struct bpf_map *map, u32 ifindex, u64 flags,
+static __always_inline int __bpf_xdp_redirect_map(struct bpf_map *map, u32 ifindex,
+						  u64 flags, const u64 flag_mask,
 						  void *lookup_elem(struct bpf_map *map, u32 key))
 {
 	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+	const u64 action_mask = XDP_ABORTED | XDP_DROP | XDP_PASS | XDP_TX;
 
 	/* Lower bits of the flags are used as return code on lookup failure */
-	if (unlikely(flags > XDP_TX))
+	if (unlikely(flags & ~(action_mask | flag_mask)))
 		return XDP_ABORTED;
 
 	ri->tgt_value = lookup_elem(map, ifindex);
-	if (unlikely(!ri->tgt_value)) {
+	if (unlikely(!ri->tgt_value) && !(flags & BPF_F_BROADCAST)) {
 		/* If the lookup fails we want to clear out the state in the
 		 * redirect_info struct completely, so that if an eBPF program
 		 * performs multiple lookups, the last one always takes
 		 * precedence.
 		 */
 		ri->map_id = INT_MAX; /* Valid map id idr range: [1,INT_MAX[ */
 		ri->map_type = BPF_MAP_TYPE_UNSPEC;
-		return flags;
+		return flags & action_mask;
 	}
 
 	ri->tgt_index = ifindex;
 	ri->map_id = map->id;
 	ri->map_type = map->map_type;
 
+	if (flags & BPF_F_BROADCAST) {
+		WRITE_ONCE(ri->map, map);
+		ri->flags = flags;
+	} else {
+		WRITE_ONCE(ri->map, NULL);
+		ri->flags = 0;
+	}
+
 	return XDP_REDIRECT;
 }
 

include/net/xdp.h

@@ -170,6 +170,7 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 struct sk_buff *xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 					 struct net_device *dev);
 int xdp_alloc_skb_bulk(void **skbs, int n_skb, gfp_t gfp);
+struct xdp_frame *xdpf_clone(struct xdp_frame *xdpf);
 
 static inline
 void xdp_convert_frame_to_buff(struct xdp_frame *frame, struct xdp_buff *xdp)

include/trace/events/xdp.h

@@ -110,7 +110,11 @@ DECLARE_EVENT_CLASS(xdp_redirect_template,
 		u32 ifindex = 0, map_index = index;
 
 		if (map_type == BPF_MAP_TYPE_DEVMAP || map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
-			ifindex = ((struct _bpf_dtab_netdev *)tgt)->dev->ifindex;
+			/* Just leave to_ifindex to 0 if do broadcast redirect,
+			 * as tgt will be NULL.
+			 */
+			if (tgt)
+				ifindex = ((struct _bpf_dtab_netdev *)tgt)->dev->ifindex;
 		} else if (map_type == BPF_MAP_TYPE_UNSPEC && map_id == INT_MAX) {
 			ifindex = index;
 			map_index = 0;

include/uapi/linux/bpf.h

@@ -2555,8 +2555,12 @@ union bpf_attr {
  * 		The lower two bits of *flags* are used as the return code if
  * 		the map lookup fails. This is so that the return value can be
  * 		one of the XDP program return codes up to **XDP_TX**, as chosen
- * 		by the caller. Any higher bits in the *flags* argument must be
- * 		unset.
+ * 		by the caller. The higher bits of *flags* can be set to
+ * 		BPF_F_BROADCAST or BPF_F_EXCLUDE_INGRESS as defined below.
+ *
+ * 		With BPF_F_BROADCAST the packet will be broadcasted to all the
+ * 		interfaces in the map, with BPF_F_EXCLUDE_INGRESS the ingress
+ * 		interface will be excluded when do broadcasting.
  *
  * 		See also **bpf_redirect**\ (), which only supports redirecting
  * 		to an ifindex, but doesn't require a map to do so.
@@ -5122,6 +5126,12 @@ enum {
 	BPF_F_BPRM_SECUREEXEC	= (1ULL << 0),
 };
 
+/* Flags for bpf_redirect_map helper */
+enum {
+	BPF_F_BROADCAST		= (1ULL << 3),
+	BPF_F_EXCLUDE_INGRESS	= (1ULL << 4),
+};
+
 #define __bpf_md_ptr(type, name)	\
 union {					\
 	type name;			\

kernel/bpf/cpumap.c

@@ -601,7 +601,8 @@ static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 
 static int cpu_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
 {
-	return __bpf_xdp_redirect_map(map, ifindex, flags, __cpu_map_lookup_elem);
+	return __bpf_xdp_redirect_map(map, ifindex, flags, 0,
+				      __cpu_map_lookup_elem);
 }
 
 static int cpu_map_btf_id;

kernel/bpf/devmap.c

@@ -198,6 +198,7 @@ static void dev_map_free(struct bpf_map *map)
 	list_del_rcu(&dtab->list);
 	spin_unlock(&dev_map_lock);
 
+	bpf_clear_redirect_map(map);
 	synchronize_rcu();
 
 	/* Make sure prior __dev_map_entry_free() have completed. */
@@ -515,6 +516,99 @@ 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)
+{
+	if (!obj || obj->dev->ifindex == exclude_ifindex ||
+	    !obj->dev->netdev_ops->ndo_xdp_xmit)
+		return false;
+
+	if (xdp_ok_fwd_dev(obj->dev, xdp->data_end - xdp->data))
+		return false;
+
+	return true;
+}
+
+static int dev_map_enqueue_clone(struct bpf_dtab_netdev *obj,
+				 struct net_device *dev_rx,
+				 struct xdp_frame *xdpf)
+{
+	struct xdp_frame *nxdpf;
+
+	nxdpf = xdpf_clone(xdpf);
+	if (!nxdpf)
+		return -ENOMEM;
+
+	bq_enqueue(obj->dev, nxdpf, dev_rx, obj->xdp_prog);
+
+	return 0;
+}
+
+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;
+	struct hlist_head *head;
+	struct xdp_frame *xdpf;
+	unsigned int i;
+	int err;
+
+	xdpf = xdp_convert_buff_to_frame(xdp);
+	if (unlikely(!xdpf))
+		return -EOVERFLOW;
+
+	if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
+		for (i = 0; i < map->max_entries; i++) {
+			dst = READ_ONCE(dtab->netdev_map[i]);
+			if (!is_valid_dst(dst, xdp, exclude_ifindex))
+				continue;
+
+			/* we only need n-1 clones; last_dst enqueued below */
+			if (!last_dst) {
+				last_dst = dst;
+				continue;
+			}
+
+			err = dev_map_enqueue_clone(last_dst, dev_rx, xdpf);
+			if (err)
+				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_rcu(dst, head, index_hlist,
+						 lockdep_is_held(&dtab->index_lock)) {
+				if (!is_valid_dst(dst, xdp, exclude_ifindex))
+					continue;
+
+				/* we only need n-1 clones; last_dst enqueued below */
+				if (!last_dst) {
+					last_dst = dst;
+					continue;
+				}
+
+				err = dev_map_enqueue_clone(last_dst, dev_rx, xdpf);
+				if (err)
+					return err;
+
+				last_dst = dst;
+			}
+		}
+	}
+
+	/* consume the last copy of the frame */
+	if (last_dst)
+		bq_enqueue(last_dst->dev, xdpf, dev_rx, last_dst->xdp_prog);
+	else
+		xdp_return_frame_rx_napi(xdpf); /* dtab is empty */
+
+	return 0;
+}
+
 int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
 			     struct bpf_prog *xdp_prog)
 {
@@ -529,6 +623,87 @@ int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
 	return 0;
 }
 
+static int dev_map_redirect_clone(struct bpf_dtab_netdev *dst,
+				  struct sk_buff *skb,
+				  struct bpf_prog *xdp_prog)
+{
+	struct sk_buff *nskb;
+	int err;
+
+	nskb = skb_clone(skb, GFP_ATOMIC);
+	if (!nskb)
+		return -ENOMEM;
+
+	err = dev_map_generic_redirect(dst, nskb, xdp_prog);
+	if (unlikely(err)) {
+		consume_skb(nskb);
+		return err;
+	}
+
+	return 0;
+}
+
+int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
+			   struct bpf_prog *xdp_prog, struct bpf_map *map,
+			   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;
+	struct hlist_head *head;
+	struct hlist_node *next;
+	unsigned int i;
+	int err;
+
+	if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
+		for (i = 0; i < map->max_entries; i++) {
+			dst = READ_ONCE(dtab->netdev_map[i]);
+			if (!dst || dst->dev->ifindex == exclude_ifindex)
+				continue;
+
+			/* we only need n-1 clones; last_dst enqueued below */
+			if (!last_dst) {
+				last_dst = dst;
+				continue;
+			}
+
+			err = dev_map_redirect_clone(last_dst, skb, xdp_prog);
+			if (err)
+				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)
+					continue;
+
+				/* we only need n-1 clones; last_dst enqueued below */
+				if (!last_dst) {
+					last_dst = dst;
+					continue;
+				}
+
+				err = dev_map_redirect_clone(last_dst, skb, xdp_prog);
+				if (err)
+					return err;
+
+				last_dst = dst;
+			}
+		}
+	}
+
+	/* consume the first skb and return */
+	if (last_dst)
+		return dev_map_generic_redirect(last_dst, skb, xdp_prog);
+
+	/* dtab is empty */
+	consume_skb(skb);
+	return 0;
+}
+
 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
@@ -755,12 +930,16 @@ static int dev_map_hash_update_elem(struct bpf_map *map, void *key, void *value,
 
 static int dev_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
 {
-	return __bpf_xdp_redirect_map(map, ifindex, flags, __dev_map_lookup_elem);
+	return __bpf_xdp_redirect_map(map, ifindex, flags,
+				      BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS,
+				      __dev_map_lookup_elem);
 }
 
 static int dev_hash_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
 {
-	return __bpf_xdp_redirect_map(map, ifindex, flags, __dev_map_hash_lookup_elem);
+	return __bpf_xdp_redirect_map(map, ifindex, flags,
+				      BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS,
+				      __dev_map_hash_lookup_elem);
 }
 
 static int dev_map_btf_id;