net/macsec: Add MACsec skb_metadata_dst Tx Data path support

In the current MACsec offload implementation, MACsec interfaces shares
the same MAC address by default.
Therefore, HW can't distinguish from which MACsec interface the traffic
originated from.

MACsec stack will use skb_metadata_dst to store the SCI value, which is
unique per Macsec interface, skb_metadat_dst will be used by the
offloading device driver to associate the SKB with the corresponding
offloaded interface (SCI).

Signed-off-by: Lior Nahmanson <liorna@nvidia.com>
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Lior Nahmanson

drivers/net/macsec.c

@@ -18,6 +18,7 @@
 #include <net/sock.h>
 #include <net/gro_cells.h>
 #include <net/macsec.h>
+#include <net/dst_metadata.h>
 #include <linux/phy.h>
 #include <linux/byteorder/generic.h>
 #include <linux/if_arp.h>
@@ -3416,6 +3417,11 @@ static netdev_tx_t macsec_start_xmit(struct sk_buff *skb,
 	int ret, len;
 
 	if (macsec_is_offloaded(netdev_priv(dev))) {
+		struct metadata_dst *md_dst = secy->tx_sc.md_dst;
+
+		skb_dst_drop(skb);
+		dst_hold(&md_dst->dst);
+		skb_dst_set(skb, &md_dst->dst);
 		skb->dev = macsec->real_dev;
 		return dev_queue_xmit(skb);
 	}
@@ -3743,6 +3749,7 @@ static void macsec_free_netdev(struct net_device *dev)
 {
 	struct macsec_dev *macsec = macsec_priv(dev);
 
+	metadata_dst_free(macsec->secy.tx_sc.md_dst);
 	free_percpu(macsec->stats);
 	free_percpu(macsec->secy.tx_sc.stats);
 
@@ -4015,6 +4022,13 @@ static int macsec_add_dev(struct net_device *dev, sci_t sci, u8 icv_len)
 		return -ENOMEM;
 	}
 
+	secy->tx_sc.md_dst = metadata_dst_alloc(0, METADATA_MACSEC, GFP_KERNEL);
+	if (!secy->tx_sc.md_dst) {
+		free_percpu(secy->tx_sc.stats);
+		free_percpu(macsec->stats);
+		return -ENOMEM;
+	}
+
 	if (sci == MACSEC_UNDEF_SCI)
 		sci = dev_to_sci(dev, MACSEC_PORT_ES);
 
@@ -4028,6 +4042,7 @@ static int macsec_add_dev(struct net_device *dev, sci_t sci, u8 icv_len)
 	secy->xpn = DEFAULT_XPN;
 
 	secy->sci = sci;
+	secy->tx_sc.md_dst->u.macsec_info.sci = sci;
 	secy->tx_sc.active = true;
 	secy->tx_sc.encoding_sa = DEFAULT_ENCODING_SA;
 	secy->tx_sc.encrypt = DEFAULT_ENCRYPT;

include/net/dst_metadata.h

@@ -4,24 +4,31 @@
 
 #include <linux/skbuff.h>
 #include <net/ip_tunnels.h>
+#include <net/macsec.h>
 #include <net/dst.h>
 
 enum metadata_type {
 	METADATA_IP_TUNNEL,
 	METADATA_HW_PORT_MUX,
+	METADATA_MACSEC,
 };
 
 struct hw_port_info {
 	struct net_device *lower_dev;
 	u32 port_id;
 };
 
+struct macsec_info {
+	sci_t sci;
+};
+
 struct metadata_dst {
 	struct dst_entry		dst;
 	enum metadata_type		type;
 	union {
 		struct ip_tunnel_info	tun_info;
 		struct hw_port_info	port_info;
+		struct macsec_info	macsec_info;
 	} u;
 };
 
@@ -82,6 +89,9 @@ static inline int skb_metadata_dst_cmp(const struct sk_buff *skb_a,
 		return memcmp(&a->u.tun_info, &b->u.tun_info,
 			      sizeof(a->u.tun_info) +
 					 a->u.tun_info.options_len);
+	case METADATA_MACSEC:
+		return memcmp(&a->u.macsec_info, &b->u.macsec_info,
+			      sizeof(a->u.macsec_info));
 	default:
 		return 1;
 	}

include/net/macsec.h

@@ -19,6 +19,8 @@
 typedef u64 __bitwise sci_t;
 typedef u32 __bitwise ssci_t;
 
+struct metadata_dst;
+
 typedef union salt {
 	struct {
 		u32 ssci;
@@ -182,6 +184,7 @@ struct macsec_tx_sa {
  * @scb: single copy broadcast flag
  * @sa: array of secure associations
  * @stats: stats for this TXSC
+ * @md_dst: MACsec offload metadata dst
  */
 struct macsec_tx_sc {
 	bool active;
@@ -192,6 +195,7 @@ struct macsec_tx_sc {
 	bool scb;
 	struct macsec_tx_sa __rcu *sa[MACSEC_NUM_AN];
 	struct pcpu_tx_sc_stats __percpu *stats;
+	struct metadata_dst *md_dst;
 };
 
 /**