[PATCH net-next 0/3] net: vrf: Add support for local traffic to local addresses

@@ -125,6 +125,9 @@ static netdev_tx_t vrf_process_v6_outbound(struct sk_buff *skb,
 	skb_dst_drop(skb);
 	skb_dst_set(skb, dst);
 
+	/* strip the ethernet header added for pass through VRF device */
+	__skb_pull(skb, skb_network_offset(skb));
+
 	ret = ip6_local_out(net, skb->sk, skb);
 	if (unlikely(net_xmit_eval(ret)))
 		dev->stats.tx_errors++;

@@ -145,29 +148,6 @@ static netdev_tx_t vrf_process_v6_outbound(struct sk_buff *skb,
 }
 #endif
 
-static int vrf_send_v4_prep(struct sk_buff *skb, struct flowi4 *fl4,
-			    struct net_device *vrf_dev)
-{
-	struct rtable *rt;
-	int err = 1;
-
-	rt = ip_route_output_flow(dev_net(vrf_dev), fl4, NULL);
-	if (IS_ERR(rt))
-		goto out;
-
-	/* TO-DO: what about broadcast ? */
-	if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
-		ip_rt_put(rt);
-		goto out;
-	}
-
-	skb_dst_drop(skb);
-	skb_dst_set(skb, &rt->dst);
-	err = 0;
-out:
-	return err;
-}
-
 static netdev_tx_t vrf_process_v4_outbound(struct sk_buff *skb,
 					   struct net_device *vrf_dev)
 {

@@ -182,10 +162,24 @@ static netdev_tx_t vrf_process_v4_outbound(struct sk_buff *skb,
 				FLOWI_FLAG_SKIP_NH_OIF,
 		.daddr = ip4h->daddr,
 	};
+	struct net *net = dev_net(vrf_dev);
+	struct rtable *rt;
 
-	if (vrf_send_v4_prep(skb, &fl4, vrf_dev))
+	rt = ip_route_output_flow(net, &fl4, NULL);
+	if (IS_ERR(rt))
 		goto err;
 
+	if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
+		ip_rt_put(rt);
+		goto err;
+	}
+
+	skb_dst_drop(skb);
+	skb_dst_set(skb, &rt->dst);
+
+	/* strip the ethernet header added for pass through VRF device */
+	__skb_pull(skb, skb_network_offset(skb));
+
 	if (!ip4h->saddr) {
 		ip4h->saddr = inet_select_addr(skb_dst(skb)->dev, 0,
 					       RT_SCOPE_LINK);

@@ -206,9 +200,6 @@ static netdev_tx_t vrf_process_v4_outbound(struct sk_buff *skb,
 
 static netdev_tx_t is_ip_tx_frame(struct sk_buff *skb, struct net_device *dev)
 {
-	/* strip the ethernet header added for pass through VRF device */
-	__skb_pull(skb, skb_network_offset(skb));
-
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 		return vrf_process_v4_outbound(skb, dev);

@@ -50,6 +50,7 @@ module_param(rule_pref, uint,  S_IRUGO);
 
 struct net_vrf {
 	struct rtable __rcu	*rth;
+	struct rtable __rcu	*rth_local;
 	struct rt6_info	__rcu	*rt6;
 	u32                     tb_id;
 };

@@ -60,9 +61,20 @@ struct pcpu_dstats {
 	u64			tx_drps;
 	u64			rx_pkts;
 	u64			rx_bytes;
+	u64			rx_drps;
 	struct u64_stats_sync	syncp;
 };
 
+static void vrf_rx_stats(struct net_device *dev, int len)
+{
+	struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
+
+	u64_stats_update_begin(&dstats->syncp);
+	dstats->rx_pkts++;
+	dstats->rx_bytes += len;
+	u64_stats_update_end(&dstats->syncp);
+}
+
 static void vrf_tx_error(struct net_device *vrf_dev, struct sk_buff *skb)
 {
 	vrf_dev->stats.tx_errors++;

@@ -97,6 +109,34 @@ static struct rtnl_link_stats64 *vrf_get_stats64(struct net_device *dev,
 	return stats;
 }
 
+/* Local traffic destined to local address. Reinsert the packet to rx
+ * path, similar to loopback handling.
+ */
+static int vrf_local_xmit(struct sk_buff *skb, struct net_device *dev,
+			  struct dst_entry *dst)
+{
+	int len = skb->len;
+
+	skb_orphan(skb);
+
+	skb_dst_set(skb, dst);
+	skb_dst_force(skb);
+
+	/* set pkt_type to avoid skb hitting packet taps twice -
+	 * once on Tx and again in Rx processing
+	 */
+	skb->pkt_type = PACKET_LOOPBACK;
+
+	skb->protocol = eth_type_trans(skb, dev);
+
+	if (likely(netif_rx(skb) == NET_RX_SUCCESS))
+		vrf_rx_stats(dev, len);
+	else
+		this_cpu_inc(dev->dstats->rx_drps);
+
+	return NETDEV_TX_OK;
+}
+
 #if IS_ENABLED(CONFIG_IPV6)
 static netdev_tx_t vrf_process_v6_outbound(struct sk_buff *skb,
 					   struct net_device *dev)

@@ -175,6 +215,34 @@ static netdev_tx_t vrf_process_v4_outbound(struct sk_buff *skb,
 	}
 
 	skb_dst_drop(skb);
+
+	/* if dst.dev is loopback or the VRF device again this is locally
+	 * originated traffic destined to a local address. Short circuit
+	 * to Rx path using our local dst
+	 */
+	if (rt->dst.dev == net->loopback_dev || rt->dst.dev == vrf_dev) {
+		struct net_vrf *vrf = netdev_priv(vrf_dev);
+		struct rtable *rth_local;
+		struct dst_entry *dst = NULL;
+
+		ip_rt_put(rt);
+
+		rcu_read_lock();
+
+		rth_local = rcu_dereference(vrf->rth_local);
+		if (likely(rth_local)) {
+			dst = &rth_local->dst;
+			dst_hold(dst);
+		}
+
+		rcu_read_unlock();
+
+		if (unlikely(!dst))
+			goto err;
+
+		return vrf_local_xmit(skb, vrf_dev, dst);
+	}
+
 	skb_dst_set(skb, &rt->dst);
 
 	/* strip the ethernet header added for pass through VRF device */

@@ -381,29 +449,48 @@ static int vrf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 static void vrf_rtable_release(struct net_vrf *vrf)
 {
 	struct rtable *rth = rtnl_dereference(vrf->rth);
+	struct rtable *rth_local = rtnl_dereference(vrf->rth_local);
 
-	rcu_assign_pointer(vrf->rth, NULL);
+	RCU_INIT_POINTER(vrf->rth, NULL);
+	RCU_INIT_POINTER(vrf->rth_local, NULL);
+	synchronize_rcu();
 
 	if (rth)
 		dst_release(&rth->dst);
+
+	if (rth_local)
+		dst_release(&rth_local->dst);
 }
 
 static int vrf_rtable_create(struct net_device *dev)
 {
 	struct net_vrf *vrf = netdev_priv(dev);
-	struct rtable *rth;
+	struct rtable *rth, *rth_local;
 
 	if (!fib_new_table(dev_net(dev), vrf->tb_id))
 		return -ENOMEM;
 
+	/* create a dst for routing packets out through a VRF device */
 	rth = rt_dst_alloc(dev, 0, RTN_UNICAST, 1, 1, 0);
 	if (!rth)
 		return -ENOMEM;
 
+	/* create a dst for local ingress routing - packets sent locally
+	 * to local address via the VRF device as a loopback
+	 */
+	rth_local = rt_dst_alloc(dev, RTCF_LOCAL, RTN_LOCAL, 1, 1, 0);
+	if (!rth_local) {
+		dst_release(&rth->dst);
+		return -ENOMEM;
+	}
+
 	rth->dst.output	= vrf_output;
 	rth->rt_table_id = vrf->tb_id;
 
+	rth_local->rt_table_id = vrf->tb_id;
+
 	rcu_assign_pointer(vrf->rth, rth);
+	rcu_assign_pointer(vrf->rth_local, rth_local);
 
 	return 0;
 }

@@ -658,10 +745,19 @@ static struct sk_buff *vrf_ip_rcv(struct net_device *vrf_dev,
 	skb->dev = vrf_dev;
 	skb->skb_iif = vrf_dev->ifindex;
 
+	/* loopback traffic; do not push through packet taps again.
+	 * Reset pkt_type for upper layers to process skb
+	 */
+	if (skb->pkt_type == PACKET_LOOPBACK) {
+		skb->pkt_type = PACKET_HOST;
+		goto out;
+	}
+
 	skb_push(skb, skb->mac_len);
 	dev_queue_xmit_nit(skb, vrf_dev);
 	skb_pull(skb, skb->mac_len);
 
+out:
 	return skb;
 }
 

@@ -52,6 +52,7 @@ struct net_vrf {
 	struct rtable __rcu	*rth;
 	struct rtable __rcu	*rth_local;
 	struct rt6_info	__rcu	*rt6;
+	struct rt6_info	__rcu	*rt6_local;
 	u32                     tb_id;
 };
 

@@ -163,6 +164,46 @@ static netdev_tx_t vrf_process_v6_outbound(struct sk_buff *skb,
 		goto err;
 
 	skb_dst_drop(skb);
+
+	/* if dst.dev is loopback or the VRF device again this is locally
+	 * originated traffic destined to a local address. Short circuit
+	 * to Rx path using our local dst
+	 */
+	if (dst->dev == net->loopback_dev || dst->dev == dev) {
+		struct net_vrf *vrf = netdev_priv(dev);
+		struct rt6_info *rt6_local;
+
+		/* release looked up dst and use cached local dst */
+		dst_release(dst);
+
+		rcu_read_lock();
+
+		rt6_local = rcu_dereference(vrf->rt6_local);
+		if (unlikely(!rt6_local)) {
+			rcu_read_unlock();
+			goto err;
+		}
+
+		/* Ordering issue: cached local dst is created on newlink
+		 * before the IPv6 initialization. Using the local dst
+		 * requires rt6i_idev to be set so make sure it is.
+		 */
+		if (unlikely(!rt6_local->rt6i_idev)) {
+			rt6_local->rt6i_idev = in6_dev_get(dev);
+			if (!rt6_local->rt6i_idev) {
+				rcu_read_unlock();
+				goto err;
+			}
+		}
+
+		dst = &rt6_local->dst;
+		dst_hold(dst);
+
+		rcu_read_unlock();
+
+		return vrf_local_xmit(skb, dev, &rt6_local->dst);
+	}
+
 	skb_dst_set(skb, dst);
 
 	/* strip the ethernet header added for pass through VRF device */

@@ -342,27 +383,38 @@ static int vrf_output6(struct net *net, struct sock *sk, struct sk_buff *skb)
 static void vrf_rt6_release(struct net_vrf *vrf)
 {
 	struct rt6_info *rt6 = rtnl_dereference(vrf->rt6);
+	struct rt6_info *rt6_local = rtnl_dereference(vrf->rt6_local);
 
-	rcu_assign_pointer(vrf->rt6, NULL);
+	RCU_INIT_POINTER(vrf->rt6, NULL);
+	RCU_INIT_POINTER(vrf->rt6_local, NULL);
+	synchronize_rcu();
 
 	if (rt6)
 		dst_release(&rt6->dst);
+
+	if (rt6_local) {
+		if (rt6_local->rt6i_idev)
+			in6_dev_put(rt6_local->rt6i_idev);
+
+		dst_release(&rt6_local->dst);
+	}
 }
 
 static int vrf_rt6_create(struct net_device *dev)
 {
+	int flags = DST_HOST | DST_NOPOLICY | DST_NOXFRM | DST_NOCACHE;
 	struct net_vrf *vrf = netdev_priv(dev);
 	struct net *net = dev_net(dev);
 	struct fib6_table *rt6i_table;
-	struct rt6_info *rt6;
+	struct rt6_info *rt6, *rt6_local;
 	int rc = -ENOMEM;
 
 	rt6i_table = fib6_new_table(net, vrf->tb_id);
 	if (!rt6i_table)
 		goto out;
 
-	rt6 = ip6_dst_alloc(net, dev,
-			    DST_HOST | DST_NOPOLICY | DST_NOXFRM | DST_NOCACHE);
+	/* create a dst for routing packets out a VRF device */
+	rt6 = ip6_dst_alloc(net, dev, flags);
 	if (!rt6)
 		goto out;
 

@@ -370,7 +422,25 @@ static int vrf_rt6_create(struct net_device *dev)
 
 	rt6->rt6i_table = rt6i_table;
 	rt6->dst.output	= vrf_output6;
+
+	/* create a dst for local routing - packets sent locally
+	 * to local address via the VRF device as a loopback
+	 */
+	rt6_local = ip6_dst_alloc(net, dev, flags);
+	if (!rt6_local) {
+		dst_release(&rt6->dst);
+		goto out;
+	}
+
+	dst_hold(&rt6_local->dst);
+
+	rt6_local->rt6i_idev  = in6_dev_get(dev);
+	rt6_local->rt6i_flags = RTF_UP | RTF_NONEXTHOP | RTF_LOCAL;
+	rt6_local->rt6i_table = rt6i_table;
+	rt6_local->dst.input  = ip6_input;
+
 	rcu_assign_pointer(vrf->rt6, rt6);
+	rcu_assign_pointer(vrf->rt6_local, rt6_local);
 
 	rc = 0;
 out:

@@ -716,6 +786,16 @@ static bool ipv6_ndisc_frame(const struct sk_buff *skb)
 static struct sk_buff *vrf_ip6_rcv(struct net_device *vrf_dev,
 				   struct sk_buff *skb)
 {
+	/* loopback traffic; do not push through packet taps again.
+	 * Reset pkt_type for upper layers to process skb
+	 */
+	if (skb->pkt_type == PACKET_LOOPBACK) {
+		skb->dev = vrf_dev;
+		skb->skb_iif = vrf_dev->ifindex;
+		skb->pkt_type = PACKET_HOST;
+		goto out;
+	}
+
 	/* if packet is NDISC keep the ingress interface */
 	if (!ipv6_ndisc_frame(skb)) {
 		skb->dev = vrf_dev;

@@ -728,6 +808,7 @@ static struct sk_buff *vrf_ip6_rcv(struct net_device *vrf_dev,
 		IP6CB(skb)->flags |= IP6SKB_L3SLAVE;
 	}
 
+out:
 	return skb;
 }