net: vrf: ipv6 support for local traffic to local addresses

Add support for locally originated traffic to VRF-local IPv6 addresses.
Similar to IPv4 a local dst is set on the skb and the packet is
reinserted with a call to netif_rx. With this patch, ping, tcp and udp
packets to a local IPv6 address are successfully routed:

    $ ip addr show dev eth1
    4: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master red state UP group default qlen 1000
        link/ether 02:e0:f9:1c:b9:74 brd ff:ff:ff:ff:ff:ff
        inet 10.100.1.1/24 brd 10.100.1.255 scope global eth1
           valid_lft forever preferred_lft forever
        inet6 2100:1::1/120 scope global
           valid_lft forever preferred_lft forever
        inet6 fe80::e0:f9ff:fe1c:b974/64 scope link
           valid_lft forever preferred_lft forever

    $ ping6 -c1 -I red 2100:1::1
    ping6: Warning: source address might be selected on device other than red.
    PING 2100:1::1(2100:1::1) from 2100:1::1 red: 56 data bytes
    64 bytes from 2100:1::1: icmp_seq=1 ttl=64 time=0.098 ms

ip6_input is exported so the VRF driver can use it for the dst input
function. The dst_alloc function for IPv4 defaults to setting the input and
output functions; IPv6's does not. VRF does not need to duplicate the Rx path
so just export the ipv6 input function.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 85 insertions, 4 deletions

diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index 203d3c78a6e5..1b214ea4619a 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -46,6 +46,7 @@ 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;
 };
 
@@ -157,6 +158,46 @@ 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 */
@@ -336,27 +377,38 @@ 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;
 
@@ -364,7 +416,25 @@ 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:
@@ -710,6 +780,16 @@ out:
 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;
@@ -722,6 +802,7 @@ static struct sk_buff *vrf_ip6_rcv(struct net_device *vrf_dev,
                 IP6CB(skb)->flags |= IP6SKB_L3SLAVE;
         }
 
+out:
         return skb;
 }