net: l3mdev: Allow send on enslaved interface

Allow udp and raw sockets to send by oif that is an enslaved interface
versus the l3mdev/VRF device. For example, this allows BFD to use ifindex
from IP_PKTINFO on a receive to send a response without the need to
convert to the VRF index. It also allows ping and ping6 to work when
specifying an enslaved interface (e.g., ping -I swp1 <ip>) which is
a natural use case.

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

3 files changed, 19 insertions, 4 deletions

diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index 4b2461ae5d3b..c8db55aa8280 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -648,6 +648,8 @@ static int vrf_get_saddr(struct net_device *dev, struct flowi4 *fl4)
 
         fl4->flowi4_flags |= FLOWI_FLAG_SKIP_NH_OIF;
         fl4->flowi4_iif = LOOPBACK_IFINDEX;
+        /* make sure oif is set to VRF device for lookup */
+        fl4->flowi4_oif = dev->ifindex;
         fl4->flowi4_tos = tos & IPTOS_RT_MASK;
         fl4->flowi4_scope = ((tos & RTO_ONLINK) ?
                              RT_SCOPE_LINK : RT_SCOPE_UNIVERSE);
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 8c8c655bb2c4..a1f2830d8110 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2146,6 +2146,7 @@ struct rtable *__ip_route_output_key_hash(struct net *net, struct flowi4 *fl4,
         unsigned int flags = 0;
         struct fib_result res;
         struct rtable *rth;
+        int master_idx;
         int orig_oif;
         int err = -ENETUNREACH;
 
@@ -2155,6 +2156,9 @@ struct rtable *__ip_route_output_key_hash(struct net *net, struct flowi4 *fl4,
 
         orig_oif = fl4->flowi4_oif;
 
+        master_idx = l3mdev_master_ifindex_by_index(net, fl4->flowi4_oif);
+        if (master_idx)
+                fl4->flowi4_oif = master_idx;
         fl4->flowi4_iif = LOOPBACK_IFINDEX;
         fl4->flowi4_tos = tos & IPTOS_RT_MASK;
         fl4->flowi4_scope = ((tos & RTO_ONLINK) ?
diff --git a/net/l3mdev/l3mdev.c b/net/l3mdev/l3mdev.c
index 898d01e0f87b..6651a78e100c 100644
--- a/net/l3mdev/l3mdev.c
+++ b/net/l3mdev/l3mdev.c
@@ -112,12 +112,18 @@ struct dst_entry *l3mdev_get_rt6_dst(struct net *net,
         struct dst_entry *dst = NULL;
         struct net_device *dev;
 
-        dev = dev_get_by_index(net, fl6->flowi6_oif);
-        if (dev) {
-                if (netif_is_l3_master(dev) &&
+        if (fl6->flowi6_oif) {
+                rcu_read_lock();
+
+                dev = dev_get_by_index_rcu(net, fl6->flowi6_oif);
+                if (dev && netif_is_l3_slave(dev))
+                        dev = netdev_master_upper_dev_get_rcu(dev);
+
+                if (dev && netif_is_l3_master(dev) &&
                     dev->l3mdev_ops->l3mdev_get_rt6_dst)
                         dst = dev->l3mdev_ops->l3mdev_get_rt6_dst(dev, fl6);
-                dev_put(dev);
+
+                rcu_read_unlock();
         }
 
         return dst;
@@ -141,6 +147,9 @@ int l3mdev_get_saddr(struct net *net, int ifindex, struct flowi4 *fl4)
                 rcu_read_lock();
 
                 dev = dev_get_by_index_rcu(net, ifindex);
+                if (dev && netif_is_l3_slave(dev))
+                        dev = netdev_master_upper_dev_get_rcu(dev);
+
                 if (dev && netif_is_l3_master(dev) &&
                     dev->l3mdev_ops->l3mdev_get_saddr)
                         rc = dev->l3mdev_ops->l3mdev_get_saddr(dev, fl4);