net: l3mdev: prefer VRF master for source address selection

When selecting an address in context of a VRF, the vrf master should be
preferred for address selection.  If it isn't, the user has a hard time
getting the system to select to their preference - the code will pick
the address off the first in-VRF interface it can find, which on a
router could well be a non-routable address.

Signed-off-by: David Lamparter <equinox@diac24.net>
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
[dsa: Fixed comment style and removed extra blank link ]
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 18d510fa7ee231a1402ef6b69d26524103973372..8c3df2ccba4581583130b7e90be25592c2449100 100644 (file)
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1217,6 +1217,23 @@ __be32 inet_select_addr(const struct net_device *dev, __be32 dst, int scope)
 no_in_dev:
        master_idx = l3mdev_master_ifindex_rcu(dev);
 
+       /* For VRFs, the VRF device takes the place of the loopback device,
+        * with addresses on it being preferred.  Note in such cases the
+        * loopback device will be among the devices that fail the master_idx
+        * equality check in the loop below.
+        */
+       if (master_idx &&
+           (dev = dev_get_by_index_rcu(net, master_idx)) &&
+           (in_dev = __in_dev_get_rcu(dev))) {
+               for_primary_ifa(in_dev) {
+                       if (ifa->ifa_scope != RT_SCOPE_LINK &&
+                           ifa->ifa_scope <= scope) {
+                               addr = ifa->ifa_local;
+                               goto out_unlock;
+                       }
+               } endfor_ifa(in_dev);
+       }
+
        /* Not loopback addresses on loopback should be preferred
           in this case. It is important that lo is the first interface
           in dev_base list.