[PATCH] rtnetlink: Handle IFLA_MASTER parameter when processing rtnl_newlink

[Theuns Verwoerd]

Allow a master interface to be specified as one of the parameters when
creating a new interface via rtnl_newlink.  Previously this would
require invoking interface creation, waiting for it to complete, and
then separately binding that new interface to a master.

In particular, this is used when creating a macvlan child interface for
VRRP in a VRF configuration, allowing the interface creator to specify
directly what master interface should be inherited by the child,
without having to deal with asynchronous complications and potential
race conditions.

Signed-off-by: Theuns Verwoerd <theuns.verwo...@alliedtelesis.co.nz>
---
 net/core/rtnetlink.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 75e3ea7bda08..a24719c98238 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2571,7 +2571,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct 
nlmsghdr *nlh)
                        return -ENODEV;
                }
 
-               if (tb[IFLA_MAP] || tb[IFLA_MASTER] || tb[IFLA_PROTINFO])
+               if (tb[IFLA_MAP] || tb[IFLA_PROTINFO])
                        return -EOPNOTSUPP;
 
                if (!ops) {
@@ -2653,6 +2653,11 @@ static int rtnl_newlink(struct sk_buff *skb, struct 
nlmsghdr *nlh)
                        if (err < 0)
                                goto out_unregister;
                }
+               if (tb[IFLA_MASTER]) {
+                       err = do_set_master(dev, nla_get_u32(tb[IFLA_MASTER]));
+                       if (err)
+                               goto out_unregister;
+               }
 out:
                if (link_net)
                        put_net(link_net);
-- 
2.11.0