[PATCH] rtnetlink: Handle IFLA_MASTER parameter when processing rtnl_newlink

rtnetlink: Handle IFLA_MASTER parameter when processing rtnl_newlink

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 <redacted>

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);