[PATCH RFC net-next 2/3] net: add ndo for setting the iflink property

[Ansuel Smith <ansuelsmth@gmail.com>]

From: Marek Behún <marek.behun@nic.cz>

In DSA the iflink value is used to report to which CPU port a given
switch port is connected to. Since we want to support multi-CPU DSA, we
want the user to be able to change this value.

Add ndo_set_iflink method into the ndo strucutre to be a pair to
ndo_get_iflink. Also create dev_set_iflink and call this from the
netlink code, so that userspace can change the iflink value.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
---
 include/linux/netdevice.h |  5 +++++
 net/core/dev.c            | 15 +++++++++++++++
 net/core/rtnetlink.c      |  7 +++++++
 3 files changed, 27 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 87a5d186faff..76054182c288 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1225,6 +1225,8 @@ struct netdev_net_notifier {
  *	TX queue.
  * int (*ndo_get_iflink)(const struct net_device *dev);
  *	Called to get the iflink value of this device.
+ * int (*ndo_set_iflink)(struct net_device *dev, int iflink);
+ *	Called to set the iflink value of this device.
  * void (*ndo_change_proto_down)(struct net_device *dev,
  *				 bool proto_down);
  *	This function is used to pass protocol port error state information
@@ -1456,6 +1458,8 @@ struct net_device_ops {
 						      int queue_index,
 						      u32 maxrate);
 	int			(*ndo_get_iflink)(const struct net_device *dev);
+	int			(*ndo_set_iflink)(struct net_device *dev,
+						  int iflink);
 	int			(*ndo_change_proto_down)(struct net_device *dev,
 							 bool proto_down);
 	int			(*ndo_fill_metadata_dst)(struct net_device *dev,
@@ -2845,6 +2849,7 @@ void dev_add_offload(struct packet_offload *po);
 void dev_remove_offload(struct packet_offload *po);
 
 int dev_get_iflink(const struct net_device *dev);
+int dev_set_iflink(struct net_device *dev, int iflink);
 int dev_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb);
 struct net_device *__dev_get_by_flags(struct net *net, unsigned short flags,
 				      unsigned short mask);
diff --git a/net/core/dev.c b/net/core/dev.c
index 0f72ff5d34ba..9e5ddcf6d401 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -822,6 +822,21 @@ int dev_get_iflink(const struct net_device *dev)
 }
 EXPORT_SYMBOL(dev_get_iflink);
 
+/**
+ *	dev_set_iflink - set 'iflink' value of an interface
+ *	@dev: target interface
+ *	@iflink: new value
+ *
+ *	Change the interface to which this interface is linked to.
+ */
+int dev_set_iflink(struct net_device *dev, int iflink)
+{
+	if (dev->netdev_ops && dev->netdev_ops->ndo_set_iflink)
+		return dev->netdev_ops->ndo_set_iflink(dev, iflink);
+
+	return -EOPNOTSUPP;
+}
+
 /**
  *	dev_fill_metadata_dst - Retrieve tunnel egress information.
  *	@dev: targeted interface
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 1bdcb33fb561..629b7685f942 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2718,6 +2718,13 @@ static int do_setlink(const struct sk_buff *skb,
 		status |= DO_SETLINK_MODIFIED;
 	}
 
+	if (tb[IFLA_LINK]) {
+		err = dev_set_iflink(dev, nla_get_u32(tb[IFLA_LINK]));
+		if (err)
+			goto errout;
+		status |= DO_SETLINK_MODIFIED;
+	}
+
 	if (tb[IFLA_CARRIER]) {
 		err = dev_change_carrier(dev, nla_get_u8(tb[IFLA_CARRIER]));
 		if (err)
-- 
2.30.2