rtnetlink: Link address family API

Each net_device contains address family specific data such as
per device settings and statistics. We already expose this data
via procfs/sysfs and partially netlink.

The netlink method requires the requester to send one RTM_GETLINK
request for each address family it wishes to receive data of
and then merge this data itself.

This patch implements a new API which combines all address family
specific link data in a new netlink attribute IFLA_AF_SPEC.
IFLA_AF_SPEC contains a sequence of nested attributes, one for each
address family which in turn defines the structure of its own
attribute. Example:

   [IFLA_AF_SPEC] = {
       [AF_INET] = {
           [IFLA_INET_CONF] = ...,
       },
       [AF_INET6] = {
           [IFLA_INET6_FLAGS] = ...,
           [IFLA_INET6_CONF] = ...,
       }
   }

The API also allows for address families to implement a function
which parses the IFLA_AF_SPEC attribute sent by userspace to
implement address family specific link options.

Signed-off-by: Thomas Graf <tgraf@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 50 insertions, 0 deletions

diff --git a/include/linux/if_link.h b/include/linux/if_link.h
index 2fc66dd783ee..443d04a66a79 100644
--- a/include/linux/if_link.h
+++ b/include/linux/if_link.h
@@ -80,6 +80,24 @@ struct rtnl_link_ifmap {
         __u8    port;
 };
 
+/*
+ * IFLA_AF_SPEC
+ *   Contains nested attributes for address family specific attributes.
+ *   Each address family may create a attribute with the address family
+ *   number as type and create its own attribute structure in it.
+ *
+ *   Example:
+ *   [IFLA_AF_SPEC] = {
+ *       [AF_INET] = {
+ *           [IFLA_INET_CONF] = ...,
+ *       },
+ *       [AF_INET6] = {
+ *           [IFLA_INET6_FLAGS] = ...,
+ *           [IFLA_INET6_CONF] = ...,
+ *       }
+ *   }
+ */
+
 enum {
         IFLA_UNSPEC,
         IFLA_ADDRESS,
@@ -116,6 +134,7 @@ enum {
         IFLA_STATS64,
         IFLA_VF_PORTS,
         IFLA_PORT_SELF,
+        IFLA_AF_SPEC,
         __IFLA_MAX
 };
 
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index e013c68bfb00..35be0bbcd7da 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -83,6 +83,37 @@ extern void	__rtnl_link_unregister(struct rtnl_link_ops *ops);
 extern int      rtnl_link_register(struct rtnl_link_ops *ops);
 extern void     rtnl_link_unregister(struct rtnl_link_ops *ops);
 
+/**
+ *      struct rtnl_af_ops - rtnetlink address family operations
+ *
+ *      @list: Used internally
+ *      @family: Address family
+ *      @fill_link_af: Function to fill IFLA_AF_SPEC with address family
+ *                     specific netlink attributes.
+ *      @get_link_af_size: Function to calculate size of address family specific
+ *                         netlink attributes exlusive the container attribute.
+ *      @parse_link_af: Function to parse a IFLA_AF_SPEC attribute and modify
+ *                      net_device accordingly.
+ */
+struct rtnl_af_ops {
+        struct list_head        list;
+        int                     family;
+
+        int                     (*fill_link_af)(struct sk_buff *skb,
+                                                const struct net_device *dev);
+        size_t                  (*get_link_af_size)(const struct net_device *dev);
+
+        int                     (*parse_link_af)(struct net_device *dev,
+                                                 const struct nlattr *attr);
+};
+
+extern int      __rtnl_af_register(struct rtnl_af_ops *ops);
+extern void     __rtnl_af_unregister(struct rtnl_af_ops *ops);
+
+extern int      rtnl_af_register(struct rtnl_af_ops *ops);
+extern void     rtnl_af_unregister(struct rtnl_af_ops *ops);
+
+
 extern struct net *rtnl_link_get_net(struct net *src_net, struct nlattr *tb[]);
 extern struct net_device *rtnl_create_link(struct net *src_net, struct net *net,
         char *ifname, const struct rtnl_link_ops *ops, struct nlattr *tb[]);