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>

3 files changed, 195 insertions, 2 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[]);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 841c287ef40a..bf69e5871b1a 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -362,6 +362,95 @@ static size_t rtnl_link_get_size(const struct net_device *dev)
         return size;
 }
 
+static LIST_HEAD(rtnl_af_ops);
+
+static const struct rtnl_af_ops *rtnl_af_lookup(const int family)
+{
+        const struct rtnl_af_ops *ops;
+
+        list_for_each_entry(ops, &rtnl_af_ops, list) {
+                if (ops->family == family)
+                        return ops;
+        }
+
+        return NULL;
+}
+
+/**
+ * __rtnl_af_register - Register rtnl_af_ops with rtnetlink.
+ * @ops: struct rtnl_af_ops * to register
+ *
+ * The caller must hold the rtnl_mutex.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int __rtnl_af_register(struct rtnl_af_ops *ops)
+{
+        list_add_tail(&ops->list, &rtnl_af_ops);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(__rtnl_af_register);
+
+/**
+ * rtnl_af_register - Register rtnl_af_ops with rtnetlink.
+ * @ops: struct rtnl_af_ops * to register
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int rtnl_af_register(struct rtnl_af_ops *ops)
+{
+        int err;
+
+        rtnl_lock();
+        err = __rtnl_af_register(ops);
+        rtnl_unlock();
+        return err;
+}
+EXPORT_SYMBOL_GPL(rtnl_af_register);
+
+/**
+ * __rtnl_af_unregister - Unregister rtnl_af_ops from rtnetlink.
+ * @ops: struct rtnl_af_ops * to unregister
+ *
+ * The caller must hold the rtnl_mutex.
+ */
+void __rtnl_af_unregister(struct rtnl_af_ops *ops)
+{
+        list_del(&ops->list);
+}
+EXPORT_SYMBOL_GPL(__rtnl_af_unregister);
+
+/**
+ * rtnl_af_unregister - Unregister rtnl_af_ops from rtnetlink.
+ * @ops: struct rtnl_af_ops * to unregister
+ */
+void rtnl_af_unregister(struct rtnl_af_ops *ops)
+{
+        rtnl_lock();
+        __rtnl_af_unregister(ops);
+        rtnl_unlock();
+}
+EXPORT_SYMBOL_GPL(rtnl_af_unregister);
+
+static size_t rtnl_link_get_af_size(const struct net_device *dev)
+{
+        struct rtnl_af_ops *af_ops;
+        size_t size;
+
+        /* IFLA_AF_SPEC */
+        size = nla_total_size(sizeof(struct nlattr));
+
+        list_for_each_entry(af_ops, &rtnl_af_ops, list) {
+                if (af_ops->get_link_af_size) {
+                        /* AF_* + nested data */
+                        size += nla_total_size(sizeof(struct nlattr)) +
+                                af_ops->get_link_af_size(dev);
+                }
+        }
+
+        return size;
+}
+
 static int rtnl_link_fill(struct sk_buff *skb, const struct net_device *dev)
 {
         const struct rtnl_link_ops *ops = dev->rtnl_link_ops;
@@ -671,7 +760,8 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev)
                + nla_total_size(4) /* IFLA_NUM_VF */
                + rtnl_vfinfo_size(dev) /* IFLA_VFINFO_LIST */
                + rtnl_port_size(dev) /* IFLA_VF_PORTS + IFLA_PORT_SELF */
-               + rtnl_link_get_size(dev); /* IFLA_LINKINFO */
+               + rtnl_link_get_size(dev) /* IFLA_LINKINFO */
+               + rtnl_link_get_af_size(dev); /* IFLA_AF_SPEC */
 }
 
 static int rtnl_vf_ports_fill(struct sk_buff *skb, struct net_device *dev)
@@ -757,7 +847,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
         struct nlmsghdr *nlh;
         struct rtnl_link_stats64 temp;
         const struct rtnl_link_stats64 *stats;
-        struct nlattr *attr;
+        struct nlattr *attr, *af_spec;
+        struct rtnl_af_ops *af_ops;
 
         nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags);
         if (nlh == NULL)
@@ -866,6 +957,36 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
                         goto nla_put_failure;
         }
 
+        if (!(af_spec = nla_nest_start(skb, IFLA_AF_SPEC)))
+                goto nla_put_failure;
+
+        list_for_each_entry(af_ops, &rtnl_af_ops, list) {
+                if (af_ops->fill_link_af) {
+                        struct nlattr *af;
+                        int err;
+
+                        if (!(af = nla_nest_start(skb, af_ops->family)))
+                                goto nla_put_failure;
+
+                        err = af_ops->fill_link_af(skb, dev);
+
+                        /*
+                         * Caller may return ENODATA to indicate that there
+                         * was no data to be dumped. This is not an error, it
+                         * means we should trim the attribute header and
+                         * continue.
+                         */
+                        if (err == -ENODATA)
+                                nla_nest_cancel(skb, af);
+                        else if (err < 0)
+                                goto nla_put_failure;
+
+                        nla_nest_end(skb, af);
+                }
+        }
+
+        nla_nest_end(skb, af_spec);
+
         return nlmsg_end(skb, nlh);
 
 nla_put_failure:
@@ -924,6 +1045,7 @@ const struct nla_policy ifla_policy[IFLA_MAX+1] = {
         [IFLA_VFINFO_LIST]      = {. type = NLA_NESTED },
         [IFLA_VF_PORTS]         = { .type = NLA_NESTED },
         [IFLA_PORT_SELF]        = { .type = NLA_NESTED },
+        [IFLA_AF_SPEC]          = { .type = NLA_NESTED },
 };
 EXPORT_SYMBOL(ifla_policy);
 
@@ -1225,6 +1347,27 @@ static int do_setlink(struct net_device *dev, struct ifinfomsg *ifm,
                         goto errout;
                 modified = 1;
         }
+
+        if (tb[IFLA_AF_SPEC]) {
+                struct nlattr *af;
+                int rem;
+
+                nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) {
+                        const struct rtnl_af_ops *af_ops;
+
+                        if (!(af_ops = rtnl_af_lookup(nla_type(af))))
+                                continue;
+
+                        if (!af_ops->parse_link_af)
+                                continue;
+
+                        err = af_ops->parse_link_af(dev, af);
+                        if (err < 0)
+                                goto errout;
+
+                        modified = 1;
+                }
+        }
         err = 0;
 
 errout: