ipv4: AF_INET link address family

Implements the AF_INET link address family exposing the per
device configuration settings via netlink using the attribute
IFLA_INET_CONF.

The format of IFLA_INET_CONF differs depending on the direction
the attribute is sent. The attribute sent by the kernel consists
of a u32 array, basically a 1:1 copy of in_device->cnf.data[].
The attribute expected by the kernel must consist of a sequence
of nested u32 attributes, each representing a change request,
e.g.
	[IFLA_INET_CONF] = {
		[IPV4_DEVCONF_FORWARDING] = 1,
		[IPV4_DEVCONF_NOXFRM] = 0,
	}

libnl userspace API documentation and example available from:
http://www.infradead.org/~tgr/libnl/doc-git/group__link__inet.html

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

1 files changed, 75 insertions, 0 deletions

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index dc94b0316b78..71afc26c2df8 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1256,6 +1256,72 @@ errout:
                 rtnl_set_sk_err(net, RTNLGRP_IPV4_IFADDR, err);
 }
 
+static size_t inet_get_link_af_size(const struct net_device *dev)
+{
+        struct in_device *in_dev = __in_dev_get_rcu(dev);
+
+        if (!in_dev)
+                return 0;
+
+        return nla_total_size(IPV4_DEVCONF_MAX * 4); /* IFLA_INET_CONF */
+}
+
+static int inet_fill_link_af(struct sk_buff *skb, const struct net_device *dev)
+{
+        struct in_device *in_dev = __in_dev_get_rcu(dev);
+        struct nlattr *nla;
+        int i;
+
+        if (!in_dev)
+                return -ENODATA;
+
+        nla = nla_reserve(skb, IFLA_INET_CONF, IPV4_DEVCONF_MAX * 4);
+        if (nla == NULL)
+                return -EMSGSIZE;
+
+        for (i = 0; i < IPV4_DEVCONF_MAX; i++)
+                ((u32 *) nla_data(nla))[i] = in_dev->cnf.data[i];
+
+        return 0;
+}
+
+static const struct nla_policy inet_af_policy[IFLA_INET_MAX+1] = {
+        [IFLA_INET_CONF]        = { .type = NLA_NESTED },
+};
+
+static int inet_parse_link_af(struct net_device *dev, const struct nlattr *nla)
+{
+        struct in_device *in_dev = __in_dev_get_rcu(dev);
+        struct nlattr *a, *tb[IFLA_INET_MAX+1];
+        int err, rem;
+
+        if (!in_dev)
+                return -EOPNOTSUPP;
+
+        err = nla_parse_nested(tb, IFLA_INET_MAX, nla, inet_af_policy);
+        if (err < 0)
+                return err;
+
+        if (tb[IFLA_INET_CONF]) {
+                nla_for_each_nested(a, tb[IFLA_INET_CONF], rem) {
+                        int cfgid = nla_type(a);
+
+                        if (nla_len(a) < 4)
+                                return -EINVAL;
+
+                        if (cfgid <= 0 || cfgid > IPV4_DEVCONF_MAX)
+                                return -EINVAL;
+                }
+        }
+
+        if (tb[IFLA_INET_CONF]) {
+                nla_for_each_nested(a, tb[IFLA_INET_CONF], rem)
+                        ipv4_devconf_set(in_dev, nla_type(a), nla_get_u32(a));
+        }
+
+        return 0;
+}
+
 #ifdef CONFIG_SYSCTL
 
 static void devinet_copy_dflt_conf(struct net *net, int i)
@@ -1619,6 +1685,13 @@ static __net_initdata struct pernet_operations devinet_ops = {
         .exit = devinet_exit_net,
 };
 
+static struct rtnl_af_ops inet_af_ops = {
+        .family           = AF_INET,
+        .fill_link_af     = inet_fill_link_af,
+        .get_link_af_size = inet_get_link_af_size,
+        .parse_link_af    = inet_parse_link_af,
+};
+
 void __init devinet_init(void)
 {
         register_pernet_subsys(&devinet_ops);
@@ -1626,6 +1699,8 @@ void __init devinet_init(void)
         register_gifconf(PF_INET, inet_gifconf);
         register_netdevice_notifier(&ip_netdev_notifier);
 
+        rtnl_af_register(&inet_af_ops);
+
         rtnl_register(PF_INET, RTM_NEWADDR, inet_rtm_newaddr, NULL);
         rtnl_register(PF_INET, RTM_DELADDR, inet_rtm_deladdr, NULL);
         rtnl_register(PF_INET, RTM_GETADDR, NULL, inet_dump_ifaddr);