netfilter: nf_tables: Add notifications for hook changes

Notify user space if netdev hooks are updated due to netdev add/remove
events. Send minimal notification messages by introducing
NFT_MSG_NEWDEV/DELDEV message types describing a single device only.

Upon NETDEV_CHANGENAME, the callback has no information about the
interface's old name. To provide a clear message to user space, include
the hook's stored interface name in the notification.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 62 insertions, 0 deletions

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index a7240736f98e..24c71ecb2179 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -9686,6 +9686,64 @@ struct nf_hook_ops *nft_hook_find_ops_rcu(const struct nft_hook *hook,
 }
 EXPORT_SYMBOL_GPL(nft_hook_find_ops_rcu);
 
+static void
+nf_tables_device_notify(const struct nft_table *table, int attr,
+			const char *name, const struct nft_hook *hook,
+			const struct net_device *dev, int event)
+{
+	struct net *net = dev_net(dev);
+	struct nlmsghdr *nlh;
+	struct sk_buff *skb;
+	u16 flags = 0;
+
+	if (!nfnetlink_has_listeners(net, NFNLGRP_NFT_DEV))
+		return;
+
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!skb)
+		goto err;
+
+	event = event == NETDEV_REGISTER ? NFT_MSG_NEWDEV : NFT_MSG_DELDEV;
+	event = nfnl_msg_type(NFNL_SUBSYS_NFTABLES, event);
+	nlh = nfnl_msg_put(skb, 0, 0, event, flags, table->family,
+			   NFNETLINK_V0, nft_base_seq(net));
+	if (!nlh)
+		goto err;
+
+	if (nla_put_string(skb, NFTA_DEVICE_TABLE, table->name) ||
+	    nla_put_string(skb, attr, name) ||
+	    nla_put(skb, NFTA_DEVICE_SPEC, hook->ifnamelen, hook->ifname) ||
+	    nla_put_string(skb, NFTA_DEVICE_NAME, dev->name))
+		goto err;
+
+	nlmsg_end(skb, nlh);
+	nfnetlink_send(skb, net, 0, NFNLGRP_NFT_DEV,
+		       nlmsg_report(nlh), GFP_KERNEL);
+	return;
+err:
+	if (skb)
+		kfree_skb(skb);
+	nfnetlink_set_err(net, 0, NFNLGRP_NFT_DEV, -ENOBUFS);
+}
+
+void
+nf_tables_chain_device_notify(const struct nft_chain *chain,
+			      const struct nft_hook *hook,
+			      const struct net_device *dev, int event)
+{
+	nf_tables_device_notify(chain->table, NFTA_DEVICE_CHAIN,
+				chain->name, hook, dev, event);
+}
+
+static void
+nf_tables_flowtable_device_notify(const struct nft_flowtable *ft,
+				  const struct nft_hook *hook,
+				  const struct net_device *dev, int event)
+{
+	nf_tables_device_notify(ft->table, NFTA_DEVICE_FLOWTABLE,
+				ft->name, hook, dev, event);
+}
+
 static int nft_flowtable_event(unsigned long event, struct net_device *dev,
 			       struct nft_flowtable *flowtable, bool changename)
 {
@@ -9733,6 +9791,7 @@ static int nft_flowtable_event(unsigned long event, struct net_device *dev,
 			list_add_tail_rcu(&ops->list, &hook->ops_list);
 			break;
 		}
+		nf_tables_flowtable_device_notify(flowtable, hook, dev, event);
 		break;
 	}
 	return 0;
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index e598a2a252b0..ac77fc21632d 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -86,6 +86,7 @@ static const int nfnl_group2type[NFNLGRP_MAX+1] = {
 	[NFNLGRP_NFTABLES]		= NFNL_SUBSYS_NFTABLES,
 	[NFNLGRP_ACCT_QUOTA]		= NFNL_SUBSYS_ACCT,
 	[NFNLGRP_NFTRACE]		= NFNL_SUBSYS_NFTABLES,
+	[NFNLGRP_NFT_DEV]		= NFNL_SUBSYS_NFTABLES,
 };
 
 static struct nfnl_net *nfnl_pernet(struct net *net)
diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c
index b16185e9a6dd..846d48ba8965 100644
--- a/net/netfilter/nft_chain_filter.c
+++ b/net/netfilter/nft_chain_filter.c
@@ -363,6 +363,8 @@ static int nft_netdev_event(unsigned long event, struct net_device *dev,
 			list_add_tail_rcu(&ops->list, &hook->ops_list);
 			break;
 		}
+		nf_tables_chain_device_notify(&basechain->chain,
+					      hook, dev, event);
 		break;
 	}
 	return 0;