[PATCH v2 3/7] netfilter: nf_tables: Report active interfaces to user space

[Phil Sutter <phil@nwl.cc>]

Since netdev family chains and flowtables now report the interfaces they
were created for irrespective of their existence, introduce new netlink
attributes holding the currently active set of interfaces.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 include/uapi/linux/netfilter/nf_tables.h |  6 +++++-
 net/netfilter/nf_tables_api.c            | 25 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index aa4094ca2444..adcac6ee619d 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -164,6 +164,7 @@ enum nft_list_attributes {
  * @NFTA_HOOK_PRIORITY: netfilter hook priority (NLA_U32)
  * @NFTA_HOOK_DEV: netdevice name (NLA_STRING)
  * @NFTA_HOOK_DEVS: list of netdevices (NLA_NESTED)
+ * @NFTA_HOOK_ACT_DEVS: list of active netdevices (NLA_NESTED)
  */
 enum nft_hook_attributes {
 	NFTA_HOOK_UNSPEC,
@@ -171,6 +172,7 @@ enum nft_hook_attributes {
 	NFTA_HOOK_PRIORITY,
 	NFTA_HOOK_DEV,
 	NFTA_HOOK_DEVS,
+	NFTA_HOOK_ACT_DEVS,
 	__NFTA_HOOK_MAX
 };
 #define NFTA_HOOK_MAX		(__NFTA_HOOK_MAX - 1)
@@ -1717,13 +1719,15 @@ enum nft_flowtable_attributes {
  *
  * @NFTA_FLOWTABLE_HOOK_NUM: netfilter hook number (NLA_U32)
  * @NFTA_FLOWTABLE_HOOK_PRIORITY: netfilter hook priority (NLA_U32)
- * @NFTA_FLOWTABLE_HOOK_DEVS: input devices this flow table is bound to (NLA_NESTED)
+ * @NFTA_FLOWTABLE_HOOK_DEVS: input devices this flow table is configured for (NLA_NESTED)
+ * @NFTA_FLOWTABLE_HOOK_ACT_DEVS: input devices this flow table is currently bound to (NLA_NESTED)
  */
 enum nft_flowtable_hook_attributes {
 	NFTA_FLOWTABLE_HOOK_UNSPEC,
 	NFTA_FLOWTABLE_HOOK_NUM,
 	NFTA_FLOWTABLE_HOOK_PRIORITY,
 	NFTA_FLOWTABLE_HOOK_DEVS,
+	NFTA_FLOWTABLE_HOOK_ACT_DEVS,
 	__NFTA_FLOWTABLE_HOOK_MAX
 };
 #define NFTA_FLOWTABLE_HOOK_MAX	(__NFTA_FLOWTABLE_HOOK_MAX - 1)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 35990fbed444..87576accc2b2 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1819,6 +1819,18 @@ static int nft_dump_basechain_hook(struct sk_buff *skb, int family,
 		    nla_put(skb, NFTA_HOOK_DEV,
 			    first->ifnamelen, first->ifname))
 			goto nla_put_failure;
+
+		nest_devs = nla_nest_start_noflag(skb, NFTA_HOOK_ACT_DEVS);
+		if (!nest_devs)
+			goto nla_put_failure;
+
+		list_for_each_entry(hook, hook_list, list) {
+			if (hook->ops.dev &&
+			    nla_put_string(skb, NFTA_DEVICE_NAME,
+					   hook->ops.dev->name))
+				goto nla_put_failure;
+		}
+		nla_nest_end(skb, nest_devs);
 	}
 	nla_nest_end(skb, nest);
 
@@ -8926,6 +8938,19 @@ static int nf_tables_fill_flowtable_info(struct sk_buff *skb, struct net *net,
 			goto nla_put_failure;
 	}
 	nla_nest_end(skb, nest_devs);
+
+	nest_devs = nla_nest_start_noflag(skb, NFTA_FLOWTABLE_HOOK_ACT_DEVS);
+	if (!nest_devs)
+		goto nla_put_failure;
+
+	list_for_each_entry_rcu(hook, hook_list, list) {
+		if (hook->ops.dev &&
+		    nla_put_string(skb, NFTA_DEVICE_NAME,
+				   hook->ops.dev->name))
+			goto nla_put_failure;
+	}
+	nla_nest_end(skb, nest_devs);
+
 	nla_nest_end(skb, nest);
 
 	nlmsg_end(skb, nlh);
-- 
2.43.0