[PATCH v2 1/7] netfilter: nf_tables: Store user-defined hook ifname

[Phil Sutter <phil@nwl.cc>]

In order to support dynamic interface binding, the name must be stored
separately. Also store the attribute length, it may serve to implement
simple wildcards (eth* for instance).

Also use the stored name when filling hook's NFTA_DEVICE_NAME attribute.
This avoids at least inadvertent changes in stored rulesets if an
interface is renamed at run-time.

Compare hooks by this stored interface name instead of the 'ops.dev'
pointer. Also prerequisite work for dynamic interface binding.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 include/net/netfilter/nf_tables.h |  2 ++
 net/netfilter/nf_tables_api.c     | 19 +++++++++++--------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 3f1ed467f951..3dec239bdb22 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -1183,6 +1183,8 @@ struct nft_hook {
 	struct list_head	list;
 	struct nf_hook_ops	ops;
 	struct rcu_head		rcu;
+	char			ifname[IFNAMSIZ];
+	u8			ifnamelen;
 };
 
 /**
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 84fa25305b4f..4f64dbac5abc 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1799,15 +1799,16 @@ static int nft_dump_basechain_hook(struct sk_buff *skb, int family,
 			if (!first)
 				first = hook;
 
-			if (nla_put_string(skb, NFTA_DEVICE_NAME,
-					   hook->ops.dev->name))
+			if (nla_put(skb, NFTA_DEVICE_NAME,
+				    hook->ifnamelen, hook->ifname))
 				goto nla_put_failure;
 			n++;
 		}
 		nla_nest_end(skb, nest_devs);
 
 		if (n == 1 &&
-		    nla_put_string(skb, NFTA_HOOK_DEV, first->ops.dev->name))
+		    nla_put(skb, NFTA_HOOK_DEV,
+			    first->ifnamelen, first->ifname))
 			goto nla_put_failure;
 	}
 	nla_nest_end(skb, nest);
@@ -2118,7 +2119,6 @@ static struct nft_hook *nft_netdev_hook_alloc(struct net *net,
 					      const struct nlattr *attr)
 {
 	struct net_device *dev;
-	char ifname[IFNAMSIZ];
 	struct nft_hook *hook;
 	int err;
 
@@ -2128,12 +2128,13 @@ static struct nft_hook *nft_netdev_hook_alloc(struct net *net,
 		goto err_hook_alloc;
 	}
 
-	nla_strscpy(ifname, attr, IFNAMSIZ);
+	nla_strscpy(hook->ifname, attr, IFNAMSIZ);
+	hook->ifnamelen = nla_len(attr);
 	/* nf_tables_netdev_event() is called under rtnl_mutex, this is
 	 * indirectly serializing all the other holders of the commit_mutex with
 	 * the rtnl_mutex.
 	 */
-	dev = __dev_get_by_name(net, ifname);
+	dev = __dev_get_by_name(net, hook->ifname);
 	if (!dev) {
 		err = -ENOENT;
 		goto err_hook_dev;
@@ -2154,7 +2155,8 @@ static struct nft_hook *nft_hook_list_find(struct list_head *hook_list,
 	struct nft_hook *hook;
 
 	list_for_each_entry(hook, hook_list, list) {
-		if (this->ops.dev == hook->ops.dev)
+		if (hook->ifnamelen == this->ifnamelen &&
+		    !strncmp(hook->ifname, this->ifname, hook->ifnamelen))
 			return hook;
 	}
 
@@ -8908,7 +8910,8 @@ static int nf_tables_fill_flowtable_info(struct sk_buff *skb, struct net *net,
 		hook_list = &flowtable->hook_list;
 
 	list_for_each_entry_rcu(hook, hook_list, list) {
-		if (nla_put_string(skb, NFTA_DEVICE_NAME, hook->ops.dev->name))
+		if (nla_put(skb, NFTA_DEVICE_NAME,
+			    hook->ifnamelen, hook->ifname))
 			goto nla_put_failure;
 	}
 	nla_nest_end(skb, nest_devs);
-- 
2.43.0