netfilter: nf_tables: skip flowtable hooknum and priority on device updates

On device updates, the hooknum and priority attributes are not required.
This patch makes optional these two netlink attributes.

Moreover, bail out with EOPNOTSUPP if userspace tries to update the
hooknum and priority for existing flowtables.

While at this, turn EINVAL into EOPNOTSUPP in case the hooknum is not
ingress. EINVAL is reserved for missing netlink attribute / malformed
netlink messages.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -6195,7 +6195,7 @@ static const struct nla_policy nft_flowtable_hook_policy[NFTA_FLOWTABLE_HOOK_MAX
 static int nft_flowtable_parse_hook(const struct nft_ctx *ctx,
 				    const struct nlattr *attr,
 				    struct nft_flowtable_hook *flowtable_hook,
-				    struct nf_flowtable *ft)
+				    struct nft_flowtable *flowtable, bool add)
 {
 	struct nlattr *tb[NFTA_FLOWTABLE_HOOK_MAX + 1];
 	struct nft_hook *hook;
@@ -6209,15 +6209,35 @@ static int nft_flowtable_parse_hook(const struct nft_ctx *ctx,
 	if (err < 0)
 		return err;
 
-	if (!tb[NFTA_FLOWTABLE_HOOK_NUM] ||
-	    !tb[NFTA_FLOWTABLE_HOOK_PRIORITY])
-		return -EINVAL;
+	if (add) {
+		if (!tb[NFTA_FLOWTABLE_HOOK_NUM] ||
+		    !tb[NFTA_FLOWTABLE_HOOK_PRIORITY])
+			return -EINVAL;
 
-	hooknum = ntohl(nla_get_be32(tb[NFTA_FLOWTABLE_HOOK_NUM]));
-	if (hooknum != NF_NETDEV_INGRESS)
-		return -EINVAL;
+		hooknum = ntohl(nla_get_be32(tb[NFTA_FLOWTABLE_HOOK_NUM]));
+		if (hooknum != NF_NETDEV_INGRESS)
+			return -EOPNOTSUPP;
+
+		priority = ntohl(nla_get_be32(tb[NFTA_FLOWTABLE_HOOK_PRIORITY]));
+
+		flowtable_hook->priority	= priority;
+		flowtable_hook->num		= hooknum;
+	} else {
+		if (tb[NFTA_FLOWTABLE_HOOK_NUM]) {
+			hooknum = ntohl(nla_get_be32(tb[NFTA_FLOWTABLE_HOOK_NUM]));
+			if (hooknum != flowtable->hooknum)
+				return -EOPNOTSUPP;
+		}
+
+		if (tb[NFTA_FLOWTABLE_HOOK_PRIORITY]) {
+			priority = ntohl(nla_get_be32(tb[NFTA_FLOWTABLE_HOOK_PRIORITY]));
+			if (priority != flowtable->data.priority)
+				return -EOPNOTSUPP;
+		}
 
-	priority = ntohl(nla_get_be32(tb[NFTA_FLOWTABLE_HOOK_PRIORITY]));
+		flowtable_hook->priority	= flowtable->data.priority;
+		flowtable_hook->num		= flowtable->hooknum;
+	}
 
 	if (tb[NFTA_FLOWTABLE_HOOK_DEVS]) {
 		err = nf_tables_parse_netdev_hooks(ctx->net,
@@ -6227,15 +6247,12 @@ static int nft_flowtable_parse_hook(const struct nft_ctx *ctx,
 			return err;
 	}
 
-	flowtable_hook->priority	= priority;
-	flowtable_hook->num		= hooknum;
-
 	list_for_each_entry(hook, &flowtable_hook->list, list) {
 		hook->ops.pf		= NFPROTO_NETDEV;
-		hook->ops.hooknum	= hooknum;
-		hook->ops.priority	= priority;
-		hook->ops.priv		= ft;
-		hook->ops.hook		= ft->type->hook;
+		hook->ops.hooknum	= flowtable_hook->num;
+		hook->ops.priority	= flowtable_hook->priority;
+		hook->ops.priv		= &flowtable->data;
+		hook->ops.hook		= flowtable->data.type->hook;
 	}
 
 	return err;
@@ -6363,7 +6380,7 @@ static int nft_flowtable_update(struct nft_ctx *ctx, const struct nlmsghdr *nlh,
 	int err;
 
 	err = nft_flowtable_parse_hook(ctx, nla[NFTA_FLOWTABLE_HOOK],
-				       &flowtable_hook, &flowtable->data);
+				       &flowtable_hook, flowtable, false);
 	if (err < 0)
 		return err;
 
@@ -6492,7 +6509,7 @@ static int nf_tables_newflowtable(struct net *net, struct sock *nlsk,
 		goto err3;
 
 	err = nft_flowtable_parse_hook(&ctx, nla[NFTA_FLOWTABLE_HOOK],
-				       &flowtable_hook, &flowtable->data);
+				       &flowtable_hook, flowtable, true);
 	if (err < 0)
 		goto err4;
 
@@ -6543,7 +6560,7 @@ static int nft_delflowtable_hook(struct nft_ctx *ctx,
 	int err;
 
 	err = nft_flowtable_parse_hook(ctx, nla[NFTA_FLOWTABLE_HOOK],
-				       &flowtable_hook, &flowtable->data);
+				       &flowtable_hook, flowtable, false);
 	if (err < 0)
 		return err;