netfilter: bridge: introduce broute meta statement

nftables equivalent for ebtables -t broute.

Implement broute meta statement to set br_netfilter_broute flag
in skb to force a packet to be routed instead of being bridged.
Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
Signed-off-by: Florian Westphal <fw@strlen.de>

include/uapi/linux/netfilter/nf_tables.h

@@ -931,6 +931,7 @@ enum nft_exthdr_attributes {
  * @NFT_META_TIME_HOUR: hour of day (in seconds)
  * @NFT_META_SDIF: slave device interface index
  * @NFT_META_SDIFNAME: slave device interface name
+ * @NFT_META_BRI_BROUTE: packet br_netfilter_broute bit
  */
 enum nft_meta_keys {
 	NFT_META_LEN,
@@ -969,6 +970,7 @@ enum nft_meta_keys {
 	NFT_META_TIME_HOUR,
 	NFT_META_SDIF,
 	NFT_META_SDIFNAME,
+	NFT_META_BRI_BROUTE,
 	__NFT_META_IIFTYPE,
 };
 

net/bridge/netfilter/nft_meta_bridge.c

@@ -8,6 +8,9 @@
 #include <net/netfilter/nf_tables.h>
 #include <net/netfilter/nft_meta.h>
 #include <linux/if_bridge.h>
+#include <uapi/linux/netfilter_bridge.h> /* NF_BR_PRE_ROUTING */
+
+#include "../br_private.h"
 
 static const struct net_device *
 nft_meta_get_bridge(const struct net_device *dev)
@@ -102,6 +105,50 @@ static const struct nft_expr_ops nft_meta_bridge_get_ops = {
 	.reduce		= nft_meta_get_reduce,
 };
 
+static void nft_meta_bridge_set_eval(const struct nft_expr *expr,
+				     struct nft_regs *regs,
+				     const struct nft_pktinfo *pkt)
+{
+	const struct nft_meta *meta = nft_expr_priv(expr);
+	u32 *sreg = &regs->data[meta->sreg];
+	struct sk_buff *skb = pkt->skb;
+	u8 value8;
+
+	switch (meta->key) {
+	case NFT_META_BRI_BROUTE:
+		value8 = nft_reg_load8(sreg);
+		BR_INPUT_SKB_CB(skb)->br_netfilter_broute = !!value8;
+		break;
+	default:
+		nft_meta_set_eval(expr, regs, pkt);
+	}
+}
+
+static int nft_meta_bridge_set_init(const struct nft_ctx *ctx,
+				    const struct nft_expr *expr,
+				    const struct nlattr * const tb[])
+{
+	struct nft_meta *priv = nft_expr_priv(expr);
+	unsigned int len;
+	int err;
+
+	priv->key = ntohl(nla_get_be32(tb[NFTA_META_KEY]));
+	switch (priv->key) {
+	case NFT_META_BRI_BROUTE:
+		len = sizeof(u8);
+		break;
+	default:
+		return nft_meta_set_init(ctx, expr, tb);
+	}
+
+	priv->len = len;
+	err = nft_parse_register_load(tb[NFTA_META_SREG], &priv->sreg, len);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
 static bool nft_meta_bridge_set_reduce(struct nft_regs_track *track,
 				       const struct nft_expr *expr)
 {
@@ -120,15 +167,33 @@ static bool nft_meta_bridge_set_reduce(struct nft_regs_track *track,
 	return false;
 }
 
+static int nft_meta_bridge_set_validate(const struct nft_ctx *ctx,
+					const struct nft_expr *expr,
+					const struct nft_data **data)
+{
+	struct nft_meta *priv = nft_expr_priv(expr);
+	unsigned int hooks;
+
+	switch (priv->key) {
+	case NFT_META_BRI_BROUTE:
+		hooks = 1 << NF_BR_PRE_ROUTING;
+		break;
+	default:
+		return nft_meta_set_validate(ctx, expr, data);
+	}
+
+	return nft_chain_validate_hooks(ctx->chain, hooks);
+}
+
 static const struct nft_expr_ops nft_meta_bridge_set_ops = {
 	.type		= &nft_meta_bridge_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_meta)),
-	.eval		= nft_meta_set_eval,
-	.init		= nft_meta_set_init,
+	.eval		= nft_meta_bridge_set_eval,
+	.init		= nft_meta_bridge_set_init,
 	.destroy	= nft_meta_set_destroy,
 	.dump		= nft_meta_set_dump,
 	.reduce		= nft_meta_bridge_set_reduce,
-	.validate	= nft_meta_set_validate,
+	.validate	= nft_meta_bridge_set_validate,
 };
 
 static const struct nft_expr_ops *