netfilter: nf_tables: store data in offload context registers

Store immediate data into offload context register. This allows follow
up instructions to take it from the corresponding source register.

This patch is required to support for payload mangling, although other
instructions that take data from source register will benefit from this
too.

Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/net/netfilter/nf_tables_offload.h

···
 	u32		len;
 	u32		base_offset;
 	u32		offset;
+	struct nft_data data;
 	struct nft_data	mask;
 };
 

net/netfilter/nft_immediate.c

···
 	return 0;
 }
 
-static int nft_immediate_offload(struct nft_offload_ctx *ctx,
-				 struct nft_flow_rule *flow,
-				 const struct nft_expr *expr)
+static int nft_immediate_offload_verdict(struct nft_offload_ctx *ctx,
+					 struct nft_flow_rule *flow,
+					 const struct nft_immediate_expr *priv)
 {
-	const struct nft_immediate_expr *priv = nft_expr_priv(expr);
 	struct flow_action_entry *entry;
 	const struct nft_data *data;
-
-	if (priv->dreg != NFT_REG_VERDICT)
-		return -EOPNOTSUPP;
 
 	entry = &flow->rule->action.entries[ctx->num_actions++];
 
···
 	default:
 		return -EOPNOTSUPP;
 	}
+
+	return 0;
+}
+
+static int nft_immediate_offload(struct nft_offload_ctx *ctx,
+				 struct nft_flow_rule *flow,
+				 const struct nft_expr *expr)
+{
+	const struct nft_immediate_expr *priv = nft_expr_priv(expr);
+
+	if (priv->dreg == NFT_REG_VERDICT)
+		return nft_immediate_offload_verdict(ctx, flow, priv);
+
+	memcpy(&ctx->regs[priv->dreg].data, &priv->data, sizeof(priv->data));
 
 	return 0;
 }