[PATCH nf-next] netfilter: nf_tables_offload: allow ethernet interface type only

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

Hardware offload support at this stage assumes an ethernet device in
place. The flow dissector provides the intermediate representation to
express this selector, so extend it to allow to store the interface
type. Flower does not uses this, so skb_flow_dissect_meta() is not
extended to allow to match on this new field.

Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
@Jiri: flower ignores this when checking for the ingress device, probably
       that should restricted there too?

 include/net/flow_dissector.h | 2 ++
 net/netfilter/nft_cmp.c      | 7 +++++++
 net/netfilter/nft_meta.c     | 4 ++++
 3 files changed, 13 insertions(+)

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index 5cd12276ae21..7d804db85442 100644
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -204,9 +204,11 @@ struct flow_dissector_key_ip {
 /**
  * struct flow_dissector_key_meta:
  * @ingress_ifindex: ingress ifindex
+ * @iiftype: interface type
  */
 struct flow_dissector_key_meta {
 	int ingress_ifindex;
+	u16 ingress_iftype;
 };
 
 /**
diff --git a/net/netfilter/nft_cmp.c b/net/netfilter/nft_cmp.c
index a0cd6e48e1a0..799acb069d59 100644
--- a/net/netfilter/nft_cmp.c
+++ b/net/netfilter/nft_cmp.c
@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/netlink.h>
 #include <linux/netfilter.h>
+#include <linux/if_arp.h>
 #include <linux/netfilter/nf_tables.h>
 #include <net/netfilter/nf_tables_core.h>
 #include <net/netfilter/nf_tables_offload.h>
@@ -113,6 +114,7 @@ static int __nft_cmp_offload(struct nft_offload_ctx *ctx,
 			     const struct nft_cmp_expr *priv)
 {
 	struct nft_offload_reg *reg = &ctx->regs[priv->sreg];
+	static u16 iftype_ether = ARPHRD_ETHER;
 	u8 *mask = (u8 *)&flow->match.mask;
 	u8 *key = (u8 *)&flow->match.key;
 
@@ -125,6 +127,11 @@ static int __nft_cmp_offload(struct nft_offload_ctx *ctx,
 	flow->match.dissector.used_keys |= BIT(reg->key);
 	flow->match.dissector.offset[reg->key] = reg->base_offset;
 
+	if (reg->key == FLOW_DISSECTOR_KEY_META &&
+	    reg->offset == offsetof(struct nft_flow_key, meta.ingress_iftype) &&
+	    memcmp(&priv->data, &iftype_ether, priv->len))
+		return -EOPNOTSUPP;
+
 	nft_offload_update_dependency(ctx, &priv->data, priv->len);
 
 	return 0;
diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
index 8fd21f436347..6fb6a6778e68 100644
--- a/net/netfilter/nft_meta.c
+++ b/net/netfilter/nft_meta.c
@@ -551,6 +551,10 @@ static int nft_meta_get_offload(struct nft_offload_ctx *ctx,
 		NFT_OFFLOAD_MATCH(FLOW_DISSECTOR_KEY_META, meta,
 				  ingress_ifindex, sizeof(__u32), reg);
 		break;
+	case NFT_META_IIFTYPE:
+		NFT_OFFLOAD_MATCH(FLOW_DISSECTOR_KEY_META, meta,
+				  ingress_iftype, sizeof(__u16), reg);
+		break;
 	default:
 		return -EOPNOTSUPP;
 	}
-- 
2.11.0