Subject: [PATCH] netfilter: nft_flow_offload: use direct xmit if hardware offload is enabled
From: Pablo Neira Ayuso <[email-masked]>
Date: Thu, 4 Mar 2021 19:24:11 +0100

If there is a forward path to reach an ethernet device and hardware
offload is enabled, then use the direct xmit path.
---

--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -131,6 +131,7 @@ struct flow_offload_tuple {
 		struct dst_entry	*dst_cache;
 		struct {
 			u32		ifidx;
+			u32		hw_ifidx;
 			u8		h_source[ETH_ALEN];
 			u8		h_dest[ETH_ALEN];
 		} out;
@@ -188,6 +189,7 @@ struct nf_flow_route {
 		} in;
 		struct {
 			u32			ifindex;
+			u32			hw_ifindex;
 			u8			h_source[ETH_ALEN];
 			u8			h_dest[ETH_ALEN];
 		} out;
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -106,6 +106,7 @@ static int flow_offload_fill_route(struc
 		memcpy(flow_tuple->out.h_source, route->tuple[dir].out.h_source,
 		       ETH_ALEN);
 		flow_tuple->out.ifidx = route->tuple[dir].out.ifindex;
+		flow_tuple->out.hw_ifidx = route->tuple[dir].out.hw_ifindex;
 		break;
 	case FLOW_OFFLOAD_XMIT_XFRM:
 	case FLOW_OFFLOAD_XMIT_NEIGH:
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -506,7 +506,7 @@ static void flow_offload_redirect(struct
 	switch (this_tuple->xmit_type) {
 	case FLOW_OFFLOAD_XMIT_DIRECT:
 		this_tuple = &flow->tuplehash[dir].tuple;
-		ifindex = this_tuple->out.ifidx;
+		ifindex = this_tuple->out.hw_ifidx;
 		break;
 	case FLOW_OFFLOAD_XMIT_NEIGH:
 		other_tuple = &flow->tuplehash[!dir].tuple;
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -66,6 +66,7 @@ static int nft_dev_fill_forward_path(con
 struct nft_forward_info {
 	const struct net_device *indev;
 	const struct net_device *outdev;
+	const struct net_device *hw_outdev;
 	struct id {
 		__u16	id;
 		__be16	proto;
@@ -76,9 +77,18 @@ struct nft_forward_info {
 	enum flow_offload_xmit_type xmit_type;
 };
 
+static bool nft_is_valid_ether_device(const struct net_device *dev)
+{
+	if (!dev || (dev->flags & IFF_LOOPBACK) || dev->type != ARPHRD_ETHER ||
+	    dev->addr_len != ETH_ALEN || !is_valid_ether_addr(dev->dev_addr))
+		return false;
+
+	return true;
+}
+
 static void nft_dev_path_info(const struct net_device_path_stack *stack,
 			      struct nft_forward_info *info,
-			      unsigned char *ha)
+			      unsigned char *ha, struct nf_flowtable *flowtable)
 {
 	const struct net_device_path *path;
 	int i;
@@ -140,6 +150,12 @@ static void nft_dev_path_info(const stru
 	}
 	if (!info->outdev)
 		info->outdev = info->indev;
+
+	info->hw_outdev = info->indev;
+
+	if (nf_flowtable_hw_offload(flowtable) &&
+	    nft_is_valid_ether_device(info->indev))
+		info->xmit_type = FLOW_OFFLOAD_XMIT_DIRECT;
 }
 
 static bool nft_flowtable_find_dev(const struct net_device *dev,
@@ -171,7 +187,7 @@ static void nft_dev_forward_path(struct
 	int i;
 
 	if (nft_dev_fill_forward_path(route, dst, ct, dir, ha, &stack) >= 0)
-		nft_dev_path_info(&stack, &info, ha);
+		nft_dev_path_info(&stack, &info, ha, &ft->data);
 
 	if (!info.indev || !nft_flowtable_find_dev(info.indev, ft))
 		return;
@@ -187,6 +203,7 @@ static void nft_dev_forward_path(struct
 		memcpy(route->tuple[dir].out.h_source, info.h_source, ETH_ALEN);
 		memcpy(route->tuple[dir].out.h_dest, info.h_dest, ETH_ALEN);
 		route->tuple[dir].out.ifindex = info.outdev->ifindex;
+		route->tuple[dir].out.hw_ifindex = info.hw_outdev->ifindex;
 		route->tuple[dir].xmit_type = info.xmit_type;
 	}
 }