[PATCH nf-next] net: pass net_device_path_ctx to dev_fill_forward_path()

[PATCH nf-next] net: pass net_device_path_ctx to dev_fill_forward_path()

[Lorenzo Bianconi]

Refactor dev_fill_forward_path() to take a struct net_device_path_ctx
pointer instead of a (dev, daddr) pair, so the caller can build and
populate the context up front and keep it after the forward path walk.

This allows additional fields (e.g. vlan and ether_type) to be carried
in the context and shared with ndo_fill_forward_path implementations,
instead of being reconstructed on the stack inside the core helper.

Update the mtk_ppe_offload, airoha_ppe and nf_flow_table_path callers to
allocate and fill the context before invoking dev_fill_forward_path().
The network topology resolution behaviour is unchanged.

This is a preliminary patch to enable HW flowtable offload for IPv4
over IPv6 tunnels.

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
---
 drivers/net/ethernet/airoha/airoha_ppe.c        |  7 ++++++-
 drivers/net/ethernet/mediatek/mtk_ppe_offload.c |  7 ++++++-
 include/linux/netdevice.h                       |  2 +-
 net/core/dev.c                                  | 18 +++++++-----------
 net/netfilter/nf_flow_table_path.c              |  7 ++++++-
 5 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_ppe.c b/drivers/net/ethernet/airoha/airoha_ppe.c
index 33ddf0d07855..53183a132100 100644
--- a/drivers/net/ethernet/airoha/airoha_ppe.c
+++ b/drivers/net/ethernet/airoha/airoha_ppe.c
@@ -283,14 +283,19 @@ static int airoha_ppe_get_wdma_info(struct net_device *dev, const u8 *addr,
 				    struct airoha_wdma_info *info)
 {
 	struct net_device_path_stack stack;
+	struct net_device_path_ctx ctx = {
+		.dev = dev,
+	};
 	struct net_device_path *path;
 	int err;
 
 	if (!dev)
 		return -ENODEV;
 
+	ether_addr_copy(ctx.daddr, addr);
+
 	rcu_read_lock();
-	err = dev_fill_forward_path(dev, addr, &stack);
+	err = dev_fill_forward_path(&ctx, &stack);
 	rcu_read_unlock();
 	if (err)
 		return err;
diff --git a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
index cc8c4ef8038f..1ec46784f018 100644
--- a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
+++ b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
@@ -92,6 +92,9 @@ static int
 mtk_flow_get_wdma_info(struct net_device *dev, const u8 *addr, struct mtk_wdma_info *info)
 {
 	struct net_device_path_stack stack;
+	struct net_device_path_ctx ctx = {
+		.dev = dev,
+	};
 	struct net_device_path *path;
 	int err;
 
@@ -101,8 +104,10 @@ mtk_flow_get_wdma_info(struct net_device *dev, const u8 *addr, struct mtk_wdma_i
 	if (!IS_ENABLED(CONFIG_NET_MEDIATEK_SOC_WED))
 		return -1;
 
+	ether_addr_copy(ctx.daddr, addr);
+
 	rcu_read_lock();
-	err = dev_fill_forward_path(dev, addr, &stack);
+	err = dev_fill_forward_path(&ctx, &stack);
 	rcu_read_unlock();
 	if (err)
 		return err;
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8db25b79573e..d2f545016f7f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3425,7 +3425,7 @@ void dev_remove_offload(struct packet_offload *po);
 
 int dev_get_iflink(const struct net_device *dev);
 int dev_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb);
-int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
+int dev_fill_forward_path(struct net_device_path_ctx *ctx,
 			  struct net_device_path_stack *stack);
 struct net_device *dev_get_by_name(struct net *net, const char *name);
 struct net_device *dev_get_by_name_rcu(struct net *net, const char *name);
diff --git a/net/core/dev.c b/net/core/dev.c
index c1c1be1a6962..e2c9fe3f7a7b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -750,41 +750,37 @@ static struct net_device_path *dev_fwd_path(struct net_device_path_stack *stack)
 	return &stack->path[k];
 }
 
-int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
+int dev_fill_forward_path(struct net_device_path_ctx *ctx,
 			  struct net_device_path_stack *stack)
 {
 	const struct net_device *last_dev;
-	struct net_device_path_ctx ctx = {
-		.dev	= dev,
-	};
 	struct net_device_path *path;
 	int ret = 0;
 
-	memcpy(ctx.daddr, daddr, sizeof(ctx.daddr));
 	stack->num_paths = 0;
-	while (ctx.dev && ctx.dev->netdev_ops->ndo_fill_forward_path) {
-		last_dev = ctx.dev;
+	while (ctx->dev && ctx->dev->netdev_ops->ndo_fill_forward_path) {
+		last_dev = ctx->dev;
 		path = dev_fwd_path(stack);
 		if (!path)
 			return -1;
 
 		memset(path, 0, sizeof(struct net_device_path));
-		ret = ctx.dev->netdev_ops->ndo_fill_forward_path(&ctx, path);
+		ret = ctx->dev->netdev_ops->ndo_fill_forward_path(ctx, path);
 		if (ret < 0)
 			return -1;
 
-		if (WARN_ON_ONCE(last_dev == ctx.dev))
+		if (WARN_ON_ONCE(last_dev == ctx->dev))
 			return -1;
 	}
 
-	if (!ctx.dev)
+	if (!ctx->dev)
 		return ret;
 
 	path = dev_fwd_path(stack);
 	if (!path)
 		return -1;
 	path->type = DEV_PATH_ETHERNET;
-	path->dev = ctx.dev;
+	path->dev = ctx->dev;
 
 	return ret;
 }
diff --git a/net/netfilter/nf_flow_table_path.c b/net/netfilter/nf_flow_table_path.c
index 98c03b487f52..b9df7453f762 100644
--- a/net/netfilter/nf_flow_table_path.c
+++ b/net/netfilter/nf_flow_table_path.c
@@ -50,6 +50,9 @@ static int nft_dev_fill_forward_path(const struct nf_flow_route *route,
 {
 	const void *daddr = &ct->tuplehash[!dir].tuple.src.u3;
 	struct net_device *dev = dst_cache->dev;
+	struct net_device_path_ctx ctx = {
+		.dev = dev,
+	};
 	struct neighbour *n;
 	u8 nud_state;
 
@@ -72,7 +75,9 @@ static int nft_dev_fill_forward_path(const struct nf_flow_route *route,
 		return -1;
 
 out:
-	return dev_fill_forward_path(dev, ha, stack);
+	ether_addr_copy(ctx.daddr, ha);
+
+	return dev_fill_forward_path(&ctx, stack);
 }
 
 struct nft_forward_info {

---
base-commit: a23b36233d4103def55dc8cf65698106d0bd1e62
change-id: 20260805-dev_fill_forward_path-ctx-arg-73366345e3b8

Best regards,
-- 
Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

Re: [PATCH nf-next] net: pass net_device_path_ctx to dev_fill_forward_path()

[Simon Horman]

On Wed, Aug 05, 2026 at 10:53:09AM +0200, Lorenzo Bianconi wrote:
> Refactor dev_fill_forward_path() to take a struct net_device_path_ctx
> pointer instead of a (dev, daddr) pair, so the caller can build and
> populate the context up front and keep it after the forward path walk.
> 
> This allows additional fields (e.g. vlan and ether_type) to be carried
> in the context and shared with ndo_fill_forward_path implementations,
> instead of being reconstructed on the stack inside the core helper.
> 
> Update the mtk_ppe_offload, airoha_ppe and nf_flow_table_path callers to
> allocate and fill the context before invoking dev_fill_forward_path().
> The network topology resolution behaviour is unchanged.
> 
> This is a preliminary patch to enable HW flowtable offload for IPv4
> over IPv6 tunnels.
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

Reviewed-by: Simon Horman <horms@kernel.org>