[PATCH net-next 6/9] net: pass dst via net_device_path in dev_fill_forward_path()

[Pablo Neira Ayuso <pablo@netfilter.org>]

Add dst_entry to tunnel device path, this will allow us to remove
a duplicated route lookup.

This is a preparation patch to retrieve the tunnel route directly
from the .fill_forward_path. This new dst_entry in the tunnel will be
used by a follow up patch.

Since dst_release() works fine on NULL interface, this is still
noop until the flowtable starts using this.

Add a new dev_fill_forward_path_release() function to drop the refcount
on the tunnel device route and use it in case of error out. Export it so
to drop the refcount on the tunnel route at a later stage.

Adjust existing drivers that recycle dev_fill_forward_path() to call
dev_fill_forward_path_release() for safety reasons.

Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 drivers/net/ethernet/airoha/airoha_ppe.c      | 10 ++++--
 .../net/ethernet/mediatek/mtk_ppe_offload.c   | 10 ++++--
 include/linux/netdevice.h                     |  2 ++
 net/core/dev.c                                | 36 ++++++++++++++++---
 4 files changed, 47 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_ppe.c b/drivers/net/ethernet/airoha/airoha_ppe.c
index 33ddf0d07855..a03af9750573 100644
--- a/drivers/net/ethernet/airoha/airoha_ppe.c
+++ b/drivers/net/ethernet/airoha/airoha_ppe.c
@@ -296,14 +296,18 @@ static int airoha_ppe_get_wdma_info(struct net_device *dev, const u8 *addr,
 		return err;
 
 	path = &stack.path[stack.num_paths - 1];
-	if (path->type != DEV_PATH_MTK_WDMA)
-		return -EINVAL;
+	if (path->type != DEV_PATH_MTK_WDMA) {
+		err = -EINVAL;
+		goto err_out;
+	}
 
 	info->idx = path->mtk_wdma.wdma_idx;
 	info->bss = path->mtk_wdma.bss;
 	info->wcid = path->mtk_wdma.wcid;
+err_out:
+	dev_fill_forward_path_release(&stack);
 
-	return 0;
+	return err;
 }
 
 static int airoha_get_dsa_port(struct net_device **dev)
diff --git a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
index cc8c4ef8038f..771d9118f94a 100644
--- a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
+++ b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
@@ -108,16 +108,20 @@ mtk_flow_get_wdma_info(struct net_device *dev, const u8 *addr, struct mtk_wdma_i
 		return err;
 
 	path = &stack.path[stack.num_paths - 1];
-	if (path->type != DEV_PATH_MTK_WDMA)
-		return -1;
+	if (path->type != DEV_PATH_MTK_WDMA) {
+		err = -EINVAL;
+		goto err_out;
+	}
 
 	info->wdma_idx = path->mtk_wdma.wdma_idx;
 	info->queue = path->mtk_wdma.queue;
 	info->bss = path->mtk_wdma.bss;
 	info->wcid = path->mtk_wdma.wcid;
 	info->amsdu = path->mtk_wdma.amsdu;
+err_out:
+	dev_fill_forward_path_release(&stack);
 
-	return 0;
+	return err;
 }
 
 
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8db25b79573e..62cfad7e6b79 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -892,6 +892,7 @@ struct net_device_path {
 			u8		h_dest[ETH_ALEN];
 		} encap;
 		struct {
+			struct dst_entry *dst;
 			union {
 				struct in_addr	src_v4;
 				struct in6_addr	src_v6;
@@ -3427,6 +3428,7 @@ 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,
 			  struct net_device_path_stack *stack);
+void dev_fill_forward_path_release(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);
 struct net_device *__dev_get_by_name(struct net *net, const char *name);
diff --git a/net/core/dev.c b/net/core/dev.c
index 429a55fff667..e50ed677de72 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -748,6 +748,27 @@ static struct net_device_path *dev_fwd_path(struct net_device_path_stack *stack)
 	return &stack->path[stack->num_paths];
 }
 
+void dev_fill_forward_path_release(struct net_device_path_stack *stack)
+{
+	struct net_device_path *path;
+	int k;
+
+	if (stack->num_paths == 0)
+		return;
+
+	for (k = stack->num_paths - 1; k >= 0; k--) {
+		path = &stack->path[k];
+		switch (path->type) {
+		case DEV_PATH_TUN:
+			dst_release(path->tun.dst);
+			break;
+		default:
+			break;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(dev_fill_forward_path_release);
+
 int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
 			  struct net_device_path_stack *stack)
 {
@@ -764,16 +785,16 @@ int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
 		last_dev = ctx.dev;
 		path = dev_fwd_path(stack);
 		if (!path)
-			return -1;
+			goto err_out;
 
 		memset(path, 0, sizeof(struct net_device_path));
 		ret = ctx.dev->netdev_ops->ndo_fill_forward_path(&ctx, path);
 		if (ret < 0)
-			return -1;
+			goto err_out;
 
 		stack->num_paths++;
 		if (WARN_ON_ONCE(last_dev == ctx.dev))
-			return -1;
+			goto err_out;
 	}
 
 	if (!ctx.dev)
@@ -781,12 +802,17 @@ int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
 
 	path = dev_fwd_path(stack);
 	if (!path)
-		return -1;
+		goto err_out;
+
 	path->type = DEV_PATH_ETHERNET;
 	path->dev = ctx.dev;
 	stack->num_paths++;
 
-	return ret;
+	return 0;
+err_out:
+	dev_fill_forward_path_release(stack);
+
+	return -1;
 }
 EXPORT_SYMBOL_GPL(dev_fill_forward_path);
 
-- 
2.47.3