[PATCH nf-next 3/4] net: pass dst via net_device_path in dev_fill_forward_path()

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.

Signed-off-by: Pablo Neira Ayuso <[email protected]>
---
 include/linux/netdevice.h |  1 +
 net/core/dev.c            | 45 +++++++++++++++++++++++++++++++--------
 2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8db25b79573e..30dc78b4f1a3 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -902,6 +902,7 @@ struct net_device_path {
 			};
 
 			u8	l3_proto;
+			struct dst_entry *dst;
 		} tun;
 		struct {
 			enum {
diff --git a/net/core/dev.c b/net/core/dev.c
index c1c1be1a6962..fed101f54a8a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -750,6 +750,23 @@ static struct net_device_path *dev_fwd_path(struct net_device_path_stack *stack)
 	return &stack->path[k];
 }
 
+static void dev_fill_forward_path_release(struct net_device_path_stack *stack)
+{
+	struct net_device_path *path;
+	int k;
+
+	for (k = stack->num_paths; k >= 0; k--) {
+		path = &stack->path[k];
+		switch (path->type) {
+		case DEV_PATH_TUN:
+			dst_release(path->tun.dst);
+			break;
+		default:
+			break;
+		}
+	}
+}
+
 int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
 			  struct net_device_path_stack *stack)
 {
@@ -765,28 +782,38 @@ int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
 	while (ctx.dev && ctx.dev->netdev_ops->ndo_fill_forward_path) {
 		last_dev = ctx.dev;
 		path = dev_fwd_path(stack);
-		if (!path)
-			return -1;
+		if (!path) {
+			ret = -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;
 
-		if (WARN_ON_ONCE(last_dev == ctx.dev))
-			return -1;
+		if (WARN_ON_ONCE(last_dev == ctx.dev)) {
+			ret = -1;
+			goto err_out;
+		}
 	}
 
 	if (!ctx.dev)
-		return ret;
+		goto err_out;
 
 	path = dev_fwd_path(stack);
-	if (!path)
-		return -1;
+	if (!path) {
+		ret = -1;
+		goto err_out;
+	}
 	path->type = DEV_PATH_ETHERNET;
 	path->dev = ctx.dev;
 
-	return ret;
+	return 0;
+err_out:
+	dev_fill_forward_path_release(stack);
+
+	return -1;
 }
 EXPORT_SYMBOL_GPL(dev_fill_forward_path);
 
-- 
2.47.3