[PATCH nf-next,v3 4/5] 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.

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

Acked-by: Lorenzo Bianconi <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>
---
v3: no changes

 include/linux/netdevice.h |  2 ++
 net/core/dev.c            | 36 +++++++++++++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 5 deletions(-)

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 96c01f6e9dea..e0c132db15b2 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