Subject: [PATCH] net: fix dev_fill_forward_path with pppoe + bridge
From: Felix Fietkau <[email-masked]>
Date: Fri, 6 May 2022 13:54:44 +0200

When calling dev_fill_forward_path on a pppoe device, the provided destination
address is invalid. In order for the bridge fdb lookup to succeed, the pppoe
code needs to update ctx->daddr to the correct value.
Fix this by storing the address inside struct net_device_path_ctx

Signed-off-by: Felix Fietkau <[email-masked]>
---

--- a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
+++ b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
@@ -91,7 +91,6 @@ mtk_flow_get_wdma_info(struct net_device
 {
 	struct net_device_path_ctx ctx = {
 		.dev = dev,
-		.daddr = addr,
 	};
 	struct net_device_path path = {};
 
@@ -101,6 +100,7 @@ mtk_flow_get_wdma_info(struct net_device
 	if (!dev->netdev_ops->ndo_fill_forward_path)
 		return -1;
 
+	memcpy(ctx.daddr, addr, sizeof(ctx.daddr));
 	if (dev->netdev_ops->ndo_fill_forward_path(&ctx, &path))
 		return -1;
 
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -988,6 +988,7 @@ static int pppoe_fill_forward_path(struc
 	path->encap.proto = htons(ETH_P_PPP_SES);
 	path->encap.id = be16_to_cpu(po->num);
 	memcpy(path->encap.h_dest, po->pppoe_pa.remote, ETH_ALEN);
+	memcpy(ctx->daddr, po->pppoe_pa.remote, ETH_ALEN);
 	path->dev = ctx->dev;
 	ctx->dev = dev;
 
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -904,7 +904,7 @@ struct net_device_path_stack {
 
 struct net_device_path_ctx {
 	const struct net_device *dev;
-	const u8		*daddr;
+	u8			daddr[ETH_ALEN];
 
 	int			num_vlans;
 	struct {
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -863,11 +863,11 @@ int dev_fill_forward_path(const struct n
 	const struct net_device *last_dev;
 	struct net_device_path_ctx ctx = {
 		.dev	= dev,
-		.daddr	= daddr,
 	};
 	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;