netdev - [PATCH v2 nf 3/4] net: fix dev_fill_forward

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Message-Id: <20220509122616.65449-3-nbd@nbd.name>
Date:   Mon,  9 May 2022 14:26:15 +0200
From:   Felix Fietkau <nbd@....name>
To:     netdev@...r.kernel.org
Cc:     pablo@...filter.org, netfilter-devel@...r.kernel.org
Subject: [PATCH v2 nf 3/4] net: fix dev_fill_forward_path with pppoe + bridge

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

Fixes: f6efc675c9dd ("net: ppp: resolve forwarding path for bridge pppoe devices")
Signed-off-by: Felix Fietkau <nbd@....name>
---
 drivers/net/ppp/pppoe.c   | 1 +
 include/linux/netdevice.h | 2 +-
 net/core/dev.c            | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index 3619520340b7..e172743948ed 100644
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -988,6 +988,7 @@ static int pppoe_fill_forward_path(struct net_device_path_ctx *ctx,
 	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;
 
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index b1fbe21650bb..f736c020cde2 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -900,7 +900,7 @@ 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 {
diff --git a/net/core/dev.c b/net/core/dev.c
index 1461c2d9dec8..2771fd22dc6a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -681,11 +681,11 @@ int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
 	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;
-- 
2.35.1