From: Felix Fietkau <nbd@nbd.name>
Date: Wed, 24 Mar 2021 02:30:36 +0100
Subject: [PATCH] net: ppp: resolve forwarding path for bridge pppoe
 devices

Pass on the PPPoE session ID, destination hardware address and the real
device.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---

--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -1466,12 +1466,34 @@ static void ppp_dev_priv_destructor(stru
 		ppp_destroy_interface(ppp);
 }
 
+static int ppp_fill_forward_path(struct net_device_path_ctx *ctx,
+				 struct net_device_path *path)
+{
+	struct ppp *ppp = netdev_priv(ctx->dev);
+	struct ppp_channel *chan;
+	struct channel *pch;
+
+	if (ppp->flags & SC_MULTILINK)
+		return -EOPNOTSUPP;
+
+	if (list_empty(&ppp->channels))
+		return -ENODEV;
+
+	pch = list_first_entry(&ppp->channels, struct channel, clist);
+	chan = pch->chan;
+	if (!chan->ops->fill_forward_path)
+		return -EOPNOTSUPP;
+
+	return chan->ops->fill_forward_path(ctx, path, chan);
+}
+
 static const struct net_device_ops ppp_netdev_ops = {
 	.ndo_init	 = ppp_dev_init,
 	.ndo_uninit      = ppp_dev_uninit,
 	.ndo_start_xmit  = ppp_start_xmit,
 	.ndo_do_ioctl    = ppp_net_ioctl,
 	.ndo_get_stats64 = ppp_get_stats64,
+	.ndo_fill_forward_path = ppp_fill_forward_path,
 };
 
 static struct device_type ppp_type = {
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -972,8 +972,31 @@ static int pppoe_xmit(struct ppp_channel
 	return __pppoe_xmit(sk, skb);
 }
 
+static int pppoe_fill_forward_path(struct net_device_path_ctx *ctx,
+				   struct net_device_path *path,
+				   const struct ppp_channel *chan)
+{
+	struct sock *sk = (struct sock *)chan->private;
+	struct pppox_sock *po = pppox_sk(sk);
+	struct net_device *dev = po->pppoe_dev;
+
+	if (sock_flag(sk, SOCK_DEAD) ||
+	    !(sk->sk_state & PPPOX_CONNECTED) || !dev)
+		return -1;
+
+	path->type = DEV_PATH_PPPOE;
+	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);
+	path->dev = ctx->dev;
+	ctx->dev = dev;
+
+	return 0;
+}
+
 static const struct ppp_channel_ops pppoe_chan_ops = {
 	.start_xmit = pppoe_xmit,
+	.fill_forward_path = pppoe_fill_forward_path,
 };
 
 static int pppoe_recvmsg(struct socket *sock, struct msghdr *m,
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -854,6 +854,7 @@ enum net_device_path_type {
 	DEV_PATH_ETHERNET = 0,
 	DEV_PATH_VLAN,
 	DEV_PATH_BRIDGE,
+	DEV_PATH_PPPOE,
 };
 
 struct net_device_path {
@@ -863,6 +864,7 @@ struct net_device_path {
 		struct {
 			u16		id;
 			__be16		proto;
+			u8		h_dest[ETH_ALEN];
 		} encap;
 		struct {
 			enum {
--- a/include/linux/ppp_channel.h
+++ b/include/linux/ppp_channel.h
@@ -28,6 +28,9 @@ struct ppp_channel_ops {
 	int	(*start_xmit)(struct ppp_channel *, struct sk_buff *);
 	/* Handle an ioctl call that has come in via /dev/ppp. */
 	int	(*ioctl)(struct ppp_channel *, unsigned int, unsigned long);
+	int	(*fill_forward_path)(struct net_device_path_ctx *,
+				     struct net_device_path *,
+				     const struct ppp_channel *);
 };
 
 struct ppp_channel {