Push the pppoe header from the flowtable xmit path, instead of passing
the packet to the pppoe device which delivers the packet to the
userspace pppd daemon for encapsulation.

This is based on a patch originally written by wenxu.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_flow_table_ip.c   | 42 ++++++++++++++++++++++++++++++
 net/netfilter/nf_flow_table_path.c |  9 ++-----
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
index 2d11c46a925c..be21600cff53 100644
--- a/net/netfilter/nf_flow_table_ip.c
+++ b/net/netfilter/nf_flow_table_ip.c
@@ -413,6 +413,44 @@ static int nf_flow_offload_forward(struct nf_flowtable_ctx *ctx,
 	return 1;
 }
 
+static int nf_flow_pppoe_push(struct sk_buff *skb, u16 id)
+{
+	int data_len = skb->len + sizeof(__be16);
+	struct ppp_hdr {
+		struct pppoe_hdr hdr;
+		__be16 proto;
+	} *ph;
+	__be16 proto;
+
+	if (skb_cow_head(skb, PPPOE_SES_HLEN))
+		return -1;
+
+	switch (skb->protocol) {
+	case htons(ETH_P_IP):
+		proto = htons(PPP_IP);
+		break;
+	case htons(ETH_P_IPV6):
+		proto = htons(PPP_IPV6);
+		break;
+	default:
+		return -1;
+	}
+
+	__skb_push(skb, PPPOE_SES_HLEN);
+	skb_reset_network_header(skb);
+
+	ph = (struct ppp_hdr *)(skb->data);
+	ph->hdr.ver	= 1;
+	ph->hdr.type	= 1;
+	ph->hdr.code	= 0;
+	ph->hdr.sid	= htons(id);
+	ph->hdr.length	= htons(data_len);
+	ph->proto	= proto;
+	skb->protocol	= htons(ETH_P_PPP_SES);
+
+	return 0;
+}
+
 static int nf_flow_encap_push(struct sk_buff *skb, struct flow_offload_tuple *tuple)
 {
 	int i;
@@ -424,6 +462,10 @@ static int nf_flow_encap_push(struct sk_buff *skb, struct flow_offload_tuple *tu
 			if (skb_vlan_push(skb, tuple->encap[i].proto, tuple->encap[i].id) < 0)
 				return -1;
 			break;
+		case htons(ETH_P_PPP_SES):
+			if (nf_flow_pppoe_push(skb, tuple->encap[i].id) < 0)
+				return -1;
+			break;
 		}
 	}
 
diff --git a/net/netfilter/nf_flow_table_path.c b/net/netfilter/nf_flow_table_path.c
index 1cb04c3e6dde..7ba6a0c4e5d8 100644
--- a/net/netfilter/nf_flow_table_path.c
+++ b/net/netfilter/nf_flow_table_path.c
@@ -122,11 +122,8 @@ static void nft_dev_path_info(const struct net_device_path_stack *stack,
 			info->encap[info->num_encaps].id = path->encap.id;
 			info->encap[info->num_encaps].proto = path->encap.proto;
 			info->num_encaps++;
-			if (path->type == DEV_PATH_PPPOE) {
-				if (!info->outdev)
-					info->outdev = path->dev;
+			if (path->type == DEV_PATH_PPPOE)
 				memcpy(info->h_dest, path->encap.h_dest, ETH_ALEN);
-			}
 			break;
 		case DEV_PATH_BRIDGE:
 			if (is_zero_ether_addr(info->h_source))
@@ -154,9 +151,7 @@ static void nft_dev_path_info(const struct net_device_path_stack *stack,
 			break;
 		}
 	}
-	if (!info->outdev)
-		info->outdev = info->indev;
-
+	info->outdev = info->indev;
 	info->hw_outdev = info->indev;
 
 	if (nf_flowtable_hw_offload(flowtable) &&
-- 
2.30.2