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Date:   Thu, 15 Oct 2020 03:16:27 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org
Subject: [PATCH net-next 6/9] netfilter: flowtable: use dev_fill_forward_path() to obtain egress device

The egress device in the tuple is obtained from route. Use
dev_fill_forward_path() instead to provide the real ingress device for
this flow whenever this is available.

Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 include/net/netfilter/nf_flow_table.h |  4 ++++
 net/netfilter/nf_flow_table_core.c    |  1 +
 net/netfilter/nf_flow_table_ip.c      | 25 +++++++++++++++++++++++--
 net/netfilter/nft_flow_offload.c      |  1 +
 4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index ecb84d4358cc..fe225e881cc7 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -117,6 +117,7 @@ struct flow_offload_tuple {
 	u8				dir;
 	enum flow_offload_xmit_type	xmit_type:8;
 	u16				mtu;
+	u32				oifidx;
 
 	struct dst_entry		*dst_cache;
 };
@@ -164,6 +165,9 @@ struct nf_flow_route {
 		struct {
 			u32		ifindex;
 		} in;
+		struct {
+			u32		ifindex;
+		} out;
 		struct dst_entry	*dst;
 	} tuple[FLOW_OFFLOAD_DIR_MAX];
 };
diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 66abc7f287a3..99f01f08c550 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -94,6 +94,7 @@ static int flow_offload_fill_route(struct flow_offload *flow,
 	}
 
 	flow_tuple->iifidx = route->tuple[dir].in.ifindex;
+	flow_tuple->oifidx = route->tuple[dir].out.ifindex;
 
 	if (dst_xfrm(dst))
 		flow_tuple->xmit_type = FLOW_OFFLOAD_XMIT_XFRM;
diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
index e215c79e6777..92f444db8d9f 100644
--- a/net/netfilter/nf_flow_table_ip.c
+++ b/net/netfilter/nf_flow_table_ip.c
@@ -228,6 +228,15 @@ static int nf_flow_offload_dst_check(struct dst_entry *dst)
 	return 0;
 }
 
+static struct net_device *nf_flow_outdev_lookup(struct net *net, int oifidx,
+						struct net_device *dev)
+{
+	if (oifidx == dev->ifindex)
+		return dev;
+
+	return dev_get_by_index_rcu(net, oifidx);
+}
+
 static unsigned int nf_flow_xmit_xfrm(struct sk_buff *skb,
 				      const struct nf_hook_state *state,
 				      struct dst_entry *dst)
@@ -267,7 +276,6 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 	dir = tuplehash->tuple.dir;
 	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 	rt = (struct rtable *)flow->tuplehash[dir].tuple.dst_cache;
-	outdev = rt->dst.dev;
 
 	if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)))
 		return NF_ACCEPT;
@@ -286,6 +294,13 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 		return NF_ACCEPT;
 	}
 
+	outdev = nf_flow_outdev_lookup(state->net, tuplehash->tuple.oifidx,
+				       rt->dst.dev);
+	if (!outdev) {
+		flow_offload_teardown(flow);
+		return NF_ACCEPT;
+	}
+
 	if (nf_flow_nat_ip(flow, skb, thoff, dir) < 0)
 		return NF_DROP;
 
@@ -517,7 +532,6 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 	dir = tuplehash->tuple.dir;
 	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 	rt = (struct rt6_info *)flow->tuplehash[dir].tuple.dst_cache;
-	outdev = rt->dst.dev;
 
 	if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)))
 		return NF_ACCEPT;
@@ -533,6 +547,13 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 		return NF_ACCEPT;
 	}
 
+	outdev = nf_flow_outdev_lookup(state->net, tuplehash->tuple.oifidx,
+				       rt->dst.dev);
+	if (!outdev) {
+		flow_offload_teardown(flow);
+		return NF_ACCEPT;
+	}
+
 	if (skb_try_make_writable(skb, sizeof(*ip6h)))
 		return NF_DROP;
 
diff --git a/net/netfilter/nft_flow_offload.c b/net/netfilter/nft_flow_offload.c
index 4b476b0a3c88..6a6633e2ceeb 100644
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -84,6 +84,7 @@ static int nft_dev_forward_path(struct nf_flow_route *route,
 	}
 
 	route->tuple[!dir].in.ifindex = info.iifindex;
+	route->tuple[dir].out.ifindex = info.iifindex;
 
 	return 0;
 }
-- 
2.20.1

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