[RFC PATCH net-next 3/7] net: ip: add drop reason to ip_route_input_slow()

[Menglong Dong]

In this commit, we make ip_route_input_slow() support skb drop reason by
adding the pointer of drop reason to its functions aeguments.

Following new skb drop reasons are added:

  SKB_DROP_REASON_IP_LOCAL_SOURCE
  SKB_DROP_REASON_IP_INVALID_SOURCE
  SKB_DROP_REASON_IP_INVALID_DEST
  SKB_DROP_REASON_IP_LOCALNET

Signed-off-by: Menglong Dong <dongml2@xxxxxxxxxxxxxxx>
---
 include/net/dropreason-core.h | 19 +++++++++++++++++++
 net/ipv4/route.c              | 32 ++++++++++++++++++++++++--------
 2 files changed, 43 insertions(+), 8 deletions(-)

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 4748680e8c88..3d1b09f70bbd 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -76,6 +76,10 @@
 	FN(INVALID_PROTO)		\
 	FN(IP_INADDRERRORS)		\
 	FN(IP_INNOROUTES)		\
+	FN(IP_LOCAL_SOURCE)		\
+	FN(IP_INVALID_SOURCE)		\
+	FN(IP_INVALID_DEST)		\
+	FN(IP_LOCALNET)			\
 	FN(PKT_TOO_BIG)			\
 	FN(DUP_FRAG)			\
 	FN(FRAG_REASM_TIMEOUT)		\
@@ -365,6 +369,21 @@ enum skb_drop_reason {
 	 * IPSTATS_MIB_INADDRERRORS
 	 */
 	SKB_DROP_REASON_IP_INNOROUTES,
+	/** @SKB_DROP_REASON_IP_LOCAL_SOURCE: the source ip is local */
+	SKB_DROP_REASON_IP_LOCAL_SOURCE,
+	/**
+	 * @SKB_DROP_REASON_IP_INVALID_SOURCE: the source ip is invalid:
+	 * 1) source ip is multicast or limited broadcast
+	 * 2) source ip is zero and not IGMP
+	 */
+	SKB_DROP_REASON_IP_INVALID_SOURCE,
+	/**
+	 * @SKB_DROP_REASON_IP_INVALID_DEST: the dest ip is invalid:
+	 * 1) dest ip is 0
+	 */
+	SKB_DROP_REASON_IP_INVALID_DEST,
+	/** @SKB_DROP_REASON_IP_LOCALNET: source or dest ip is local net */
+	SKB_DROP_REASON_IP_LOCALNET,
 	/**
 	 * @SKB_DROP_REASON_PKT_TOO_BIG: packet size is too big (maybe exceed the
 	 * MTU)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 385efe6d71a7..ab70917c62e5 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2202,8 +2202,10 @@ static struct net_device *ip_rt_get_dev(struct net *net,
 
 static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 			       u8 tos, struct net_device *dev,
-			       struct fib_result *res)
+			       struct fib_result *res,
+			       enum skb_drop_reason *reason)
 {
+	enum skb_drop_reason __reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	struct in_device *in_dev = __in_dev_get_rcu(dev);
 	struct flow_keys *flkeys = NULL, _flkeys;
 	struct net    *net = dev_net(dev);
@@ -2231,8 +2233,10 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		fl4.flowi4_tun_key.tun_id = 0;
 	skb_dst_drop(skb);
 
-	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr))
+	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr)) {
+		__reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
 		goto martian_source;
+	}
 
 	res->fi = NULL;
 	res->table = NULL;
@@ -2242,21 +2246,29 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	/* Accept zero addresses only to limited broadcast;
 	 * I even do not know to fix it or not. Waiting for complains :-)
 	 */
-	if (ipv4_is_zeronet(saddr))
+	if (ipv4_is_zeronet(saddr)) {
+		__reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
 		goto martian_source;
+	}
 
-	if (ipv4_is_zeronet(daddr))
+	if (ipv4_is_zeronet(daddr)) {
+		__reason = SKB_DROP_REASON_IP_INVALID_DEST;
 		goto martian_destination;
+	}
 
 	/* Following code try to avoid calling IN_DEV_NET_ROUTE_LOCALNET(),
 	 * and call it once if daddr or/and saddr are loopback addresses
 	 */
 	if (ipv4_is_loopback(daddr)) {
-		if (!IN_DEV_NET_ROUTE_LOCALNET(in_dev, net))
+		if (!IN_DEV_NET_ROUTE_LOCALNET(in_dev, net)) {
+			__reason = SKB_DROP_REASON_IP_LOCALNET;
 			goto martian_destination;
+		}
 	} else if (ipv4_is_loopback(saddr)) {
-		if (!IN_DEV_NET_ROUTE_LOCALNET(in_dev, net))
+		if (!IN_DEV_NET_ROUTE_LOCALNET(in_dev, net)) {
+			__reason = SKB_DROP_REASON_IP_LOCALNET;
 			goto martian_source;
+		}
 	}
 
 	/*
@@ -2315,7 +2327,10 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 
 make_route:
 	err = ip_mkroute_input(skb, res, in_dev, daddr, saddr, tos, flkeys);
-out:	return err;
+out:
+	if (reason && err)
+		*reason = __reason;
+	return err;
 
 brd_input:
 	if (skb->protocol != htons(ETH_P_IP))
@@ -2406,6 +2421,7 @@ out:	return err;
 
 e_nobufs:
 	err = -ENOBUFS;
+	__reason = SKB_DROP_REASON_NOMEM;
 	goto out;
 
 martian_source:
@@ -2462,7 +2478,7 @@ static int ip_route_input_rcu(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		return err;
 	}
 
-	return ip_route_input_slow(skb, daddr, saddr, tos, dev, res);
+	return ip_route_input_slow(skb, daddr, saddr, tos, dev, res, reason);
 }
 
 int ip_route_input_noref(struct sk_buff *skb, __be32 daddr, __be32 saddr,
-- 
2.39.5