[RFC PATCH net-next 6/7] net: ip: make ip_mc_validate_source() return drop reason

[Menglong Dong <menglong8.dong@xxxxxxxxx>]

Make ip_mc_validate_source() return drop reason, and adjust the call of
it in ip_route_input_mc().

Another caller of it is ip_rcv_finish_core->udp_v4_early_demux, and the
errno is not checked in detail, so we don't do more adjustment for it.

Signed-off-by: Menglong Dong <dongml2@xxxxxxxxxxxxxxx>
---
 include/net/route.h |  7 ++++---
 net/ipv4/route.c    | 33 ++++++++++++++++++---------------
 2 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/include/net/route.h b/include/net/route.h
index cb9f31080517..cd0f585dacf0 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -198,9 +198,10 @@ static inline struct rtable *ip_route_output_gre(struct net *net, struct flowi4
 	fl4->fl4_gre_key = gre_key;
 	return ip_route_output_key(net, fl4);
 }
-int ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
-			  u8 tos, struct net_device *dev,
-			  struct in_device *in_dev, u32 *itag);
+enum skb_drop_reason
+ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
+		      u8 tos, struct net_device *dev,
+		      struct in_device *in_dev, u32 *itag);
 int ip_route_input_noref(struct sk_buff *skb, __be32 dst, __be32 src,
 			 u8 tos, struct net_device *devin,
 			 enum skb_drop_reason *reason);
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 3e11a1849ac0..fa27f2120334 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1665,34 +1665,37 @@ struct rtable *rt_dst_clone(struct net_device *dev, struct rtable *rt)
 EXPORT_SYMBOL(rt_dst_clone);
 
 /* called in rcu_read_lock() section */
-int ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
-			  u8 tos, struct net_device *dev,
-			  struct in_device *in_dev, u32 *itag)
+enum skb_drop_reason
+ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
+		      u8 tos, struct net_device *dev,
+		      struct in_device *in_dev, u32 *itag)
 {
 	int err;
 
 	/* Primary sanity checks. */
 	if (!in_dev)
-		return -EINVAL;
+		return SKB_DROP_REASON_NOT_SPECIFIED;
 
-	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr) ||
-	    skb->protocol != htons(ETH_P_IP))
-		return -EINVAL;
+	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr))
+		return SKB_DROP_REASON_IP_INVALID_SOURCE;
+
+	if (skb->protocol != htons(ETH_P_IP))
+		return SKB_DROP_REASON_INVALID_PROTO;
 
 	if (ipv4_is_loopback(saddr) && !IN_DEV_ROUTE_LOCALNET(in_dev))
-		return -EINVAL;
+		return SKB_DROP_REASON_IP_LOCALNET;
 
 	if (ipv4_is_zeronet(saddr)) {
 		if (!ipv4_is_local_multicast(daddr) &&
 		    ip_hdr(skb)->protocol != IPPROTO_IGMP)
-			return -EINVAL;
+			return SKB_DROP_REASON_IP_INVALID_SOURCE;
 	} else {
 		err = fib_validate_source(skb, saddr, 0, tos, 0, dev,
 					  in_dev, itag);
 		if (err < 0)
-			return err;
+			return -err;
 	}
-	return 0;
+	return SKB_NOT_DROPPED_YET;
 }
 
 /* called in rcu_read_lock() section */
@@ -1701,14 +1704,14 @@ ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		  u8 tos, struct net_device *dev, int our)
 {
 	struct in_device *in_dev = __in_dev_get_rcu(dev);
+	enum skb_drop_reason reason;
 	unsigned int flags = RTCF_MULTICAST;
 	struct rtable *rth;
 	u32 itag = 0;
-	int err;
 
-	err = ip_mc_validate_source(skb, daddr, saddr, tos, dev, in_dev, &itag);
-	if (err)
-		return err;
+	reason = ip_mc_validate_source(skb, daddr, saddr, tos, dev, in_dev, &itag);
+	if (reason)
+		return reason;
 
 	if (our)
 		flags |= RTCF_LOCAL;
-- 
2.39.5