[PATCH bpf-next v4 3/9] net: ip: make ip_mc_validate_source() return drop reason

[Menglong Dong <menglong8.dong@gmail.com>]

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.

The drop reason "SKB_DROP_REASON_IP_LOCALNET" is added in this commit.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
---
 include/net/dropreason-core.h |  3 +++
 include/net/route.h           |  7 ++++---
 net/ipv4/route.c              | 35 +++++++++++++++++++----------------
 3 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 62a60be1db84..a2a1fb90e0e5 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -78,6 +78,7 @@
 	FN(IP_INNOROUTES)		\
 	FN(IP_LOCAL_SOURCE)		\
 	FN(IP_INVALID_SOURCE)		\
+	FN(IP_LOCALNET)			\
 	FN(PKT_TOO_BIG)			\
 	FN(DUP_FRAG)			\
 	FN(FRAG_REASM_TIMEOUT)		\
@@ -383,6 +384,8 @@ enum skb_drop_reason {
 	 * 2) source ip is zero and not IGMP
 	 */
 	SKB_DROP_REASON_IP_INVALID_SOURCE,
+	/** @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/include/net/route.h b/include/net/route.h
index 586e59f7ed8a..a828a17a6313 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -199,9 +199,10 @@ static inline struct rtable *ip_route_output_gre(struct net *net, struct flowi4
 	return ip_route_output_key(net, fl4);
 }
 
-int ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
-			  dscp_t dscp, 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,
+		      dscp_t dscp, struct net_device *dev,
+		      struct in_device *in_dev, u32 *itag);
 int ip_route_input_noref(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 			 dscp_t dscp, struct net_device *dev);
 int ip_route_use_hint(struct sk_buff *skb, __be32 daddr, __be32 saddr,
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index e579fe5bd3d3..61e316f93291 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,
-			  dscp_t dscp, 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,
+		      dscp_t dscp, struct net_device *dev,
+		      struct in_device *in_dev, u32 *itag)
 {
 	enum skb_drop_reason reason;
 
 	/* 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 {
 		reason = fib_validate_source_reason(skb, saddr, 0, dscp, 0,
 						    dev, in_dev, itag);
 		if (reason)
-			return -EINVAL;
+			return reason;
 	}
-	return 0;
+	return SKB_NOT_DROPPED_YET;
 }
 
 /* called in rcu_read_lock() section */
@@ -1702,14 +1705,14 @@ ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 {
 	struct in_device *in_dev = __in_dev_get_rcu(dev);
 	unsigned int flags = RTCF_MULTICAST;
+	enum skb_drop_reason reason;
 	struct rtable *rth;
 	u32 itag = 0;
-	int err;
 
-	err = ip_mc_validate_source(skb, daddr, saddr, dscp, dev, in_dev,
-				    &itag);
-	if (err)
-		return SKB_DROP_REASON_NOT_SPECIFIED;
+	reason = ip_mc_validate_source(skb, daddr, saddr, dscp, dev, in_dev,
+				       &itag);
+	if (reason)
+		return reason;
 
 	if (our)
 		flags |= RTCF_LOCAL;
-- 
2.39.5