net: ip: make ip_route_input_mc() return drop reason

JIRA: https://issues.redhat.com/browse/RHEL-88891
Upstream Status: linux.git
Conflicts:\
 - Minor code differences as the tos to dscp conversion wasn't done in
   c10s yet.

commit c6c6707
Author: Menglong Dong <menglong8.dong@gmail.com>
Date:   Thu Nov 7 20:55:54 2024 +0800

    net: ip: make ip_route_input_mc() return drop reason

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

    Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Signed-off-by: Antoine Tenart <atenart@redhat.com>

Author: atenart

net/ipv4/route.c

@@ -1707,8 +1707,9 @@ int ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 }
 
 /* called in rcu_read_lock() section */
-static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
-			     u8 tos, struct net_device *dev, int our)
+static enum skb_drop_reason
+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);
 	unsigned int flags = RTCF_MULTICAST;
@@ -1718,7 +1719,7 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 
 	err = ip_mc_validate_source(skb, daddr, saddr, tos, dev, in_dev, &itag);
 	if (err)
-		return err;
+		return SKB_DROP_REASON_NOT_SPECIFIED;
 
 	if (our)
 		flags |= RTCF_LOCAL;
@@ -1729,7 +1730,7 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	rth = rt_dst_alloc(dev_net(dev)->loopback_dev, flags, RTN_MULTICAST,
 			   false);
 	if (!rth)
-		return -ENOBUFS;
+		return SKB_DROP_REASON_NOMEM;
 
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	rth->dst.tclassid = itag;
@@ -1745,7 +1746,7 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 
 	skb_dst_drop(skb);
 	skb_dst_set(skb, &rth->dst);
-	return 0;
+	return SKB_NOT_DROPPED_YET;
 }
 
 
@@ -2446,12 +2447,12 @@ static int ip_route_input_rcu(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	 * route cache entry is created eventually.
 	 */
 	if (ipv4_is_multicast(daddr)) {
+		enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
 		struct in_device *in_dev = __in_dev_get_rcu(dev);
 		int our = 0;
-		int err = -EINVAL;
 
 		if (!in_dev)
-			return err;
+			return -EINVAL;
 		our = ip_check_mc_rcu(in_dev, daddr, saddr,
 				      ip_hdr(skb)->protocol);
 
@@ -2472,10 +2473,10 @@ static int ip_route_input_rcu(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		     IN_DEV_MFORWARD(in_dev))
 #endif
 		   ) {
-			err = ip_route_input_mc(skb, daddr, saddr,
-						tos, dev, our);
+			reason = ip_route_input_mc(skb, daddr, saddr, tos,
+						   dev, our);
 		}
-		return err;
+		return reason ? -EINVAL : 0;
 	}
 
 	return ip_route_input_slow(skb, daddr, saddr, tos, dev, res);