net: ip: make ip_mkroute_input/__mkroute_input return drop reasons

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 d9340d1
Author: Menglong Dong <menglong8.dong@gmail.com>
Date:   Thu Nov 7 20:56:00 2024 +0800

    net: ip: make ip_mkroute_input/__mkroute_input return drop reasons

    In this commit, we make ip_mkroute_input() and __mkroute_input() return
    drop reasons.

    The drop reason "SKB_DROP_REASON_ARP_PVLAN_DISABLE" is introduced for
    the case: the packet which is not IP is forwarded to the in_dev, and
    the proxy_arp_pvlan is not enabled.

    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

include/net/dropreason-core.h

@@ -104,6 +104,7 @@
 	FN(IP_TUNNEL_ECN)		\
 	FN(TUNNEL_TXINFO)		\
 	FN(LOCAL_MAC)			\
+	FN(ARP_PVLAN_DISABLE)		\
 	FNe(MAX)
 
 /**
@@ -477,6 +478,12 @@ enum skb_drop_reason {
 	 * the MAC address of the local netdev.
 	 */
 	SKB_DROP_REASON_LOCAL_MAC,
+	/**
+	 * @SKB_DROP_REASON_ARP_PVLAN_DISABLE: packet which is not IP is
+	 * forwarded to the in_dev, and the proxy_arp_pvlan is not
+	 * enabled.
+	 */
+	SKB_DROP_REASON_ARP_PVLAN_DISABLE,
 	/**
 	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
 	 * shouldn't be used as a real 'reason' - only for tracing code gen

net/ipv4/route.c

@@ -1780,11 +1780,12 @@ static void ip_handle_martian_source(struct net_device *dev,
 }
 
 /* called in rcu_read_lock() section */
-static int __mkroute_input(struct sk_buff *skb,
-			   const struct fib_result *res,
-			   struct in_device *in_dev,
-			   __be32 daddr, __be32 saddr, u32 tos)
+static enum skb_drop_reason
+__mkroute_input(struct sk_buff *skb, const struct fib_result *res,
+		struct in_device *in_dev, __be32 daddr,
+		__be32 saddr, u32 tos)
 {
+	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	struct fib_nh_common *nhc = FIB_RES_NHC(*res);
 	struct net_device *dev = nhc->nhc_dev;
 	struct fib_nh_exception *fnhe;
@@ -1798,13 +1799,13 @@ static int __mkroute_input(struct sk_buff *skb,
 	out_dev = __in_dev_get_rcu(dev);
 	if (!out_dev) {
 		net_crit_ratelimited("Bug in ip_route_input_slow(). Please report.\n");
-		return -EINVAL;
+		return reason;
 	}
 
 	err = fib_validate_source(skb, saddr, daddr, tos, FIB_RES_OIF(*res),
 				  in_dev->dev, in_dev, &itag);
 	if (err < 0) {
-		err = -EINVAL;
+		reason = -err;
 		ip_handle_martian_source(in_dev->dev, in_dev, skb, daddr,
 					 saddr);
 
@@ -1832,7 +1833,7 @@ static int __mkroute_input(struct sk_buff *skb,
 		 */
 		if (out_dev == in_dev &&
 		    IN_DEV_PROXY_ARP_PVLAN(in_dev) == 0) {
-			err = -EINVAL;
+			reason = SKB_DROP_REASON_ARP_PVLAN_DISABLE;
 			goto cleanup;
 		}
 	}
@@ -1855,7 +1856,7 @@ static int __mkroute_input(struct sk_buff *skb,
 	rth = rt_dst_alloc(out_dev->dev, 0, res->type,
 			   IN_DEV_ORCONF(out_dev, NOXFRM));
 	if (!rth) {
-		err = -ENOBUFS;
+		reason = SKB_DROP_REASON_NOMEM;
 		goto cleanup;
 	}
 
@@ -1869,9 +1870,9 @@ static int __mkroute_input(struct sk_buff *skb,
 	lwtunnel_set_redirect(&rth->dst);
 	skb_dst_set(skb, &rth->dst);
 out:
-	err = 0;
- cleanup:
-	return err;
+	reason = SKB_NOT_DROPPED_YET;
+cleanup:
+	return reason;
 }
 
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
@@ -2129,11 +2130,10 @@ int fib_multipath_hash(const struct net *net, const struct flowi4 *fl4,
 }
 #endif /* CONFIG_IP_ROUTE_MULTIPATH */
 
-static int ip_mkroute_input(struct sk_buff *skb,
-			    struct fib_result *res,
-			    struct in_device *in_dev,
-			    __be32 daddr, __be32 saddr, u32 tos,
-			    struct flow_keys *hkeys)
+static enum skb_drop_reason
+ip_mkroute_input(struct sk_buff *skb, struct fib_result *res,
+		 struct in_device *in_dev, __be32 daddr,
+		 __be32 saddr, u32 tos, struct flow_keys *hkeys)
 {
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 	if (res->fi && fib_info_num_path(res->fi) > 1) {
@@ -2348,9 +2348,8 @@ 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);
-	if (!err)
-		reason = SKB_NOT_DROPPED_YET;
+	reason = ip_mkroute_input(skb, res, in_dev, daddr, saddr, tos,
+				  flkeys);
 
 out:
 	return reason;