Merge branch 'net-ipv4-some-drop-reason-cleanup-and-improvements'

Antoine Tenart says:

====================
net: ipv4: some drop reason cleanup and improvements

A few patches that were laying around cleaning up and improving drop
reasons in net/ipv4.
====================

Link: https://patch.msgid.link/20250915091958.15382-1-atenart@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 21 insertions, 22 deletions

diff --git a/include/net/udp.h b/include/net/udp.h
index eecd64097f91..059a0cee5f55 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -404,7 +404,7 @@ static inline struct sk_buff *skb_recv_udp(struct sock *sk, unsigned int flags,
 	return __skb_recv_udp(sk, flags, &off, err);
 }
 
-int udp_v4_early_demux(struct sk_buff *skb);
+enum skb_drop_reason udp_v4_early_demux(struct sk_buff *skb);
 bool udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst);
 int udp_err(struct sk_buff *, u32);
 int udp_abort(struct sock *sk, int err);
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index a09aca2c8567..273578579a6b 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -263,10 +263,11 @@ int ip_local_deliver(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(ip_local_deliver);
 
-static inline bool ip_rcv_options(struct sk_buff *skb, struct net_device *dev)
+static inline enum skb_drop_reason
+ip_rcv_options(struct sk_buff *skb, struct net_device *dev)
 {
-	struct ip_options *opt;
 	const struct iphdr *iph;
+	struct ip_options *opt;
 
 	/* It looks as overkill, because not all
 	   IP options require packet mangling.
@@ -277,7 +278,7 @@ static inline bool ip_rcv_options(struct sk_buff *skb, struct net_device *dev)
 	*/
 	if (skb_cow(skb, skb_headroom(skb))) {
 		__IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INDISCARDS);
-		goto drop;
+		return SKB_DROP_REASON_NOMEM;
 	}
 
 	iph = ip_hdr(skb);
@@ -286,7 +287,7 @@ static inline bool ip_rcv_options(struct sk_buff *skb, struct net_device *dev)
 
 	if (ip_options_compile(dev_net(dev), opt, skb)) {
 		__IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
-		goto drop;
+		return SKB_DROP_REASON_IP_INHDR;
 	}
 
 	if (unlikely(opt->srr)) {
@@ -298,17 +299,15 @@ static inline bool ip_rcv_options(struct sk_buff *skb, struct net_device *dev)
 					net_info_ratelimited("source route option %pI4 -> %pI4\n",
 							     &iph->saddr,
 							     &iph->daddr);
-				goto drop;
+				return SKB_DROP_REASON_NOT_SPECIFIED;
 			}
 		}
 
 		if (ip_options_rcv_srr(skb, dev))
-			goto drop;
+			return SKB_DROP_REASON_NOT_SPECIFIED;
 	}
 
-	return false;
-drop:
-	return true;
+	return SKB_NOT_DROPPED_YET;
 }
 
 static bool ip_can_use_hint(const struct sk_buff *skb, const struct iphdr *iph,
@@ -319,7 +318,7 @@ static bool ip_can_use_hint(const struct sk_buff *skb, const struct iphdr *iph,
 }
 
 int tcp_v4_early_demux(struct sk_buff *skb);
-int udp_v4_early_demux(struct sk_buff *skb);
+enum skb_drop_reason udp_v4_early_demux(struct sk_buff *skb);
 static int ip_rcv_finish_core(struct net *net,
 			      struct sk_buff *skb, struct net_device *dev,
 			      const struct sk_buff *hint)
@@ -335,7 +334,6 @@ static int ip_rcv_finish_core(struct net *net,
 			goto drop_error;
 	}
 
-	drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
 	    !skb_dst(skb) &&
 	    !skb->sk &&
@@ -354,7 +352,6 @@ static int ip_rcv_finish_core(struct net *net,
 				drop_reason = udp_v4_early_demux(skb);
 				if (unlikely(drop_reason))
 					goto drop_error;
-				drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
 
 				/* must reload iph, skb->head might have changed */
 				iph = ip_hdr(skb);
@@ -372,7 +369,6 @@ static int ip_rcv_finish_core(struct net *net,
 						   ip4h_dscp(iph), dev);
 		if (unlikely(drop_reason))
 			goto drop_error;
-		drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	} else {
 		struct in_device *in_dev = __in_dev_get_rcu(dev);
 
@@ -391,8 +387,11 @@ static int ip_rcv_finish_core(struct net *net,
 	}
 #endif
 
-	if (iph->ihl > 5 && ip_rcv_options(skb, dev))
-		goto drop;
+	if (iph->ihl > 5) {
+		drop_reason = ip_rcv_options(skb, dev);
+		if (drop_reason)
+			goto drop;
+	}
 
 	rt = skb_rtable(skb);
 	if (rt->rt_type == RTN_MULTICAST) {
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 0c40426628eb..85cfc32eb2cc 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2811,7 +2811,7 @@ static struct sock *__udp4_lib_demux_lookup(struct net *net,
 	return NULL;
 }
 
-int udp_v4_early_demux(struct sk_buff *skb)
+enum skb_drop_reason udp_v4_early_demux(struct sk_buff *skb)
 {
 	struct net *net = dev_net(skb->dev);
 	struct in_device *in_dev = NULL;
@@ -2825,7 +2825,7 @@ int udp_v4_early_demux(struct sk_buff *skb)
 
 	/* validate the packet */
 	if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct udphdr)))
-		return 0;
+		return SKB_NOT_DROPPED_YET;
 
 	iph = ip_hdr(skb);
 	uh = udp_hdr(skb);
@@ -2834,12 +2834,12 @@ int udp_v4_early_demux(struct sk_buff *skb)
 		in_dev = __in_dev_get_rcu(skb->dev);
 
 		if (!in_dev)
-			return 0;
+			return SKB_NOT_DROPPED_YET;
 
 		ours = ip_check_mc_rcu(in_dev, iph->daddr, iph->saddr,
 				       iph->protocol);
 		if (!ours)
-			return 0;
+			return SKB_NOT_DROPPED_YET;
 
 		sk = __udp4_lib_mcast_demux_lookup(net, uh->dest, iph->daddr,
 						   uh->source, iph->saddr,
@@ -2850,7 +2850,7 @@ int udp_v4_early_demux(struct sk_buff *skb)
 	}
 
 	if (!sk)
-		return 0;
+		return SKB_NOT_DROPPED_YET;
 
 	skb->sk = sk;
 	DEBUG_NET_WARN_ON_ONCE(sk_is_refcounted(sk));
@@ -2877,7 +2877,7 @@ int udp_v4_early_demux(struct sk_buff *skb)
 						     ip4h_dscp(iph),
 						     skb->dev, in_dev, &itag);
 	}
-	return 0;
+	return SKB_NOT_DROPPED_YET;
 }
 
 int udp_rcv(struct sk_buff *skb)