[PATCH net-next 3/6] net: ipv4: use kfree_skb_reason() in ip_rcv_finish_core()

[menglong8.dong@xxxxxxxxx]

From: Menglong Dong <imagedong@xxxxxxxxxxx>

Replace kfree_skb() with kfree_skb_reason() in ip_rcv_finish_core(),
following drop reasons are introduced:

SKB_DROP_REASON_IP_ROUTE_INPUT
SKB_DROP_REASON_IP_RPFILTER
SKB_DROP_REASON_EARLY_DEMUX
SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST

Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx>
---
 include/linux/skbuff.h     |  4 ++++
 include/trace/events/skb.h |  5 +++++
 net/ipv4/ip_input.c        | 22 ++++++++++++++++------
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index f3028028b83e..8942d32c0657 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -324,6 +324,10 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_OTHERHOST,
 	SKB_DROP_REASON_IP_CSUM,
 	SKB_DROP_REASON_IP_INHDR,
+	SKB_DROP_REASON_IP_ROUTE_INPUT,
+	SKB_DROP_REASON_IP_RPFILTER,
+	SKB_DROP_REASON_EARLY_DEMUX,
+	SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST,
 	SKB_DROP_REASON_MAX,
 };
 
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index d1b0d9690e62..1dcdcc92cf08 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -20,6 +20,11 @@
 	EM(SKB_DROP_REASON_OTHERHOST, OTHERHOST)		\
 	EM(SKB_DROP_REASON_IP_CSUM, IP_CSUM)			\
 	EM(SKB_DROP_REASON_IP_INHDR, IP_INHDR)			\
+	EM(SKB_DROP_REASON_IP_ROUTE_INPUT, IP_ROUTE_INPUT)	\
+	EM(SKB_DROP_REASON_IP_RPFILTER, IP_RPFILTER)		\
+	EM(SKB_DROP_REASON_EARLY_DEMUX, EARLY_DEMUX)		\
+	EM(SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST,		\
+	   UNICAST_IN_L2_MULTICAST)				\
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index ab9bee4bbf0a..77bb9ddc441b 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -318,8 +318,10 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
 {
 	const struct iphdr *iph = ip_hdr(skb);
 	int (*edemux)(struct sk_buff *skb);
+	int err, drop_reason;
 	struct rtable *rt;
-	int err;
+
+	drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
 
 	if (ip_can_use_hint(skb, iph, hint)) {
 		err = ip_route_use_hint(skb, iph->daddr, iph->saddr, iph->tos,
@@ -339,8 +341,10 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
 		if (ipprot && (edemux = READ_ONCE(ipprot->early_demux))) {
 			err = INDIRECT_CALL_2(edemux, tcp_v4_early_demux,
 					      udp_v4_early_demux, skb);
-			if (unlikely(err))
+			if (unlikely(err)) {
+				drop_reason = SKB_DROP_REASON_EARLY_DEMUX;
 				goto drop_error;
+			}
 			/* must reload iph, skb->head might have changed */
 			iph = ip_hdr(skb);
 		}
@@ -353,8 +357,10 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
 	if (!skb_valid_dst(skb)) {
 		err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
 					   iph->tos, dev);
-		if (unlikely(err))
+		if (unlikely(err)) {
+			drop_reason = SKB_DROP_REASON_IP_ROUTE_INPUT;
 			goto drop_error;
+		}
 	}
 
 #ifdef CONFIG_IP_ROUTE_CLASSID
@@ -396,19 +402,23 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
 		 * so-called "hole-196" attack) so do it for both.
 		 */
 		if (in_dev &&
-		    IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST))
+		    IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST)) {
+			drop_reason = SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST;
 			goto drop;
+		}
 	}
 
 	return NET_RX_SUCCESS;
 
 drop:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, drop_reason);
 	return NET_RX_DROP;
 
 drop_error:
-	if (err == -EXDEV)
+	if (err == -EXDEV) {
+		drop_reason = SKB_DROP_REASON_IP_RPFILTER;
 		__NET_INC_STATS(net, LINUX_MIB_IPRPFILTER);
+	}
 	goto drop;
 }
 
-- 
2.34.1