Subject: [PATCH net-next v5 04/12] net: vxlan: add skb drop reasons to vxlan_rcv()

From: Menglong Dong <[email-masked]>
Date: Sun, 6 Oct 2024 14:56:08 +0800

Introduce skb drop reasons to the function vxlan_rcv(). Following new
drop reasons are added:

  SKB_DROP_REASON_VXLAN_INVALID_HDR
  SKB_DROP_REASON_VXLAN_VNI_NOT_FOUND
  SKB_DROP_REASON_IP_TUNNEL_ECN

Signed-off-by: Menglong Dong <[email-masked]>
Reviewed-by: Simon Horman <[email-masked]>
---
v3:
- modify vxlan_set_mac() and vxlan_remcsum() after this patch
v2:
- rename the drop reasons, as Ido advised.
- document the drop reasons
---
 drivers/net/vxlan/vxlan_core.c | 26 ++++++++++++++++++++------
 include/net/dropreason-core.h  | 16 ++++++++++++++++
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 0359c750d81e..4997a2c09c14 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -1671,13 +1671,15 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 	struct vxlan_metadata _md;
 	struct vxlan_metadata *md = &_md;
 	__be16 protocol = htons(ETH_P_TEB);
+	enum skb_drop_reason reason;
 	bool raw_proto = false;
 	void *oiph;
 	__be32 vni = 0;
 	int nh;
 
 	/* Need UDP and VXLAN header to be present */
-	if (!pskb_may_pull(skb, VXLAN_HLEN))
+	reason = pskb_may_pull_reason(skb, VXLAN_HLEN);
+	if (reason)
 		goto drop;
 
 	unparsed = *vxlan_hdr(skb);
@@ -1686,6 +1688,7 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 		netdev_dbg(skb->dev, "invalid vxlan flags=%#x vni=%#x\n",
 			   ntohl(vxlan_hdr(skb)->vx_flags),
 			   ntohl(vxlan_hdr(skb)->vx_vni));
+		reason = SKB_DROP_REASON_VXLAN_INVALID_HDR;
 		/* Return non vxlan pkt */
 		goto drop;
 	}
@@ -1699,8 +1702,10 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 	vni = vxlan_vni(vxlan_hdr(skb)->vx_vni);
 
 	vxlan = vxlan_vs_find_vni(vs, skb->dev->ifindex, vni, &vninode);
-	if (!vxlan)
+	if (!vxlan) {
+		reason = SKB_DROP_REASON_VXLAN_VNI_NOT_FOUND;
 		goto drop;
+	}
 
 	/* For backwards compatibility, only allow reserved fields to be
 	 * used by VXLAN extensions if explicitly requested.
@@ -1713,8 +1718,10 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 	}
 
 	if (__iptunnel_pull_header(skb, VXLAN_HLEN, protocol, raw_proto,
-				   !net_eq(vxlan->net, dev_net(vxlan->dev))))
+				   !net_eq(vxlan->net, dev_net(vxlan->dev)))) {
+		reason = SKB_DROP_REASON_NOMEM;
 		goto drop;
+	}
 
 	if (vs->flags & VXLAN_F_REMCSUM_RX)
 		if (unlikely(!vxlan_remcsum(&unparsed, skb, vs->flags)))
@@ -1728,8 +1735,10 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 		tun_dst = udp_tun_rx_dst(skb, vxlan_get_sk_family(vs), flags,
 					 key32_to_tunnel_id(vni), sizeof(*md));
 
-		if (!tun_dst)
+		if (!tun_dst) {
+			reason = SKB_DROP_REASON_NOMEM;
 			goto drop;
+		}
 
 		md = ip_tunnel_info_opts(&tun_dst->u.tun_info);
 
@@ -1753,6 +1762,7 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 		 * is more robust and provides a little more security in
 		 * adding extensions to VXLAN.
 		 */
+		reason = SKB_DROP_REASON_VXLAN_INVALID_HDR;
 		goto drop;
 	}
 
@@ -1773,7 +1783,8 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 
 	skb_reset_network_header(skb);
 
-	if (!pskb_inet_may_pull(skb)) {
+	reason = pskb_inet_may_pull_reason(skb);
+	if (reason) {
 		DEV_STATS_INC(vxlan->dev, rx_length_errors);
 		DEV_STATS_INC(vxlan->dev, rx_errors);
 		vxlan_vnifilter_count(vxlan, vni, vninode,
@@ -1785,6 +1796,7 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 	oiph = skb->head + nh;
 
 	if (!vxlan_ecn_decapsulate(vs, oiph, skb)) {
+		reason = SKB_DROP_REASON_IP_TUNNEL_ECN;
 		DEV_STATS_INC(vxlan->dev, rx_frame_errors);
 		DEV_STATS_INC(vxlan->dev, rx_errors);
 		vxlan_vnifilter_count(vxlan, vni, vninode,
@@ -1799,6 +1811,7 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 		dev_core_stats_rx_dropped_inc(vxlan->dev);
 		vxlan_vnifilter_count(vxlan, vni, vninode,
 				      VXLAN_VNI_STATS_RX_DROPS, 0);
+		reason = SKB_DROP_REASON_DEV_READY;
 		goto drop;
 	}
 
@@ -1811,8 +1824,9 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 	return 0;
 
 drop:
+	reason = reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
 	/* Consume bad packet */
-	kfree_skb(skb);
+	kfree_skb_reason(skb, reason);
 	return 0;
 }
 
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 4748680e8c88..98259d2b3e92 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -92,6 +92,9 @@
 	FN(PACKET_SOCK_ERROR)		\
 	FN(TC_CHAIN_NOTFOUND)		\
 	FN(TC_RECLASSIFY_LOOP)		\
+	FN(VXLAN_INVALID_HDR)		\
+	FN(VXLAN_VNI_NOT_FOUND)		\
+	FN(IP_TUNNEL_ECN)		\
 	FNe(MAX)
 
 /**
@@ -418,6 +421,19 @@ enum skb_drop_reason {
 	 * iterations.
 	 */
 	SKB_DROP_REASON_TC_RECLASSIFY_LOOP,
+	/**
+	 * @SKB_DROP_REASON_VXLAN_INVALID_HDR: VXLAN header is invalid. E.g.:
+	 * 1) reserved fields are not zero
+	 * 2) "I" flag is not set
+	 */
+	SKB_DROP_REASON_VXLAN_INVALID_HDR,
+	/** @SKB_DROP_REASON_VXLAN_VNI_NOT_FOUND: no VXLAN device found for VNI */
+	SKB_DROP_REASON_VXLAN_VNI_NOT_FOUND,
+	/**
+	 * @SKB_DROP_REASON_IP_TUNNEL_ECN: skb is dropped according to
+	 * RFC 6040 4.2, see __INET_ECN_decapsulate() for detail.
+	 */
+	SKB_DROP_REASON_IP_TUNNEL_ECN,
 	/**
 	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
 	 * shouldn't be used as a real 'reason' - only for tracing code gen
-- 
2.39.5