Subject: Re: [PATCH net-next 06/10] net: vxlan: add skb drop reasons to vxlan_rcv()

From: Jakub Kicinski <[email-masked]>
Date: Fri, 16 Aug 2024 19:22:43 -0700

On Thu, 15 Aug 2024 20:42:58 +0800 Menglong Dong wrote:
>  #define VXLAN_DROP_REASONS(R)			\
> +	R(VXLAN_DROP_FLAGS)			\
> +	R(VXLAN_DROP_VNI)			\
> +	R(VXLAN_DROP_MAC)			\

Drop reasons should be documented.
I don't think name of a header field is a great fit for a reason.

>  	/* deliberate comment for trailing \ */
>  
>  enum vxlan_drop_reason {
> diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
> index e971c4785962..9a61f04bb95d 100644
> --- a/drivers/net/vxlan/vxlan_core.c
> +++ b/drivers/net/vxlan/vxlan_core.c
> @@ -1668,6 +1668,7 @@ static bool vxlan_ecn_decapsulate(struct vxlan_sock *vs, void *oiph,
>  /* Callback from net/ipv4/udp.c to receive packets */
>  static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
>  {
> +	enum skb_drop_reason reason = pskb_may_pull_reason(skb, VXLAN_HLEN);

Do not call complex functions inline as variable init..

>  	struct vxlan_vni_node *vninode = NULL;
>  	struct vxlan_dev *vxlan;
>  	struct vxlan_sock *vs;
> @@ -1681,7 +1682,7 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
>  	int nh;
>  
>  	/* Need UDP and VXLAN header to be present */
> -	if (!pskb_may_pull(skb, VXLAN_HLEN))
> +	if (reason != SKB_NOT_DROPPED_YET)

please don't compare against "not dropped yet", just:

	if (reason)

> @@ -1815,8 +1831,9 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
>  	return 0;
>  
>  drop:
> +	SKB_DR_RESET(reason);

the name of this macro is very confusing, I don't think it should exist
in the first place. nothing should goto drop without initialing reason

>  	/* Consume bad packet */
> -	kfree_skb(skb);
> +	kfree_skb_reason(skb, reason);
>  	return 0;
>  }