Re: [PATCH net-next v2 06/12] net: vxlan: make vxlan_set_mac() return drop reasons

[Alexander Lobakin]

From: Menglong Dong <menglong8.dong@xxxxxxxxx>
Date: Fri, 30 Aug 2024 09:59:55 +0800

> Change the return type of vxlan_set_mac() from bool to enum
> skb_drop_reason. In this commit, two drop reasons are introduced:
> 
>   VXLAN_DROP_INVALID_SMAC
>   VXLAN_DROP_ENTRY_EXISTS
> 
> To make it easier to document the reasons in drivers/net/vxlan/drop.h,
> we don't define the enum vxlan_drop_reason with the macro
> VXLAN_DROP_REASONS(), but hand by hand.
> 
> Signed-off-by: Menglong Dong <dongml2@xxxxxxxxxxxxxxx>
> ---
>  drivers/net/vxlan/drop.h       |  9 +++++++++
>  drivers/net/vxlan/vxlan_core.c | 12 ++++++------
>  2 files changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/vxlan/drop.h b/drivers/net/vxlan/drop.h
> index 6bcc6894fbbd..876b4a9de92f 100644
> --- a/drivers/net/vxlan/drop.h
> +++ b/drivers/net/vxlan/drop.h
> @@ -9,11 +9,20 @@
>  #include <net/dropreason.h>
>  
>  #define VXLAN_DROP_REASONS(R)			\
> +	R(VXLAN_DROP_INVALID_SMAC)		\
> +	R(VXLAN_DROP_ENTRY_EXISTS)		\

To Jakub:

In our recent conversation, you said you dislike templates much. What
about this one? :>

>  	/* deliberate comment for trailing \ */
>  
>  enum vxlan_drop_reason {
>  	__VXLAN_DROP_REASON = SKB_DROP_REASON_SUBSYS_VXLAN <<
>  				SKB_DROP_REASON_SUBSYS_SHIFT,
> +	/** @VXLAN_DROP_INVALID_SMAC: source mac is invalid */
> +	VXLAN_DROP_INVALID_SMAC,
> +	/**
> +	 * @VXLAN_DROP_ENTRY_EXISTS: trying to migrate a static entry or
> +	 * one pointing to a nexthop
> +	 */

Maybe you'd do a proper kdoc for this enum at the top?

> +	VXLAN_DROP_ENTRY_EXISTS,
>  };
>  
>  static inline void
> diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
> index 76b217d166ef..58c175432a15 100644
> --- a/drivers/net/vxlan/vxlan_core.c
> +++ b/drivers/net/vxlan/vxlan_core.c
> @@ -1607,9 +1607,9 @@ static void vxlan_parse_gbp_hdr(struct vxlanhdr *unparsed,
>  	unparsed->vx_flags &= ~VXLAN_GBP_USED_BITS;
>  }
>  
> -static bool vxlan_set_mac(struct vxlan_dev *vxlan,
> -			  struct vxlan_sock *vs,
> -			  struct sk_buff *skb, __be32 vni)
> +static enum skb_drop_reason vxlan_set_mac(struct vxlan_dev *vxlan,
> +					  struct vxlan_sock *vs,
> +					  struct sk_buff *skb, __be32 vni)
>  {
>  	union vxlan_addr saddr;
>  	u32 ifindex = skb->dev->ifindex;
> @@ -1620,7 +1620,7 @@ static bool vxlan_set_mac(struct vxlan_dev *vxlan,
>  
>  	/* Ignore packet loops (and multicast echo) */
>  	if (ether_addr_equal(eth_hdr(skb)->h_source, vxlan->dev->dev_addr))
> -		return false;
> +		return (u32)VXLAN_DROP_INVALID_SMAC;
>  
>  	/* Get address from the outer IP header */
>  	if (vxlan_get_sk_family(vs) == AF_INET) {
> @@ -1635,9 +1635,9 @@ static bool vxlan_set_mac(struct vxlan_dev *vxlan,
>  
>  	if ((vxlan->cfg.flags & VXLAN_F_LEARN) &&
>  	    vxlan_snoop(skb->dev, &saddr, eth_hdr(skb)->h_source, ifindex, vni))
> -		return false;
> +		return (u32)VXLAN_DROP_ENTRY_EXISTS;
>  
> -	return true;
> +	return (u32)SKB_NOT_DROPPED_YET;

Redundant cast.

>  }

Don't you need to adjust the call site accordingly? Previously, this
function returned false in case of error and true otherwise, now it
returns a non-zero in case of error and 0 (NOT_DROPPED_YET == 0) if
everything went fine.
IOW the call site now needs to check whether the return value !=
NOT_DROPPED_YET instead of checking whether it returned false. You
inverted the return code logic, but didn't touch the call site.

>  
>  static bool vxlan_ecn_decapsulate(struct vxlan_sock *vs, void *oiph,

Thanks,
Olek