netdev - Re: [PATCH net 1/2] net: Add netif_get_gro_max

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Message-ID: <78ae85b7-39e4-46ca-9903-3beb07edf3ac@gmail.com>
Date: Tue, 24 Sep 2024 14:14:40 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: Add netif_get_gro_max_size helper for GRO


On 9/23/24 11:22 PM, Daniel Borkmann wrote:
> Add a small netif_get_gro_max_size() helper which returns the maximum IPv4
> or IPv6 GRO size of the netdevice.
>
> We later add a netif_get_gso_max_size() equivalent as well for GSO, so that
> these helpers can be used consistently instead of open-coded checks.
>
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Paolo Abeni <pabeni@...hat.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
> ---
>   include/linux/netdevice.h | 9 +++++++++
>   net/core/gro.c            | 9 ++-------
>   2 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index e87b5e488325..d571451638de 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -5029,6 +5029,15 @@ void netif_set_tso_max_segs(struct net_device *dev, unsigned int segs);
>   void netif_inherit_tso_max(struct net_device *to,
>   			   const struct net_device *from);
>   
> +static inline unsigned int
> +netif_get_gro_max_size(const struct net_device *dev, const struct sk_buff *skb)
> +{
> +	/* pairs with WRITE_ONCE() in netif_set_gro(_ipv4)_max_size() */
> +	return skb->protocol == htons(ETH_P_IPV6) ?
> +	       READ_ONCE(dev->gro_max_size) :
> +	       READ_ONCE(dev->gro_ipv4_max_size);
> +}
> +
>   static inline bool netif_is_macsec(const struct net_device *dev)
>   {
>   	return dev->priv_flags & IFF_MACSEC;
> diff --git a/net/core/gro.c b/net/core/gro.c
> index 802b4a062400..d1f44084e978 100644
> --- a/net/core/gro.c
> +++ b/net/core/gro.c
> @@ -98,7 +98,6 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb)
>   	unsigned int headlen = skb_headlen(skb);
>   	unsigned int len = skb_gro_len(skb);
>   	unsigned int delta_truesize;
> -	unsigned int gro_max_size;
>   	unsigned int new_truesize;
>   	struct sk_buff *lp;
>   	int segs;
> @@ -112,12 +111,8 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb)
>   	if (p->pp_recycle != skb->pp_recycle)
>   		return -ETOOMANYREFS;
>   
> -	/* pairs with WRITE_ONCE() in netif_set_gro(_ipv4)_max_size() */
> -	gro_max_size = p->protocol == htons(ETH_P_IPV6) ?
> -			READ_ONCE(p->dev->gro_max_size) :
> -			READ_ONCE(p->dev->gro_ipv4_max_size);
> -
> -	if (unlikely(p->len + len >= gro_max_size || NAPI_GRO_CB(skb)->flush))
> +	if (unlikely(p->len + len >= netif_get_gro_max_size(p->dev, p) ||
> +		     NAPI_GRO_CB(skb)->flush))
>   		return -E2BIG;
>   
>   	if (unlikely(p->len + len >= GRO_LEGACY_MAX_SIZE)) {