netdev - Re: [RFCv7 PATCH net-next 23/36] net: adjust the build check for net_gso

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Date:   Wed, 10 Aug 2022 13:09:17 +0200
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Jian Shen <shenjian15@...wei.com>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        davem@...emloft.net, kuba@...nel.org, andrew@...n.ch,
        ecree.xilinx@...il.com, hkallweit1@...il.com, saeed@...nel.org,
        leon@...nel.org, netdev@...r.kernel.org, linuxarm@...neuler.org
Subject: Re: [RFCv7 PATCH net-next 23/36] net: adjust the build check for net_gso_ok()

From: Jian Shen <shenjian15@...wei.com>
Date: Wed, 10 Aug 2022 11:06:11 +0800

> Introduce macro GSO_INDEX(x) to replace the NETIF_F_XXX
> feature shift check, for all the macroes NETIF_F_XXX will
> be remove later.
> 
> Signed-off-by: Jian Shen <shenjian15@...wei.com>
> ---
>  include/linux/netdevice.h | 40 ++++++++++++++++++++-------------------
>  1 file changed, 21 insertions(+), 19 deletions(-)
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 1bd5dcbc884d..b01af2a3838d 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -4886,28 +4886,30 @@ netdev_features_t netif_skb_features(struct sk_buff *skb);
>  
>  static inline bool net_gso_ok(netdev_features_t features, int gso_type)
>  {
> +#define GSO_INDEX(x)	((1ULL << (x)) >> NETIF_F_GSO_SHIFT)

What if we get a new GSO offload which's corresponding bit will be
higher than 64?
You could instead do

#define __SKB_GSO_FLAG(x)	(1ULL << (x))

enum {
	SKB_GSO_TCPV4_BIT	= 0,
	SKB_GSO_DODGY_BIT	= 1,
	...,
};
enum {
	SKB_GSO_TCPV4		= __SKB_GSO_FLAG(TCPV4),
	SKB_GSO_DODGY		= __SKB_GSO_FLAG(DODGY),
	...,
};

and then just

#define ASSERT_GSO_TYPE(fl, feat)	\
	static_assert((fl) == (feat) - NETIF_F_GSO_SHIFT)

	...
	ASSERT_GSO_TYPE(SKB_GSO_TCPV4_BIT, NETIF_F_TSO_BIT);
	ASSERT_GSO_TYPE(SKB_GSO_DODGY, NETIF_F_GSO_ROBUST_BIT);
	...

> +
>  	netdev_features_t feature = (netdev_features_t)gso_type << NETIF_F_GSO_SHIFT;
>  
>  	/* check flags correspondence */
> -	BUILD_BUG_ON(SKB_GSO_TCPV4   != (NETIF_F_TSO >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_DODGY   != (NETIF_F_GSO_ROBUST >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_TCP_ECN != (NETIF_F_TSO_ECN >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_TCP_FIXEDID != (NETIF_F_TSO_MANGLEID >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_TCPV6   != (NETIF_F_TSO6 >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_FCOE    != (NETIF_F_FSO >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_GRE     != (NETIF_F_GSO_GRE >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_GRE_CSUM != (NETIF_F_GSO_GRE_CSUM >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_IPXIP4  != (NETIF_F_GSO_IPXIP4 >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_IPXIP6  != (NETIF_F_GSO_IPXIP6 >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_UDP_TUNNEL != (NETIF_F_GSO_UDP_TUNNEL >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_UDP_TUNNEL_CSUM != (NETIF_F_GSO_UDP_TUNNEL_CSUM >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_PARTIAL != (NETIF_F_GSO_PARTIAL >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_TUNNEL_REMCSUM != (NETIF_F_GSO_TUNNEL_REMCSUM >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_SCTP    != (NETIF_F_GSO_SCTP >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_ESP != (NETIF_F_GSO_ESP >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_UDP != (NETIF_F_GSO_UDP >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_UDP_L4 != (NETIF_F_GSO_UDP_L4 >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_FRAGLIST != (NETIF_F_GSO_FRAGLIST >> NETIF_F_GSO_SHIFT));
> +	BUILD_BUG_ON(SKB_GSO_TCPV4   != GSO_INDEX(NETIF_F_TSO_BIT));
> +	BUILD_BUG_ON(SKB_GSO_DODGY   != GSO_INDEX(NETIF_F_GSO_ROBUST_BIT));
> +	BUILD_BUG_ON(SKB_GSO_TCP_ECN != GSO_INDEX(NETIF_F_TSO_ECN_BIT));
> +	BUILD_BUG_ON(SKB_GSO_TCP_FIXEDID != GSO_INDEX(NETIF_F_TSO_MANGLEID_BIT));
> +	BUILD_BUG_ON(SKB_GSO_TCPV6   != GSO_INDEX(NETIF_F_TSO6_BIT));
> +	BUILD_BUG_ON(SKB_GSO_FCOE    != GSO_INDEX(NETIF_F_FSO_BIT));
> +	BUILD_BUG_ON(SKB_GSO_GRE     != GSO_INDEX(NETIF_F_GSO_GRE_BIT));
> +	BUILD_BUG_ON(SKB_GSO_GRE_CSUM != GSO_INDEX(NETIF_F_GSO_GRE_CSUM_BIT));
> +	BUILD_BUG_ON(SKB_GSO_IPXIP4  != GSO_INDEX(NETIF_F_GSO_IPXIP4_BIT));
> +	BUILD_BUG_ON(SKB_GSO_IPXIP6  != GSO_INDEX(NETIF_F_GSO_IPXIP6_BIT));
> +	BUILD_BUG_ON(SKB_GSO_UDP_TUNNEL != GSO_INDEX(NETIF_F_GSO_UDP_TUNNEL_BIT));
> +	BUILD_BUG_ON(SKB_GSO_UDP_TUNNEL_CSUM != GSO_INDEX(NETIF_F_GSO_UDP_TUNNEL_CSUM_BIT));
> +	BUILD_BUG_ON(SKB_GSO_PARTIAL != GSO_INDEX(NETIF_F_GSO_PARTIAL_BIT));
> +	BUILD_BUG_ON(SKB_GSO_TUNNEL_REMCSUM != GSO_INDEX(NETIF_F_GSO_TUNNEL_REMCSUM_BIT));
> +	BUILD_BUG_ON(SKB_GSO_SCTP    != GSO_INDEX(NETIF_F_GSO_SCTP_BIT));
> +	BUILD_BUG_ON(SKB_GSO_ESP != GSO_INDEX(NETIF_F_GSO_ESP_BIT));
> +	BUILD_BUG_ON(SKB_GSO_UDP != GSO_INDEX(NETIF_F_GSO_UDP_BIT));
> +	BUILD_BUG_ON(SKB_GSO_UDP_L4 != GSO_INDEX(NETIF_F_GSO_UDP_L4_BIT));
> +	BUILD_BUG_ON(SKB_GSO_FRAGLIST != GSO_INDEX(NETIF_F_GSO_FRAGLIST_BIT));
>  
>  	return (features & feature) == feature;
>  }
> -- 
> 2.33.0

Thanks,
Olek