netdev - Re: [PATCH net-next 10/10] bnxt_en: Implement .ndo_features

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Date:   Sat, 24 Apr 2021 14:52:05 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Michael Chan <michael.chan@...adcom.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, gospo@...adcom.com
Subject: Re: [PATCH net-next 10/10] bnxt_en: Implement
 .ndo_features_check().

On Sat, 24 Apr 2021 16:14:31 -0400 Michael Chan wrote:
> +	features = vlan_features_check(skb, features);
> +	if (!skb->encapsulation)
> +		return features;
> +
> +	switch (vlan_get_protocol(skb)) {
> +	case htons(ETH_P_IP):
> +		l4_proto = ip_hdr(skb)->protocol;
> +		break;
> +	case htons(ETH_P_IPV6):
> +		l4_proto = ipv6_hdr(skb)->nexthdr;
> +		break;
> +	default:
> +		return features;
> +	}
> +
> +	/* For UDP, we can only handle 1 Vxlan port and 1 Geneve port. */
> +	if (l4_proto == IPPROTO_UDP) {
> +		struct bnxt *bp = netdev_priv(dev);
> +		__be16 udp_port = udp_hdr(skb)->dest;
> +
> +		if (udp_port != bp->vxlan_port && udp_port != bp->nge_port)
> +			return features & ~(NETIF_F_CSUM_MASK |
> +					    NETIF_F_GSO_MASK);
> +	}
> +	return features;

This is still written a little too much like a block list.

What if, for example it's a UDP tunnel but with extension headers?
Is there any particular case that is served by not writing it as:

	if (l4_proto == UDP && (port == bp->vxl_port ||
				port == bp->nge_port))
		return features;
	return features & ~(CSUM | GSO);
?

Sorry for not realizing this earlier.