Re: [RFC PATCH net-next] net: Modify CSUM capability check for USO

[Paolo Abeni <pabeni@redhat.com>]

On 3/12/25 12:54 PM, Radharapu Rakesh wrote:
>  net/core/dev.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 1cb134ff7327..a22f8f6e2ed1 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -10465,11 +10465,13 @@ static void netdev_sync_lower_features(struct net_device *upper,
>  
>  static bool netdev_has_ip_or_hw_csum(netdev_features_t features)
>  {
> -	netdev_features_t ip_csum_mask = NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
> -	bool ip_csum = (features & ip_csum_mask) == ip_csum_mask;
> +	netdev_features_t ipv4_csum_mask = NETIF_F_IP_CSUM;
> +	netdev_features_t ipv6_csum_mask = NETIF_F_IPV6_CSUM;
> +	bool ipv4_csum = (features & ipv4_csum_mask) == ipv4_csum_mask;
> +	bool ipv6_csum = (features & ipv6_csum_mask) == ipv6_csum_mask;
>  	bool hw_csum = features & NETIF_F_HW_CSUM;
>  
> -	return ip_csum || hw_csum;
> +	return ipv4_csum || ipv6_csum || hw_csum;
>  }

The above will additionally affect TLS offload, and will likely break
i.e. USO over IPv6 traffic landing on devices supporting only USO over
IPv4, unless such devices additionally implement a suitable
ndo_features_check().

Such situation will be quite bug prone, I'm unsure we want this kind of
change - even without looking at the TLS side of it.

/P