Re: [PATCH net v2 1/3] net: gro: add {inner_}network_offset to napi_gro_cb

From: Richard Gobert
Date: Mon Apr 22 2024 - 04:32:39 EST


Willem de Bruijn wrote:
> Richard Gobert wrote:
>> This patch adds network_offset and inner_network_offset to napi_gro_cb, and
>> makes sure both are set correctly. In the common path there's only one
>> write (skb_gro_reset_offset, which replaces skb_set_network_header).
>>
>> Signed-off-by: Richard Gobert <richardbgobert@xxxxxxxxx>
>> ---
>> drivers/net/geneve.c | 1 +
>> drivers/net/vxlan/vxlan_core.c | 1 +
>> include/net/gro.h | 18 ++++++++++++++++--
>> net/8021q/vlan_core.c | 2 ++
>> net/core/gro.c | 1 +
>> net/ethernet/eth.c | 1 +
>> net/ipv4/af_inet.c | 5 +----
>> net/ipv4/gre_offload.c | 1 +
>> net/ipv6/ip6_offload.c | 8 ++++----
>> 9 files changed, 28 insertions(+), 10 deletions(-)
>>
>
>> +static inline int skb_gro_network_offset(const struct sk_buff *skb)
>> +{
>> + return NAPI_GRO_CB(skb)->network_offsets[NAPI_GRO_CB(skb)->encap_mark];
>> +}
>> +
>
>
>> @@ -236,8 +236,6 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head,
>> if (unlikely(!iph))
>> goto out;
>>
>> - skb_set_network_header(skb, off);
>> -
>
> Especially for net, this is still a large patch.
>
> Can we avoid touching all those tunnel callbacks and just set the
> offsets in inet_gro_receive and ipv6_gro_receive themselves, just
> as skb_set_network_header now:
>
> @@ -236,7 +236,7 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head,
> if (unlikely(!iph))
> goto out;
>
> - skb_set_network_header(skb, off);
> + NAPI_GRO_CB(skb)->network_offsets[NAPI_GRO_CB(skb)->encap_mark] = off;
>

Thanks for the reply!

Setting network_offset on dev_gro_receive and inner_network_offset only
in the tunnel callbacks is the best option IMO. I agree that
we want a small patch to net that solves the problem, although I
think always using ->encap_mark in the common path is not ideal.

We can avoid changing all the tunnel callbacks by always setting
inner_network_offset in {ipv6,inet}_gro_receive and initialize
network_offset to 0 in dev_gro_receive. It will result in a small
change, without using ->encap_mark.

What are your thoughts?