linux-kernel - Re: [PATCH net-next v7 1/3] net: gro: add {inner_}network_offset to napi_gro

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Date: Wed, 17 Apr 2024 15:57:20 +0200
From: Richard Gobert <richardbgobert@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, dsahern@...nel.org,
 shuah@...nel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v7 1/3] net: gro: add {inner_}network_offset to
 napi_gro_cb

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).
>>
>> Signed-off-by: Richard Gobert <richardbgobert@...il.com>
>> ---
>>  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(-)
>>
>> diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
>> index d4520c3f7c09..ae596285d78c 100644
>> --- a/net/ipv4/gre_offload.c
>> +++ b/net/ipv4/gre_offload.c
>> @@ -224,6 +224,7 @@ static struct sk_buff *gre_gro_receive(struct list_head *head,
>>  	/* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
>>  	skb_gro_postpull_rcsum(skb, greh, grehlen);
>>  
>> +	NAPI_GRO_CB(skb)->inner_network_offset = hlen;
>>  	pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
>>  	flush = 0;
> 
> Nice that this even works for ETH_P_TEB, as eth_gro_receive will
> overwrite the offset written here.
>   
>   
>>  	list_for_each_entry(p, head, list) {
>>  		const struct ipv6hdr *iph2;
>> @@ -327,6 +325,7 @@ static struct sk_buff *sit_ip6ip6_gro_receive(struct list_head *head,
>>  	}
>>  
>>  	NAPI_GRO_CB(skb)->encap_mark = 1;
>> +	NAPI_GRO_CB(skb)->inner_network_offset = skb_gro_offset(skb);
>>  
>>  	return ipv6_gro_receive(head, skb);
>>  }
>> @@ -342,6 +341,7 @@ static struct sk_buff *ip4ip6_gro_receive(struct list_head *head,
>>  	}
>>  
>>  	NAPI_GRO_CB(skb)->encap_mark = 1;
>> +	NAPI_GRO_CB(skb)->inner_network_offset = skb_gro_offset(skb);
> 
> Do we still need encap_mark, or is it always set at the same time that
> inner_network_offset becomes non-zero?
> 

This would require setting inner_network_header to 0 before dev_gro_receive
which would not be favorable to the common case. (As opposed to encap_mark
which is already set to 0 as being part of NAPI_GRO_CB->zeroed). In my
opinion, it might also be less readable.