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SubjectRe: [PATCH v2 net-next v2 3/5] net: add code for TCP fraglist GRO
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On 25.04.24 17:18, Willem de Bruijn wrote:
> Felix Fietkau wrote:
>> This implements fraglist GRO similar to how it's handled in UDP, however
>> no functional changes are added yet. The next change adds a heuristic for
>> using fraglist GRO instead of regular GRO.
>>
>> Signed-off-by: Felix Fietkau <nbd@nbd.name>
>> ---
>> net/ipv4/tcp_offload.c | 22 ++++++++++++++++++++++
>> net/ipv6/tcpv6_offload.c | 9 +++++++++
>> 2 files changed, 31 insertions(+)
>>
>> diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
>> index e455f884190c..68157130c264 100644
>> --- a/net/ipv4/tcp_offload.c
>> +++ b/net/ipv4/tcp_offload.c
>> @@ -336,6 +336,19 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
>> flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
>> flush |= skb_cmp_decrypted(p, skb);
>>
>> + if (NAPI_GRO_CB(p)->is_flist) {
>> + flush |= (__force int)(flags ^ tcp_flag_word(th2));
>
> What is the purpose of this check, given the existing check above
>
> flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
> ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));

The fraglist codepath is not updating the TCP flags of the first packet,
so the extra check ensures it doesn't have to.

- Felix

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