Yes,  It's better to do it before the tcp_dl check.

 

1. /* trim the tail padding bytes */  
2. ip_tlen = rte_be_to_cpu_16(ipv4_hdr->total_length);  
3. if (pkt->pkt_len > (uint32_t)(ip_tlen + pkt->l2_len))  
4.     rte_pktmbuf_trim(pkt, pkt->pkt_len - ip_tlen - pkt->l2_len);  
5.   
6. /* 
7.  * Don't process the packet whose payload length is less than or 
8.  * equal to 0. 
9.  */  
10. tcp_dl = pkt->pkt_len - hdr_len;  
11. if (tcp_dl <= 0)  
12.     return -1;  

From: kumaraparameshwaran rathinavel <kumaraparamesh92@gmail.com>
Sent: Tuesday, October 11, 2022 1:48 PM
To: dev@dpdk.org; David Marchand <david.marchand@redhat.com>; Hu, Jiayu <jiayu.hu@intel.com>; Jun Qiu <jun.qiu@jaguarmicro.com>
Subject: Fwd: [PATCH] gro : fix pkt length when extra bytes are padded to ethernet frame

 

 

 

On Tue, Oct 11, 2022 at 1:03 AM David Marchand <david.marchand@redhat.com> wrote:

On Mon, Oct 10, 2022 at 7:51 PM Kumara Parameshwaran
<kumaraparamesh92@gmail.com> wrote:
>
> From: Kumara Parameshwaran <kumaraparamesh92@gmail.com>
>
> When GRO packets are merged the packet length is used while
> merging the adjacent packets. If the padded bytes are accounted
> we would end up acking unsent TCP segments.
>
> Signed-off-by: Kumara Parameshwaran <kumaraparamesh92@gmail.com>
> v1:
>         If there is padding to the ethernet frame cases where timestamp is disabled
>         the packet length should be validated with the total ip length as packet length
>         is used in the GRO merging logic

Please, can you test with current main branch?
We recently merged a fix:
https://git.dpdk.org/dpdk/commit/?id=b8a55871d5af6f5b8694b1cb5eacbc629734e403

Thanks, David. I did look at the patch. This would fix the problem, but lets say for a case of an ACK packet where TCP data length would be zero and if the packet contains the padded bytes, this check should be done before the follwing check and not after this. @Hu, Jiayu  @Jun Qiu  please let me know your thoughts. 

/*
* Don't process the packet whose payload length is less than or
* equal to 0.
*/
tcp_dl = pkt->pkt_len - hdr_len;
if (tcp_dl <= 0)
return -1; 

--
David Marchand