Re: [dpdk-dev] [PATCH v2] gso: fix pyld_unit_size issue for udp gso

["Hu, Jiayu" <jiayu.hu@intel.com>]

Acked-by: Jiayu Hu <jiayu.hu@intel.com>

> -----Original Message-----
> From: yang_y_yi@163.com <yang_y_yi@163.com>
> Sent: Thursday, September 17, 2020 10:13 AM
> To: dev@dpdk.org
> Cc: Hu, Jiayu <jiayu.hu@intel.com>; thomas@monjalon.net;
> yangyi01@inspur.com; yang_y_yi@163.com
> Subject: [PATCH v2] gso: fix pyld_unit_size issue for udp gso
> 
> From: Yi Yang <yangyi01@inspur.com>
> 
> Fragment offset of IPv4 header is measured in units of
> 8 bytes. Fragment offset of UDP fragments will be wrong
> after GSO if pyld_unit_size isn't multiple of 8. Say
> pyld_unit_size is 1500, fragment offset of the second
> UDP fragment will be 187 (i.e. 1500 / 8), which means 1496,
> and it will result in 4-byte data loss (1500 - 1496 = 4).
> So UDP GRO will reassemble out a wrong packet.
> 
> Fixes: b166d4f30b66 ("gso: support UDP/IPv4 fragmentation")
> 
> Signed-off-by: Yi Yang <yangyi01@inspur.com>
> ---
>  lib/librte_gso/gso_udp4.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_gso/gso_udp4.c b/lib/librte_gso/gso_udp4.c
> index 21fea09..6fa68f2 100644
> --- a/lib/librte_gso/gso_udp4.c
> +++ b/lib/librte_gso/gso_udp4.c
> @@ -69,7 +69,10 @@
>  		return 1;
>  	}
> 
> -	pyld_unit_size = gso_size - hdr_offset;
> +	/* pyld_unit_size must be a multiple of 8 because frag_off
> +	 * uses 8 bytes as unit.
> +	 */
> +	pyld_unit_size = (gso_size - hdr_offset) & ~7U;
> 
>  	/* Segment the payload */
>  	ret = gso_do_segment(pkt, hdr_offset, pyld_unit_size, direct_pool,
> --
> 1.8.3.1