RE: [PATCH v5 net-next 2/2] net: hns3: fix GSO_ECN flag setting in the RX path

> -----Original Message-----
> From: Jijie Shao <[email protected]> 
> Sent: Tuesday, August 11, 2026 3:32 PM
> To: Chia-Yu Chang (Nokia) <[email protected]>; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; Koen De Schepper (Nokia) <[email protected]>; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]
> Cc: [email protected]
> Subject: Re: [PATCH v5 net-next 2/2] net: hns3: fix GSO_ECN flag setting in the RX path
> 
> 
> on 2026/8/5 5:35, [email protected] wrote:
> > From: Chia-Yu Chang <[email protected]>
> >
> > Currently, the hns3 Rx path sets the SKB_GSO_TCP_ECN flag when a TCP 
> > segment with the CWR flag set is received. This is incorrect because 
> > the hns3 hardware GRO resets the IP ToS byte to 0 during packet 
> > aggregation. Consequently, no valid ECN signals are carreid, meaning 
> > that it cannot support RFC3168 ECN or Accurate ECN protocols. Setting 
> > SKB_GSO_TCP_ECN or SKB_GSO_TCP_ACCECN under these conditions misleads 
> > the upper network stack.
> >
> > Fix this by removing the incorrect SKB_GSO_TCP_ECN flag assignment in 
> > hns3_gro_complete().
> 
> 
> Tested on hns3 HW (2x 100G, direct cable, openEuler 24.03, kernel 7.2.0-rc6).
> 
> tcpdump confirms HW GRO zeroes IP ToS: aggregated (>MTU) packets carry tos 0x0, while non-aggregated packets keep their ToS/ECN marks — so the zeroing is done by HW GRO, not the sender. Before patch, CWR packets had SKB_GSO_TCP_ECN set (0x5 = SKB_GSO_TCPV4 | SKB_GSO_TCP_ECN). After patch, all GRO events gso_type=0x1 (SKB_GSO_TCPV4 only), no 0x5 observed.
> 
> Tested-by: Jijie Shao <[email protected]>

Thanks Jijie for confirmation, I will submit to net in the next round.