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]>