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[195.231.47.232]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49fe5b44db6sm77245595e9.0.2026.09.24.07.02.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Sep 2026 07:02:15 -0700 (PDT) Message-ID: <6c73d85b-55f3-4273-8090-6a7826c70f3e@redhat.com> Date: Thu, 24 Sep 2026 16:02:14 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v2 3/4] net: core: resegment oversized TCP GSO skbs To: Willem de Bruijn , Wang Zhan , netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, horms@kernel.org, keyong.sun@smartx.com, Ilya Maximets , Aaron Conole , Eelco Chaudron , dev@openvswitch.org, Andrew Lunn , Jason Wang , Neal Cardwell , Kuniyuki Iwashima , Alice Mikityanska References: <20260918084651.3022878-1-wang.zhan@smartx.com> <20260918084651.3022878-4-wang.zhan@smartx.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/19/26 17:37, Willem de Bruijn wrote: >> @@ -4088,10 +4168,29 @@ static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device >> if (unlikely(!skb)) >> goto out_null; >> >> - if (netif_needs_gso(skb, features)) { >> + /* >> + * An oversized skb loses its GSO feature bits and is segmented >> + * down to MSS sized skbs below. A TCP skb can instead be split >> + * into GSO skbs which do fit the device, so keep the bits and >> + * bound the resegmentation. The features computed without the >> + * limit checks say whether the device offloads the GSO type at >> + * all. >> + */ >> + if (skb_is_gso(skb) && skb_is_gso_tcp(skb) && !skb->encapsulation && >> + !gso_within_device_limits(skb, dev)) { >> + netdev_features_t offload = __netif_skb_features(skb, false); >> + >> + resegment_max_segs = >> + skb_gso_resegment_max_segs(skb, dev, offload); >> + if (resegment_max_segs) >> + features = offload; >> + } >> + > > This is a lot to put in the hot path for a rare use case. +1 > Consider how to make this less expensive. I think that performing all the resegs check only in the netif_needs_gso(skb, features) case would address this concern. /P