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Date: Wed, 24 May 2023 08:30:08 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: "mengyuanlou@net-swift.com" <mengyuanlou@net-swift.com>
Cc: netdev@vger.kernel.org, Jiawen Wu <jiawenwu@trustnetic.com>
Subject: Re: [PATCH net-next v6 1/8] net: wangxun: libwx add tx offload
 functions
Message-ID: <20230524083008.4ab6937d@kernel.org>
In-Reply-To: <5B88318B-4944-43CB-8EF6-4942A2696480@net-swift.com>
References: <20230523030658.17738-1-mengyuanlou@net-swift.com>
	<20230523030658.17738-2-mengyuanlou@net-swift.com>
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On Wed, 24 May 2023 14:59:54 +0800 mengyuanlou@net-swift.com wrote:
> > 2023=E5=B9=B45=E6=9C=8824=E6=97=A5 12:06=EF=BC=8CJakub Kicinski <kuba@k=
ernel.org> =E5=86=99=E9=81=93=EF=BC=9A
> > On Tue, 23 May 2023 11:06:51 +0800 Mengyuan Lou wrote: =20
> >> + if (skb->encapsulation) {
> >> + union network_header hdr;
> >> +
> >> + switch (first->protocol) {
> >> + case htons(ETH_P_IP):
> >> + tun_prot =3D ip_hdr(skb)->protocol;
> >> + if (ip_is_fragment(ip_hdr(skb)))
> >> + return WX_PTYPE_PKT_IP | WX_PTYPE_TYP_IPFRAG;
> >> + ptype =3D WX_PTYPE_TUN_IPV4;
> >> + break;
> >> + case htons(ETH_P_IPV6):
> >> + wx_get_ipv6_proto(skb, skb_network_offset(skb), &tun_prot);
> >> + if (tun_prot =3D=3D NEXTHDR_FRAGMENT)
> >> + return WX_PTYPE_PKT_IP | WX_PTYPE_PKT_IPV6 |
> >> +       WX_PTYPE_TYP_IPFRAG;
> >> + ptype =3D WX_PTYPE_TUN_IPV6; =20
> >=20
> > Why does the HW care about fragmented packets?
> > AFAIU fragmented packets won't have any offloads enabled.
>=20
> According to hardware spec(Packet type table), try to tell the ptypes for=
 hardware.

Extracting information from the packet consumes CPU cycles.
If HW will not use the information anyway (because no offload=20
is requested for the packet) those cycles are wasted.