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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5136.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 96dfc634-d13b-47dd-68dd-08da39bdd8cd X-MS-Exchange-CrossTenant-originalarrivaltime: 19 May 2022 17:34:37.4976 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Ocxqgsrwx2rUhrkYkDoHyeE+bnuFXQRSwpyZKYUjEak5FsFsslI3SiQnmxpf1Yukpm7SZULhhi9hWbzubii+dA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR04MB4098 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Thu, May 19, 2022 at 10:11:13AM -0700, Florian Fainelli wrote: > unless we somehow manage to put it in the linear portion of > the SKB to avoid using any control buffer or extension. But how? Essentially the DSA master has to look at a packet and determine whether it came from DSA based on something which non-DSA code could not have done. In fact, I'm looking at the calls to skb_reset_mac_{header,len} from net/core/skbuff.c, specifically at VLAN and MPLS, and I believe (but haven't tested) that pushing such headers would also alter skb->mac_len to some value !=3D ETH_HLEN. So simply having the DSA master check whether DSA was there by checking whether skb->mac_len is ETH_HLEN + DSA tag len could easily confuse DSA with some other protocol of same header size.=