From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_HIGH,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1A63C4321D for ; Tue, 21 Aug 2018 23:36:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE014217C7 for ; Tue, 21 Aug 2018 23:36:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="nyPxyRXK"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=fb.onmicrosoft.com header.i=@fb.onmicrosoft.com header.b="Z97aNEn7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE014217C7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=fb.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727673AbeHVC6h (ORCPT ); Tue, 21 Aug 2018 22:58:37 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:53186 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726814AbeHVC6g (ORCPT ); Tue, 21 Aug 2018 22:58:36 -0400 Received: from pps.filterd (m0089730.ppops.net [127.0.0.1]) by m0089730.ppops.net (8.16.0.22/8.16.0.22) with SMTP id w7LNXmqt012991; Tue, 21 Aug 2018 16:36:17 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=facebook; bh=0t4Lv7ojukoc4r/7k5CvrGC4MYTkebO8zOvnBi8FhrA=; b=nyPxyRXK9LcqLbz5qjFQlUsEci0Ny+aKWudVf8HUiv+vfQY5K/HGPnlSwd+yx6WBfYec snatiF1swPXQTnkcLBBSrdsKyCHia7azwjFDIaMAdpUwJUVkQt/d8n0p/hWjrNjUecIz fcA4Sexry8MwfiCsHn0fYwJnDIT5xSetO1U= Received: from maileast.thefacebook.com ([199.201.65.23]) by m0089730.ppops.net with ESMTP id 2m0uhnr546-1 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NOT); Tue, 21 Aug 2018 16:36:17 -0700 Received: from NAM01-SN1-obe.outbound.protection.outlook.com (192.168.183.28) by o365-in.thefacebook.com (192.168.177.28) with Microsoft SMTP Server (TLS) id 14.3.361.1; Tue, 21 Aug 2018 19:36:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.onmicrosoft.com; s=selector1-fb-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=0t4Lv7ojukoc4r/7k5CvrGC4MYTkebO8zOvnBi8FhrA=; b=Z97aNEn7o5XOX7d92sb50ZmXcwPkVU4xabmb+lX5/sW2cerROovmDJ930tKWDN5jYh0uAeO8QYh26oGBqPUoHMOKi7Scd6bdsdFlHFQ6ie/QkfSNWEZY9wqK1px1PTJ8c7MVB70HMv03Yfm28TaAn8IfDlnLE83al8VvGrdNbXM= Received: from doronrk-mbp.dhcp.thefacebook.com (2620:10d:c090:200::4:3df0) by CY1PR15MB0476.namprd15.prod.outlook.com (2a01:111:e400:c436::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.1059.21; Tue, 21 Aug 2018 23:35:56 +0000 Date: Tue, 21 Aug 2018 16:35:49 -0700 From: Doron Roberts-Kedes To: Dominique Martinet CC: Tom Herbert , Dave Watson , "David S. 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The line count is not the source of the complexity. The undue complexity is having strparser operate in two modes: one for clients that properly use the API by respecting the value of offset, and another for clients that do not. > I don't think bpf itself needs to be changed here -- the offset is > stored in a strparser specific struct so short of such a skb_pull I > think we'd need to change the type of the bpf function, pass it it the > extra parameter, and make it a user visible change breaking the kcm > API... And I have no idea for sockmap but probably something similar. I'm not sure I follow you here. Any rcv_msg callback implementation receives an skb. Calling strp_msg() on the skb gives you the strp_msg which has the offset value. Can you explain why passing an extra parameter is necessary to get the offset? > I can't think of that as better than adding a flag to strparser. > > (Also, note that pskb_pull will not copy any data or allocate memory > unless we're pulling past the end of the skb, which seems pretty > unlikely in that situation as we should have consumed any fully "eaten" > skb before getting to a new one here -- so in practice this patch just > adds a skb->data += offset with safety guards "just in case") Yes, no data will be copied if the you don't pull beyond the linear buffer. Adding overhead even in a small percentage of cases still requires a good justification. In this particular case, I think a good justification would be demonstrating that it is impractical for the buggy strparser users you've pointed out to use the existing API and respect the value of offset. You have indicated that you are not super familiar with the bpf code, which is fine (I'm not either), but this isn't a good reason to make a change to strparser instead of bpf.