From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id ACB4EA034C; Mon, 8 Aug 2022 18:42:30 +0200 (CEST) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 75E0C4014F; Mon, 8 Aug 2022 18:42:30 +0200 (CEST) Received: from mail-pj1-f52.google.com (mail-pj1-f52.google.com [209.85.216.52]) by mails.dpdk.org (Postfix) with ESMTP id C205C42B83 for ; Mon, 8 Aug 2022 18:42:29 +0200 (CEST) Received: by mail-pj1-f52.google.com with SMTP id gj1so9352960pjb.0 for ; Mon, 08 Aug 2022 09:42:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20210112.gappssmtp.com; s=20210112; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=cKM0AMXsbVGhkv1tOfO1m2DVxxWTz6rFFbTadJRRvdA=; b=rERkbrl4wLrfaYdvjyKoN7PKcwS/Xwvd+zhEx0lRRev9w7YOlQv8Ul37Jcg8tqckKD 4AN/38YtCuROXbiuWxV0wZXIm3Q1pPGN4gTM+ffhQlvqPMMo05QwiJvSC9eE9HbIdtZG LdYYInjkUIbK1T0Fabr0bvG0gUXOLlv0CUwcwEmtYHPQXWTqZct5jQgz4RbPZgddMmEA YVAzKkDbt2hfsiaGkcW0qnbm8sKn1VjMcL77jOwH0YujQBNKPeCau2lcqdyY7Otx5HJo SIVzSyoajuo0q0g2jO2XGPfOu/4TK/1Yz/QwShYGu8gAzpCBm1iTorwcxHIyT0lTedBJ 6KJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=cKM0AMXsbVGhkv1tOfO1m2DVxxWTz6rFFbTadJRRvdA=; b=tD6adwOwytolBnONd7RthjmA94183fCB2XKaU6qBYDr+MteTFUj3itEUWU0b62AF1+ 3SkLe4/cpANz+Ugkg9h+s5hWhVxN8LZpMWU6kizEe8L8e5y4k1sjvDtakdSDGX6MtwRI iBUff5aBSanhDuLa1wAZ2bCqLapHmyITzID4vJPQmBEYi7hUXqBVjkWvO4UoMUAbVIoj wtccq+eEBPdN3vA+U5Z1rkxpZjMu7RvDjC6B6wnLOqJ0IjJYtxnYLna+O1YY3fDtAuUd UbfC5nP9B61rypEJz16pSfUKyZfpndk5/hnbJnqJdQ7ag79HdC1R9BgIuhtafOapIIfv 1yZQ== X-Gm-Message-State: ACgBeo0S6xGuiwYW9UKL8w1c2Lx1CpdLP5WZzpk2ToVdTf0pnfjgx0fs +DaUhzoZ+fhNwvS4zORxkjCci9An3Y5jgQ== X-Google-Smtp-Source: AA6agR6GikCFED/vqciZdGy/S4glGcGa0Vb3USHzsE+JrDvQ9kguLVOZnmTY3dQnY2PHPWRhO8yvSg== X-Received: by 2002:a17:90b:3842:b0:1f5:32be:8a1a with SMTP id nl2-20020a17090b384200b001f532be8a1amr30470000pjb.130.1659976948615; Mon, 08 Aug 2022 09:42:28 -0700 (PDT) Received: from hermes.local (204-195-120-218.wavecable.com. [204.195.120.218]) by smtp.gmail.com with ESMTPSA id z23-20020aa79597000000b00528c066678csm8934294pfj.72.2022.08.08.09.42.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Aug 2022 09:42:28 -0700 (PDT) Date: Mon, 8 Aug 2022 09:42:26 -0700 From: Stephen Hemminger To: Francesco Mancino Cc: dev@dpdk.org Subject: Re: [PATCH v7] net/tap: Allow jumbo frames Message-ID: <20220808094226.4775124e@hermes.local> In-Reply-To: <93cbc18c-fcc4-d34d-4419-5268513f7b87@tutus.se> References: <315474c3-7004-2114-9e24-8344da7aca9e@tutus.se> <20220808080323.53f303fe@hermes.local> <93cbc18c-fcc4-d34d-4419-5268513f7b87@tutus.se> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Mon, 8 Aug 2022 17:38:21 +0200 Francesco Mancino wrote: > Thank you for the feedback. > > I am sorry for the email spam, it was a learning process. > > I am not sure what results we would get by querying the MTU > before configuring it, since we can (and do) set the MTU using > SIOCSIFMTU. > > On 2022-08-08 17:03, Stephen Hemminger wrote: > > On Mon, 8 Aug 2022 16:49:44 +0200 > > Francesco Mancino wrote: > > > >> eth_dev_validate_mtu, introduced in 990912e676e, validates configured > >> MTU plus overhead against max_rx_pktlen. > >> Since TAP is a virtual device, it should support as big MTU as possible. > >> > >> Signed-off-by: Francesco Mancino > > dev_info->min_rx_bufsize = 0; > > > > > > Thanks for your patience. > > > > Since tap is built on top of an existing kernel network device a more > > complete solution would be to query the kernel device to find out what > > its MTU is. > > > > Acked-by: Stephen Hemminger > > > There is an attribute IFLA_MAX_MTU reported by devices over netlink. $ ip -d li show dev enp2s0 2: enp2s0: mtu 1500 qdisc fq state UP mode DEFAULT group default qlen 1000 link/ether d8:5e:d3:06:5d:13 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 9194 addrgenmode none numtxqueues 1 numrxqueues 1 gso_max_size 64000 gso_max_segs 64 gro_max_size 65536 parentbus pci parentdev 0000:02:00.0 Notice maxmtu of 9194 reported. Tap device already has a netlink infrastructure