From owner-freebsd-net@freebsd.org Thu Apr 6 11:24:12 2017 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 699A9D2F914 for ; Thu, 6 Apr 2017 11:24:12 +0000 (UTC) (envelope-from bu7cher@yandex.ru) Received: from forward5j.cmail.yandex.net (forward5j.cmail.yandex.net [IPv6:2a02:6b8:0:1630::18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "forwards.mail.yandex.net", Issuer "Yandex CA" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id E3AB79E7 for ; Thu, 6 Apr 2017 11:24:11 +0000 (UTC) (envelope-from bu7cher@yandex.ru) Received: from smtp3o.mail.yandex.net (smtp3o.mail.yandex.net [37.140.190.28]) by forward5j.cmail.yandex.net (Yandex) with ESMTP id AFABD20F0D; Thu, 6 Apr 2017 14:24:07 +0300 (MSK) Received: from smtp3o.mail.yandex.net (localhost.localdomain [127.0.0.1]) by smtp3o.mail.yandex.net (Yandex) with ESMTP id A42642940D4A; Thu, 6 Apr 2017 14:24:06 +0300 (MSK) Received: by smtp3o.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id qDpdNmgcOF-O0tmDnH2; Thu, 06 Apr 2017 14:24:00 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.ru; s=mail; t=1491477840; bh=T59YNsu9S1OLUuNCsJutqUbMbyr7317CAqHcvfBIGf4=; h=Subject:To:References:From:Message-ID:Date:In-Reply-To; b=RxA2ZIINmb0S39SgzKxWlIKwhMrWs7ncw9Cea2e6Rx4EX9OFy8Tipj/UfSOmyBYhk jcAOKZ/olvtCjbC8GwR0z89uwI3LlY1LiCLCxUNyhesI8cCOSHXKeTLl0xbc5Jtuau RLZ4ynewAFWVjgYg+RNn66+bONzq3rEI3Jvi/BO8= Authentication-Results: smtp3o.mail.yandex.net; dkim=pass header.i=@yandex.ru X-Yandex-Suid-Status: 1 0,1 0 Subject: Re: if_igb(4) VLAN(4) and [RT]XCSUM_IPV6, TSO6 To: Harry Schmalzbauer , "freebsd-net@freebsd.org" References: <58CAD8CB.3060101@omnilan.de> From: "Andrey V. Elsukov" Openpgp: id=E6591E1B41DA1516F0C9BC0001C5EA0410C8A17A Message-ID: <5c2fb7b8-5289-deff-618d-16495addf96c@yandex.ru> Date: Thu, 6 Apr 2017 14:23:01 +0300 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:52.0) Gecko/20100101 Thunderbird/52.0 MIME-Version: 1.0 In-Reply-To: <58CAD8CB.3060101@omnilan.de> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Sah625pKv3Tr25lSijItIuQQOEM7r8hFw" X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 06 Apr 2017 11:24:12 -0000 This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --Sah625pKv3Tr25lSijItIuQQOEM7r8hFw Content-Type: multipart/mixed; boundary="Lfj8CcMb0B6Q4eBtaNHB65DOT5dGLi9bq"; protected-headers="v1" From: "Andrey V. Elsukov" To: Harry Schmalzbauer , "freebsd-net@freebsd.org" Message-ID: <5c2fb7b8-5289-deff-618d-16495addf96c@yandex.ru> Subject: Re: if_igb(4) VLAN(4) and [RT]XCSUM_IPV6, TSO6 References: <58CAD8CB.3060101@omnilan.de> In-Reply-To: <58CAD8CB.3060101@omnilan.de> --Lfj8CcMb0B6Q4eBtaNHB65DOT5dGLi9bq Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 16.03.2017 21:26, Harry Schmalzbauer wrote: > So TSO6 is inherited, but RC/TXCSUM_IPV6 dropped? >=20 > In general, how is offloading implemented? If enabled, does the API > simply generate packets lacking the checksum header and NIC (silicon) > fills in the checksum if not adviesd not to do so (by the driver)? > Or is the driver utilizing NIC registers for calculation, but ensures > every packet will have a checksum? Since IPv6 header doesn't have checksum, such offloading is related to TCP/UDP/SCTP checksums. When RXCSUM_IPV6 is enabled, the NIC calculates the checksum and saves its value into the auxiliary packet's data. When the network stack handles the packet, it checks the presence of this data, and it uses stored checksum to reduce the needed calculation. For outgoing packets the L4 protocol marks a packet that the checksum calculation is needed before sending. And when TXCSUM_IPV6 is enabled, IPv6 output routine sees this flag and skips checksum calculation. And the NIC does this calculation. --=20 WBR, Andrey V. 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