Date: Thu, 6 Apr 2017 14:23:01 +0300 From: "Andrey V. Elsukov" <bu7cher@yandex.ru> To: Harry Schmalzbauer <freebsd@omnilan.de>, "freebsd-net@freebsd.org" <freebsd-net@FreeBSD.org> Subject: Re: if_igb(4) VLAN(4) and [RT]XCSUM_IPV6, TSO6 Message-ID: <5c2fb7b8-5289-deff-618d-16495addf96c@yandex.ru> In-Reply-To: <58CAD8CB.3060101@omnilan.de> References: <58CAD8CB.3060101@omnilan.de>
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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" <bu7cher@yandex.ru> To: Harry Schmalzbauer <freebsd@omnilan.de>, "freebsd-net@freebsd.org" <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. Elsukov --Lfj8CcMb0B6Q4eBtaNHB65DOT5dGLi9bq-- --Sah625pKv3Tr25lSijItIuQQOEM7r8hFw Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEzBAEBCAAdFiEE5lkeG0HaFRbwybwAAcXqBBDIoXoFAljmJRUACgkQAcXqBBDI oXqy7Af/QPD2Sl+ugwEU1H6oIB9Ie/4aQP1Up9IfDkuoxUjU2PSoCBC32Nnr/iF9 U4Kz6/MJ7K2TPS4tN1mSAKz59g14C3l2qgsE/OtblsR1WYQaHG+9ZACCO5d96DKd 9GowtkhqGDhsc+qW670bwNSSZQm7y97QjrtkSAefDMcUNohTsrVh1zT/lJdivr1i 3r5v2cxfnV+6CVqCo4uyWpdsoCQ45DCn5uCQM/657HvTAxpO91zwv0ReqYgJ5Q1C 6buDW84kgEaRoK4Ggl1E1nSxWy+xaiN6HXwfZl2OaO1o1v1cT1LZFHRultz78FCa /2eEZjDvvGL5oggy8tJv2WUjrMIoew== =3mp7 -----END PGP SIGNATURE----- --Sah625pKv3Tr25lSijItIuQQOEM7r8hFw--
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