From owner-freebsd-current@freebsd.org Mon Mar 8 22:14:33 2021 Return-Path: Delivered-To: freebsd-current@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 6F23555AEAE for ; Mon, 8 Mar 2021 22:14:33 +0000 (UTC) (envelope-from lars@gustik.eu) Received: from troy.gustik.eu (troy.gustik.eu [165.227.162.104]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4DvXgr3jKqz3rSt for ; Mon, 8 Mar 2021 22:14:32 +0000 (UTC) (envelope-from lars@gustik.eu) Received: from troy.gustik.eu (localhost [IPv6:::1]) by troy.gustik.eu (Postfix) with ESMTP id D06C72ADCD6 for ; Mon, 8 Mar 2021 23:14:30 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=gustik.eu; s=troy; t=1615241670; bh=U2g+bWDbCpUenbQR67SaY1gULPx+0r8NaYTRBcxe4l4=; h=Subject:From:To:Date:In-Reply-To:References; b=HS4GkbLe8JRYYsRjj8OKCps6mSmaEilPBvLWLn2o6tim/JEmQmBVAvFFUUMA6yp6r /sb0uvTECPI70j0x+8MRmCrrOvc1XO1w0GQnHUPRhM67gueHh4omHLqrTQUUdsTCnH uH9M/1XIqMmKd7ia4CaVF3kCpEkzqfvse1tvxwNo= Received: from romy.j20.helspy.pw ([2a01:c844:241d:bf20:4767:2cb8:97e4:8e2d]) by troy.gustik.eu with ESMTPSA id yPMGMMahRmCnCgAADR3MKA (envelope-from ) for ; Mon, 08 Mar 2021 23:14:30 +0100 Message-ID: Subject: Re: FreeBSD 13.0-RC1 ethertype IPv6 (0x86dd), length 2942 on 1500 MTU From: Lars Schotte To: freebsd-current@freebsd.org Date: Mon, 08 Mar 2021 23:14:32 +0100 In-Reply-To: <2a8d7089955ca70cd4e0e644aef988ca4a9019e3.camel@gustik.eu> References: <2a8d7089955ca70cd4e0e644aef988ca4a9019e3.camel@gustik.eu> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-16.el8) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 4DvXgr3jKqz3rSt X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gustik.eu header.s=troy header.b=HS4GkbLe; dmarc=none; spf=pass (mx1.freebsd.org: domain of lars@gustik.eu designates 165.227.162.104 as permitted sender) smtp.mailfrom=lars@gustik.eu X-Spamd-Result: default: False [-3.00 / 15.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; MV_CASE(0.50)[]; R_SPF_ALLOW(-0.20)[+mx]; TO_DN_NONE(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_TRACE(0.00)[gustik.eu:+]; NEURAL_HAM_SHORT(-1.00)[-1.000]; FROM_EQ_ENVFROM(0.00)[]; RCVD_TLS_LAST(0.00)[]; RBL_DBL_DONT_QUERY_IPS(0.00)[165.227.162.104:from]; ASN(0.00)[asn:14061, ipnet:165.227.160.0/20, country:US]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[gustik.eu:s=troy]; FREEFALL_USER(0.00)[lars]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-current@freebsd.org]; DMARC_NA(0.00)[gustik.eu]; RCPT_COUNT_ONE(0.00)[1]; SPAMHAUS_ZRD(0.00)[165.227.162.104:from:127.0.2.255]; MAILMAN_DEST(0.00)[freebsd-current] X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Mar 2021 22:14:33 -0000 It looks like vtnet driver ignored MTU setting on 13.0-RC1. I see this on both, IPv4 and IPv6 ... however IPv4 works maybe because DigitalOcean and Vultr do split those frames on KVM virt host, but don't do this for IPv6 (I suppose). Everything about this is strange but so far I have been able to reproduce this problem only with vtnet driver. On Mon, 2021-03-08 at 20:18 +0100, Lars Schotte wrote: > Hey friends, > > I am running this FreeBSD 13.0-RC1 and I am experiencing strange > Ethernet frame sizes, TCP sizes well above 2500 on an MTU of 1500. > Somehow it seems that this problem only applies on IPv6, > IPv4 works fine. > > I have seen some strange network behaviour with TCP connections > randomly dropping under load, and now I see that they are too big. > MSS-MAX on PF also does not help. It seems to ignore my 1440 setting. > > Something is broken here and I do not know what. > > Is anyone else experiencing this on IPv6? > -- Lars Schotte Mudroňova 13 92101 Piešťany