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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 0CAB0C10F14 for ; Wed, 10 Apr 2019 15:34:39 +0000 (UTC) Received: from krantz.zx2c4.com (krantz.zx2c4.com [192.95.5.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 53FCC20818 for ; Wed, 10 Apr 2019 15:34:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 53FCC20818 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=romanrm.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=wireguard-bounces@lists.zx2c4.com Received: from krantz.zx2c4.com (localhost [IPv6:::1]) by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTP id cd9276af; Wed, 10 Apr 2019 15:34:36 +0000 (UTC) Received: from krantz.zx2c4.com (localhost [127.0.0.1]) by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 04fa98c1 for ; Wed, 10 Apr 2019 15:34:34 +0000 (UTC) Received: from len.romanrm.net (len.romanrm.net [IPv6:2001:41d0:1:8055::1]) by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 5326f978 for ; Wed, 10 Apr 2019 15:34:34 +0000 (UTC) Received: from natsu (unknown [IPv6:fd39::e99e:8f1b:cfc9:ccb8]) by len.romanrm.net (Postfix) with SMTP id 99DAD202C1 for ; Wed, 10 Apr 2019 15:34:32 +0000 (UTC) Date: Wed, 10 Apr 2019 20:34:31 +0500 From: Roman Mamedov To: "WireGuard mailing list" Subject: Revisiting the weird MTU issue Message-ID: <20190410203431.24b55c89@natsu> MIME-Version: 1.0 X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" Hello, I use WireGuard over IPv6 on a PPPoE connection. The Internet interface MTU is 1492. By my calculations MTU 1412 on the WG interface should fit. However, the following occurs on various MTU combinations between the Remote (a server in a DC with full 1500 wire MTU) and Local WG interface MTUs: Fails or not, is whether a within-WG Remote->Local TCP connection (iperf3) works fine or hangs up after transferring a few initial bits of data. Remote Local Result ==================== 1420 1420 Fails (as expected) 1420 1412 Fails (weird) 1412 1412 Works (fair enough) 1420 1408 Works (super weird!!!) Now I hope I described the situation clearer than the last time posting about this, so maybe someone has an idea what could be the culprit? So far this doesn't cause too much issue, as I'm using on designated p2p links for when one of the peers is on this PPPoE, I just use 1412 on both sides. But still, surely the above shouldn't happen? -- With respect, Roman _______________________________________________ WireGuard mailing list WireGuard@lists.zx2c4.com https://lists.zx2c4.com/mailman/listinfo/wireguard