From owner-freebsd-net@FreeBSD.ORG Wed Dec 10 18:25:34 2014 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 14B5669C for ; Wed, 10 Dec 2014 18:25:34 +0000 (UTC) Received: from mail-ig0-x236.google.com (mail-ig0-x236.google.com [IPv6:2607:f8b0:4001:c05::236]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id D1BDBDEB for ; Wed, 10 Dec 2014 18:25:33 +0000 (UTC) Received: by mail-ig0-f182.google.com with SMTP id hn15so3395339igb.15 for ; Wed, 10 Dec 2014 10:25:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=i8BdwOpmuecYGb6ZC5rnf6hmPd/ezZmyiEm9jzBA9zA=; b=rjfTNazCntdRkHktxjQQ5VTgKmfFzPgIdJXek3YRs8Zh6gZ2OIRNjtd3WV3zo0dUql Xlns29DaW5ICBMxzMXCTNictkY1+meNnoMVTqL890CEVIvfOWb5WqhcEZD4v9offSiK7 yGIoEcmCmLDhd25UeKgaM+W8SDlTVlrxxWk6zwje42Der6FrRl4XNtRyM6J8rGB2uOHs aL0t4olOD5PZPd5NO/ks2P3dSfWaHxJO5KJNxgppdChLPzFcDCLDIOeQPcwsMhESrl3E dlXdVECPOBx6FBqTYaY1RRhrSfzSfHt+nkQzHkcOGaPErIFpx9FVS8QxK5gVuvfr66G/ /vWg== MIME-Version: 1.0 X-Received: by 10.50.56.15 with SMTP id w15mr27394233igp.39.1418235933204; Wed, 10 Dec 2014 10:25:33 -0800 (PST) Received: by 10.107.10.31 with HTTP; Wed, 10 Dec 2014 10:25:33 -0800 (PST) In-Reply-To: References: Date: Wed, 10 Dec 2014 13:25:33 -0500 Message-ID: Subject: Re: EM(4) - Link flap when bridged and adding members (em bridge flap) From: Ryan Stone To: "David P. Discher" Content-Type: text/plain; charset=UTF-8 Cc: FreeBSD Net X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Dec 2014 18:25:34 -0000 >From a quick look at the code, whenever an interface is added to a bridge, if that interface does not support a feature currently enabled on the bridge then it has to disable that feature on all member interfaces of that bridge. That would re-init the em interface, which would cause a link flap. Take a look at the ifconfig output for em0 and epair0 before epair0 is added to the bridge. You will probably see that one or more features that em supports is not supported by epair (I would bet on something like LRO or TSO).. The solution would be to disable those features from em0 before adding it to the bridge (you can persist this in rc.conf with ifconfig_em0="...")