From owner-freebsd-net@FreeBSD.ORG Mon Dec 16 21:04:21 2013 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 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 170E3E97; Mon, 16 Dec 2013 21:04:21 +0000 (UTC) Received: from mail-n.franken.de (drew.ipv6.franken.de [IPv6:2001:638:a02:a001:20e:cff:fe4a:feaa]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 9A09F1D6B; Mon, 16 Dec 2013 21:04:20 +0000 (UTC) Received: from [192.168.1.200] (p508F0515.dip0.t-ipconnect.de [80.143.5.21]) (Authenticated sender: macmic) by mail-n.franken.de (Postfix) with ESMTP id B7EF01C0C0692; Mon, 16 Dec 2013 22:04:18 +0100 (CET) Content-Type: text/plain; charset=iso-8859-1 Mime-Version: 1.0 (Mac OS X Mail 6.6 \(1510\)) Subject: Re: A small fix for if_em.c, if_igb.c, if_ixgbe.c From: Michael Tuexen In-Reply-To: Date: Mon, 16 Dec 2013 22:04:18 +0100 Content-Transfer-Encoding: quoted-printable Message-Id: References: <521B9C2A-EECC-4412-9F68-2235320EF324@lurchi.franken.de> <201312131326.28952.jhb@freebsd.org> <201312131717.10863.jhb@freebsd.org> <0BC9D25E-639A-4305-A51A-222AE645152C@lurchi.franken.de> To: Adrian Chadd X-Mailer: Apple Mail (2.1510) Cc: Yong-Hyeon Pyun , FreeBSD Net , John-Mark Gurney , Jack F Vogel , John Baldwin X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 16 Dec 2013 21:04:21 -0000 On Dec 16, 2013, at 9:15 PM, Adrian Chadd wrote: > On 16 December 2013 12:06, Michael Tuexen > wrote: >=20 >>> i agree. if_transmit() should return 0 only if: >>>=20 >>> * the driver queued it internally and intends to try transmitting it = later; >>> * the driver directly dispatched the frame to the hardware. >>>=20 >>> If it failed to do either of the above, it should return an error. >>>=20 >>> How's that sound? >> That sounds good. However, The transport layer is interested in the = case >> where if_transmit() returns a non-zero value. >> Does your statement imply: >> if_transmit() returns a non-zero value only if the packet will not >> make it on the wire (for example, it failed to queue it). >=20 > If there's a queuing layer in the middle then we can't know that for > certain. If the driver can't transmit the frame (eg it fails because > of collisions, for example) then again, we can't know that for > certain. >=20 > What we can only know is that it was either queued and may or may not > make it on the wire, or it wasn't queued/transmitted and it definitely > _won't_ make it on the wire. Correct. And I'm only interested in the "it wasn't queued/transmitted and it definitely _won't_ make it on the wire." part. So I would need something like if_transmit() returns an error only if it wasn't queued/transmitted and it definitely _won't_ make it on the wire. Acceptable for you? Best regards Michael >=20 >=20 >=20 > -a >=20