Date: Mon, 16 Dec 2013 22:04:18 +0100 From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> To: Adrian Chadd <adrian@freebsd.org> Cc: Yong-Hyeon Pyun <pyunyh@gmail.com>, FreeBSD Net <freebsd-net@freebsd.org>, John-Mark Gurney <jmg@funkthat.com>, Jack F Vogel <jfv@freebsd.org>, John Baldwin <jhb@freebsd.org> Subject: Re: A small fix for if_em.c, if_igb.c, if_ixgbe.c Message-ID: <FBA7A484-BFA6-4A9E-B910-5E8CA799DC45@lurchi.franken.de> In-Reply-To: <CAJ-VmomHnQVP9s3EXuNOVwGaB-JiT_imAqzYT_U6PETvR6KMDw@mail.gmail.com> References: <521B9C2A-EECC-4412-9F68-2235320EF324@lurchi.franken.de> <201312131326.28952.jhb@freebsd.org> <CAJ-VmokoujrNBO21oOdTuzncamS%2BtAjCUKjt4ywJaySL2rAo6g@mail.gmail.com> <201312131717.10863.jhb@freebsd.org> <CAJ-VmomXPiWbYztWxTDSRJkPcee%2B3pQmUHHk=2U3HG72bcKoyw@mail.gmail.com> <0BC9D25E-639A-4305-A51A-222AE645152C@lurchi.franken.de> <CAJ-VmomHnQVP9s3EXuNOVwGaB-JiT_imAqzYT_U6PETvR6KMDw@mail.gmail.com>
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On Dec 16, 2013, at 9:15 PM, Adrian Chadd <adrian@freebsd.org> wrote: > On 16 December 2013 12:06, Michael Tuexen > <Michael.Tuexen@lurchi.franken.de> 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
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