Date: Fri, 6 Dec 2013 21:17:15 +0100 From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> To: John-Mark Gurney <jmg@funkthat.com> Cc: Yong-Hyeon Pyun <pyunyh@gmail.com>, Jack F Vogel <jfv@freebsd.org>, Adrian Chadd <adrian@freebsd.org>, "freebsd-net@freebsd.org list" <freebsd-net@freebsd.org> Subject: Re: A small fix for if_em.c, if_igb.c, if_ixgbe.c Message-ID: <3576B69E-E943-46E0-83E5-0B2194A44ED0@lurchi.franken.de> In-Reply-To: <20131205223711.GB55638@funkthat.com> References: <521B9C2A-EECC-4412-9F68-2235320EF324@lurchi.franken.de> <20131202022338.GA3500@michelle.cdnetworks.com> <B9593E83-E687-49E9-ABDC-B2DD615180E9@lurchi.franken.de> <20131203021658.GC2981@michelle.cdnetworks.com> <CAJ-Vmo=kfoPMYjZ0WAtqmoJMz1utXH50SW9N92RA83EMUzY7WA@mail.gmail.com> <B89B1E2D-BAF0-4815-B3AB-EB226F4F76DE@lurchi.franken.de> <CAJ-Vmo=4Zwv5V6ZYDuDLtt%2BowgbvmqyvrnrfnU%2BHeXQ3vAn-KA@mail.gmail.com> <20131205223711.GB55638@funkthat.com>
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On Dec 5, 2013, at 11:37 PM, John-Mark Gurney <jmg@funkthat.com> wrote: > Adrian Chadd wrote this message on Thu, Dec 05, 2013 at 14:01 -0800: >> On 5 December 2013 13:05, Michael Tuexen >> <Michael.Tuexen@lurchi.franken.de> wrote: >> >>> Just to be clear: This would mean that xxx_transmit() would return >>> an error even if the packet provided in the call xxx_transmit() is >>> enqueued and not dropped? >>> This would also be problem with the current SCTP stack. >> >> I think it'll return an error only if: >> >> * it queued the frame to the tail of the drbd; >> * it then tried to transmit a frame from the head of the drbd; >> * it failed to transmit the first frame in the drbd and it couldn't >> put it back into the queue for whatever reason. >> >> So I think it should be "ok enough" for both TCP and SCTP. > > IMO it should only return an error if the specific frame failed to be > sent or queued. If you cannot determine at return time if the frame > failed to be transmitted/queued, then it should return success. Yes, this is exactly what I think too. This is what my first patch realizes. > > In the above case, if there were other frames queued ahead, and the > first one failed, then it sounds like the frame may eventually be sent > and we will end up sending a duplicate frame. Correct. SCTP will consider the frame even unsent... So the SCTP stack behaves strange and sends a packet at wirespeed over and over again (which is not good...). Best regards Michael > >> Give it a go and let me know how it goes. >> >> It's an interesting architectural problem to completely solve. > > -- > John-Mark Gurney Voice: +1 415 225 5579 > > "All that I will do, has been done, All that I have, has not." >
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